385 results about "Phase distortion" patented technology

A prefilter (5) for an audio system comprising a loudspeaker (1) in a room (2), which corrects both amplitude and phase errors due to the loudspeaker (1) by a linear phase correction filter response and corrects the amplitude response of the room (2) whilst introducing the minimum possible amount of extra phase distortion by employing a minimum phase correction filter stage. A test signal generator (8) generates a signal comprising a periodic frequency sweep with a greater phase repetition period than the frequency repetition period. A microphone (7) positioned at various points in the room (2) measures the audio signal processed by the room (2) and loudspeaker (1), and a coefficient calculator (6) (e.g. a digital signal processor device) derives the signal response of the room and thereby a requisite minimum phase correction to be cascaded with the linear phase correction already calculated for the loudspeaker (1). Filter (5) may comprise the same digital signal processor as the coefficient calculator (6). Applications in high fidelity audio reproduction, and in car stereo reproduction.

A wireless communication apparatus receives an quadrature modulated signal, generate a local signal having a frequency different from a center frequency of the quadrature modulated signal, performs quadrature demodulation on the quadrature modulated signal by using the local signal, to obtain an I channel signal and a Q channel signal, performs Fourier transform on the I channel signal and the Q channel signal, to obtain signals in a frequency domain, and calculates a first correction coefficient for correcting phase distortion and amplitude distortion caused by the quadrature demodulation by using pairs of signals among the signals, each of the pairs are located at symmetrical frequency positions with respect to the frequency of the local signal.

A method for an adaptive equalization apparatus in a multiple-link hopping radio system includes hopping among a plurality of radio links to receive variable-length bursts of radio signals on the plurality of radio links and equalizing amplitude and phase variations of a slow channel for each radio link from a received burst on the radio link. Further, the method includes storing the estimated tap coefficients pertinent to each radio link and using the tap weights of the current burst of the radio link to reliably pre-compensate the channel amplitude and phase distortion of a next received burst on the radio link.

A method of suppressing effects of aliasing in a system for digitally processing a high speed signal having a symbol rate of 1/T. The high speed signal is sampled at a fractional multiple (N) of the symbol rate, wherein 1<N<2, to generate a corresponding sample stream, and filtered using a low-pass filter characteristic having a cut-off frequency corresponding to 1/2T. Phase distortions due to the filtering are compensated by digitally processing the sample stream.

A power amplifier controller circuit controls a power amplifier based upon an amplitude correction signal indicating the amplitude difference between the amplitude of the input signal and an attenuated amplitude of the output signal. The power amplifier controller circuit comprises an amplitude control loop and a phase control loop. The amplitude control loop adjusts the supply voltage to the power amplifier based upon the amplitude correction signal. The amplitude correction signal may also be split into two or more signals with different frequency ranges and provided respectively to different types of power supplies with different efficiencies to generate the adjusted supply voltage to the power amplifier. The phase control loop adjusts the phase of the input signal based upon a phase error signal indicating a phase difference between phases of the input signal and the output signal to reduce phase distortion generated by the power amplifier.

Linearity of an RF/microwave power amplifier is enhanced by an amplitude and phase distortion correction mechanism based upon signal envelope feedback, that operates directly on the RF signal passing through the power amplifier. A phase-amplitude controller responds to changes in gain and phase through the RF/microwave power amplifier signal path caused by changes in RF input power, DC power supply voltages, time, temperature and other variables, and controls the operation of a gain and phase adjustment circuit, so as to maintain constant gain and transmission phase through the RF/microwave power amplifier.

A power amplifier controller circuit controls a power amplifier based upon an amplitude correction signal indicating the amplitude difference between the amplitude of the input signal and an attenuated amplitude of the output signal. The power amplifier controller circuit comprises an amplitude control loop and a phase control loop. The amplitude control loop adjusts the supply voltage to the power amplifier based upon the amplitude correction signal. The amplitude control loop may also compensate for impedance mismatch with the load by increasing the power delivered from the power amplifier to the load, or decrease the output power of the power amplifier upon detection of excessive power dissipation in the power amplifier. The phase control loop adjusts the phase of the input signal based upon a phase error signal indicating a phase difference between phases of the input signal and the output signal to reduce phase distortion generated by the power amplifier.

An adaptive free-space laser communication system and a method of communication between laser communication transceivers of the system. Communication channel condition information communicated via laser beams transmitted between a first laser communication transceiver and a second laser communication transceiver is monitored and the information is shared between the transceivers. A wave-front phase of the laser beams is shaped with wave-front correctors of the first and second laser communication transceivers.

A transmission signal to be transmitted from a radio transmitter is predistorted in order to compensate for the signal distortion caused by a power amplifier. The transmission signal and a signal modeling a power supply voltage applied to the power amplifier are compared with distortion properties of the power amplifier using these signals. The distortion information is comprised in an amplitude distortion lookup table and a phase distortion lookup table. Transmission signal and power supply signal values are associated with envelope and phase predistortion information comprised in the respective lookup tables and the envelope and the phase of the transmission signal is predistorted accordingly.

This invention relates to a multichannel sound field system with limited sound sources and an analog method for sound field including: a microphone array used in recording M paths of audio information and detecting the sound field property, an audio collection subsystem used in A/D conversion of each channel audio information, packing audio data, channel number and timestamps, a server processing audio data of the microphones, finishing separation and process of sound source and compressing and storing the data and mixing the sound source data and converting them to the output data and control signals of N paths of loudspeakers, an audio recovery subsystem forming multichannel analog signals with the audio data of different sound sources and controlling synchronization of the loudspeakers and a loudspeaker array used in playing N paths of audio signals.

The invention relates to a self-adapting method for filtering vehicle dynamic shaft load signal, aiming to effectively eliminate weighing error due to vehicle dynamic load and remarkably improve the vehicle weighing accuracy. The invention processes the original shaft load signal by zero phase offset and low-pass filtering, so as to eliminate white noise interference and inhibit phase distortion of the shaft load signal during low-pass filtering process. The invention also adopts optimized cut-off to the original weighing signal by searching average value of extreme points of shaft load signal, so as to better inhibit gravitation impulse interference in the weighing signal. Further, the invention decomposes the weighing signal by empirical mode decomposition method, meanwhile, adopts end point continuation method in empirical mode decomposition, so as to eliminate end effect, effectively inhibit the generation of false mode and make the decomposed result relatively true. The invention eliminates low-frequency interference through empirical mode decomposition, so as to obtain true shaft load signal.

An objective is to provide a digital receiver and a method of compensating waveform that are capable of compensating waveform distortion without increasing the circuit size. A digital receiver 100 according to the present invention includes distortion compensation filters 103 that compensate waveform distortion included in an input signal, skew compensation amount setting units 106 for setting a skew compensation amount used for compensating phase distortion among the waveform distortion, amplitude compensation amount setting units 107 for setting an amplitude compensation amount used for compensating amplitude of the input signal that attenuates upon the compensation of the phase distortion using the skew compensation amount, and filter coefficient calculation circuits 108 for determining a filter coefficient to be set to the distortion compensation filters 103 based on the skew compensation amount and the amplitude compensation amount.

An automatic frequency controller includes a frequency offset estimating section that calculates phase distortion quantities and the average thereof from known signals contained in a received signal. The frequency offset estimating section obtains, from the average distortion quantity, signal powers corresponding to a plurality of candidate frequency offsets set at frequency offset estimation accuracy intervals in a frequency offset estimation range. The frequency offset estimating section looks at the signal powers through a frequency window with a frequency width corresponding to a transmission path state. This makes it possible to maximize the signal power of a frequency of a radio wave or radio waves corresponding to the transmission path state, and to place the radio wave or radio waves corresponding to the transmission path state as a frequency controlled object. This can improve demodulation accuracy. Fine adjustment of the candidate frequency offsets can improve the estimation accuracy of the frequency offset without changing the frequency offset estimation range.

The invention discloses a space phase compensation system in orbital angular momentum optical communication, and a method thereof, and relates to the liquid crystal space spatial modulation technology, and in particular to phase compensation of vortex beams in space optical communication. The system comprises a light source, a modulation OAM, mode multiplexing, a free space, a demodulation OAM andcoherent detection, which communicate with each other in sequence; and any beam phase reflected by a liquid crystal spatial light modulator is compensated on a sending end and a receiving end by using an iterative phase recovery algorithm, thereby improving the imperfect state of the symmetry of the vortex beams caused by atmosphere turbulence, improving the quality of the beams and facilitatingthe subsequent utilization and transmission.Compared with the prior art, the space phase compensation system disclosed by the invention realizes the phase distortion existing in a stepwise correctionspatial optical communication system, (2) improves the quality of the generated vortex beams and the quality of receiving demodulation to a certain extent,comprehensively improves the signal to noiseratio of the whole system and reduces the bit error rate; and the space phase compensation system is simple in structure and is easy to implement.

The invention relates to the technical field of lasers, and discloses a device and method for controlling quality of a laser beam. The device comprises a gain medium, a pumping source, a first optical element, a second optical element, a detector and a controller, wherein the grain medium is arranged on a laser path, the controller is connected with the pumping source, pumping lights enters the gain medium through the first optical element, laser enters the second optical element after being transmitted by the first optical element, and the controller is connected with the first optical element and is used for controlling the first optical element to regulate the light intensity distribution of the pumping light. According to the invention, the grain medium is arranged on the laser path and can absorb the pumping light, and the controller controls the light intensity distribution of the pumping lights so regulate the light intensity distribution of the lasers, thus the quality of the laser beam is improved; furthermore, a laser wave front corrector is additionally arranged, and the phase distortion of the lasers can be compensated simultaneously so that the quality of the laser beam is further improved.

The application discloses an adaptive biasing radio frequency power amplifier comprising a biasing circuit and a power level amplifying circuit. The biasing circuit is used for providing dynamic bias voltage for a transistor II in the power level amplifying circuit; the work voltage I is connected to one end of a resistor I; the other end of the resistor I is used as an output end of the biasing circuit; the work voltage II is connected to the anode of a diode I; the cathode of the diode I is connected to the output end of the biasing circuit; the value of the work voltage II makes the diode I in a default critical conduction status. the power level amplifying circuit comprises a transistor I and the transistor II, which adopt common source and common gate structures; the transistor I adopts common source connection and the grid of the transistor I receives radio frequency input signals; the transistor II adopts common grade connection and the drain electrode of the transistor II outputs drain voltage II. The application provides adaptive biasing voltage postponing gain compression and reducing phase distortion caused by non-linear capacity.

The invention relates to a circuit capable of improving the linearity of a power amplifier. The circuit comprises a power amplifier circuit, wherein a linearity compensating circuit is arranged at the front end of the power amplifier circuit and comprises a current source, a voltage clamp transistor, a state compensating transistor and an isolation resistor, the current source and the voltage clamp transistor are connected to the ground in series and provide bias voltage for the power amplifier circuit, the isolation resistor is connected between the current source and the signal input end of the power amplifier circuit in series, the state compensating transistor is connected between the current source and the signal input end of the power amplifier circuit in series, and the voltage clamp transistor and the state compensating transistor can be diodes, audios, NMOS tubes and the like. The amplitude distortion and phase distortion generated by the power amplifier can be compensated effectively through the simulated predistortion technology. The circuit is simple in structure, convenient to control, and easy to integrate and implement, and the effect of improvement on the linearity of the power amplifier is remarkable.

A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orientation, determining angles of incidence of incoming GNSS satellite signals with respect the antenna array and calculating expected carrier phase differences between respective pairs of antennas, calculating measured carrier phase differences between the respective pairs of antennas, and determining carrier phase difference errors using the expected and measured carrier phase differences. The carrier phase difference errors are then recorded in the look-up mechanism, with the maps and, as appropriate, look-up tables for the respective pairs of antennas being indexed by angles of incidence. Thereafter, the system utilizes the look-up mechanism when determining the unknown orientation of the antenna structure. For respective pairs of antennas, the system enters the look-up mechanism based on angles of incidence determined from a calculated orientation, and uses the retrieved values in the calculation of a corrected orientation, to compensate for phase distortion.

An OFDM receiver apparatus comprises a receiver to receive an OFDM signal, an estimator to estimate a distortion, a distortion compensator subjecting the sub-carrier to distortion compensation according to a control signal to generate a distortion-compensated sub-carrier, a demodulator to demodulate the distortion-compensated sub-carrier, an estimator to generate first phase distortion information, using the distortion-compensated sub-carrier and the distortion information, a weighting synthesizer to weight the first phase distortion information by weighting factors with time function over symbol intervals and then synthesize the first phase distortion information, to generate second phase distortion information, and a control signal generator to generate the control signal using the distortion information and the second phase distortion information.