Abstract: A communication system (20) includes a base station (22) and a number of peak-managed user equipment apparatuses (26) that simultaneously transmit peak-reduced FDMA communication signals (128) to the base station (22). The communication system (20) exclusively assigns payload subcarriers (44) to the apparatuses (26) and assigns a few noise-bearing subcarriers (48) for common simultaneous use by all apparatuses (26). Each user equipment apparatus (26) includes a peak reduction section (92) that distorts an otherwise undistorted modulated communication signal (86) into a distorted, peak-reduced communication signal (128) by generating and adding peak-reduction noise (131) to the undistorted signal (86). The peak-reduction noise (131) is primarily mapped onto the noise-bearing subcarriers (48) without conforming to an in-band noise constraint and may be mapped onto the assigned payload subcarriers (44) to the extent permitted by an in-band noise constraint.

Abstract: A communication system (20) includes a base station (22) and a number of peak-managed user equipment apparatuses (26) that simultaneously transmit peak-reduced FDMA communication signals (128) to the base station (22). The communication system (20) exclusively assigns payload subcarriers (44) to the apparatuses (26) and assigns a few noise-bearing subcarriers (48) for common simultaneous use by all apparatuses (26). Each user equipment apparatus (26) includes a peak reduction section (92) that distorts an otherwise undistorted modulated communication signal (86) into a distorted, peak-reduced communication signal (128) by generating and adding peak-reduction noise (131) to the undistorted signal (86). The peak-reduction noise (131) is primarily mapped onto the noise-bearing subcarriers (48) without conforming to an in-band noise constraint and may be mapped onto the assigned payload subcarriers (44) to the extent permitted by an in-band noise constraint.

Abstract: Optimized impedance characteristics of a variable impedance device causes the apparatus to transmit wireless signals with minimal out-of-band transmission at an optimized efficiency of the power amplifier. The variation of impedance characteristics of an antenna cause a change in the coefficients of a mapping function. The relatively fast variations to the power supply voltage of a power amplifier are applied to the mapping function to generate control signals which vary the impedance characteristics of a variable impedance device. The output of the mapping function includes control signals that control optimized impedance characteristics of a variable impedance device as a function of the variation of the supply voltage to a power amplifier. The coefficients of the mapping function may be regularly determined based on a comparison of out-of-band power and in-band power transmitted by an antenna.

Abstract: A transmitter (32) generates a time-varying stabilized bias signal (82) from which sub-RF distortion signals (26, 29) have been cancelled. The distortion signals (26, 29) are byproducts of imperfect amplification and of biasing networks. An envelope amplifier (84) includes a high bandwidth differential input, linear, bias signal amplifier (120) and a low bandwidth switching amplifier (122) coupled together to achieve both a high bandwidth and high efficiency. A control loop (154) feeds a portion of the voltage V(t) from a conduction node (146) of the RF power amplifier (36) to one of the differential inputs of the linear bias signal amplifier (120), while a bias control signal (92) drives the other differential input. The portion of voltage V(t) fed to bias signal amplifier (120) is a low power portion from which the RF portion has been removed. A bias signal (128) may be predistorted to cancel distortion signals (26, 29).

Abstract: A communication system (20) includes a base station (22) and a number of peak-managed user equipment apparatuses (26) that simultaneously transmit peak-reduced FDMA communication signals (128) to the base station (22). The communication system (20) exclusively assigns payload subcarriers (44) to the apparatuses (26) and assigns a few noise-bearing subcarriers (48) for common simultaneous use by all apparatuses (26). Each user equipment apparatus (26) includes a peak reduction section (92) that distorts an otherwise undistorted modulated communication signal (86) into a distorted, peak-reduced communication signal (128) by generating and adding peak-reduction noise (131) to the undistorted signal (86). The peak-reduction noise (131) is primarily mapped onto the noise-bearing subcarriers (48) without conforming to an in-band noise constraint and may be mapped onto the assigned payload subcarriers (44) to the extent permitted by an in-band noise constraint.

Abstract: A transmitter (32) generates a time-varying stabilized bias signal (82) from which an amplifier-generated, sub-RF distortion signal (26) has been canceled. The distortion signal (26) is a byproduct of amplification and is generated due to imperfect linearity and/or other characteristics of a linear RF power amplifier (36). An envelope amplifier (84) includes a high bandwidth differential input, linear, bias signal amplifier (120) and a low bandwidth switching amplifier (122) coupled together to achieve both a high bandwidth and high efficiency. A control loop (154) feeds a portion of the voltage V(t) from a conduction node (146) of the RF power amplifier (36) to one of the differential inputs of the linear bias signal amplifier (120), while a bias control signal (92) drives the other differential input. The portion of voltage V(t) fed to bias signal amplifier (120) is a low power portion from which the RF portion has been removed.

Abstract: A transmitter (50) includes a low power nonlinear predistorter (58) that inserts predistortion configured to compensate for a memoryless nonlinearity (146) corresponding to gain droop and another memoryless nonlinearity (148) corresponding to a video signal. When efforts are taken to reduce memory effects, such as configuring a network of components (138) that couple to an HPA (114) to avoid resonance frequencies substantially throughout a video bandwidth (140), high performance linearization at low power results without extending linearization beyond that provided by the memoryless nonlinear predistorter (58). A look-up table (282) has address inputs responsive to a magnitude parameter (152) of a communication signal (54). A pre-distorted communication signal (60) is responsive to the output of the look-up table, a derivative signal (204), and possibly one or more variable bias parameters (85). The look-up table (282) is updated in response to an LMS control loop.

Abstract: A transmitter (32) generates a time-varying stabilized bias signal (82) from which sub-RF distortion signals (26, 29) have been cancelled. The distortion signals (26, 29) are byproducts of imperfect amplification and of biasing networks. An envelope amplifier (84) includes a high bandwidth differential input, linear, bias signal amplifier (120) and a low bandwidth switching amplifier (122) coupled together to achieve both a high bandwidth and high efficiency. A control loop (154) feeds a portion of the voltage V(t) from a conduction node (146) of the RF power amplifier (36) to one of the differential inputs of the linear bias signal amplifier (120), while a bias control signal (92) drives the other differential input. The portion of voltage V(t) fed to bias signal amplifier (120) is a low power portion from which the RF portion has been removed. A bias signal (128) may be predistorted to cancel distortion signals (26, 29).

Abstract: An RF transmitter (10) includes an RF amplifier (28) that generates an amplified RF signal (36) including a linear RF signal (92) and a spurious baseband signal (94). The spurious baseband signal (94) interacts with bias feed networks (56, 66) to cause the RF amplifier (28) to generate an unwanted RF distortion at or near the allocated RF bandwidth. A baseband compensation signal (98) is generated and equalized in an adaptive equalizer (102) then fed to the RF amplifier (28). A feedback signal (46) is obtained from the RF amplifier (28) and used to drive the adaptive equalizer (102). A feedback loop causes the adaptive equalizer to adjust a baseband signal (24, 32) supplied to the RF amplifier (28) so that the RF distortion is minimized.

Abstract: A transmitter (20) includes a peak reduction section (30), a predistorter (98), and an amplifying section (102) biased by a variable bias signal generator (118). The peak reduction section (30) is controlled by a signal magnitude threshold (36) that defines maximum magnitudes for local peaks (32) of a reduced-peak communication signal (38). The bias signal generator (118) is controlled by a bias control signal (110). Both the signal magnitude threshold (36) and the bias control signal (110) are derived from a common reduced bandwidth (50) peak-tracking signal (42). The peak-tracking signal (42) is derived from an inflated-peak communication signal (26). The predistorter (98) applies distortion to the reduced-peak communication signal (38) that is configured, at least in part, by the bias control signal (110).

Abstract: A transmitter (70) generates a time-varying, detroughed, biasing signal (154) for an RF power amplifier (10) so that the RF power amplifier (10) is biased in accordance with an envelope tracking scheme. A trough-filling section (94) is responsive to an envelope tracking signal (86), which in turn is responsive to a magnitude signal (90) extracted from a complex baseband communication signal (76). The trough-filing section (94) includes a limiting stage (108) that forms a raw troughing signal (110) which expands the bandwidth of the envelope tracking signal (86). A filtering stage (116) reduces the bandwidth of the raw troughing signal (110) to form a trough-filling signal (122) that is combined back into the envelope tracking signal (86) using a linear process that maintains the bandwidth of the envelope tracking signal (86).

Abstract: A communication system includes a transmitting unit with a peak to average power (PAPR) reduction section. The PAPR reduction section modifies the PAPR reduction it effects in a communication signal in accordance with two different error vector magnitude (EVM) constraints for each channel type, where a channel type is a distinct combination of a modulation order and a coding rate. The EVM constraint followed for each subcarrier in an OFDM or OFDMA application is selected in response to whether the subcarrier conveys voice or non-voice data. The PAPR reduction section may include a scaling filter. The scaling filter is efficiently defined through the use of a predetermined sinc function and a first stage scale factor that is calculated in response to a weighted average of excursion signal subcarrier gains, where the weighting follows the distribution of channel types through the subcarriers.

Abstract: A communication system (20) includes a transmitter (22) having a peak controller (38) which controls PAPR to operate in accordance with a noise constraint. A backoff controller (60) operates in conjunction with an amplifier section (46) to cause the amplifier section (46) to maximize the amplification it applies while maintaining a predetermined degree of amplifier linearity. The noise constraint is provided by an equilibrium estimator (64) that provides a noise target parameter (66) to the peak controller (38). The noise target parameter (66) is configured to identify the transmitter's equilibrium point (126). The equilibrium point (126) is that signal-to-noise ratio (SNR) for the signal (26) broadcast from the transmitter (22) where a demodulator (118) in a receiver (24) will experience a reduced SNR if the transmitted signal (26) SNR either increases or decreases.

Abstract: A communication system (20) includes a transmitter (22) having a peak controller (38) which controls PAPR to operate in accordance with a noise constraint. A backoff controller (60) operates in conjunction with an amplifier section (46) to cause the amplifier section (46) to maximize the amplification it applies while maintaining a predetermined degree of amplifier linearity. The noise constraint is provided by an equilibrium estimator (64) that provides a noise target parameter (66) to the peak controller (38). The noise target parameter (66) is configured to identify the transmitter's equilibrium point (126). The equilibrium point (126) is that signal-to-noise ratio (SNR) for the signal (26) broadcast from the transmitter (22) where a demodulator (118) in a receiver (24) will experience a reduced SNR if the transmitted signal (26) SNR either increases or decreases.

Abstract: A transceiver (10) includes an RF transmitter (12) and an RF receiver (14) coupled together through a duplexer (30) or non-filtering multiport device (30?). Either device may leak significant portions (56, 58) of the transmit signal (20) into the receive signal (44), and may significantly distort the transmit signal (20). Distortion is compensated in the transmitter (12) through the use of a linear predistorter (68) that is adjusted in response to an RF feedback signal obtained from the antenna-side of the device. Transmit signal leakage is compensated in the receiver (14) by producing an RF cancellation signal (106) that, when combined with the receive signal (44) at RF at least partially cancels the transmit signal portions (56, 58) leaked into the receive signal (44). Residual leakage signal and intermodulation products thereof may be cancelled digitally.

Abstract: A transmitter (20) includes a peak reduction section (30), a predistorter (98), and an amplifying section (102) biased by a variable bias signal generator (118). The peak reduction section (30) is controlled by a signal magnitude threshold (36) that defines maximum magnitudes for local peaks (32) of a reduced-peak communication signal (38). The bias signal generator (118) is controlled by a bias control signal (110). Both the signal magnitude threshold (36) and the bias control signal (110) are derived from a common reduced bandwidth (50) peak-tracking signal (42). The peak-tracking signal (42) is derived from an inflated-peak communication signal (26). The predistorter (98) applies distortion to the reduced-peak communication signal (38) that is configured, at least in part, by the bias control signal (110).

Abstract: An RF transmitter (10) includes an RF amplifier (28) that generates an amplified RF signal (36) including a linear RF signal (92) and a spurious baseband signal (94). The spurious baseband signal (94) interacts with bias feed networks (56, 66) to cause the RF amplifier (28) to generate an unwanted RF distortion at or near the allocated RF bandwidth. A baseband compensation signal (98) is generated and equalized in an adaptive equalizer (102) then fed to the RF amplifier (28). A feedback signal (46) is obtained from the RF amplifier (28) and used to drive the adaptive equalizer (102). A feedback loop causes the adaptive equalizer to adjust a baseband signal (24, 32) supplied to the RF amplifier (28) so that the RF distortion is minimized.

Abstract: A transmitter (50) includes a nonlinear predistorter (58) having two instances of an inverting transform (106, 106?) that may be implemented in a look-up table (122) and that implements a transform which is the inverse of an average terms component (96) of a nonlinear transform model (94) for an amplifier (70). The look-up table (122) may be updated using a continuous process control loop that avoids Cartesian to polar coordinate conversions. One of the two instances of the inverting transform (106) is cascaded with a non-inversing transform (108) within a residual cancellation section (110) of the predistorter (58). The non-inversing transform (108) implements a transform which is an estimate of a deviation terms component (98) of the nonlinear transform model (94). The residual cancellation section (110) produces a weak signal that replaces an unwanted residual term in an amplified communication signal (76) with a much weaker residual term.

Abstract: A transmitter (50) includes a low power nonlinear predistorter (58) that inserts predistortion configured to compensate for a memoryless nonlinearity (146) corresponding to gain droop and another memoryless nonlinearity (148) corresponding to a video signal. When efforts are taken to reduce memory effects, such as configuring a network of components (138) that couple to an HPA (114) to avoid resonance frequencies within a video bandwidth (140), high performance linearization at low power results without extending linearization beyond that provided by the memoryless nonlinear predistorter (58). A look-up table (282) has address inputs responsive to a magnitude parameter (152) of a communication signal (54), a magnitude derivative parameter (204) of the communication signal (54), and possibly one or more variable bias parameters (85). The look-up table (282) produces a gain-correcting signal (284) that adjusts the gain applied to the communication signal (54) prior to amplification.

Abstract: A transmitter (50) includes a low power nonlinear predistorter (58) that inserts predistortion configured to compensate for a memoryless nonlinearity (146) corresponding to gain droop and another memoryless nonlinearity (148) corresponding to a video signal. When efforts are taken to reduce memory effects, such as configuring a network of components (138) that couple to an HPA (114) to avoid resonance frequencies within a video bandwidth (140), high performance linearization at low power results without extending linearization beyond that provided by the memoryless nonlinear predistorter (58). A unadaptable look-up table (370) has address inputs responsive to a magnitude parameter (152) of a communication signal (54), a magnitude derivative parameter (204) of the communication signal (54), and a parameter (346, 366) related either directly or indirectly to battery voltage.