HK1180465B - Transmitter front end with programmable notch filter and methods for use therewith - Google Patents

Abstract

The present invention is directed to a transmitter front end with programmable notch filter and methods for use therewith. A radio transmitter front end for use in a radio frequency (RF) transceiver includes at least one amplifier stage operable to generate a transmit signal in response to an upconverted signal. A feedback generator is operable to generate a transmit feedback signal in response to the transmit signal. A control signal generator is operable to generate at least one filter control signal in response to the transmit feedback signal. A notch filter is operable to filter out of band noise while passing in-band frequencies to the at least one amplifier stage, under control of the at least one filter control signal.

Description

Transmitter front end with programmable notch filter and method of use

Cross reference to related patent

This application claims priority to united states provisional application No. 61/552,835 filed on 28/10/2011 and united states application No. 13/329,300 filed on 18/12/2011, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates generally to wireless communications, and more particularly to antennas for supporting wireless communications.

Background

Known communication systems support wireless and wired communication between wireless and/or wired communication devices. The communication system covers a range from national and/or international cellular telephone systems to the internet and to point-to-point home wireless networks to Radio Frequency Identification (RFID) systems. Each type of communication system is constructed and operates in accordance with one or more communication standards. For example, a wireless communication system may operate in accordance with one or more standards including, but not limited to, RFID, IEEE 802.11, Bluetooth, Advanced Mobile Phone Service (AMPS), digital AMPS, Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), Local Multipoint Distribution System (LMDS), Multi-channel multipoint distribution System (MMDS), and/or variations thereof.

Depending on the type of wireless communication system, wireless communication devices, such as cellular phones, two-way radios, Personal Digital Assistants (PDAs), Personal Computers (PCs), notebook computers, home entertainment equipment, RFID readers, RFID tags, etc., communicate directly or indirectly with other wireless communication devices. For direct communication (also referred to as point-to-point communication), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of a plurality of Radio Frequency (RF) carriers of the wireless communication system) and communicate via the channel. For indirect wireless communication, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for in-home or in-building wireless networks) via an assigned channel. To enable a communication connection between wireless communication devices, the associated base stations and/or associated access points communicate directly with each other via the system controller, via the public switched telephone network, via the internet, and/or via some other wide area network.

For each wireless communication device participating in wireless communication, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for a home and/or in-building wireless communication network, an RF modem, etc.). As is well known, the receiver is coupled to an antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives the inbound RF signal via the antenna and then amplifies it. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signals to baseband signals or Intermediate Frequency (IF) signals. The filtering stage filters the baseband signal or the IF signal to attenuate undesired out-of-band signals to produce a filtered signal. The data recovery stage recovers the original data from the filtered signal in accordance with a particular wireless communication standard.

It is also known for a transmitter to include a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts the raw data to a baseband signal according to a particular wireless communication standard. One or more intermediate frequency stages mix the baseband signal with one or more local oscillations to generate an RF signal. The power amplifier amplifies the RF signal before transmission via the antenna.

Currently, wireless communication occurs within licensed or unlicensed spectrum. For example, Wireless Local Area Network (WLAN) communications occur within the unlicensed industrial, scientific, and medical (ISM) spectrum at 900MHz, 2.4GHz, and 5 GHz. Although the ISM spectrum is not licensed, it has limitations on power, modulation techniques, and antenna gain. Another unlicensed spectrum is the V-band at 55-64 GHz.

Other drawbacks of conventional approaches will be apparent to those skilled in the art when given the ensuing disclosure.

Disclosure of Invention

The present invention is directed to apparatus and methods of operation further described in the following brief description of the drawings, detailed description of the invention, and the appended claims. Other features and advantages of the present invention will become apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings.

According to an aspect of the present invention, there is provided a radio transmitter front-end for use in a Radio Frequency (RF) transceiver, the radio transmitter front-end comprising: at least one amplifier stage operable to generate a transmit signal in response to the upconverted signal; a feedback generator coupled to the at least one amplifier stage operable to generate a transmit feedback signal in response to the transmit signal; a control signal generator, coupled to the feedback generator, operable to generate at least one filter control signal in response to the transmit feedback signal; a notch filter, coupled to the control signal generator and the at least one amplifier stage, operable to filter out-of-band noise while passing in-band frequencies to the at least one amplifier stage under control of the at least one filter control signal.

Preferably, the feedback generator comprises a transmitted signal strength indicator.

Preferably, the feedback generator comprises at least a part of a receive path comprised in a receiver of the RF transceiver.

Preferably, the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and wherein the notch filter is coupled between the power amplifier driver and the power amplifier.

Preferably, the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and wherein a notch filter is coupled to filter an input signal of the power amplifier driver.

Preferably, the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and the radio transmitter front end comprises a switch matrix coupled to the power amplifier driver and the power amplifier, the switch matrix being operable to selectively couple the notch filter between the power amplifier driver and the power amplifier in response to a configuration control signal generated by the control signal generator to filter the input signal of the power amplifier in the first mode of operation and to couple the notch filter to filter the input signal of the power amplifier driver in the second mode of operation.

Preferably, the at least one amplifier stage comprises a cascode amplifier having a plurality of cascode (cascode) transistors and a plurality of transconductance transistors, and wherein the notch filter is coupled between the plurality of cascode transistors and the plurality of transconductance transistors.

Preferably, the notch filter comprises an inductor and a first capacitor forming a series tank with the inductor, and a second capacitor in parallel with the series tank, wherein the capacitance of at least one of the first capacitor and the second capacitor is controlled via the at least one filter control signal. The notch filter includes an active quality (Q) boost circuit having at least one transistor coupled to the Q boost circuit to boost the quality of the series tank.

Preferably, the RF transceiver operates according to the 802.11ac standard.

According to another aspect of the present invention, there is provided a method in a Radio Frequency (RF) transceiver, the method comprising: generating a transmit signal via at least one amplifier stage in response to the upconverted signal; generating a transmission feedback signal in response to the transmission signal; generating at least one filter control signal in response to the transmit feedback signal; and controlling the programmable notch filter to filter out-of-band noise while passing in-band frequencies to the at least one amplifier stage based on at least one filter control signal.

Preferably, the transmission feedback signal is indicative of a transmission signal strength of said in-band frequency.

Preferably, generating the transmit feedback signal uses at least a portion of a receive path of a receiver included in the RF transceiver.

Preferably, the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and the method further comprises: a notch filter is coupled between the power amplifier driver and the power amplifier.

Preferably, the at least one amplifier stage comprises a power amplifier driver and a power amplifier, the method further comprising: a notch filter is coupled to filter an input signal of the power amplifier driver.

Preferably, the at least one amplifier stage comprises a power amplifier driver, a power amplifier and a switch matrix, the method further comprising: controlling a switch matrix to selectively couple a notch filter between a power amplifier driver and a power amplifier to filter an input signal of the power amplifier in a first mode of operation; and selectively coupling the notch filter to filter the input signal of the power amplifier driver in the second mode of operation.

Preferably, the at least one amplifier stage comprises a cascode amplifier having a plurality of cascode transistors and a plurality of transconductance transistors, the method further comprising: a notch filter is coupled between the plurality of cascode transistors and the plurality of transconductance transistors.

Preferably, the notch filter comprises an inductor and a first capacitor forming a series tank with the inductor and a second capacitor in parallel with the series tank, and the controlling the programmable notch filter is operable by controlling a capacitance of at least one of the first capacitor and the second capacitor via at least one filter control signal. The method further includes boosting the quality of the series tank via an active quality (Q) boosting circuit having at least one transistor.

Preferably, the RF transceiver operates according to the 802.11ac standard.

Drawings

Fig. 1 is a schematic block diagram of an embodiment of a wireless communication system according to the present invention;

FIG. 2 is a schematic block diagram of another embodiment of a wireless communication system in accordance with the present invention;

FIG. 3 is a schematic block diagram of an embodiment of a wireless transceiver 125 in accordance with the present invention;

FIG. 4 is a schematic block diagram of one embodiment of a radio transmitter front end in accordance with the present invention;

FIG. 5 is a schematic block diagram of one embodiment of a notch filter in accordance with the present invention;

FIG. 6 is a schematic block diagram of one embodiment of a notch filter in accordance with the present invention;

FIG. 7 is a schematic block diagram of one embodiment of a radio transmitter front end in accordance with the present invention;

fig. 8 is a schematic block diagram of an embodiment of a radio transmitter front end according to the present invention;

fig. 9 is a schematic block diagram of an embodiment of a notch filter according to the present invention.

Fig. 10 is a flow chart of an embodiment of a method according to the present invention.

FIG. 11 is a schematic block diagram of an embodiment of a notch filter according to the present invention.

Detailed Description

Fig. 1 is a schematic block diagram of an embodiment of a communication system according to the present invention. In particular, a communication system is shown that includes a communication device 10 wirelessly communicating non-real time data 24 and/or real time data 26 with one or more other devices, such as a base station 18, a non-real time device 20, a real time device 22, and a non-real time and/or real time device 25. Further, communication device 10 may also optionally communicate with network 15, non-real time devices 12, real time devices 14, non-real time and/or real time devices 16 via a wired connection.

In embodiments of the present invention, the wired connection 28 may be a wired connection that operates according to one or more standard protocols, such as Universal Serial Bus (USB), Institute of Electrical and Electronics Engineers (IEEE) 488, IEEE 1394 (firewire), ethernet, Small Computer System Interface (SCSI), serial or parallel advanced technology attachment (SATA or PATA), or other standard or proprietary wired communication protocols. The wireless connection may communicate in accordance with a wireless network protocol (such as WiHD, NGMS, IEEE 802.11a, ac, b, g, n, or other 802.11 standard protocols, bluetooth, Ultra Wideband (UWB), WIMAX, or other wireless network protocols), a radiotelephone data/voice protocol (such as global system for mobile communications (GSM), General Packet Radio Service (GPRS), enhanced data rates for global evolution (EDGE), Personal Communication Services (PCS), or other mobile wireless protocols), or other standard or proprietary wireless communication protocols. Further, the wireless communication path may include separate transmit and receive paths using separate carrier frequencies and/or separate frequency channels. Alternatively, a single frequency or frequency channel may be used to bi-directionally transfer data to and from the communication device 10.

The communication device 10 may be a mobile telephone such as a cellular telephone, a local area network device, a personal area network device or other wireless network device, a personal digital assistant, a game console, a personal computer, a notebook computer, or other device that performs one or more functions including communication of voice and/or data via a wired connection 28 and/or a wireless communication pathway. Further, the communication device 10 may be an access point, base station, or other network access device coupled to a public or private network 15, such as the internet or other wide area network, via a wired connection 28. In embodiments of the present invention, the real-time and non-real-time devices 12, 14, 16, 18, 20, 22, and 25 may be personal computers, notebooks, PDAs, mobile phones such as cellular phones, devices equipped with wireless local area networks or bluetooth transceivers, FM tuners, TV tuners, digital cameras, digital video cameras, or other devices that produce, process, or use audio, video signals, or other data or communications.

In operation, the communication device includes one or more applications including voice communications such as standard telephone applications, voice over internet protocol (VoIP) applications, local games, internet games, e-mail, instant messaging, multimedia messaging, web browsers, audio/video recording, audio/video playback, audio/video downloading, streaming audio/video playback, office applications such as databases, spreadsheets, word processing, image creation and processing, and other voice and data applications. In conjunction with these applications, real-time data 26 includes voice, audio, video, and multimedia applications including internet gaming and the like. Non-real-time data 24 includes text messages, e-mail, web browsing, file uploads and downloads, and the like.

In embodiments of the present invention, the communication device 10 includes a wireless transceiver that includes one or more features or functions of the present invention. Such a wireless transceiver will be described in more detail in connection with subsequent fig. 3-11.

Fig. 2 is a schematic block diagram of an embodiment of another communication system according to the present invention. In particular, fig. 2 shows a communication system comprising a plurality of identical elements of fig. 1, which are denoted by identical reference numerals. The communication device 30 is similar to the communication device 10 and is provided with any of the applications, functions and features attributed to the communication device 10 as discussed in connection with fig. 1. However, the communication device 30 includes more than two separate wireless transceivers for communicating with the data device 32 and/or the data base station 34 via the RF data 40 and the voice base station 36 and/or the voice device 38 via the RF voice signals 42 simultaneously over two or more wireless communication protocols.

Fig. 3 is a schematic block diagram of one embodiment of a wireless transceiver 125 in accordance with the present invention. RF transceiver 125 represents a wireless transceiver used in conjunction with communication devices 10 or 30, base station 18, non-real time devices 20, real time devices 22 and non-real time and/or real time devices 25, data devices 32 and/or data base stations 34, and voice base stations 36 and/or voice devices 38. The RF transceiver 125 includes an RF transmitter 129 and an RF receiver 127. The RF receiver 127 includes an RF front end 140, a down conversion module 142, and a receiver processing module 144. The RF transmitter 129 includes a transmitter processing module 146, an up-conversion module 148, and a radio transmitter front end 150.

As shown, the receiver and transmitter are coupled to an antenna through an antenna interface 171 and a duplexer (diplexer) 177 that couples the transmit signal 155 to the antenna to generate the outbound RF signal 170 and the inbound signal 152 to generate the receive signal 153, respectively. Alternatively, a transmit/receive switch may be used in place of the duplexer 177. Although a single antenna is shown, the receiver and transmitter may share a multi-antenna structure including more than two antennas. In another embodiment, the receiver and transmitter may share a multiple-input multiple-output (MIMO) antenna structure, a diversity antenna structure, a phased array or other controllable antenna structure including multiple antennas, and other RF transceivers similar to RF transceiver 125. Each of these antennas may be fixed, programmable, and an antenna array or other antenna configuration. In addition, the antenna structure of the wireless transceiver may depend on the particular standard to which the wireless transceiver is following and its application.

In operation, the RF transmitter 129 receives outbound data 162. The transmitter processing module 146 packetizes the outbound data 162 in accordance with a standard or proprietary millimeter-wave protocol or a wireless telephony protocol to produce a baseband or low Intermediate Frequency (IF) Transmit (TX) signal 164, the signal 164 comprising an outbound symbol stream that includes the outbound data 162. The baseband or low IF TX signal 164 may be a digital baseband signal (e.g., with zero IF) or a digital low IF signal, where the low IF will typically be in the frequency range of one hundred kilohertz to several megahertz. Note that the processing performed by transmitter processing module 146 may include, but is not limited to, scrambling, encoding, adding and deleting, mapping, modulating, and/or digital baseband to IF conversion.

The up-conversion module 148 includes a digital-to-analog conversion (DAC) module, a filtering and/or gain module, and a mixing section. The DAC module converts the baseband or low IF TX signal 164 from the digital domain to the analog domain. The filtering and/or gain module filters and/or adjusts the gain of the analog signal before providing it to the mixing section. The mixing section converts the analog baseband or low IF signal to an up-converted signal 166 based on the transmitter local oscillation.

The radio transmitter front end 150 includes a power amplifier and may also include a transmit filtering module. The power amplifier amplifies the upconverted signal 166 to generate an outbound RF signal 170, and if included, the signal 170 may be filtered by a transmit filter module. The antenna structure transmits the outbound RF signal 170 via an antenna interface 171 coupled to an antenna that provides impedance matching and optional bandpass filtering.

The RF receiver 127 receives the inbound RF signals 152 via an antenna and an antenna interface 171 that operates to process the inbound RF signals 152 into received signals 153 for the receiver front end 140. In general, the antenna interface 171 provides impedance matching of the antenna to the RF front end 140, optional bandpass filtering of the inbound RF signal 152.

The down conversion module 142 includes a mixing section, an analog-to-digital conversion (ADC) module, and may also include a filtering and/or gain module. The mixing section converts the desired RF signal 154 to a down-converted signal 156, such as an analog baseband or low IF signal, based on a receiver local oscillation 158. The ADC module converts the analog baseband or low IF signal to a digital baseband or low IF signal. The filtering and/or gain module high pass and/or low pass filters the digital baseband or low IF signal to produce a baseband or low IF signal 156 that includes the inbound symbol stream. Note that the order of the ADC module and the filtering and/or gain module may be interchanged, making the filtering and/or gain module an analog module.

The receiver processing module 144 processes the baseband or low IF signal 156 according to a standard or proprietary millimeter wave protocol to generate inbound data 160, such as probe data received from the probe device 105 or the devices 100 or 101. The processing performed by the receiver processing module 144 may include, but is not limited to, digital intermediate frequency to baseband conversion, demodulation, demapping, de-scrambling, decoding, and/or descrambling.

In embodiments of the present invention, the receiver processing module 144 and the transmitter processing module 146 may be implemented via any means using microprocessors, microcontrollers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, and/or manipulating signals (analog and/or digital) based on operational instructions. The associated memory may be a single memory device or a plurality of memory devices, on-chip or off-chip. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. Note that when the processing device implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the associated memory storing the corresponding operational instructions for that circuitry is embedded within the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry.

Although processing module 144 and transmit processing module 146 are shown separately, it should be understood that these elements may be implemented separately, together through operation of one or more shared processing devices, or in combination with separate and shared processing.

Additional details including optional functions and features of the RF transceiver are discussed in connection with subsequent fig. 4-11.

Fig. 4 is a schematic block diagram of a radio transmitter front end according to the present invention. In particular, a radio transmitter front end, such as radio transmitter front end 150, generates transmit signal 155 from upconverted signal 166. The out-of-band noise output by the RF transmitter needs to be small enough not to degrade the receiver performance of the other bands/standards.

The radio frequency transmitter front end includes at least one amplification stage such as two stages of amplification shown as a power amplifier driver 300 and a power amplifier 308. The out-of-band noise output by the RF transmitter needs to be small enough not to degrade the receiver performance of the other bands/standards. The notch and in-band frequencies are adjustable using switched capacitors.

In addition to any existing bandpass characteristics of the transmit path, additional noise filtering for a particular frequency band is obtained by using a high-Q (quality) passive notch filter 304. In particular, a notch filter 304 is included to generate a notch filtered signal 306 from the first amplified signal 302. The notch filter 304 is programmable based on a filter control signal 316 generated by a control signal generator 314, wherein the filter control signal 316 is generated based on the transmit signal feedback 312 generated by the transmit feedback generator 310. In particular, transmit feedback generator 310 generates a Transmit Signal Strength Indicator (TSSI) or other indication of signal strength, signal-to-noise ratio, or out-of-band signal attenuation. An appropriate filter control signal 316, such as a digital tuning code or other control signal, is generated to adjust the notch frequency after sweeping the frequency response and measuring the transmit signal feedback 312. The structure and component values are selected to not affect the in-band response and to filter out noise in the particular frequency band of interest. The position of the notch filter in the transmitter chain is chosen to minimize its impact on the transmitter gain.

The circuit operates to detect a frequency response near the notch frequency using the looped-back signal and generate a filter control signal 316 to control the notch frequency of notch filter 304. As shown, although transmit signal feedback 312 is generated via TSSI generator 310, a common RX path may also be used as a source of this feedback. The notch and in-band frequencies are then adjusted by switched capacitors included in notch filter 304.

Calibrating the notch/in-band frequency, increasing the digital programming capability for Q enhancement strength, and placing the notch filter properly in the TX chain allows great flexibility for multiple radios.

Fig. 5 is a schematic block diagram of an embodiment of a notch filter according to the present invention. The notch filter is shown with a single inductor 11 and two capacitors C1 and C2 that are adjustable based on the filter control signal 316 to filter out-of-band noise while passing in-band frequencies of interest to the RF transceiver. The circuit generates a low impedance Zmin at a notch frequency set to a frequency corresponding to the out-of-band TX noise and a high impedance Zpeak at a selected in-band frequency.

The circuit may be implemented in a differential configuration or a single-ended configuration with one end grounded. The resonant frequency of the series tank circuit (L1-C1) determines the notch frequency. The value of C2 affects the in-band impedance peak. It should be noted that the capacitor C2 may be implemented via any existing capacitance or parasitic capacitance that is dedicated. Assuming that the quality (Q) of the capacitor is high, the quality (Q) of the inductor L1 determines the rate of attenuation, | Zpeak |/| Zmin |.

The following table shows sample values of circuit components for different notch and in-band frequencies according to three different examples of a transmitter used in an implementation of an 802.11acWLAN device.

Fig. 6 is a schematic block diagram of an embodiment of a notch filter according to the present invention. In this embodiment, a negative transconductance is added via a circuit with transistors T1 and T2 to boost the filter Q, and its strength is digitally controlled to prevent potential oscillation (linear attenuation) and minimize linear attenuation.

For example, the Q boost circuit is added to increase the decay rate. The strength of the Q boost is adjustable in response to the filter control signal 316 to trade off between attenuation rate and circuit linearity. For example, the gains of transistors T1 and T2 are adjustable based on the filter control signal 316 to adjust the amount of Q enhancement. The value of L1 may be selected to minimize the effect on the in-band impedance. When the impedance is low, a small value of L1 is preferred.

Fig. 7 is a schematic block diagram of an embodiment of a radio transmission front end according to the present invention. In this embodiment, notch filter 304 is implemented early in the transmit path. This configuration may be preferred due to low signal swing and improved linearity when using active Q enhancement circuits. As shown in fig. 4, it is preferable to have notch filter 304 located at a later position in the transmission path or at the output of power amplifier 308 to attenuate noise from the previous stage.

Fig. 8 is a schematic block diagram of an embodiment of a radio transmitter front end according to an embodiment of the present invention. Specifically, in this configuration, switch matrix 320 programmably locates notch filter 304 at different positions in the transmit chain based on the implementation — increasing design flexibility. In the example shown, control signal generator 314 not only programs notch filter 304 via filter control signal 316, but also generates configuration control signal 318 to control switch matrix 320 to control the position of notch filter 304 in the transmit path. For example, for one value of configuration control signal 318, the switch matrix connects notch filter 304 in the path before PA driver 300. In this manner, upconverted signal 166 is notch filtered before being input to PA drive 300, and first amplified signal 302 from the output of PA drive 300 is connected to power amplifier 308 via switch matrix 320. For another value of configuration control signal 318, the switch matrix connects notch filter 304 in the path after PA driver 300. In this manner, the upconverted signal 166 is input to the PA drive 300 and the first amplified signal 302 from the output of the PA drive 300 is notch filtered by a notch filter 304 before being input to a power amplifier 308.

Fig. 9 is a schematic block diagram of an embodiment of a notch filter according to the present invention. It should be noted that fig. 4, 7 and 8 show notch filters at different positions in the transmit path, but other configurations are equally possible. Specifically, notch filter 304 is present in a cascode amplifier, such as PA driver 300 or power amplifier 306. In this configuration, notch filter 304 is located between transconductance transistor 330 and series transistor 332, where the signal swing and impedance are generally low.

Fig. 10 is a flow chart of an embodiment of a method according to the present invention. In particular, the method is shown for use in conjunction with one or more of the functions and features described with reference to fig. 1-9. In step 400, a transmit signal is generated via at least one amplifier stage in response to the upconverted signal. In step 402, a transmit feedback signal is generated in response to the transmit signal. In step 404, at least one filter control signal is generated in response to the transmit feedback signal. In step 406, the programmable notch filter is controlled to filter out-of-band noise while passing in-band frequencies to at least one amplifier stage based on at least one filter control signal.

In an embodiment of the present invention, the transmission feedback signal indicates the transmission signal strength of the in-band frequency. Step 402 may use at least a portion of a receive path of a receiver included in the RF transceiver. The at least one amplifier stage may include a power amplifier driver and a power amplifier, and the method may further include: coupling a notch filter between the power amplifier driver and the power amplifier; or a notch filter coupled to filter the input signal of the power amplifier driver. The at least one amplifier stage may further include a switch matrix, and the method may further include controlling the switch matrix to selectively couple a notch filter between the power amplifier driver and the power amplifier to filter an input signal of the power amplifier in the first mode of operation; and control the switch matrix to selectively couple the notch filter to filter the input signal of the power amplifier driver in the second mode of operation.

The at least one amplifier stage may include a cascode amplifier having a plurality of cascode transistors and a plurality of transconductance transistors, and the method may further include coupling a notch filter between the plurality of cascode transistors and the plurality of transconductance transistors. The notch filter may include an inductor and a first capacitor forming a series tank with the inductor, and a second capacitor in parallel with the series tank, and step 406 may include controlling a capacitance of at least one of the first capacitor and the second capacitor via at least one filter control signal. The method may also include boosting the quality of the series tank circuit via an active quality (Q) boost circuit having at least one transistor.

FIG. 11 is a schematic block diagram of an embodiment of a notch filter according to the present invention. In the present embodiment, a negative transconductance is added via a circuit with transistors T1 and T2 to improve the Q of the filter and its strength is digitally controlled to prevent potential oscillation and minimize degradation of linearity.

As in the circuit of fig. 6, a Q-enhancement circuit is added to boost the decay rate. The strength of the Q boost is adjustable in response to the filter control signal 316 to trade off between the decay rate and circuit linearity. For example, the gains of transistors T1 and T2 are adjustable based on the filter control signal 316 to adjust the amount of Q enhancement.

As used herein, the terms "substantially" and "about" provide an industry-accepted tolerance for their respective items and/or relatedness between items. Such industry-accepted tolerances range from less than one percent to fifty percent and correspond to, but are not limited to, component values, integrated circuit process variables, temperature variations, rise and fall times, and/or thermal noise. Such correlations between items range from a few percent difference to large differences. Also as used herein, the terms "operatively coupled to," "coupled to," and/or "coupled to" include direct couplings between items and/or indirect couplings between items via intervening items (e.g., items include, but are not limited to, components, elements, circuits, and/or modules), where for indirect couplings, intervening items do not modify signal information, but may adjust their current levels, voltage levels, and/or power levels. Also as used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as "coupled to". Further as used herein, the term "operable" or "operably coupled to" indicates that the item includes one or more of a power connection, input, output, etc. to perform one or more of its respective functions when activated, and may also include an inferred coupling to one or more other items. As also used herein, the term "associated with …" includes direct and/or indirect coupling of separate items and/or embedding of one item within another item. As used herein, the term "favorable comparison" indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater amplitude than signal 2, a favorable comparison may be obtained when the amplitude of signal 1 is greater than the amplitude of signal 2 or when the amplitude of signal 2 is less than the amplitude of signal 1.

Also as used herein, the terms "processing module," "processing circuit," and/or "processing unit" may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard-coded and/or operational instructions for the circuitry. The processing module, processing circuit, and/or processing unit may be or further include memory and/or may be an integrated memory element of a single memory device, multiple memory devices, and/or embedded circuitry of other processing modules, processing circuits, and/or processing units. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, any device that caches and/or stores digital information. Note that if the processing module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributed (e.g., employing cloud computing via indirect coupling via a local area network and/or a wide area network). It is further noted that if the processing module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or storage elements storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. It is further noted that the memory elements may store, and the processing modules, processing circuits and/or processing units may be capable of executing, hard-coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the figures. Such a memory device or memory element may be included in an article of manufacture.

The invention has been described above with method steps illustrating the performance of specified functions and relationships thereof. Boundaries and the order of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences may be defined so long as the specified functions and relationships are appropriately performed. Accordingly, any such alternate boundaries or sequences are within the scope and spirit of the claimed invention. Further, for convenience of description, boundaries of these functional building blocks have been arbitrarily defined. Alternate boundaries may be defined so long as certain important functions are properly performed. Similarly, flow diagram blocks may be arbitrarily defined herein to illustrate certain significant functions. To the extent used, the boundaries and sequence of flowchart blocks may be otherwise defined and still perform the specified important functions. Accordingly, alternative definitions and sequences of such functional building blocks and flow diagram blocks are within the scope and spirit of the claimed invention. Those of ordinary skill in the art will also appreciate that the functional building blocks, as well as other exemplary blocks, modules, and components herein, may be implemented as shown or by discrete components, application specific integrated circuits, processors executing appropriate software, etc., or any combination thereof.

The present invention may also be described, at least in part, in terms of one or more embodiments. Embodiments of the present invention are used herein to describe the present invention, aspects thereof, features thereof, concepts thereof and/or examples thereof. The physical embodiments of the device, article of manufacture, machine, and/or process implementing the invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more embodiments discussed herein. Further, from figure to figure, these embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers, and thus, these functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different functions, steps, modules, etc.

Although the transistors in the above figures are shown as Field Effect Transistors (FETs), as one of ordinary skill in the art will recognize, the transistors may be implemented using any type of transistor structure including, but not limited to, bipolar transistors, Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), N-well transistors, P-well transistors, enhancement mode transistors, depletion mode transistors, and zero Voltage Threshold (VT) transistors.

Unless specifically stated to the contrary, in any of the figures shown herein, signals to, from, and/or between elements may be analog or digital, continuous-time or discrete-time, and single-ended or differential. For example, if the signal path is shown as a single ended path, it also represents a differential signal path. Similarly, if the signal path is shown as a differential path, it also represents a single-ended signal path. Although one or more specific architectures are described herein, other architectures may similarly be implemented using one or more data buses that are not explicitly shown, direct connections between elements, and/or indirect couplings between other elements, as will be appreciated by those of ordinary skill in the art.

The term "module" is used in the description of the various embodiments of the present invention. The modules include processing modules, functional blocks, hardware, and/or software stored on memory for performing one or more functions as described herein. Note that if the modules are implemented via hardware, the hardware may work alone and/or in combination with software and/or firmware. As used herein, a module may include one or more sub-modules, each of which may be one or more modules.

Although specific combinations of features and functions are described herein, other combinations of features and functions are also possible. The invention is not limited by the specific examples disclosed herein, and these other combinations are expressly incorporated.

Claims (10)

1. A radio transmitter front-end for use in a Radio Frequency (RF) transceiver, the radio transmitter front-end comprising:

at least one amplifier stage operable to generate a transmit signal in response to the upconverted signal;

a feedback generator, coupled to the at least one amplifier stage, operable to generate a transmit feedback signal in response to the transmit signal by determining an out-of-band signal attenuation of the transmit signal;

a control signal generator, coupled to the feedback generator, operable to generate at least one filter control signal in response to the transmit feedback signal; and

a notch filter, coupled to the control signal generator and the at least one amplifier stage, operable to filter out-of-band noise while passing in-band frequencies to the at least one amplifier stage under control of the at least one filter control signal.

2. A radio transmitter front end according to claim 1, wherein the feedback generator comprises a transmitted signal strength indicator.

3. The radio transmitter front end of claim 1, wherein the feedback generator comprises at least a portion of a receive path of a receiver included in the RF transceiver.

4. The radio transmitter front end of claim 1, wherein the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and wherein the notch filter is coupled between the power amplifier driver and the power amplifier.

5. The radio transmitter front-end of claim 1, wherein the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and wherein the notch filter is coupled to filter an input signal of the power amplifier driver.

6. The radio transmitter front end of claim 1, wherein the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and the radio transmitter front end comprises a switch matrix coupled to the power amplifier driver and the power amplifier, the switch matrix operable to selectively couple the notch filter between the power amplifier driver and the power amplifier in response to a configuration control signal generated by the control signal generator to filter an input signal of the power amplifier in a first mode of operation and to couple the notch filter to filter an input signal of the power amplifier driver in a second mode of operation.

7. A method for use in a Radio Frequency (RF) transceiver, the method comprising:

generating a transmit signal via at least one amplifier stage in response to the upconverted signal;

generating a transmit feedback signal in response to the transmit signal by determining an out-of-band signal attenuation of the transmit signal;

generating at least one filter control signal in response to the transmit feedback signal; and

controlling a programmable notch filter to filter out-of-band noise while passing in-band frequencies to the at least one amplifier stage based on the at least one filter control signal.

8. The method of claim 7, wherein the transmit feedback signal is indicative of a transmit signal strength of the in-band frequency.

9. The method of claim 7, wherein generating the transmit feedback signal uses at least a portion of a receive path of a receiver included in the RF transceiver.

10. The method of claim 7, wherein the at least one amplifier stage comprises a power amplifier driver and a power amplifier, and the method further comprises:

coupling the notch filter between the power amplifier driver and the power amplifier.