Abstract: Apparatus and methods for radio frequency (RF) signal limiting are provided. In certain embodiments, an RF signal limiting system includes a cascade of a front limiter and a biased limiter. Additionally, the front limiter provides an initial amount of limiting to an RF signal, while the biased limiter serves to further limit the RF signal. The biased limiter is adaptively biased such that the amount of limiting provided to the RF signal increases in response to an increase in the RF signal level. Such an RF signal limiting system can be used in a variety of applications, including protecting an input of a low noise amplifier (LNA).

Abstract: RFID readers may be configured to supply power to tags during frequency hops. When a reader is supplying power to a passive RFID tag via a first RF waveform having a first radio frequency and determines that it is to frequency-hop, the reader may determine whether the tag requires power during the hop. If so, the reader begins (or continues) to synthesize a second RF waveform with a second radio frequency while also synthesizing the first RF waveform, and frequency-hops by transitioning from transmitting the first RF waveform to transmitting the second RF waveform such that the power transmitted during the transition is sufficient for the tag to operate.

Abstract: Methods, systems, and devices for wireless communications are described. The described methods, systems, and devices may include sampling an input signal to obtain one or more signal windows. An amplitude of a first sample within a first signal window of the one or more signal windows may be determined to exceed an amplitude threshold. A series of cancellation pulses may be combined with the first sample within the first signal window to obtain a reduced signal, the reduced signal including one or more reduced samples each having an amplitudes within the amplitude threshold. The series of cancellation pulses may be based on a characteristic of the first sample. The reduced signal may then be transmitted. The series of cancellation pulses may be based on, for example, an envelope of the first sample. In some cases, the series of cancellation pulses may be based on a phase of the first sample.

Abstract: An embodiment of the disclosure provides a system for determining information on one or more constituents in a medium. The system includes N light emitters L1 . . . LN, wherein each light emitter Lx provides an amplitude modulated (AM) light at modulation frequency fx into a flow path of the medium from one side of a containment vessel for the medium. The system further includes a photodetector, for receiving the AM light from each light emitter after it passes through the flow path of the medium, and converting the AM light to an electrical signal characterized by a summation of frequency components from each modulation frequency fx. The system further includes one or more measuring circuits providing information about a concentration of one or more constituents in the medium determined from log ratios of a pair of amplitudes of fy and fz frequency components in the electrical signal.

Abstract: A transmitter circuit coupled to output image data from an image sensor includes a plurality of transmitters. The transmitters may include a plurality of drivers coupled to receive a data signal, and output a differential signal in response to receiving the data signal. A de-emphasis circuit is coupled between a first output of a first driver in the plurality of drivers, and a second output of a second driver in the plurality of drivers. The de-emphasis circuit is coupled to receive a de-emphasis control signal, and in response to receiving the de-emphasis control signal, the de-emphasis circuit reduces a magnitude of the differential signal.

Abstract: Techniques for using a narrow filter located before a power amplifier to reduce interference in an adjacent frequency band are disclosed. In an exemplary design, an apparatus (e.g., a wireless device) includes the narrow filter and the power amplifier. The narrow filter is for a first frequency band (e.g., Band 40) and has a first bandwidth that is more narrow than the first frequency band. The narrow filter receives and filters an input radio frequency (RF) signal and provides a filtered RF signal. The power amplifier receives and amplifies the filtered RF signal and provides an amplified RF signal. The apparatus may further include a full filter for the first frequency band and located after the power amplifier. The full filter receives and filters the amplified RF signal and provides an output RF signal when it is selected for use.

Abstract: A mixing stage includes a first modulation stage that receives an input signal from a first common node of the mixing stage, a first local oscillator input that receives a local oscillator signal, and a first modulation signal output adapted to provide a first modulated signal. A second modulation stage of the mixing stage includes a second input that receives a phase inverted representation of the input signal from a second common node of the mixing stage, a second local oscillator input that receives the local oscillator signal, and a second modulation signal output adapted to provide a second modulated signal. A current generation circuit provides a supply current to the first common node and to the second common node. A current control circuit is adapted to superimpose an offset current to the current of at least one node of the first common node and the second common node.

Abstract: The present invention provides a method and system for reducing the peak to average power ratio (PAP) of a signal with low computational complexity. According to one embodiment, the present invention is applied to reduce the PAP of an OFDM signal. According to an alternative embodiment, the present invention, is applied to reduce the PAP of a CDMA signal. Rather than seeking the optimum solution, which involves significant computational complexity, the present invention provides for a number of sub-optimal techniques for reducing the PAP of an OFDM signal but with much lower computational complexity.

Abstract: Systems and methods are provided for generating an amplitude modulation signal to a switchmode power amplifier. A DC to DC switch is configured to receive a DC input voltage and to provide a DC output voltage. A low dropout regulator is configured to provide the amplitude modulation signal according to a modulation control signal received by the low dropout regulator. A control circuit is configured to establish a nominal operating power level for the power amplifier via the amplitude modulation signal and to maintain a minimum voltage difference between the DC output voltage and the low dropout regulator output. A modulator control circuit is configured to provide the modulation control signal to the low dropout regulator. The modulator control circuit provides the transition from a high amplitude to a low amplitude and a transition from the low amplitude to the high amplitude at configurable first and second slopes, respectively.

Abstract: Systems and methods are provided for generating an amplitude modulation signal to a switchmode power amplifier. A DC to DC switch is configured to receive a DC input voltage and to provide a DC output voltage. A low dropout regulator is configured to provide the amplitude modulation signal according to a modulation control signal received by the low dropout regulator. A control circuit is configured to establish a nominal operating power level for the power amplifier via the amplitude modulation signal and to maintain a minimum voltage difference between the DC output voltage and the low dropout regulator output. A modulator control circuit is configured to provide the modulation control signal to the low dropout regulator. The modulator control circuit provides the transition from a high amplitude to a low amplitude and a transition from the low amplitude to the high amplitude at configurable first and second slopes, respectively.

Abstract: A parametric audio system that permits greater control over the bandwidth of a modulated signal. The system includes a carrier signal generator for generating a carrier signal, at least one audio signal source for generating at least one audio signal, and a modulation component for generating an envelope signal based on the at least one audio signal, modulating the phase of the carrier signal based on a predetermined function to generate a first modulated signal, and multiplying the envelope signal and the first modulated signal to generate a second modulated signal. By selection of the predetermined function, the modulation component can alter the spectrum of the second modulated signal, thereby permitting greater control over the bandwidth of the second modulated signal.

Abstract: A polar modulator of the present invention includes: a first function block which generates an amplitude signal and a phase signal; a second function block which adjusts the signal delay between the amplitude signal and the phase signal; a third function block which allows the low frequency component of the amplitude signal to pass therethrough; a fourth function block which modulates the phase of the phase signal; a fifth function block which outputs a modulation voltage, based on the amplitude signal; a sixth function block which modulates the amplitude of the phase signal, based on the modulation voltage; a seventh function block which measures the temperature of at least one function block; and an eighth function block which calculates a compensation amount for the signal delay, based on the measured temperature. The second function block adjusts the signal delay, based on the compensation amount.

Abstract: A calibration system may be provided for calibrating wireless communications circuitry in an electronic device during manufacturing. The calibration system may include data acquisition equipment for receiving an amplitude-modulated calibration signal from the electronic device. The calibration system may include calibration computing equipment for extracting pre-distortion coefficients from the amplitude-modulated calibration signal. The calibration computing equipment may be configured to detect a bulk phase drift in the amplitude-modulated calibration signal. The calibration computing equipment may be configured to remove the bulk phase drift from the amplitude-modulated calibration signal. The wireless communications circuitry may include a power amplifier that distorts a signal generated by the wireless communications circuitry. The wireless communications circuitry may include a pre-distortion compensator for countering the distortion.

Abstract: A multi-band signal is generated by combining two or more input signals separated in frequency. The input signals are combined either before or after predistortion depending on the bandwidth of the multi-band signal. If the bandwidth of the multi-band signal is less than a predetermined bandwidth threshold, the input signals are combined and predistortion is applied to the combined signal to generate the multi-band signal. If the bandwidth of the multi-band signal is greater than the bandwidth threshold, the individual input signals are predistorted and subsequently combined to generate the multi-band signal.

Abstract: A wireless network (20) with at least a first radio communication unit (24) and a second radio communication unit (26) transmits and receives signals with minimal interference from the surrounding environment of the first unit (24) and second unit (26). The first radio communication unit (24) determines frequencies (54) having power level above a threshold (52), and creates a list of these frequencies (50) to be transmitted to the second radio communication unit (26). The second radio communication unit (26) places notches (140) in its transmission band (88) based on frequencies (54) in the list (50), reserved frequencies (132), and local frequencies (92) having signal energy above a threshold (90). When transmitting a signal (42), the second radio communication unit (26) avoids transmitting in frequencies that have notches (140).

Abstract: The present disclosure relates to using windowing to reduce the bandwidth of an amplitude modulation (AM) power supply input signal (PSIS), which is fed to an AM power supply to provide envelope power to an RF power amplifier stage via an AM power supply output signal. By reducing the bandwidth, noise levels from the AM power supply may be reduced. However, although the bandwidth of the AM PSIS is reduced, the AM power supply output signal may track the AM of the RF power amplifier stage closely enough to meet linearity requirements and to provide high efficiency. The windowing may be based on dividing a stream of AM input samples into a stream of input windows, from which a stream of output windows is created to provide a stream of windowed AM input samples that are used to provide a windowed AM PSIS to the AM power supply.

Abstract: Low noise phase quadrature signals are generated after receiving a clock signal and adjusting the clock signal in response to a feedback signal to generate a phase adjusted clock signal. The clock signal and the phase adjusted clock signal are exclusive-ored to generate a frequency doubled signal. An in-phase local oscillator signal and a quadrature local oscillator signal are generated from the frequency doubled signal such that the in-phase local oscillator and the quadrature local oscillator signal are out-of-phase with each other. In addition, a phase relationship between the in-phase local oscillator signal and the quadrature local oscillator signal are detected, and the feedback signal is generated based upon the phase relationship between the in-phase local oscillator signal and the quadrature local oscillator signal.

Abstract: A wireless communication device corrects data transmission errors caused by the simultaneous transmission of multiple streams of data in a Multiple-Input Multiple-Output (MIMO) network. The wireless communication device corrects data transmission errors by removing the signal contribution associated with one or more received signal components from a corresponding received composite signal, thus allowing the remaining components to be decoded relatively free from the signal contribution of the removed components. In one embodiment, the wireless communication device comprises a plurality of antennas and a baseband processor. The antennas are configured to receive a composite signal having a plurality of received signal components.

Abstract: Methods and apparatus for reconstructing discrete-time amplitude modulation signals in polar modulation transmitters. An exemplary polar modulation transmitter includes a symbol generator, a rectangular-to-polar converter, a peak phase detector, and an amplitude modulation reconstruction circuit. The symbol generator generates rectangular-coordinate modulation symbols from which the rectangular-to-polar converter generates an amplitude modulation signal containing discrete-time amplitude samples and an angle modulation signal containing discrete-time angle samples. The peak phase detector circuit detects phase reversals or near phase reversals represented in samples of the angle modulation signal. The amplitude modulation reconstruction circuit responds by reconstructing samples in the amplitude modulation signal that correspond to detected phase reversals or a near phase reversals represented in samples of the angle modulation signal.

Abstract: A modulator includes a first converter, a second converter and a mixer. The first converter is configured to receive a first bit and provide a first current that is a function of the first bit. The second converter is configured to receive a second bit and provide a second current that is a function of the second bit. The mixer is configured to receive an input current that is a sum of the first current and the second current and a frequency signal and provide an output signal that is a function of the input current and the frequency signal.

Abstract: Embodiments of the present invention include amplitude-modulated or polar-modulated radio frequency (RF) power amplifier circuitry, in which an envelope power supply input to an RF power amplifier is powered by a pre-distorted amplitude modulation (AM) power supply. The pre-distorted AM power supply receives an AM signal, which is then pre-distorted and amplified to provide an AM power supply signal to the RF power amplifier. The pre-distortion of the AM signal is used to improve the linearity, the efficiency, or both, of the RF power amplifier. The pre-distortion provides a feed-forward system, which may allow use of a reduced bandwidth pre-distorted AM signal to an AM power supply and a reduced bandwidth AM power supply, which may increase efficiency.

Abstract: Aspects of a method and system for direct and polar modulation using a two input PLL are presented. Aspects of the system may include generating digital signals Wn and Vn from an input data signal Un and a feedback signal Yn. The generated digital signals Wn and Vn combined may carry the information content of Un while they compensate the non-idealities of the two-input analog phase locked loop (PLL). The digital signal Wn, which may be scaled appropriately in frequency, and the digital signal Vn may be provided as inputs to the PLL. The feedback signal Yn may be a digital signal that may correspond to the analog feedback signal Pt that may be generated by the PLL. Accordingly, the PLL may be adaptively controlled via the digital signals Wn and Vn for properly transmitting the input data signal Un.

Abstract: A system and method for providing a peak power reduced OFDM communications signal are disclosed. The system and method provide peak reduction processing in the time domain followed by inter-symbol interference (ISI) control processing in the frequency domain to maintain modulation errors introduced by the peak reduction processing to an acceptable level. The processing is preferably done on a parallel signal path and the peak corrections with ISI control are added into the main signal path to provide the peak reduced OFDM signal.

Abstract: Aspects of a method and system for a high-precision frequency generator using a direct digital frequency synthesizer for transmitters and receivers may include generating a second signal from a first signal by frequency translating an inphase component of the first signal utilizing a high-precision oscillating signal that may be generated using at least a direct digital frequency synthesizer (DDFS) and at least a Phase-Locked Loop (PLL). A corresponding quadrature component of the first signal may be frequency translated utilizing a phase-shifted version of the high-precision oscillating signal. The inphase component of the first signal may be multiplied with the high-precision oscillating signal and the quadrature component of the first signal may be multiplied with the phase-shifted version of the high-precision oscillating signal. The second signal may be generated from the first signal by adding the frequency translated inphase component to the frequency translated quadrature component.

Abstract: A predistortion linearized amplifier system that uses analog polynomial based predistortion is disclosed. An analog polynomial function generator receives polynomial parameter updates from a polynomial parameter generator. The polynomial parameter generator uses a combination of analog and digital signal processing to create the parameter updates. This processing is performed on input signal amplitude, detected using analog circuits, and RF coupled samples of the input signal, and the output signal. By using a combination of analog and digital signal processing means, digital processing can be performed at sub-Nyquist rates, significantly reducing the cost of digital circuits. Also, since the predistortion modulation signal is created with an analog function generator, time correlating delay is minimized reducing circuit costs.

Abstract: A distortion compensating technique applied to a transmitter for transmitting a quadrature modulated signal in a wireless digital communication system is provided. A phase adjustment value is determined for a quadrature demodulated feedback signal based on comparison between the feedback signal and a reference signal to be transmitted from the transmitter. This phase adjustment value is compared with the previous phase adjustment value. If the comparison result between the current and previous phase adjustment values satisfies a prescribed condition, correction for quadrature modulation, such as DC offset correction, orthogonality correction, or IQ amplitude correction, is performed.

Abstract: A hybrid modulator apparatus includes a modulator that amplitude modulates a power supply signal. A correction circuit coupled in parallel with the modulator reduces errors caused by the modulator. In one embodiment the modulator includes a digital pulse-width modulator (PWM) and a buck converter. The K most significant bits (MSBs) of N-bit input digital words are used by the digital PWM and a buck converter to generate an amplitude modulated power supply signal having a plurality of quantized voltage levels. The remaining N?K bits of each N-bit words may be used to dither the input drive to the PMW, to produce an error signal at the output of the modulator representing quantization errors caused by only applying the K MSBs to the PWM. The correction circuit compares the error signal to a signal formed form all N bits of the N-bit words in reducing the quantization errors.

Abstract: A polar modulator arrangement has a first and a second node to receive a digital signal with a first and a second component corresponding to a digital amplitude component and a digital phase component. A digital interpolation filter generates an interpolated first component by interpolating and filtering the first component. A polar modulated radio frequency signal is generated by a combination element as a function of the interpolated first component and the second component.

Abstract: A power management device providing a power amplifier with power supply voltage is provided. The power management unit includes a parallel-hybrid amplitude modulator apparatus having a linear part configured to track frequency components of an input signal above a determined threshold frequency and a switching part arranged in parallel with the linear part and configured to track frequency components of the input signal below the determined threshold frequency. Additionally, the power management unit includes a current sensing and controlling part configured to determine the level of a direct current component at an output of the linear part and control the switching part to produce an output signal compensating for the direct current component at the output of the linear part to decrease the absolute level of the direct current at the output of the linear part.

Abstract: A feed-forward amplifier having a signal cancellation loop including a cancellation node that includes a gain controller and a phase controller. Each controller provides a discrete tap steering signal and modulates the corresponding tap steering signal with a discrete tracer signal that takes on a preselected sequence of values. The sequence chosen so that the tracer signal is mutually orthogonal to each other tracer signal over a preselected period. A gain and phase adjuster connected to the outputs of the controllers provides a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the gain and phase adjuster by the controllers. A detector, the input of which is connected to the cancellation node and the output of which is connected to the controllers, outputs a measure of the envelope of the signal at the cancellation node.

Abstract: A fixed wireless access communications system comprises an access point and a plurality of subscriber units. Each subscriber unit (502) contends for access to a communications channel to the access point by transmitting a contention word to the access point during a contention time slot. The contention word is predistorted to compensate for the channel impulse response of the transmission channel so that the access point can decode the contention words without using equalisation. A control unit (512), which may comprise a microprocessor, loads the predistorted contention word (a) into a memory (520) and causes the stored predistorted contention word (a) to be applied to a transmitter (508) during a contention time slot when the subscriber unit (502) wishes to request a transmission channel to transmit data to the access point.

Abstract: A transmitting station side transmits a transmitting signal obtained by a process of segmenting transmission information into a plurality of frames, of encoding each frame, of power amplifying each encoded signal with different amplitude, and of interleaving all signals with each amplitude signal collected into one. A receiving station side reproduces of the above transmitting signal into original segmental frames by a process of de-interleaving the above transmitting signal, of successively decoding codes of the signal in descending order of SINR, and of re-encoding the decoded signal to successively cancel the re-encoded signal from the above transmitting signal.

Abstract: A method and device for reducing error components of a multi-channel modulator. The method comprises the steps of inverting substantially half of the channels of a modulator, and reducing error components between said inverted channels and said non inverted channels by inductive and/or capacitive summing. The method is especially suitable for synchronized pulses and similar signals to be modulated.

Abstract: Mixing circuitry for quadrature processing in communication systems and related methods are disclosed. The weighted mixing circuitry allows for arbitrary dividers to be utilized in generating the mixing signals for quadrature processing and thereby provides a significant advantage over prior architectures where 90 degree offset I and Q mixing signals were needed for quadrature mixing.

Abstract: Provided is a transmission circuit 1 which is capable of precisely compensating for an offset characteristic of an amplitude modulation section 15, and operating with low distortion and high efficiency over a wide output electric power range. A signal generation section 11 outputs an amplitude signal and an angle modulation signal. An amplitude amplifying section 14 inputs, to the amplitude modulation section 15, a signal corresponding to a magnitude of the amplitude signal having been inputted. The amplitude modulation section 15 amplitude-modulates the angle modulation signal with the signal inputted from the amplitude amplifying section 14, and outputs a resultant signal as a modulation signal. The power measuring section 18 measures an output power of the amplitude modulation section 15.

Abstract: An IQ modulator's performance is optimized through determination of suitable control parameters by the application of known DC biases as the I and Q inputs. Also known are the relative amplitude and actual phase of the sine and cosine carriers to be modulated before they are summed. It is shown that by measuring an RMS voltage Atotal an appropriate number of times for a related combination of the applied DC biases in conjunction with the other known input parameters, a number of behavior parameters that are indicative of mixer performance can be discovered through analysis, such as the solution of a system of linear equations. The combination of behavior parameters may be assigned a Figure Of Merit (FOM) that can be taken as an indication of the degree to which mixer operation approaches ideal behavior. The control parameters may be perturbed over a selected range, and the extraction of the behavior parameters repeated.

Abstract: A predistorer configured for use with an RF power amplifier having an input loop configured to be coupled to the input of the RF power amplifier and peak control circuit. Such an input loop includes a look-up table containing predistortion values to be applied to an input signal, in response to the power in the input signal, for forming a predistorted input signal. The predistorter may further include an output loop, such an output loop configured to measure an intermodulation distortion product of the RF power amplifier output resulting from the predistorted input signal, and operable to update the predistortion values in the look-up table. Such a peak control circuit configured to select a power supply voltage for the RF power amplifier in response to the power in the input signal.

Abstract: A multi-channel RF receiver uses an image rejection mixer (e.g. double quadrature mixer) in the IF down conversion stage for image side band rejection (whereby use of an IF narrow band filter for image rejection may be omitted if desired) and comprises a simplified frequency synthesizer which generates both a “wandering” IF oscillator frequency and an RF oscillator frequency for the up/down conversion stages (being, for down conversion, from RF to IF and from IF to base band. The IF used for a particular RF carrier (channel) is selected so as to be both an integer (N) sub-harmonic of that RF carrier and within the operating frequency band of the image rejection mixer. Advantageously, the synthesizer comprises only one loop and one VCO, wherein the IF oscillator signal is produced from the RF oscillator signal by means of a frequency divider.

Abstract: A single side band transmitter having reduced DC offset includes a current source modulation module, a current mirror module, a 1st mixing module, a 2nd mixing module, a summing module, and a power amplifier. The current source module is operably coupled to modulate, in accordance with a modulation protocol (e.g., FSK) data to produce an in-phase current component and a quadrature current component. The current mirror module is operably coupled to mirror the in-phase current component to produce a mirrored in-phase current component and is also operably coupled to mirror the quadrature current component to produce a mirrored quadrature current component. The 1st mixing module is operably coupled to mix the mirrored in-phase current component with an in-phase current component of a local oscillation to produce a 1st mixed current signal.

Abstract: Systems and methods for providing baseband predistortion within a transmitter. In a simplified embodiment, the transmitter contains a main signal path that receives an input signal and generates a main signal in response thereto. A filter in the main signal path is used for removing unwanted signal components from the main signal. A power amplifier having non-linearity is also located within the transmitter. A digital predistortion module is used by the transmitter to digitally process the input signal to generate a predistortion signal that models an inverse of the non-linearity of the power amplifier. In addition, means, located between the filter and the power amplifier, for combining the predistortion signal with the main signal to generate a combined signal, and for providing the combined signal to the power amplifier, is located within the transmitter.

Abstract: A phase-amplitude modulator for mobile communications employs a phase lock loop as an input to a nonlinear power amplifier providing phase information with amplitude information used to modulate the power amplifier output to synthesize phase-amplitude for the RF transmission signal.

Abstract: A polar loop transmitter circuit arrangement includes a circuit input, a circuit output, a controllable signal source, a modulator connected between the signal source and the output, a first amplifier having its input connected to the circuit input, a second amplifier having its input connected to the circuit output, and a comparator. Each amplifier preferably includes respective amplitude detector and signal modifier portions connected in series between their respective inputs and outputs. An output of each of the amplifiers is connected to a respective input of the comparator, and an output of the comparator is connected to a control input of the modulator. The amplifiers may each be characterized by transfer functions that are generally logarithmic. Each amplifier's signal modifier portion may further include an analog-to-digital converter, a digital signal modifier, and a digital-to-analog converter.

Abstract: A modulation circuit includes a band restriction filter 2, an attenuator 3, a modulator 4, a reference voltage generator 8, a comparing reference voltage generator 9, a voltage comparator 10 and an attenuator controller 7. The band restriction filter 2 receives modulation data. The attenuator 3 is connected to the band restriction filter 2 for adjusting its attenuation in response to an attenuator control signal. The reference voltage generator 8 is connected to the attenuator 3 for providing a reference voltage independent of a temperature and a power supply voltage to the attenuator. The comparing reference voltage generator 9 is connected to the reference voltage generator 8 for providing a comparing reference voltage independent of the temperature and the power supply voltage. The modulator 4 is connected to the attenuator 3.

Abstract: In an SSB transmitter, a problem such that the central frequency of a BPF for extracting one of sideband signals from the modulated signals obtained by modulating a carrier frequency signal by an input sound signal is changed by temperatures, causing a drop in suppression ration and a deterioration in sound is solved. The microcomputer circuit 23 determines the change of the central frequency (−&Dgr;&agr;) of the BPF 5 from the compensation table related to the BPF 5 stored in the ROM 32 based on a temperature information of the BPF 5 detected by the temperature sensor 21; controls local oscillators 4a and 7a that output modulated signals and VHF band signals to the balanced modulator 3 and the mixer 6; and changes the frequency of each signal by −&Dgr;&agr; from the standard condition.

Abstract: In a digital broadcast transmission system (60), a power amplifier (66) amplifies an information signal to a power level suitable to excite an antenna to emit a broadcast signal. Prior to, an subsequent to, the amplification processing circuitry (68, 70) processes the signal. In particular, the information signal is bandpass filtered. The power amplifier (66) causes non-linear distortion to the information signal. The processing circuitry (68, 70) causes linear distortions to the information signal. A single, memoryful filter (76) pre-distorts the information signal to compensate for all of the linear and non-linear distortions. Preferably, the memoryful filter (76) is a volterra filter. In another embodiment, a memoryful filter (112) pre-distorts an information signal to compensate for linear distortion from a power amplifier (102) and non-linear distortion from pre-amplification processing circuitry (104).

Abstract: A system and method for predistorting a signal which is to be amplified by a non-linear amplifier. The system and method uses additional predistortion circuits to eliminate the predistortion caused by amplifier input circuits and amplifier output circuits. In one aspect of the invention, the system and method uses a frequency response and phase corrector circuit to modify the amplitude versus frequency of the signal independent of phase.

Abstract: A modulated signal, having a varying magnitude signal envelope, is conditioned, such as to facilitate amplification (500). Minimum values are determined values for portions of the signal envelope (520, 530), and a window expansion function applied to scale each portion of the signal envelope having a minimum value below a particular threshold, such that each scaled portion has a new minimum value of at least the particular threshold (535, 540, 550, 555).

Abstract: An apparatus comprising a modulator circuit, a first and a second control circuit. The modulator circuit may be configured to generate a modulated differential output signal in response to a differential input signal. The first control circuit may be configured to control a first predistortion of the differential input signal in response to a first portion of the differential output signal. The second control circuit may be configured to control a second predistortion of the differential input signal in response to a second portion of the differential output signal.

Abstract: A device for linearizing a transmitter in a digital radio communication system. In the device, a predistortion lookup table stores predistortion data determined by measuring in advance distortion characteristics of the transmitter with respect to input baseband data. During transmission, the device synthesizes the input baseband data with the predistortion data to predistort the input data so as to compensate for the distortion characteristics caused by non-linear elements constituting the transmitter.

Abstract: A transmission front-end processor modulates the amplitude of a carrier wave with baseband data, and sets the power of the resultant modulated wave at a required value while controlling power leakage to adjoining channel to thereby output transmission data. The processor includes a first filter connected to an input terminal to which the baseband data are applied, for removing frequency components which would otherwise cause the power of the baseband data to leak to adjoining channels. The carrier wave and the baseband data passed through the first filter are applied to a power modulator. The power modulator controls the amplitude of the carrier wave with the baseband data, sets the power of the result of the control at the required value, and then outputs the power. A second filter removes higher order components from the carrier wave included in the output of the power modulator to thereby output the transmission data.