HK1078177A - Gain control for communications device - Google Patents

Description

Gain control for communication device

Background

FIELD

The present invention relates to communication systems, and more particularly, to systems and techniques for controlling the gain of a communication device.

Background

Communication systems typically support the exchange of information between two or more communication devices. These communication devices typically include an analog front end that interfaces with the communication medium and also includes a digital processor for manipulating information. Depending on the type of communication device, the analog front end may be designed with a transmitter, a receiver, etc. The function of the transmitter is to modulate, upconvert and amplify the information for transmission to free space. The function of the receiver is to detect the signal in the presence of noise and interference and provide amplification, down-conversion and demodulation of the detected signal so that it can be displayed or used by a digital processor.

The receiver typically includes gain control, which is commonly referred to in the art as Automatic Gain Control (AGC). One function of the AGC function in a receiver is to maintain a constant output power over a range of signal input variations. This is typically achieved with an AGC that averages the output power from the receiver and feeds this average back to the receiver to control the receiver gain.

In mobile radio applications, the AGC function may also be used in a mobile transmitter to prevent a mobile user close to a base station from interfering with a mobile user further away from the base station. The AGC function is implemented in the mobile station by feeding back the average receiver output power to follow the receiver to control the transmitter gain. Thus, if the mobile station moves closer to the base station increasing the received power, the AGC will scale down the gain of the receiver and transmitter. This would result in a proportional reduction in mobile transmitter power as the mobile user approaches the base station. This power control technique is commonly referred to as open loop control.

The non-linear gain characteristics of the receiver and transmitter may prevent the AGC from operating in an optimal manner. Accordingly, linearizers are often used in AGCs as a way to compensate for non-linearities in the receiver and transmitter. The linearizer can be implemented in any manner. One common technique involves the use of a "look-up table" stored in memory to convert the average receiver power to a power control signal, which can compensate for the nonlinear gain characteristics of the receiver or transmitter. The contents of the "look-up table" are determined during the calibration process. The calibration process generally requires tracking the average power output from the receiver as the input power to the receiver is swept over a particular operating range for different frequency and temperature variations using an AGC closed loop.

To maintain the commercial viability of communication devices, manufacturers often seek simple calibration procedures that reduce the demand on human resources. Unfortunately, this process often dictates a calibration process that is implemented on an absolute minimum number of operating frequencies and temperatures that meet the accuracy requirements of the AGC. The potential drawbacks of the relatively simple calibration procedure are even more pronounced as multimedia communication devices are introduced into the market. As an example, a multimedia communication device that supports both previous voice devices and new data services may require separate calibration procedures for each. Accordingly, there is a need for a communication device that can be supported with a simple calibration procedure that cannot only support different frequencies and temperatures, but also can support a multimedia mode of operation.

SUMMARY

In one aspect of the invention, a method of gain control includes amplifying a signal with an amplifier, the amplifier gain represented by one of a plurality of gain curves dependent on a value of a parameter, the signal being amplified at a first value of the parameter, and controlling the gain of the amplified signal from a predetermined gain curve associated with the amplifier gain curve for a second value of the parameter by adjusting a gain control signal corresponding to a point on the predetermined gain curve as a function of the first value of the parameter and applying the adjusted gain control signal to the amplifier.

In another aspect of the invention, an apparatus includes an amplifier having a gain represented by one of a plurality of gain curves dependent on a value of a parameter; and a gain control for controlling the gain of the amplified signal from the predetermined gain curve associated with the gain curve of the amplifier for a second value of the parameter value by adjusting the gain control signal corresponding to a point on the predetermined gain curve as a function of the first value of the parameter value and applying the adjusted gain control signal to the amplifier.

In another aspect of the invention, a computer-readable medium embodies a method of controlling the gain of an amplifier having a gain represented by one of a plurality of gain curves based on parameter values, the method including storing a predetermined gain curve associated with the gain curve of the amplifier for a first one of the parameter values, adjusting a gain control signal corresponding to a point on the predetermined gain curve as a function of a second one of the parameter values, and applying the adjusted gain control signal to the amplifier.

In another aspect of the invention, an apparatus includes amplifier means for amplifying a signal, the amplifier means having a gain represented by one of a plurality of gain curves dependent on a value of a parameter, and gain control means for controlling the gain of the amplified signal from a predetermined gain curve associated with the gain curve of the amplifier for a first one of the parameter values by adjusting a gain control signal corresponding to a point on the predetermined gain curve as a function of a second one of the parameter values and applying the adjusted gain control signal to the amplifier.

In another aspect of the invention, an apparatus includes a receiver with a gain represented by one of a plurality of receiver gain curves that depends on a value of a receiver parameter; a transmitter having a gain represented by one of a plurality of transmitter gain curves dependent on a transmitter parameter value; a gain control for adjusting the receiver gain control signal corresponding to a point on the predetermined gain curve and applying the adjusted receiver gain control signal to the receiver by a second value function as a value of a receiver parameter, the gain control controlling the gain of the amplified signal from the predetermined receiver gain curve associated with the receiver gain curve of the receiver for a first value of the receiver parameter, the gain control further for adjusting the transmitter gain control signal corresponding to a point on the predetermined transmitter gain curve and applying the adjusted transmitter gain control signal to the transmitter by the second value function as a value of a transmitter parameter, the gain control controlling the gain of the amplified signal from the predetermined transmitter gain curve associated with the transmitter gain curve of the transmitter for the first value of the transmitter parameter.

It is understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein only exemplary embodiments of the invention are shown and described, simply by way of illustration. It is to be understood that the invention is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

Brief description of the drawings

Aspects of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

FIG. 1 is a functional block diagram of an exemplary analog front end with gain control;

FIG. 2 is a functional block diagram of an example gain control with multiple linearizers;

FIG. 3 is a graphical representation of the non-linear gain characteristics of an amplifier within an exemplary analog front end, and an exemplary predetermined gain curve for compensating for the non-linearity of the amplifier;

FIG. 4 is a functional block diagram of an exemplary linearizer for use in the gain control of FIG. 2; and

fig. 5 is a functional block diagram of an example core linearizer for use in the linearizer of fig. 4.

Figure 6 is an exemplary analog front end functional block diagram of a multimedia application using an HDR communications device with a prior voice device.

Detailed Description

The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The term "exemplary" used in this description means "serving as an example, instance, or illustration," and should not be construed as optimal or advantageous over other embodiments. The detailed description includes specific details for a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the present invention.

In an exemplary embodiment of the communication device, the predetermined gain curve compensates for the non-linear characteristic of the amplifier, which curve may be calculated by a calibration procedure at a fixed operating temperature and frequency. The predetermined gain curve can then be used to calculate a gain control signal for the amplifier by adjusting a point on the predetermined gain curve related to the output power of the amplifier as a function of operating frequency and temperature. The amplifier may be a stand-alone amplifier or one or more amplifiers making up a receiver or transmitter. The concept can be further extended to support multimedia devices where the point on a predetermined curve related to the output power of the amplifier is adjusted according to the mode of operation.

Various aspects of these gain control techniques are described in the context of a CDMA communication system, however, those skilled in the art will appreciate that these gain control techniques are equally applicable in a variety of other communication environments. Accordingly, any reference to a CDMA communications system is intended only to illustrate the inventive aspects of the present invention, with the understanding that such inventive aspects have a wide range of applications.

CDMA is a modulation and multiple access scheme based on spread spectrum communications. In a CDMA communication system, a large number of signals share the same frequency, with the result that user capacity is increased. This may be accomplished by transmitting each signal with a different pseudo-random noise (PN) code that modulates a carrier wave, thereby spreading the spectrum of the signal waveform. The transmitted signals are separated in the receiver by correlators which despread the desired signal spectrum using the corresponding PN codes. The undesired signal does not match its PN code and is not despread in bandwidth as noise.

Fig. 1 illustrates an example analog front end for a subscriber station, such as a mobile CDMA communications device. Or alternatively. The analog front end may be used for a base station. The analog front end may operate in a transmit or receive mode. In a transmit mode, transmitter 102 may be coupled to antenna 104 through duplexer 106 for reverse link transmission (not shown) to a base station. The reverse link refers to transmission from a subscriber station to a base station. In a receive mode, duplexer 106 directs forward link transmissions received by antenna 104 to receiver 108. The forward link refers to transmission from the base station to the subscriber station. The position of the duplexer 106 may be controlled by means known in the art. The output of the receiver is fed back to control the transmitter and receiver gains through AGC 109. In the example embodiment depicted, the AGC 109 is responsive to temperature and frequency variations. In multimedia applications, the AGC 109 may be used to support different modes of operation, such as voice or data applications. For purposes of illustration, AGC techniques are described with reference to the reverse link, however, as will be appreciated by those skilled in the art, these AGC techniques are equally applicable to the forward link.

In the depicted example embodiment, receiver 108 may be based on a heterodyne complex (I-Q) architecture. For ease of explanation, the example receiver 108 is functionally described without reference to separate I (in-phase) and Q (quadrature) channels. A variable gain RF attenuator 110 in combination with dual low noise amplifiers 112a and 112b (lnas) may be used to provide a good gain profile through the receiver 108. In at least one receiver embodiment, the LNA may be equipped with bypass capability. An image reject cancellation filter 114 may be located between LNAs 112a and 112b to suppress image noise. A digital-to-analog converter (DAC)116 may be used at the AGC 109 output to convert the digital RF gain control signal to an analog signal for controlling the attenuation level of the variable RF attenuator 110. AGC 109 may further be used to bypass one or more LNAs 112a and 112b via an LNA control signal.

The output from LNA112 b may be coupled to IF mixer 118 where it is mixed with a reference signal generated by a local oscillator (L0) (not shown). A bandpass filter 120 at the output of the IF mixer 118 may be used to select the Intermediate Frequency (IF), i.e. the beat frequency between the received transmitted and reference signals. The IF output from bandpass filter 120 may be provided to an IF Variable Gain Amplifier (VGA)122 before being mixed with the second reference signal from L0 by bandpass mixer 124. A low pass filter 126 at the output of the baseband mixer 124 may be used to send the baseband component of the mixed signal to an analog-to-digital converter (ADC) 128. The digital baseband signal from ADC 128 may be provided to a processor (not shown) where it may be quadrature demodulated with short PN codes, decovered with Walsh codes, descrambled using long PN codes, and decoded with forward error correction. A second DAC130 may be used at the AGC 109 output to convert the digital IF gain control signal to an analog signal for controlling the gain of the IF VGA 122.

The digital baseband signal from ADC 128 may also be used to drive AGC 109. Alternatively, the digital baseband signal may also be provided to a rake receiver (not shown) within the processor. A rake receiver may be equipped with multiple demodulation elements (fingers) and a searcher. The searcher identifies strong multipath arrivals and assigns a finger to demodulate at the identified offset. The demodulated digital baseband signal of the best finger can then be used to drive the AGC 109.

In the example embodiment described above, the transmitter 102 uses a direct conversion architecture. Alternatively, the transmitter 102 may be designed with one or more IF stages. Transmitter 102 may be implemented to receive multiple Walsh channels spread with long PN codes and quadrature modulated with short PN codes. The baseband filter 132 may be used to suppress from the frequency band components of the quadrature modulated signal and for pulse shaping. The filtered signal may be provided to an RF mixer 134 where it is modulated onto a carrier waveform. The modulated carrier waveform may then be coupled to a transmitter VGA 136 and ultimately to a power amplifier 138 for transmission to free space via the antenna 104. A bandpass filter (not shown) may be arranged after the power amplifier 138 to filter out unwanted frequencies before transmission through the antenna 104. The power amplifier 138 may be used to support four driver states with the ability to turn off and bypass the power amplifier 138 if the transmitter power is low enough to enable the transmitter VGA 136 to support reverse link transmission. The AGC 109 can be used to control the state of the power amplifier 138 and the gain of the transmitter VGA 136. The third DAC 140 may be used to convert a digital transmitter gain control signal into an analog signal for controlling the gain of the transmitter VGA 136.

A functional block diagram of an example AGC 109 is shown in fig. 2 in the context of a High Data Rate (HDR) CDMA communication system. HDR communication systems are typically designed to conform to one or more standards such as "cdma 2000 HighRate Packet Data, Air Interface Specification", 3GPP2 c.s0024, Version2, October 27, 2000, promulgated by the organization of the "third generation partnership project". An example of such HDR communications is described in U.S. patent application No. 08/963386, entitled "Method and Apparatus for high Rate Packet Data Transmission", filed on 3.11.1997. The contents of the above-mentioned standards and patent applications are incorporated herein by reference. As will be appreciated by those skilled in the art, the inventive concepts of AGC discussed herein are equally applicable to other communication devices.

In the described example embodiment, the AGC may be used to measure the power output from the receiver and provide feedback to control the gain of the transmitter and receiver. The feedback signal may be generated by comparing the output power measured by the receiver to an AGC set point. If the measured output power of the receiver is below the AGC set point, the feedback signal provided to the transmitter and receiver can be used to increase the gain accordingly. Conversely, if the measured output power of the receiver is above the set point, the feedback signal provided to the transmitter and receiver may be used to reduce the gain accordingly.

Referring to fig. 2, a digital baseband signal from a receiver of an analog front end or a rake receiver from a processor may be coupled to an energy estimator 202. The energy estimator 202 accumulates (I) during the gated pilot burst by accumulating²+Q²) The output power of the receiver is calculated. In an HDR communication system, a base station typically transmits a gated pilot signal on the forward link. In other communication systems using the inventive AGC technique described above, the accumulation period may be determined by one of ordinary skill in the art to optimize performance. The AGC set point may be subtracted from the calculated output power from the energy estimator 202 by a subtractor 206. The resulting difference between the AGC set point and the calculated output power is indicative of the error between the output power of the receiver and the AGC set point. The error signal is scaled by multiplier 208 with an AGC gain. The scaled error signal may then be provided to AGC accumulator 210 for averaging over one or more pilot bursts. In at least one embodiment, AGC accumulator 210 saturates at maximum and minimum thresholds. The average produced by the scaled error signal is called the "AGC value" and is used to control the gain of the receiver and transmitter.

The LNA state machine 212 can be used to determine which of the two front-end LNAs within the receiver will be bypassed based on the average output power of the receiver, i.e., the AGC value. As the AGC value increases, the LNA state machine 212 can be used to switch or bypass the LNAs one after the other. Using this approach, the dynamic range of the variable gain RF attenuator in the receiver may be smaller because less attenuation is required for one or both LNAs to switch off (switch out). Conversely, the LNA state machine 212 may be used to switch the LNAs back to the receiver signal path one after the other as the average output power of the receiver is reduced.

The RF attenuator control 214 may be used to control the degree of attenuation of a variable gain RF attenuator within the receiver. The attenuation characteristics of the RF attenuator control 214 may take various forms depending on the particular application and overall design parameters. For example, the RF attenuator control 214 may be used to provide zero attenuation below a minimum AGC value. When the AGC value exceeds the minimum threshold, the degree of attenuation increases linearly with the AGC value until the AGC value reaches a maximum. The attenuation characteristics of the RF attenuation control 214 may have a relatively flat response after the maximum is reached.

When one or both LNAs are switched out in the receiver, the gain of the IF VGA should be increased to maintain the overall gain of the receiver constant. This can be done by adjusting the AGC value, which controls the gain of the IF VGA in the receiver with the LNA offset. The LNA offset is a function of the state of the LNA state machine 212. Similarly, IF the attenuation of the variable gain RF attenuator is increased, the AGC value that controls the IF VGA gain in the receiver should be further adjusted by the RF attenuator offset. These adjustments may be implemented with subtractors 216 and 218 shown in fig. 2. Subtractors 216 and 218 may be used in an AGC configuration in which the gain of the IF VGA in the receiver is varied in inverse proportion to the IF gain control signal from the AGC. The IF gain control signals from subtractors 216 and 218 and the RF gain control signal from RF attenuator control 214 may be provided to their respective linearizers 220 and 222.

The linearizer can be used to compensate for the nonlinear RF and IF gain control of the receiver. The linearizer can be implemented in a variety of ways depending on the particular design criteria. In at least one embodiment, the linearizer can be provided with a memory that stores a predetermined gain curve. Fig. 3 shows such a predetermined gain curve. The actual gain curve of the receiver can be shown by curve 302. The memory may be used to store a predetermined gain curve obtained by calibration, which is the inverse of the actual gain curve of the receiver. The predetermined gain curve is shown by curve 304. When a predetermined gain curve 304 stored in memory is applied to the AGC value, the result is a linear relationship between the receiver output power and the gain control of the variable gain RF attenuator, with the IF VGA as shown by curve 306.

The actual gain curve of the receiver typically varies as a function of temperature and carrier frequency. In at least one embodiment, any number of predetermined gain curves may be stored in memory to provide linearized gain at various temperatures and frequencies. Depending on the number of curves, this approach consumes a lot of memory. Alternatively, the linearizer may be implemented with a single predetermined gain curve with temperature and frequency compensation. Fig. 4 shows a functional block diagram of an example linearizer using this concept. The linearizer includes a core linearizer 402 to store a predetermined gain curve at a reference frequency and temperature. Frequency compensation can be achieved by applying compensation by operator 404 to a point on a predetermined curve along the x-axis, i.e., the horizontal axis. An operator is any hardware or software that implements a mathematical function. For example, in the example linearizer depicted, operator 404 is an adder. The output of operator 404 may be provided to core linearizer 402 to read out data points on a predetermined gain curve. The output of the operator 404 may also be provided to a second operator 406. The second operator 406 can be used to offset the slope of the predetermined gain to compensate for temperature changes. The operator may also be implemented with a scaling function, and thus the second operator 406 may be implemented with a multiplier. The third operator 408 may be used to combine the output of the core linearizer and the second operator with an offset in the y-axis, i.e., the vertical axis, to further compensate for temperature variations. In the example linearizer depicted, the third operator 408 may be an adder. The output of the third operator 408 is a digital gain control signal applied to the receiver.

The core linearizer may be implemented in various ways depending on the particular application and the overall design constraints. In at least one embodiment, the core linearizer may be implemented in memory with a digital RF or IF gain control value for each AGC value. Thus, if the AGC value input is 16 bits wide and the gain control signal is also 16 bits wide, a 64K x 16 memory is required. Alternatively, the memory requirements can be greatly reduced while maintaining the same resolution by using memory in conjunction with a linear interpolator. Fig. 5 is a functional block diagram of an example core linear circuit using this concept. In the illustrated example embodiment, the Most Significant Bit (MSB) of the AGC is applied to the memory 502 by truncating the Least Significant Bit (LSB). One skilled in the art can determine the number of LSBs to truncate from the AGC value to best balance the performance tradeoff between memory consumption and processing complexity. Two values from a predetermined gain curve are output to the linear interpolator 504, depending on the AGC value applied truncated at the input of the memory 502. The first value represents the digital gain control signal for the truncated AGC value input and sets a minimum value for the interpolator process. The second value represents the digital gain control signal for the next highest truncated AGC value and sets the maximum value for the interpolator process. Linear interpolator 504 interpolates the correct digital gain control signal between the limits defined by the two values from memory 502.

The linear interpolator 504 can be implemented in a variety of ways, and one skilled in the art can construct a linear interpolator that meets its particular design criteria. However, for completeness, an example linear interpolator is described herein. In this example linear interpolator, the minimum value from memory is applied to adder 506. Next, a value between zero and the difference between the maximum and minimum values is calculated and applied to an adder 506 to determine the interpolated digital gain control signal. This may be done by subtracting the minimum value from the maximum value by subtractor 508. The resulting difference is provided to multiplier 510 for a scaling operation. The scaling operation may be implemented by shifting the AGC value up by 5 bits and implementing with a gate 512 with 0xFFFF_HEXAND operation of (c). The 16 LSBs from gate 512 may be multiplied by the 16-bit difference at multiplier 510. The 16 LSBs of the 32-bit resulting product from multiplier 510 may be truncated to arrive at the appropriate interpolated value that is added by adder 506 to the minimum value from memory 502. The output of the summer 506 provides a digital gain control signal that varies linearly with the estimated output power from the receiver.

Returning to fig. 2, the gain of the transmitter VGA can be controlled by two power loops. Open loop control 224 may be used to generate an estimate of the optimal reverse link transmission based on the AGC value from AGC attenuator 210. The open loop estimate may be calculated by means known in the art to compensate for system parameters such as path loss, base station loading effects, and environmentally induced phenomena such as fading and shadowing.

The second power control loop is closed loop control 226. The closed loop control 226 has the function of correcting the open loop estimate to obtain a desired signal-to-noise ratio (SNR) at the base station. This may be accomplished by measuring the reverse link transmission power at the base station and providing feedback to the subscriber station to adjust the reverse link transmission power. The feedback signal may be in the form of a Reverse Power Control (RPC) command generated by comparing the reverse link transmission power measured at the base station to a power control set point. If the measured reverse link transmit power is below the set point, an RPC up command is provided to the subscriber station to increase the reverse link transmit power. If the measured reverse link transmission power is above the set point, the subscriber station is provided with an RPC down command to reduce the reverse link transmission power. Closed loop control is well known in CDMA communication systems. An adder 228 may be used for combining the open-loop estimation result with the output of the closed-loop control 226.

A power amplifier state machine 230 may be used to control the driver state of the power amplifier in the transmitter. As an example, a power amplifier may be configured with four different operating power levels by switching in or out within one or more of the four driver stages. The power amplifier state machine 230 may be used to switch in and out the individual driver stages one after the other according to a combined open and closed loop calculation function. In at least one embodiment, the power amplifier includes the capability to bypass and shut down completely if the transmit power is low enough that the transmitter VGA can support the transmit power requirements. Using this approach, the power requirements of the transmitter VGA can be reduced by increasing the power level of the power amplifier.

Whenever the driver state of the power amplifier changes, it introduces a gain or attenuation step in the transmitter signal path, which should be compensated by adjusting the gain of the transmitter VGA in the same or the opposite way. This can be done by adjusting a combined closed and open loop calculation that controls the gain of the transmitter VGA with the power amplifier bias. The power amplifier bias is a function of the state of the power amplifier state machine 230. This adjustment may be implemented with a subtractor 232 as shown in fig. 2.

The transmitter VGA linearizer 234 may be used to compensate the power control value generated from the subtractor 232 for the non-linearity of the AGC. The transmitter VGA linearizer 234 may be implemented with a linearizer similar to the one described above in connection with fig. 3-5.

The linearizer concept described throughout may be extended to support multimedia applications. This approach is particularly attractive when integrating new data services into existing voice devices. For example, the linearizer concept can be used to provide a more robust communication device, integrating an HDR communication system into an existing CDMA cellular telephone. Existing CDMA Cellular telephones may be implemented in the manner described in U.S. patent No. 4901307, entitled "Spread Spectrum Multiple Access communication system Using Satellite or Terrestrial applications," and in U.S. patent No. 5103459, entitled "system and Method for Generating wave forms in a CDMA Cellular telephone system," both of which are assigned to the assignee of the present invention and which are incorporated herein by reference.

Figure 6 shows an example analog front end functional block diagram for a multimedia application using an HDR communications device with a previous voice device. The analog front end includes a duplexer 106 that couples the transmitter 102 or receiver 108 to the antenna 104. The operation of the transmitter 102 and receiver 108 is the same as described in fig. 1 and therefore is not repeated here, except that the HDR communication and the previous voice device share the same transmitter 102 and receiver 108.

In the described example multimedia application, the HDR communication device and the previous voice device each have their own AGC. The AGC (HDR AGC) of the HDR communication device 602 controls the analog front end when operating in HDR mode, and the AGC (voice AGC) for the previous voice device 604 controls the analog front end when operating in voice mode. For commercialization purposes, it is envisioned that the existing voice AGC 604 in previous voice devices will be used. Previous voice devices used in CDMA cellular telephones in the past typically included AGC implemented in hardware. Hardware implementation appears to be a very practical approach at the speed at which the AGC operates within the previous speech device. However, as will be appreciated by those skilled in the art, the AGC of previous speech devices may be implemented in any manner without departing from the inventive concepts described above. A microprocessor is used to calculate a new predetermined gain curve based on frequency and temperature changes to compensate for non-linear operation of the transmitter or receiver and to reload the linearizer in the hardware.

The HDR AGC 602 may be implemented with a Digital Signal Processor (DSP) with temperature and frequency compensation, as described in detail above. DSP is an effective implementation of HDR AGC, but is not a practical way to implement AGC in previous speech, which typically runs 32 times faster than AGC for HDR, as it does not necessarily increase the load on DSP. Since rake receivers are typically implemented in DSPs, this AGC configuration can be used very simply to support energy estimation on a per-finger basis, selecting the best finger to drive the AGC.

In the multimedia application example embodiment shown in fig. 6, a single calibration procedure may be used to load the hardware linearizer in the voice AGC 602 based on the calibration procedure of the previous voice device. The predetermined gain curve loaded into the hardware linearizer in the voice AGC 602 can be reformatted by software and loaded into the DSP linearizer in the HDRAGC 604 to be transparent to the device manufacturer. This approach is particularly attractive to device manufacturers because only one calibration process is required to support both HDR communications devices as well as previous voice devices, while at the same time providing the device manufacturers with the convenience of previous voice devices and familiarity with existing calibration processes.

Returning to fig. 6, the digital baseband signal from the receiver 108 may be fed to a voice AGC 602 and an HDR AGC 604. The AGCs 602 and 604 generate gain control signals for the transmitter 102 and the receiver 108. The appropriate gain control signal may be selected by the multiplexer 606 based on a common selection signal indicating that the multimedia application is operating in the voice or HDR mode.

Those of skill would appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various logical blocks, modules, and circuits disclosed in the illustrative embodiments herein may be implemented or performed in the manner of: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, to implement the functions described herein. A general purpose processor is preferably a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary processor is preferably coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an application specific integrated circuit, ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

While the specification describes particular embodiments of the present invention, those skilled in the art may devise variations of the present invention without departing from the inventive concept.

Claims (86)

1. A method of gain control, comprising:

amplifying a signal with an amplifier, the amplifier gain being represented by one of a plurality of gain curves dependent on a value of a parameter, the signal being amplified at a first value of the parameter value; and

the gain of the amplified signal is controlled from a predetermined gain curve associated with the gain curve of the amplifier for a second value of the parameter value by adjusting the gain control signal corresponding to a point on the predetermined gain curve as a function of the first value of the parameter value and applying the adjusted gain control signal to the amplifier.

2. The method of claim 1, wherein each gain curve is non-linear, and wherein the predetermined gain curve is used to compensate the second one of the parameter values for the non-linear gain curve.

3. The method of claim 2 wherein the gain control signal is adjusted to compensate for the non-linear gain of the amplifier at the first one of the parameter values.

4. The method of claim 1, wherein the parameter comprises a frequency of the received signal.

5. The method of claim 1, wherein the parameter comprises amplifier temperature.

6. The method of claim 1, wherein the predetermined gain curve is stored in a memory.

7. The method of claim 6, wherein the amplifier includes a receiver, and wherein the adjusting of the gain control signal includes estimating a power of an amplified signal from the receiver and adjusting the estimated power as a function of the first of the parameter values to address the memory.

8. The method of claim 6, wherein the amplifier comprises a transmitter, the method further comprising amplifying the received signal with a receiver, and wherein the adjusting of the gain control signal comprises estimating the power of the amplified signal from the receiver and adjusting the estimated power as a first function of the parameter value to address the memory.

9. The method of claim 6 wherein the adjusting of the gain control signal comprises adjusting the gain control signal in memory as a function of the first of the parameter values.

10. A method as claimed in claim 6, characterized in that each gain curve of the amplifier is also determined by interpolation between two points on the predetermined gain curve.

11. The method of claim 1, wherein each gain curve of the amplifier is further dependent on a second parameter value, the signal being amplified at one of the second parameter values, and wherein the predetermined gain curve further relates to a second one of the second parameter values, and the adjusting of the gain control signal further comprises adjusting the gain control signal as a function of the first one of the second parameter values.

12. The method of claim 11, wherein the parameter further comprises a frequency of the received signal and the second parameter comprises an amplifier temperature.

13. The method of claim 11, wherein the predetermined gain curve is stored in a memory.

14. The method of claim 13, wherein the amplifier includes a receiver, and wherein the adjusting of the gain control signal further comprises estimating the power of the amplified signal from the receiver, adjusting the estimated power as a function of a first one of the parameter values to address the memory, reading the gain control signal from the predetermined gain curve corresponding to the address from the memory, adjusting the address as a function of a first one of the second parameter values, and adjusting the reading of the gain control signal from the memory as a function of the first one of the second parameter values and the adjusted address.

15. The method of claim 13, wherein the amplifier comprises a transmitter, the method further comprising amplifying the received signal with a receiver, and wherein the adjusting of the gain control signal further comprises estimating a power of the amplified signal from the receiver, adjusting the estimated power as a function of the first of the parameter values to address a memory, reading the gain control signal from a predetermined gain curve corresponding to the address from the memory, adjusting the address as a function of the first of the second parameter values, and reading the gain control signal from the memory as a function of the first of the second parameter values and the adjusted address.

16. The method of claim 15, wherein the gain control signal is determined by interpolating between two points on a predetermined gain curve.

17. The method of claim 1, further comprising copying a predetermined gain curve from the first memory to the second memory, the gain control signal corresponding to a point on the predetermined gain curve from the second memory.

18. An apparatus, comprising:

an amplifier with a gain represented by one of a plurality of gain curves depending on a value of the parameter; and

gain control for controlling the gain of the amplified signal from a predetermined gain curve associated with the gain curve of the amplifier for a first one of the parameter values by adjusting the gain control signal corresponding to a point on the predetermined gain curve as a function of a second one of the parameter values and applying the adjusted gain control signal to the amplifier.

19. The apparatus of claim 18, wherein the parameter comprises a frequency of the signal to be amplified by the amplifier.

20. The apparatus of claim 18 wherein said parameter comprises amplifier temperature.

21. The apparatus of claim 18 wherein each gain curve is non-linear and the predetermined gain curve is used to compensate the non-linear gain curve for the first of the parameter values.

22. The apparatus of claim 21 wherein the gain control is further for adjusting the gain control signal to compensate for the non-linear gain of the amplifier at the second one of the parameter values.

23. The apparatus of claim 18 wherein said gain control comprises a memory for storing a predetermined gain curve.

24. The apparatus of claim 23 wherein said gain control further comprises an interpolator for determining the gain control signal from two points on a predetermined gain curve.

25. The apparatus of claim 23 wherein the amplifier comprises a receiver, and wherein the gain control further comprises a power estimator for estimating a power output from the receiver, and an operator for adjusting the power as a function of the second one of the parameter values to address the memory.

26. The apparatus of claim 23 further comprising a receiver, wherein the amplifier comprises a transmitter, and wherein the gain control further comprises a power estimator for estimating a power output from the receiver, and wherein an operator is used to adjust the estimated power as a function of the second one of the parameter values to address the storage.

27. The apparatus of claim 26, wherein said operator comprises an adder.

28. The apparatus of claim 23 wherein the gain control further comprises a combiner for adjusting the gain control signal as a function of the second one of the parameter values.

29. The apparatus of claim 28, wherein said operator comprises an adder.

30. The apparatus of claim 18 wherein each gain curve of the amplifier is further dependent on a second parameter value and the predetermined gain curve is further related to a first one of the second parameter values, and wherein the gain control adjusts the gain control signal as a function of a second one of the second parameter values.

31. The apparatus of claim 30 wherein the parameter further comprises a frequency of a signal to be amplified by the amplifier and the second parameter comprises an amplifier temperature.

32. The apparatus of claim 30 wherein said gain control further comprises a memory for storing a predetermined gain curve.

33. The apparatus of claim 32 wherein said gain control further comprises an interpolator for determining the gain control signal from two points on a predetermined gain curve.

34. The apparatus of claim 32 wherein the amplifier includes a receiver, the gain control further comprising a power estimator for estimating a power output from the receiver, a first operator for adjusting the estimated power as a function of a second one of the parameters to address the memory, a second operator for adjusting the address as a function of the second one of the second parameter values, and a third operator for adjusting the gain control signal from the memory as a function of the second one of the second parameter values, the second parameter value being a function of the adjusted address.

35. The apparatus of claim 32 further comprising a receiver, wherein the amplifier comprises a transmitter, and wherein the gain control further comprises a power estimator for estimating a power output from the receiver, a first operator for adjusting the estimated power as a function of a second one of the parameter values to address the memory, a second operator for adjusting the address as a function of the second one of the second parameter values, and a third operator for adjusting the gain control signal from the memory as a function of the second one of the second parameter values, the second parameter value being a function of the adjusted address.

36. The apparatus of claim 35 wherein said first and third operators each comprise an adder and the second operator comprises a multiplier.

37. The apparatus of claim 18, further comprising a first memory for storing a predetermined gain curve, and wherein the gain control comprises a second memory, the gain control further being configured to copy the predetermined gain curve from the first memory to the second memory, the gain control signal corresponding to a point on the predetermined gain curve from the second memory.

38. A computer-readable medium embodying a method of controlling gain of an amplifier with gain represented by one of a plurality of gain curves based on a parameter value, the method comprising:

storing a predetermined gain curve associated with the amplifier gain curve for a first one of the parameter values;

adjusting the gain control signal corresponding to a point on the predetermined gain curve as a function of the second one of the parameter values; and

the adjusted gain control signal is applied to the amplifier.

39. The computer-readable medium of claim 38, wherein each gain curve is non-linear, and wherein the predetermined gain curve is used to compensate the non-linear gain curve for the first one of the parameter values.

40. The apparatus of claim 39 wherein the gain control signal is adjusted to compensate for the amplifier nonlinear gain at the second one of the parameter values.

41. The computer-readable medium of claim 38, wherein the parameter comprises a frequency of the signal to be amplified.

42. The computer-readable medium of claim 38, wherein the parameter comprises amplifier temperature.

43. The computer-readable medium of claim 38, wherein the predetermined gain curve is stored in a memory.

44. The computer-readable medium of claim 43 wherein the amplifier includes a receiver, and wherein the adjusting of the gain control signal includes estimating a power output received from the receiver and adjusting the estimated power as a function of the second one of the parameter values to address the memory.

45. The computer-readable media of claim 43 wherein the amplifier comprises a transmitter, the method further comprising amplifying the received signal with a receiver, and wherein adjusting the gain control signal comprises estimating a power output from the receiver and adjusting the estimated power as a function of the second one of the parameter values to address the memory.

46. The computer-readable medium of claim 43 wherein the adjustment of the gain control signal comprises adjusting the gain control signal as a function of the second one of the parameter values.

47. The computer-readable medium of claim 43 wherein the gain control signal is determined by interpolation between two points on a predetermined gain curve.

48. The computer-readable media of claim 38 wherein each gain curve of the amplifier is further dependent on a value of a second parameter, and wherein the predetermined gain curve further relates to a first one of the values of the second parameter, and the gain control signal adjusting further comprises adjusting the gain control signal as a function of the second one of the values of the second parameter.

49. The computer-readable medium of claim 48 wherein the parameter further comprises a frequency of a signal to be amplified by the amplifier and the second parameter comprises an amplifier temperature.

50. The computer-readable medium of claim 48 wherein the predetermined gain curve is stored in a memory.

51. The computer-readable media of claim 50 wherein the amplifier includes a receiver, and wherein the adjustment of the gain control signal further comprises estimating a power output from the receiver, adjusting the estimated power as a function of the second one of the parameter values to address the memory, reading the gain control signal from the predetermined gain curve corresponding to the address from the memory, adjusting the address as a function of the second one of the second parameter values, and reading the gain control signal from the memory as a function of the second one of the second parameter values and the adjusted address.

52. The computer-readable media of claim 50 wherein the amplifier comprises a transmitter, the method further comprising amplifying the received signal with a receiver, and wherein the adjusting of the gain control signal further comprises estimating a power output from the receiver, adjusting the estimated power as a function of the second one of the parameter values to address the memory, reading the gain control signal from the predetermined gain curve corresponding to the address from the memory, adjusting the address as a function of the first one of the second parameter values, and adjusting the reading of the gain control signal from the memory as a function of the second one of the second parameter values and the adjusted address.

53. The computer-readable medium of claim 50 wherein the gain control signal is determined by interpolating between two points on a predetermined gain curve.

54. The computer-readable medium of claim 38 wherein the method further comprises copying a predetermined gain curve from the first memory to the second memory, the gain control signal corresponding to a point on the predetermined gain curve from the second memory.

55. An apparatus, comprising:

amplifier means for amplifying a signal, said amplifier means having a gain represented by one of a plurality of gain curves dependent on a value of a parameter; and

gain control means for controlling the gain of the amplifier from a predetermined gain curve associated with the gain curve of the amplifier means for a first one of the parameter values by adjusting a gain control signal corresponding to a point on the predetermined gain curve as a function of a second one of the parameter values and applying the adjusted gain control signal to the amplifier.

56. The apparatus of claim 55 wherein the parameter comprises a frequency of the received signal.

57. The apparatus of claim 55 wherein said parameter comprises a temperature of the amplifier device.

58. The apparatus of claim 55 wherein each gain curve is non-linear and the predetermined gain curve is used to compensate the non-linear gain curve for the first one of the parameter values.

59. The apparatus of claim 58 wherein said gain control means signal generator is further for adjusting the gain control signal to compensate for the non-linear gain of the amplifier means at the second one of the parameter values.

60. The apparatus of claim 55 wherein said gain control means comprises memory means for storing a predetermined gain curve.

61. The apparatus of claim 60 wherein said gain control further comprises means for determining a gain control signal by interpolating from two points on a predetermined gain curve.

62. The apparatus of claim 60 wherein the amplifier means comprises a receiver, and wherein the gain control means further comprises means for estimating the power output from the receiver, and further comprising means for adjusting the estimated power as a function of the second one of the parameter values to address the memory.

63. The apparatus of claim 60 further comprising a receiver, wherein said amplifier means comprises a transmitter, and wherein said gain control means further comprises means for estimating the power output from the receiver, and means for adjusting the estimated power as a function of the second of the parameter values to address the memory.

64. The apparatus of claim 60 wherein said gain control means further comprises means for adjusting the gain control signal from the memory as a function of the second one of the parameter values.

65. The apparatus of claim 55 wherein each gain curve of said amplifier is further dependent on a second parameter value and the predetermined gain curve is further related to a first one of the second parameter values, and wherein said gain control means adjusts the gain control signal as a function of a second one of the second parameter values.

66. An apparatus as in claim 65 wherein said parameter comprises a frequency of a signal to be amplified by the amplifier means and the second parameter comprises a temperature of the amplifier means.

67. The apparatus of claim 65 wherein said gain control means further comprises memory means for storing a predetermined gain curve.

68. The apparatus of claim 67 wherein said gain control means further comprises means for determining the gain control signal by interpolating from two points on a predetermined gain curve.

69. The apparatus of claim 65 wherein the amplifier means comprises a receiver, the gain control means further comprising means for estimating a power output from the receiver, means for adjusting the estimated power as a function of a second one of the parameters to address the memory, means for adjusting the address as a function of the second one of the second parameter values, and means for adjusting the gain control signal from the memory as a function of the adjusted address.

70. The apparatus of claim 65 further comprising a receiver, wherein the amplifier means comprises a transmitter, and wherein the gain control means further comprises means for estimating a power output from the receiver, means for adjusting the estimated power as a function of a second one of the parameter values to address the memory, means for adjusting the address as a function of the second one of the second parameter values, and means for adjusting the gain control signal from the memory as a function of the adjusted address. .

71. The apparatus of claim 55 further comprising first memory means for storing a predetermined gain curve, and wherein the gain control means comprises second memory means and means for copying the predetermined gain curve from the first memory means to the second memory means, the gain control signal corresponding to a point on the predetermined gain curve from the second memory means.

72. An apparatus, comprising:

a receiver having a gain represented by one of a plurality of receiver gain curves dependent on a value of a receiver parameter;

a transmitter having a gain represented by one of a plurality of transmitter gain curves dependent on a transmitter parameter value;

a gain control for controlling the gain of the amplified signal from a predetermined receiver gain curve associated with the receiver's receiver gain curve by adjusting a receiver gain control signal corresponding to a point on the predetermined gain curve as a function of a second value of the receiver parameter value and applying the adjusted receiver gain control signal to the receiver, and for adjusting a transmitter gain control signal corresponding to a point on the predetermined transmitter gain curve and applying the adjusted transmitter gain control signal to the transmitter by adjusting a transmitter gain control signal corresponding to a point on the predetermined transmitter gain curve as a function of a second value of the transmitter parameter value and controlling the gain of the amplified signal from a predetermined transmitter gain curve associated with the transmitter's transmitter gain curve for the first value of the transmitter parameter value.

73. The apparatus of claim 72, wherein the receiver parameters comprise a frequency of a signal to be amplified by the receiver and the transmitter parameters comprise a frequency of a signal to be amplified by the transmitter.

74. The apparatus of claim 72 wherein said receiver parameter comprises a receiver temperature and said transmitter parameter comprises a transmitter temperature.

75. The apparatus of claim 72 wherein each of the receiver and transmitter gain curves is non-linear, and wherein the predetermined receiver gain curve is used to compensate the non-linear receiver gain curve for the first one of the receiver parameter values and the predetermined transmitter gain curve is used to compensate the non-linear transmitter gain curve for the first one of the transmitter parameter values.

76. The apparatus of claim 75 wherein the gain control is further for adjusting the receiver gain control signal to compensate for the receiver nonlinear gain at the second one of the receiver parameter values and adjusting the transmitter gain control signal to compensate for the transmitter nonlinear gain at the second one of the transmitter parameter values.

77. The apparatus of claim 72 wherein the gain control further comprises a power estimator for estimating power output from the receiver, and a memory for storing predetermined receiver and transmitter gain curves, the adjustment of the receiver and transmitter gain signals from their respective predetermined gain curves being a function of the estimated power.

78. The apparatus of claim 77 wherein the memory comprises a receiver memory for storing a predetermined receiver gain curve and a transmitter memory for storing a predetermined transmitter gain curve.

79. The apparatus of claim 78 wherein the gain control further comprises a receiver interpolator for determining the receiver gain control signal from two points on a predetermined receiver gain curve from the receiver memory, and the transmitter interpolator is for determining the transmitter gain control signal from two points on a predetermined transmitter gain curve from the transmitter memory.

80. The apparatus of claim 72, wherein each receive gain curve of the receiver is further dependent on a value of a second receiver parameter, and the predetermined receiver gain curve is further related to a first one of the values of the second receiver parameter, and wherein the gain control adjusts the receiver gain control signal as a function of the second one of the values of the second receiver parameter, and wherein each transmitter gain curve of the transmitter is further dependent on the value of the second transmitter parameter, and the predetermined transmitter gain curve is further related to the first one of the values of the second transmitter parameter, and wherein the gain control adjusts the transmitter gain control signal as a function of the second one of the values of the second transmitter parameter.

81. The apparatus of claim 80 wherein the receiver parameter comprises a frequency of a signal to be amplified by the receiver and the transmitter parameter comprises a frequency of a signal to be amplified by the transmitter, the second receiver parameter comprises a receiver temperature and the second transmitter parameter comprises a transmitter temperature.

82. The apparatus of claim 80 wherein the gain control comprises a power estimator for estimating power output from the receiver and the memory is for storing receiver and transmitter predetermined gain curves, the adjustment of the receiver and transmitter gain control signals from their respective predetermined gain curves being a function of the estimated power.

83. The apparatus of claim 82 wherein said memory comprises a receiver memory for storing a predetermined receiver gain curve and a transmitter memory for storing a predetermined transmitter gain curve.

84. The apparatus of claim 83 wherein the gain control further comprises a first operator for adjusting the estimated power as a function of a second one of the receiver parameter values to address the receiver memory, a second operator for adjusting an address to the receiver memory as a function of the second one of the second receiver parameter values, a third operator for adjusting the receiver gain control signal from the receiver memory as a function of the second one of the second receiver parameter values, wherein the second receiver parameter value is a function of the adjusted address to the receiver memory, a fourth operator for adjusting the estimated power as a function of the second one of the transmitter parameter values to address the transmitter memory, a fifth operator for adjusting an address to the transmitter memory as a function of the second one of the second transmitter parameter values, a sixth operator, for adjusting a transmitter gain control signal from a transmitter memory as a function of a second one of a second transmitter parameter, wherein the second transmitter parameter value is a function of an adjusted address to the transmitter memory.

85. The apparatus of claim 84, wherein said first, third, fourth and sixth operators each comprise an adder, and wherein said second and fifth operators each comprise a multiplier.

86. The apparatus of claim 72 further comprising a first memory for storing predetermined receiver and transmitter gain curves, and wherein the gain control comprises a second memory, the gain control further for copying the predetermined receiver and transmitter gain curves from the first memory to the second memory, the receiver and transmitter gain control signals each corresponding to a point on their respective predetermined gain curves from the second memory.