Abstract: Disclosed herein is a demodulator, including: a splitting/matching section for carrying out a matching process of making the amplitude and phase of a first modulated signal match respectively the amplitude and phase of a second modulated signal; and a demodulation section for generating a demodulated signal on the basis of the first modulated signal and the second modulated signal, which have been subjected to the matching process carried out by the splitting/matching section, wherein the splitting/matching section has a splitting section, a first matching section, and a second matching section, the first circuit-element constants determining the first input impedance of the first matching section and the second circuit-element constants determining the second input impedance of the second matching section are set at values determined in advance in order to make the first input impedance equal to the second input impedance.

Abstract: In accordance with some embodiments, methods for controlling the second order intercept point in a receiver are provided, the methods comprising: generating an amplitude modulated test tone; causing the test tone to be received by a receiver; determining a characteristic of a second order intercept point of the receiver based on the received test tone; and based on the characteristic, adjusting a parameter of the receiver. In accordance with some embodiments, systems for controlling the second order intercept point in a receiver are provided, the systems comprising: a test tone generator that generates an amplitude modulated test tone; a receiver that receives the test tone; a correlator that determines a characteristic of a second order intercept point of the receiver based on the received test tone; and digital logic that, based on the characteristic, adjusts a parameter of the receiver.

Abstract: A receiver estimates I/Q imbalance in I and Q input signals using circuitry to separate different frequency components of the I and Q input signals, and estimation circuitry arranged to estimate I/Q imbalance at the different frequency bands. The separating of the bands may be carried out in the frequency domain, and may involve combining corresponding values representing corresponding negative and positive frequency bands, and converting the separated frequency domain representations to a time domain representation before the estimation. The estimated imbalance may be used to correct the I and Q signals at the different frequency bands.

Abstract: A system for reducing signal interference in modulated signal communication includes a measurement processor. The measurement processor measures amplitudes of noise components of a received amplitude modulated signal prior to demodulation. The measurement processor also identifies a frequency of a noise component having an amplitude larger than the amplitude of another noise component. A carrier frequency generator generates a carrier frequency substantially at a harmonic of the identified noise component. The carrier frequency is used to generate and demodulate the amplitude modulated signal.

Abstract: An algorithm for correcting the output of an analog I/Q demodulator without the need for calibration or storing state information. The output of the analog I/Q demodulator is digitized, and the discrete-time samples are divided into segments. A digital frequency transform (e.g., a Discrete Fourier Transform) is computed for each segment. The effects of the non-ideal I/Q demodulator are removed by identifying a set of image frequency candidates for each digital frequency transform, and for each image frequency candidate, estimating a set of demodulator imbalance parameters to characterize the demodulator imbalance at that frequency and correcting the digital frequency transform at the image frequency candidate using the imbalance parameters in order to minimize the effects of the imbalance. Each digital frequency transform is corrected independently and consequently no persistent state information needs to be saved between transforms.

Abstract: An algorithm for correcting the output of an analog I/Q demodulator without the need for calibration or storing state information. The output of the analog I/Q demodulator is digitized, and the discrete-time samples are divided into segments. A digital frequency transform (e.g., a Discrete Fourier Transform) is computed for each segment. The effects of the non-ideal I/Q demodulator are removed by identifying a set of image frequency candidates for each digital frequency transform, and for each image frequency candidate, estimating a set of demodulator imbalance parameters to characterize the demodulator imbalance at that frequency and correcting the digital frequency transform at the image frequency candidate using the imbalance parameters in order to minimize the effects of the imbalance. Each digital frequency transform is corrected independently and consequently no persistent state information needs to be saved between transforms.

Abstract: A radio transmitter has a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. A nonlinearity-caused distortion compensating system provided in the radio transmitter includes a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other. First distortion compensating coefficients are determined in response to the calculated power-related value. The first distortion compensating coefficients are designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion. Second distortion compensating coefficients are determined in response to the calculated power-related value. The second distortion compensating coefficients are designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier.

Abstract: A reference generator includes a memory that stores reference data which, when clocked out of the memory, produces an ATSC compliant VSB reference signal substantially free of sub-harmonics of the clock signal. A digital-to-analog converter converts the clocked out reference data to an analog signal. The analog signal may be at low IF. An up converter is arranged to upconvert the output of the digital-to-analog converter to an RF reference signal. The RF reference signal can be used, for example, to calibrate a VSB demodulator.

Abstract: In a circuit arrangement for demodulating an intermediate-frequency video signal generated while using a Nyquist edge, having a phase-locked loop (1) including a phase detector (3), a loop filter (4) and a voltage-controlled oscillator (5), and a video demodulator (2), the intermediate-frequency video signal being applied to the phase detector (3) and the output signal of the phase-locked loop (1) being applied to the video demodulator (2), which converts the intermediate-frequency video signal into a baseband video signal, phase fluctuations contained in the carrier of the intermediate-frequency video signal due to its generation while using a Nyquist edge are compensated in that the phase comparator (3) operates, by approximation, independently of modulation in the control range of the intermediate-frequency video signal, in that the baseband video signal is present in an inverted form with respect to the intermediate-frequency video signal, and in that a correction signal is derived from the baseband video

Abstract: A reference signal source produces a substantially distortion free reference signal which is supplied to a demodulator that is arranged to demodulate the substantially distortion free reference signal. A calibration filter and an equalizer are included downstream of the demodulator. A controller sets the calibration filter to initially pass the reference signal to the equalizer without substantial change to the reference signal. The controller subsequently calibrates the calibration filter in accordance with the demodulator caused distortion reduced by the equalizer.

Abstract: An improved superregenerative detector including input elements for receiving a high frequency carrier signal having an amplitude envelope upon which an information signal is impressed, the detector also including a first and a second oscillator and output elements for producing an output signal corresponding to the information signal. The detector features use of feedback components among the output elements, the feedback components including an operational amplifier and reference signal connected to the first and second oscillators such that the output signal of the operational amplifier may be used to constrain a transistor that defines the first amplifier to operate within its linear portion.