HK1148158B - Continuous alternating closed-open loop power control - Google Patents

Description

Continuously alternating closed-open loop power control

The present application is a divisional application of invention patent application No.200680004542.x entitled "continuously alternating closed loop-open loop power control" filed on 8/10/2007 (application date: 1/12/2006) to the chinese patent office and entered the chinese national phase.

Technical Field

The present invention relates generally to power control for wireless transmitters, and more particularly to variable gain amplifier circuits for wireless transmitters.

Background

Wireless communication systems employ power control to reduce interference and increase system capacity while maintaining minimum signal quality standards. The capacity of a wireless communication system, i.e., a WCDMA (wideband code division multiple access) system, depends mainly on the precise implementation of uplink power control. Many wireless communication standards, such as 3GPP TS 25.101, include specific requirements for transmission power control accuracy in wireless communication devices. These device requirements include absolute accuracy transmit power requirements and relative accuracy transmit power requirements. The absolute requirements define a lower limit transmission power and an upper limit transmission power with respect to the nominal transmission power. The relative requirements define a minimum transmission power difference and a maximum transmission power difference between two transmission slots (not necessarily adjacent slots), and an aggregate transmission power difference for a plurality of slots.

Closed loop power control represents a method for controlling transmission power within a wireless communication device to meet relative and absolute transmission power requirements. As used herein, closed loop power control refers to feedback power control performed in a wireless communication device. The closed loop power control system determines an error between the measured transmit power and the desired transmit power. Based on the error, the closed loop power control system adjusts the transmission power by adjusting the gain of a variable gain amplifier in a wireless transmitter of the wireless communication device.

Because the power detector has a limited dynamic range, the wireless communication device may not be able to accurately measure low transmission power, causing closed loop power control to become unreliable at low transmission powers. To avoid this, the wireless communication device may alternatively use open loop power control. As used herein, open loop power control refers to power control performed in a wireless communication device to adjust transmission power in response to power control commands based on known device operating parameters and/or environmental conditions. Open loop power control enables compliance with relative power requirements. However, since open loop power control does not include any means for verifying the accuracy of the transmit power, open loop power control may produce transmit powers that deviate from the desired transmit power, thereby violating the absolute power requirement.

Another approach may employ a combination of closed loop and open loop power control. The wireless communication device performs closed loop power control when the measured transmission power reaches or exceeds a predetermined threshold. Otherwise, the wireless communication device performs open loop power control.

It should be appreciated that such a combined approach generally addresses the above-described problems associated with fully closed loop power control systems and fully open loop power control systems. However, since the open loop transmission power is relatively uncertain before switching to closed loop, the power step (step) generated when switching from open loop to closed loop power control will also be relatively uncertain, which may result in discontinuities during the transition. Furthermore, since the gain control signal during closed-loop power control may be significantly different from the gain control signal generated after switching from closed-loop to open-loop power control, a discontinuity may also be created when switching from closed-loop to open-loop power control. These discontinuities may cause the power step between adjacent time slots to exceed the relative transmission power requirements during the transition between open-loop and closed-loop power control. Therefore, the transition between open loop and closed loop power control must be carefully controlled to ensure compliance with the relative transmission power requirements.

Disclosure of Invention

The present invention includes a method and apparatus for continuously controlling the gain of an amplifier circuit when switching between open loop power control and closed loop power control. According to one exemplary embodiment, an amplification system comprises: amplifier circuit, detection circuitry and power control circuit. During the open-loop and closed-loop power control modes, the power control circuit controls the gain of a variable gain amplifier in the amplifier circuit based on an open-loop power control reference and a closed-loop power control reference, respectively. The detection circuit measures the output power of the amplifier circuit. The power control circuit determines a closed loop power control reference based on an output power measured prior to switching from open loop power control to closed loop power control. After switching from open-loop to closed-loop power control, the power control circuit controls the gain of the variable gain amplifier based on the determined closed-loop power control reference.

According to another exemplary embodiment, the power control circuit controls the gain of the variable gain amplifier based on the open-loop gain control signal when switching from closed-loop to open-loop power control. For this embodiment, the power control circuit generates a difference between the current open-loop power control reference and the previous open-loop power control reference. After switching from closed-loop to open-loop power control, the power control circuit applies the difference to the previous closed-loop gain control signal to generate a new open-loop gain control signal.

Drawings

Fig. 1 is a block diagram illustrating an exemplary amplification system according to the present invention.

Fig. 2 is a block diagram representing an exemplary amplifier circuit for the amplification system of fig. 1.

Fig. 3 is a block diagram representing an exemplary detection circuit for the amplification system of fig. 1.

Fig. 4A and 4B are block diagrams representing two exemplary closed-loop controllers for the amplification system of fig. 1.

Fig. 5 is a block diagram illustrating an exemplary gain controller for the amplification system of fig. 1.

Fig. 6 illustrates a method of controlling an amplifier circuit according to an exemplary embodiment of the invention.

Fig. 7 illustrates a method of determining a closed loop power control reference according to an exemplary embodiment of the present invention.

Fig. 8 is a block diagram representing an exemplary interpolation circuit for the amplification system of fig. 1.

Fig. 9 illustrates a method of controlling an amplifier circuit according to an exemplary embodiment of the invention.

Fig. 10 is a block diagram representing an exemplary open loop controller for the amplification system of fig. 1.

Fig. 11A and 11B show a comparison between closed loop power control performance and open loop power control performance.

Fig. 12A and 12B show a comparison between closed loop power control performance and the performance of a discontinuous open loop/closed loop power control system.

Fig. 13A and 13B show a comparison between closed loop power control performance and performance of a continuous open loop/closed loop continuous power control system according to the present invention.

Detailed Description

Fig. 1 is a block diagram illustrating an amplification system 100 according to an exemplary embodiment of the present invention. In the following, the invention is described by an amplification system 100 in a wireless transmitter of a wireless communication device (e.g., a cellular telephone, a satellite telephone, a Personal Communication Services (PCS) device, a Personal Data Assistant (PDA), a palm top computer, a pager, etc.). However, it should be understood that the present invention is applicable to any amplification system 100 in any electronic device requiring a controlled output power level. Furthermore, although the present invention is described below by a wireless communication device in a WCDMA system, it will be understood by those skilled in the art that the present invention is also applicable to other wireless communication systems such as a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiplexing (OFDM) system, and the like.

The amplification system 100 controls the power level of an output signal, such as a WCDMA transmission signal. The power control commands may include differential power control commands or absolute power control commands. In differential power control, a wireless communication device steps up and down power in fixed steps in response to up and down commands. In one exemplary embodiment, a base station in communication with a wireless communication device transmits power control commands to the wireless communication device. Alternatively, a processor in the wireless communication device may generate the power control commands. Since the generation and/or reception of power control commands is well known, it is not discussed here.

According to an exemplary embodiment, the amplification system 100 comprises: amplifier circuit 110, detection circuit 120, and digital power control circuit 130. The amplifier circuit 110 is responsive to a gain control signal a provided by a power control circuit 130_GAnd amplifies the input signal to obtain an amplified signal A of a desired power level_O. The detection circuit 120 extracts the amplified signal a_OMeasuring the power of the extracted portion and comparing the measured power P_MTo the power control circuit 130. In addition, the detection circuit 120 provides an output signal for the amplifier system 100. Power control circuit 130 responds to power control commands and/or measured power P from detection circuit 120_MGenerating a gain control signal A_G。

As shown in fig. 2, the amplifier circuit 110 includes at least one Variable Gain Amplifier (VGA) for amplifying an input signal to obtain an output signal at a desired power level. In general, the gain of variable gain amplifier 112 is responsive to a gain control signal A provided by power control circuit 130_GBut may vary. In addition, the amplifier circuit 110 may also include one or more additional amplifiers 114 to help the variable gain amplifier 112 amplify the input signal to an output signal at a desired output power level.

The detection circuit 120 shown in fig. 3 measures the power level of the output signal and measures the measured value P in digitized form_MTo the power control circuit 130. In an exemplary embodiment, the detection circuit 120 includes: a splitter 122, a power detector 124, and an analog-to-digital converter (ADC) 126. The splitter 122 derives the amplified signal a from the amplified signal a_OExtracts a fraction of the signal and provides the extracted fraction to the power detector 124. The power detector 124 measures the power of the extracted portion, and the ADC 126 converts the analog measurement to a digital power measurement P_M. The power detector 124 may comprise any known power detection circuit. Since power detectors are well known, they will not be discussed here.

Power control circuit 130Responsive to power control commands and/or power P measured during open-loop and closed-loop power control_MGenerating a gain control signal A for the amplifier circuit 110_G. In addition, according to the present invention, power control circuit 130 adjusts gain control signal A in such a way that the transition between open-loop and closed-loop power control does not produce a relative power offset_G。

One exemplary power control circuit 130 includes a closed-loop controller 132, an open-loop controller 140, a gain controller 150, and a processor 160, as shown in fig. 1. Processor 160 generates a selection signal for controlling gain control 150, as discussed further below. In addition, processor 160 is responsive to power control commands P_CAnd/or measured power P_MAnd open and closed loop power control references are generated. During closed-loop power control, closed-loop controller 132 controls reference T based on closed-loop power_CAnd the measured power P_MGenerating a closed-loop gain adjustment value G_C. During open-loop power control, open-loop controller 140 controls reference T based on open-loop power_OGenerating an open-loop gain adjustment value G_OThe open loop power control reference T_OIs based on power control commands P_CAnd (4) selecting. The gain controller 150 generates the gain control signal a based on a value selected from the closed-loop gain adjustment value and the open-loop gain adjustment value_G。

Processor 160 includes a lookup table 162 and an interpolation circuit 164. Although fig. 1 shows lookup table 162 and interpolation circuit 164 as being part of processor 160, those skilled in the art will appreciate that one or both of lookup table 162 and interpolation circuit 164 may be implemented independently of processor 160.

The look-up table 162 stores a plurality of open-loop and closed-loop power control references in an ordered list corresponding to a plurality of power control levels. According to one embodiment, the stored open-loop power control reference may comprise a reference VGA control signal and the stored closed-loop power control reference may comprise a target power level. In response to power control commands P_CProcessor 160 executes look-up table 162 to select the closed loop power control reference and the open loop power control reference. Power control command P_CMay be generated according to any known method. For example, power control command P may be calculated by the wireless communication device based on measured pilot signal strength_C。

Interpolation circuit 164 may modify closed loop power control reference T_CTo provide a higher resolution than can be obtained by the look-up table 162 alone. As a result, a reference T is set for closed loop power control at the time of transition from open loop power control to closed loop power control_CThe modification may be made to avoid large steps that may result in the undesirable discontinuities described above. The operation of interpolation circuit 164 is discussed further below.

FIG. 4A illustrates an exemplary embodiment of closed-loop controller 132 based on a measured output power P_MAnd a closed loop power control reference T_CThe difference between to produce a closed loop gain adjustment value. Closed-loop controller 132 includes a combiner 134 and a VGA converter 136. During normal operation, the combiner 134 determines the measured power P_MAnd a closed loop power control reference T_CIn which the closed loop power controls the reference T_CIncluding a digitized target power level selected from the look-up table 162 based on the power control command. Converter 136 maps the power difference to a digitized VGA value to produce a closed loop gain adjustment value G_C。

Although the embodiment shown in fig. 4A shows VGA converter 136 after combiner 134, VGA converter 136 may alternatively precede combiner 134, as shown in fig. 4B. In this embodiment, VGA converter 136 digitizes measured power P_MMapped to digitized VGA values. The combiner 134 determines P_MDigital VGA value and closed loop power control reference T_CDifference between them to produce a closed loop gain adjustment value G_C. In this embodiment, the closed loop power control reference T during normal closed loop operation_CIncluding selection from look-up table 162 based on power control commandsThe target VGA values are digitized.

Closed-loop controller 132 adjusts the closed-loop gain by a value G_CWhich represents the digitized VGA adjustment value, is provided to gain controller 150. It should be appreciated that the closed loop power control reference T, although selected from the look-up table 162_COnly in response to step-up or step-down power control commands, but only for the measured power P_MRelative to the selected closed loop power control reference T_CChanged, closed loop gain adjustment value G_CIt changes.

Open-loop controller 140 controls reference T based on the selected open-loop power_OGenerating an open-loop gain adjustment value G_OAnd G is_OIs provided to the gain controller 150. In general, processor 160 selects an open-loop power control reference T from look-up table 162 based on power control commands_O. Thus, with the closed loop power control reference T_CSimilarly, the open loop power control reference T_OIn response to a step up or step down power control command. However, the closed loop gain adjustment value G may be varied independently of the power control command_CDifferent, open loop gain adjustment value G₀Only in response to changes in power control commands and therefore only in response to the open loop power control reference T_OMay vary.

As described above, the power control circuit 130 adjusts the gain of the variable gain amplifier 112 to meet the transmission power requirements. To this end, the gain controller 150 selects one of a closed-loop gain adjustment value and an open-loop gain adjustment value, and adjusts the gain control signal a based on the selected gain adjustment value_G. According to an exemplary embodiment, the gain controller 150 includes a switch 152, a combiner 154, and a register 156, as shown in fig. 5. Switch 152 (which may comprise any well-known switch, including a hardware switch, a software switch, or any combination thereof) selects the closed-loop gain adjustment value G in response to the selection signal S_CAnd open loop gain adjustment value G_OOne of them.

Processor 160 may respondResponsive to the measured power P provided by the detection circuit 120_MA selection signal S is generated. When P is present_MWhen the predetermined threshold is reached or exceeded, processor 160 generates a selection signal S to instruct gain controller 150 to select the closed-loop gain adjustment value G_C. When P is present_MLess than the threshold, processor 160 generates a selection signal S to instruct gain controller 150 to select an open-loop gain adjustment value G_O。

Alternatively, the processor 160 may generate the selection signal S in response to the current position of the selected reference in the look-up table 162. When the reference is selected from the closed-loop portion of the look-up table 162, the processor 160 generates a selection signal S to instruct the gain controller 150 to select the closed-loop gain adjustment value G_C. Alternatively, when the reference is selected from the open-loop portion of the look-up table 162, the processor 160 generates a selection signal S to instruct the gain controller 150 to select the open-loop gain adjustment value G_O。

In an exemplary embodiment, processor 160 may employ a combination of these techniques to select between open-loop and closed-loop gain adjustment values. According to this embodiment, when the measured power P is_MWhen the predetermined threshold is reached or exceeded, processor 160 generates a selection signal S to instruct gain controller 150 to select the closed-loop gain adjustment value G_C. However, when the reference is selected from the open-loop portion of the look-up table 162, the processor 160 generates a selection signal S to instruct the gain controller 150 to select the open-loop gain adjustment value G_O。

After selecting one of the open-loop or closed-loop gain adjustment values, gain controller 150 adjusts the previous gain control signal A stored in register 156 by adjusting the previous gain control signal A based on the selected gain adjustment value_GTo generate a new gain control signal A_G. According to an exemplary embodiment, the combiner 154 combines the selected gain adjustment value with the previous gain control signal stored in the register 156 to generate a new gain control signal. Register 156 then stores the new gain control signal for future useThe preparation is used.

The gain controller 150 may control the digital gain control signal A_GDirectly to the amplifier circuit 110 to control the gain of the variable gain amplifier 112. Alternatively, if the variable gain amplifier 112 requires an analog control signal, the gain controller 150 may further include a digital-to-analog converter (DAC)158 to simulate the gain control signal A_GThe digital gain control signal A is provided to the amplifier circuit 110_GConversion to an analog gain control signal A_G。

Closed loop power control provides accurate power control when the power of the output of the amplifier circuit 110 is within the dynamic range of the power detector 124. When the output power level is outside this range, open loop power control is more appropriate. However, as described above, when switching between open loop power control and closed loop power control, discontinuities may occur. As a result, the output power may violate the relative power requirements of the wireless communication device during the transition between open-loop and closed-loop power control.

Fig. 6 illustrates an exemplary process 200 for preventing large step changes in output signal power caused by a transition from open-loop to closed-loop power control. In general, the power control circuit 130 determines the closed loop power control reference T in the following manner_C: during open loop power control, a reference T is found in the LUT for closed loop power control based on the power measured at the output of the amplifier circuit 110 (block 210)_C(p) (block 220). After switching from open-loop to closed-loop power control, power control circuit 130 controls reference T based on the determined closed-loop power_CTo adjust the gain control signal A_G(block 230). In this way, the present invention prevents large step changes in the transmission power during the transition from open-loop to closed-loop power control. Adjustment of the closed loop power control reference is performed by interpolation circuit 164.

The interpolation circuit 164 passes the reference signal based on the measured power P_MCalculation IF circuit167 to determine a closed loop power control reference T_C. Interpolation circuit 164 then applies the interpolation factor to the selected closed loop power control reference. Fig. 7 illustrates an exemplary process 220 for using this method. According to this method 220, the interpolation circuit 164 selects in the look-up table 162 such that the output power P measured during open loop power control is such that_MTwo closed loop power control references located between them (block 222). The two selected closed loop power control references may be denoted as T_C(p) and T_C(p +1), where p represents a position in the look-up table 162 and T_C(p +1) represents a larger closed loop power control reference. IF p is equal to the predetermined maximum value (block 224), processor 160 sets an Interpolation Factor (IF) to zero (block 226) to prevent the closed loop power control reference from exceeding the maximum value T_C(p ═ max). Even during non-conversion operations. IF, however, p is less than the maximum value, then IF circuit 167 calculates T as the two selected closed loop power control references_C(p) and T_C(P +1) and the measured output power P_MThe interpolation factor of the function of (block 228). In one exemplary embodiment, IF circuit 167 may calculate the interpolation factor according to:

after the interpolation factor is calculated, the interpolation circuit 164 determines the closed loop power control reference T_C(block 229) the closed loop power control reference T_CIs the interpolation factor, IF and selected closed loop power control reference T_C(p) and T_CFunction of (p + 1). For the embodiment of FIG. 4A, T_CThen becomes equal to the measured power P_M. To this end, the interpolation circuit 164 may include combiners 166 and 170 and a multiplier 168, as shown in FIG. 8. The multiplier 168 applies the calculated interpolation factor to the two selected closed-loop power control references T calculated by the combiner 166_C(p) and T_CThe difference between (p + 1). The combiner 170 then combines the output of the multiplier 168 with T_C(p) combining to determine a closed loop power control reference T_C。

It should be understood that the interpolation circuit 164 is not limited to the above-described embodiment. For example, interpolation circuit 164 may be coupled to T_C(p +1) applying the calculated interpolation factor directly to the closed loop power control reference T_C. Alternatively, IF circuit 167 may calculate a reference T for a larger closed loop power control_CA negative interpolation factor of (p +1), and determined as T_C(p +1) and a closed loop power control reference T as a function of the interpolation factor_C。

After completing the transition from open-loop to closed-loop power control, closed-loop controller 132 continues to calculate the measured power P_MAnd an adjusted closed loop power control reference T_CDifference between them to produce a closed loop gain adjustment value G_C. During this particular closed loop mode, interpolation circuit 164 uses the same interpolation factor as calculated during the transition, according to an exemplary embodiment of the present invention. Thus, whenever processor 160 selects a new closed loop power control reference in response to a power control command, the interpolation circuit applies the same interpolation factorBased on the selected closed loop power control reference. However, it should be understood that a new interpolation factor may be calculated during closed loop power control in response to a new power control command.

The above discussion is directed to a discontinuous solution that occurs when transitioning from open-loop to closed-loop power control. However, as noted above, discontinuities may also occur when transitioning from closed-loop to open-loop power control. To address this issue, the present invention also adjusts the closed-loop gain control signal generated prior to the transition from closed-loop to open-loop power control based on the open-loop gain adjustment value generated after the transition, as shown in the exemplary process 300 in FIG. 9. During closed loop operation, processor 160 loads an open loop power control reference selected based on the current power control command into delay 142 of open loop controller 140. Just prior to transitioning from closed-loop to open-loop power control, open-loop controller 140 generates an open-loop gain adjustment value G based on the difference between the current open-loop power control reference selected according to the new power control command and the previous open-loop power control reference in delay 142_O(block 310). During the transition, gain controller 150 adjusts the value G by adjusting the open-loop gain_OA new open-loop gain control signal is generated (block 320) applied to the closed-loop gain control signal generated prior to switching from closed-loop to open-loop power control. After switching from closed-loop to open-loop power control, gain controller 150 is then based on a new open-loop gain control signal A_GTo control the gain of the variable gain amplifier 112 (block 330).

The open-loop controller 140 for performing the method of fig. 9 may include a delayer 142 and a combiner 144, as shown in fig. 10. When switching from closed-loop to open-loop power control, the combiner 144 subtracts the previous open-loop power control reference stored in the delay 142 from the new open-loop power control reference selected in the look-up table 162 based on the step-down power control command. Further, after calculating the difference, the open-loop controller 140 stores the new open-loop power control reference in the delayer 142.

In the exemplary embodiment depicted, the open loop power control reference comprises a digitized VGA value. Thus, the difference provided by combiner 144 represents the digitized VGA open loop gain adjustment value G_O. According to an alternative embodiment, the open loop power control reference may represent a reference power level. According to this alternative embodiment, combiner 144 generates a power difference between the previous power level stored in delay 142 and the new open loop power control reference power level selected from look-up table 162. For such an embodiment, FIG. 10 would also include a VGA converter (not shown) for mapping the power difference from combiner 144 to a digitized VGA value to produce a digitized VGA open-loop gain adjustment value G_O。

After switching from closed-loop to open-loop power control, a combiner 154 in gain controller 150 combines the open-loop gain adjustment value with the previous closed-loop gain control signal stored in a register 156 to generate a new digitized open-loop gain control signal. If variable gain amplifier 112 is controlled by an analog gain control signal, optional digital-to-analog converter 158 converts the digitized open-loop gain control signal to an analog gain control signal and provides the analog gain control signal to amplifier circuit 110.

After completing the transition from closed-loop to open-loop power control, open-loop controller 140 continues to generate open-loop gain adjustment values due to the difference between the previous open-loop power control reference stored in delay 142 and the new open-loop power control reference selected from look-up table 162 based on the power control command. However, once the conversion is complete, gain controller 150 adjusts value G based on the open-loop gain_OTo adjust the open loop gain control signal stored in register 156.

Fig. 11A and 11B compare the performance of full closed-loop power control with the performance of full open-loop power control. The inability of the open loop power control to track the absolute power prevents the open loop power control from reaching the absolute power requirement, as shown by the dashed line in fig. 11A. However, open loop power control tends to meet relative power requirements, as shown by the dashed lines in fig. 11B.

Fig. 12A and 12B compare conventional discontinuous open loop/closed loop power control with full closed loop power control. Fig. 12A shows that conventional open/closed loop power control achieves the absolute power requirement by switching from open loop to closed loop when the output power level reaches or exceeds a predetermined threshold. However, as shown by the dashed line in fig. 12B, after switching from open-loop to closed-loop around time slot 24, the closed-loop power control automatically locks to the look-up table power without taking into account the measured output power before the switch. Since the value of the look-up table for controlling the gain of the variable gain amplifier 112 is based on the power control command P_CThe value of the look-up table may be significantly different from the output power measured before the switch. As a result, the power difference before and after switching may violate the accuracy of the relative power step, as shown in fig. 12B.

The present invention meets the requirement of relative power accuracy as shown in fig. 13A and 13B. Fig. 13A and 13B show that relative accuracy is maintained when switching from open to closed loop by employing a reference selected from a look-up table prior to switching from open to closed loop (see dashed line in fig. 13B). This accuracy cannot be maintained only if the selected closed loop power control reference corresponds to the maximum look-up table value. However, as noted above, most specifications do not maintain relative accuracy requirements when stepping to a minimum or maximum power level. Thus, this situation does not violate these requirements.

The invention described above comprises a number of advantages over the prior art. First, the present invention applies closed loop power control at higher power and open loop power control at lower power without experiencing the transition discontinuities experienced by the prior art. Second, implementations of the present invention allow for the use of power detectors with limited dynamic range and still meet relative power accuracy requirements when a specified output power range is exceeded. Furthermore, the present invention is very flexible to implement, since it can be implemented by hardware, software, or a combination of hardware and software. Furthermore, it should be appreciated that the present invention may be implemented by software in a fast processing unit, which provides a flexible interface and implementation.

In addition, since the power control circuit 130 is implemented in the digital domain, the hardware used to implement the power control circuit 130 is not dependent on a custom analog ASIC (application specific integrated circuit), thus freeing up the choice of a variety of off-the-shelf ASICs. Furthermore, due to the development of digital hardware technology, hardware may benefit in terms of cost and power consumption improvements. Furthermore, digital implementations may provide lower current consumption than analog implementations and enable flexibility in combining open and closed loop power steps with other control signals synchronized with power control.

The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Claims (12)

1. A method of continuously controlling the gain of an amplifier circuit, the method comprising:

determining a reference difference between a current open-loop power control reference and a previous open-loop power control reference during closed-loop power control;

determining an open-loop gain adjustment value based on the reference difference value;

adjusting, during a transition from closed-loop to open-loop power control, a closed-loop gain control signal generated prior to switching from closed-loop to open-loop power control based on the open-loop gain adjustment value to generate an open-loop gain control signal; and

controlling a gain of the amplifier circuit using the generated open-loop gain control signal.

2. The method of claim 1, wherein adjusting the closed-loop gain control signal comprises: adding the open-loop gain adjustment value to a closed-loop gain control signal to generate the open-loop gain control signal.

3. The method of claim 1, further comprising: the current open-loop power control reference is selected from a look-up table constructed to have an open-loop power control portion and a closed-loop power control portion based on the current power control command, and the plurality of open-loop power control references and the plurality of closed-loop power control references are stored in an ordered list corresponding to the plurality of power control commands.

4. The method of claim 3, further comprising: storing the previous open loop power control reference in a delay memory, wherein the previous open loop power control reference is selected from a look-up table according to a previous power control command.

5. The method of claim 1, further comprising:

measuring an output power of the amplifier circuit during open loop power control;

adjusting a closed loop power control reference based on the measured output power to produce an adjusted closed loop power control reference; and

controlling a gain of the amplifier circuit based on the adjusted closed-loop power control reference after switching from open-loop to closed-loop power control.

6. An amplification system, comprising:

an amplifier circuit comprising at least one variable gain amplifier;

a power control circuit configured to determine an open-loop gain adjustment value based on a difference between a current open-loop power control reference and a previous open-loop power control reference during closed-loop power control, and the power control circuit is further configured to adjust a closed-loop gain control signal generated prior to switching from closed-loop power control to open-loop power control based on the open-loop gain adjustment value during a transition from closed-loop power control to open-loop power control to generate an open-loop gain control signal,

wherein the power control circuit comprises a gain controller configured to control a gain of the at least one variable gain amplifier using the generated open loop gain control signal.

7. The amplification system of claim 6 wherein the power control circuit comprises a combiner configured to adjust the closed-loop gain control signal by adding the open-loop gain adjustment value to the closed-loop gain control signal to generate the open-loop gain control signal.

8. The amplification system of claim 6 wherein the power control circuit comprises a look-up table structured to have an open-loop power control portion and a closed-loop power control portion and to store a plurality of open-loop power control references and a plurality of closed-loop power control references in an ordered list corresponding to a plurality of power control commands.

9. The amplification system of claim 8 wherein the power control circuit is further configured to select a current open loop power control reference and a previous open loop power control reference based on the current power control command and the previous power control command, respectively.

10. The amplification system of claim 6, further comprising a detection circuit configured to measure an output power of the amplifier circuit.

11. The amplification system of claim 10 wherein the power control circuit is further configured to adjust the closed loop power control reference based on the output power measured by the detection circuit when switching from open loop power control to closed loop power control.

12. The amplification system of claim 6 wherein the amplification system is provided in a wireless transmitter used in a wireless communication system.