Abstract: Examples of front-end modules, apparatuses and methods for coupling compensation in a closed-loop digital pre-distortion (DPD) system are described. The closed-loop DPD circuit may include a PA and a loopback path. The PA may receive a PA input signal and amplify the PA input signal to provide a PA output signal proportional to a product of the PA input signal and a gain of the PA. The loopback path may receive the PA output signal to output a loopback signal. A forward coupling and a backward coupling may exist between the PA input signal and an output of the loopback path. The output of the loopback path may be proportional to a product of the PA output signal and a gain of the loopback path. The loopback path may include a coupling cancellation mechanism configured to cancel couplings between the PA input signal and the loopback signal.

Abstract: It is intended to provide a transmitter capable of correcting signal distortion with high accuracy. Provided are a test signal generator; a frequency characteristics corrector for correcting an amplitude characteristic and a phase characteristic of a test signal; a modulator; an envelope detector; a frequency characteristics calculator for calculating frequency characteristics of an envelope signal; and a coefficients calculator for calculating, on the basis of the frequency characteristics, correction coefficients to be used for correcting the amplitude characteristic and the phase characteristic of the test signal. The test signal generator generates a test signal in which signal loci in each of at least two pairs of quadrants of first to fourth quadrants of the IQ plane are not symmetrical with each other.

Abstract: Disclosed is a transmission apparatus, a radio communication apparatus, and a transmission method for making it possible to obtain stable characteristics by controlling the difference of time between an amplitude signal and a phase signal to an optimal point, without depending on a modulated signal nor making the circuit size larger. A multiplier (170) generates, in a pseudo manner, a digital modulated signal corresponding to a signal that is obtained by performing analog to digital conversion on a modulated signal that is generated by an amplitude modulator (140), by multiplying a digital amplitude signal that is obtained by performing analog to digital conversion on an amplitude signal by a digital angle modulated signal corresponding to a signal that is obtained by performing analog to digital conversion on an angle modulated signal.

Abstract: A transmitter compensates for AM/PM distortion and operates with low distortion and high efficiency. A compensation section calculates an amplitude signal M representing the magnitude of a vector consisting of IPL and QPL signals which pass through LPFs, respectively, thereby predicting variation of the envelope of a radio frequency signal Pi, which variation occurs due to Ip? and Qp? signals passing through LPFs, respectively. The compensation section calculates a phase compensation amount ?comp, based on the calculated amplitude signal M, and adds the phase compensation amount ?comp to a phase signal ?.

Abstract: It is intended to provide a transmitter capable of correcting signal distortion with high accuracy. Provided are a test signal generator; a frequency characteristics corrector for correcting an amplitude characteristic and a phase characteristic of a test signal; a modulator; an envelope detector; a frequency characteristics calculator for calculating frequency characteristics of an envelope signal; and a coefficients calculator for calculating, on the basis of the frequency characteristics, correction coefficients to be used for correcting the amplitude characteristic and the phase characteristic of the test signal. The test signal generator generates a test signal in which signal loci in each of at least two pairs of quadrants of first to fourth quadrants of the IQ plane are not symmetrical with each other.

Abstract: Disclosed are an angle modulator, a transmission apparatus, and a radio communication apparatus that can compensate phase discontinuity when an operational mode of a voltage controlled oscillator is switched. Angle modulator (100) includes phase difference detection section (150) that detects a difference of phases between an input signal of subtractor (141) and an angle modulated signal, using the result of subtraction by subtractor (141) of frequency locked loop circuit (140); correction control section (160) that generates a control signal for compensating that difference of phases based on that difference of phases; correction section (120) that corrects the phase of the angle modulated signal by adding the control signal to an input signal of angle modulator (100), an input signal of loop filter (142), or an input signal of VCO (143) during a predetermined period after VCO (143) switches the operational mode (from time t3 to time t4).

Abstract: A transmitter includes: a decoder for transforming an IQ signal into a linear sum of two vectors which have non-negative coefficients, respectively, which form an angle of (?/4), and which are included in eight vectors representing directions indicated by eight angles of (??/2), 0, (?/2), ?, (?3?/4), (??/4), (?/4), and (3?/4), respectively, and for outputting information upon magnitudes and angles of the two vectors; a phase generator for generating eight phase signals corresponding to phases of (??/2), 0, (?/2), ?, (?3?/4), (??/4), (?/4), and (3?/4), respectively, and outputting the eight phase signals; and a selector for selecting two phase signals having phases equivalent to angles of the two vectors, from among the eight phase signals, and amplifying the two phase signals having been selected, based on the information upon the magnitudes and the angles, and outputting, as a plurality of amplification signals, the two phase signals having been amplified.

Abstract: Phase errors are reduced in an RFDAC. The RFDAC includes: a multi-phase radio-frequency signal generator that generates multiple radio-frequency signal pairs each having a phase difference of ?; a vector selector that combines each of the multiple radio-frequency signals which has passed through at least one path; a test signal generator that generates a test signal; a multiplexer that selects either the test signal or the baseband signal; a vector controller that controls the vector selector so as to select a path for each of the multiple radio-frequency signal pairs; a detector that detects output signals outputted from the vector selector; a calibrator that, based on the output signals, calculates a calibration coefficient of a phase error between the radio-frequency signals of each of the multiple radio-frequency signal pairs, and calibrates the multiple radio-frequency signals or the baseband signal.

Abstract: A transmission circuit that performs modulation based on a phase difference signal and an amplitude signal includes an asymmetrical phase rotation device. The asymmetrical phase rotation device performs an operation of subtracting 2? from a value of the phase difference signal when the value of the phase difference signal is greater than a predetermined positive threshold value, or an operation of adding 2? to the value of the phase difference signal when the value of the phase difference signal is less than a predetermined negative threshold value. Accordingly, the transmission circuit has distortion reduction characteristics improved uniformly over a range of frequencies higher or lower than a carrier wave band.

Abstract: The RFDAC includes: a multi-phase radio-frequency signal generator configured to generate radio-frequency signals that are different in phase; a vector selector configured to select two radio-frequency signals therefrom, cause each of the two radio-frequency signals to pass through at least one transmission path, combine the two radio-frequency signals; a test signal generator configured to output a test signal; a multiplexer configured to select either the test signal or the baseband signal; a vector controller configured to control the vector selector based on the selected signal and a predetermined selection pattern such that the two radio-frequency signals, and transmission paths thereof are selected; a detector configured to detect an output signal from the vector selector; and a calibrator configured to calibrate a phase error between the selected two radio-frequency signals, based on an envelope of the output signal.

Abstract: A communications transmitter configured to reduce the average-to-minimum magnitude ratio (AMR) of a communications signal includes a symbol mapper, a pulse-shaping filter, an AMR reduction circuit, and a modulator. The symbol mapper operates to generate a sequence of symbols from a binary-source data stream containing a message to be transmitted, and the pulse-shaping filter generates a baseband signal based on the sequence of symbols. The AMR reduction circuit is configured to compare a magnitude of a local minimum of samples of the baseband signal to various magnitude threshold levels, and to modify the baseband signal in one of two manners depending on the relationship of the magnitude of the local minimum and the various threshold levels. Finally, the modulator operates to modulate a carrier signal based on the modulation information contained in the modified baseband signal.

Abstract: A transmitter includes: a decoder for transforming an IQ signal into a linear sum of two vectors which have non-negative coefficients, respectively, which form an angle of (?/4), and which are included in eight vectors representing directions indicated by eight angles of (??/2), 0, (?/2), ?, (?3?/4), (??/4), (?/4), and (3?/4), respectively, and for outputting information upon magnitudes and angles of the two vectors; a phase generator for generating eight phase signals corresponding to phases of (??/2), 0, (?/2), ?, (?3?/4), (??/4), (?/4), and (3?/4), respectively, and outputting the eight phase signals; and a selector for selecting two phase signals having phases equivalent to angles of the two vectors, from among the eight phase signals, and amplifying the two phase signals having been selected, based on the information upon the magnitudes and the angles, and outputting, as a plurality of amplification signals, the two phase signals having been amplified.

Abstract: The present invention provides a DAC (Digital to Analog Converter) capable of generating a transfer function having a notch for reducing an error signal level in a desired frequency band. The DAC of the present invention includes a switch bank to which at least two reference signals are inputted and which selects any of these signals and outputs the selected signal through a plurality of paths, and an amplitude-phase control section which controls a reference signal selection operation of the switch bank on the basis of an input signal.

Abstract: A low cost high-efficiency all-digital transmitter using all-digital power amplifiers (“DPA”) and various mapping techniques to generate an output signal, which substantially reproduces a baseband signal at a carrier frequency. A baseband signal generator generates a baseband signal which is quantized by a signal processor using a quantization map. A DPA control mapper outputs control signals to phase selectors using the quantized signal and a quantization table. Each phase selector receives one of the control signals and outputs a waveform at a carrier frequency with a phase corresponding to the control signals, or an inactive signal. Each DPA in a DPA array has an assigned weight, receives one of the waveforms from the phase selectors, and outputs a power signal according to the weight of the DPA and the phase of the received waveform. The combined power signal substantially reproduces the baseband signal at the carrier frequency.

Abstract: The present invention provides a DAC (Digital to Analog Converter) capable of generating a transfer function having a notch for reducing an error signal level in a desired frequency band. The DAC of the present invention includes a switch bank to which at least two reference signals are inputted and which selects any of these signals and outputs the selected signal through a plurality of paths, and an amplitude-phase control section which controls a reference signal selection operation of the switch bank on the basis of an input signal.

Abstract: The disclosure relates to a method and apparatus for providing efficient signal transmission. Conventional linear amplifiers are most efficient when operated in compressed mode. In the compressed mode, the digital power amplifier switches between the on and off modes. A digital power amplifier operates in compressed mode only if the incoming signal is an on-off constant envelop signal. In one embodiment, the disclosure provides a method and apparatus for converting a digital baseband signal to on-off constant envelop signals for processing through binary-weighted or thermometer-weighted amplifier which are operated in compressed mode.

Abstract: A nonlinear filter includes: a determination unit that determines, based on I and Q signals inputted into the determination unit, whether or not to perform pulse insertion; a rotation detector that detects a rotation direction of the I and Q signals on an IQ plane with respect to the origin of the IQ plane; a pulse generator that generates, when the determination unit determines to perform the pulse insertion, a pulse of which at least one of the direction and the magnitude is determined in accordance with at least the detected rotation direction; and an adder that inserts the pulse into the I and Q signals and outputs resultant I and Q signals.

Abstract: Provided is a transmitter that compensates for AM/PM distortion and operate with low distortion and high efficiency. A compensation section 22 calculates an amplitude signal M representing the magnitude of a vector consisting of IPL and QPL signals which pass through LPFs 14 and 15, respectively, thereby predicting variation of the envelope of a radio frequency signal Pi, which variation occurs due to Ip? and Qp? signals passing through LPFs 12 and 13, respectively. The compensation section 22 calculates a phase compensation amount ?comp, based on the calculated amplitude signal M, and adds the phase compensation amount ?comp to a phase signal ?.

Abstract: An amplitude signal and a frequency signal are generated through processing of data. The frequency signal is angle modulated. The amplitude signal is adjusted based on a delay time and is amplitude amplified. The resultant signal from the angle modulation is amplitude modulated based on the resultant signal from the amplitude amplification to obtain a modulated signal. The modulated signal is used to calculate a delay between the amplitude signal and the frequency signal, which is used for feedback control of the delay time by which the amplitude signal is adjusted until no delay exists only in a test period. Through the signal generating, a sinusoidal signal is outputted as each of the amplitude signal and the frequency signal during the test period.

Abstract: A signal generation section generates an amplitude signal and an angle-modulated signal. An adaptive compensation filter performs waveform shaping on the amplitude signal in accordance with a magnitude of the amplitude signal. An amplitude amplification section outputs a signal proportional to a magnitude of the signal subjected to waveform shaping in the adaptive compensation filter. An amplitude modulation section amplitude-modulates the angle-modulated signal by the signal outputted from the amplitude amplification section and outputs the resulting signal as a modulated signal. Characteristics of the adaptive compensation filter are inverse characteristics of transfer characteristics from an input of the amplitude amplification section to an output of the amplitude modulation section.