64 results about "Complex gain" patented technology

A digital direct conversion receiving apparatus, including: a phase conversion unit to down-convert a Radio Frequency (RF) signal into a plurality of sample signals, and generate a certain phase difference among the plurality of sample signals when the RF signal is down-converted; and a variable complex gain unit to remove an image component from the plurality of sample signals using the generated phase difference.

Symbols are transmitted in a Cartesian transmitter by pre-distorting an input signal X having in-phase and quadrature components using a first compensation lookup table operable to hold complex valued entries to carry out in-phase and quadrature compensation pre-distortion with respect to the input signal to form a pre-distorted signal Z. The pre-distorted signal Z is processed to form an output signal Y using a nonlinear element. A complex gain normalization parameter adaptively updated to reflect varying gain of a linear region of the nonlinear element. A normalized feed back signal {tilde over (Y)} is formed using the adaptively updated complex gain normalization parameter. The first compensation lookup table is updated based on the pre-distorted input signal Z and the adaptively normalized feedback signal {tilde over (Y)}.

A physical layer (PHY) module includes N_T radio frequency (RF) channels and a mapping module. The N_T RF channels each include N subcarriers. The mapping module includes N_s inputs receiving corresponding ones of N_S data streams. The mapping module further includes N_T outputs communicating with corresponding ones of the N_T RF channels. Each of the N_T outputs includes N outputs. The mapping module further includes a mapping matrix that maps the N_S data streams to the N_T outputs. N_T, N_S, and N are integers greater than or equal to 2. The N_T RF channels include N_T gain modules that apply N_T different complex gains to the N_T outputs, respectively. One of the N_T different complex gains is applied to each of the N outputs of a corresponding one of the N_T outputs. The N_T different complex gains correspond to N_T transmit antennas of the N_T RF channels, respectively.

An iterative arrangement of channel estimator (12), a Kalman filter unit (14), and a soft demodulator (16) is provided for producing an estimate of complex gain of a CDMA communications channel carrying data and pilot channels, and demodulated data of the data channel. An initial channel estimate is produced by the estimator (12) using only the low-power pilot channel. This later is improved by the iterative process using the data channel. The complex gains is represented by a sum of sinusoidal signals with different frequencies and randomly variable amplitude and phase.

A bank of complex gain elements is used to provide a step-wise approximation of an arbitrary complex-gain predistortion function for a nonlinear transmitter. The bank of gain elements is in an adaptive loop realizing adaptive control. The adaptive loop is closed between an Input of the gain bank and an output of the transmitter through a linear receiver at an adaptive controller composed of a bank of proportional-integral (PI) controllers. The real and imaginary parts of each predistortion gain element are controlled by a corresponding adaptive PI controller. The signals processed by the adaptive controller are represented in orthogonal coordinates in terms of real and imaginary number pairs of complex numbers. The adaptive controller achieves unconditionally stable operation independently from the arbitrary phase rotation in the input signal or the adaptive loop.

A method for calibration of a magnetic resonance imaging system having a bore, a body coil mounted in the bore, a patient mat, a number of local coils mounted in the patient mat, an upconversion stage having a number of upconverters, and a processing stage, includes the steps of generating a calibration signal in the body coil; receiving the calibration signal at the local coils, upconverting the signal from the local coils in the upconversion stage, transmitting the upconverted signal to the processing stage, synchronously downconverting the signal in the processing stage using the calibration signal generated in the body coil, and processing the downconverted signal to generate an overall path complex gain.

The invention discloses a method for realizing fast channel estimation in a DMB-T system by using an FWT, which realizes multipath acquisition by using the FWT. The steps for related to the matching of a PN sequence are as follows: a cyclic convolution with length of N receives signal vector sequence r, and the signal vector sequence r is transformed into time-domain channel impulse response h; the strong number S and the corresponding impulse response hsi are obtained. The interference cancellation steps are as follows: as for all strong impulse response complex gains, the interference is entirely cancelled through all strong interference components hsi, and a real channel impulse response sequence h and the channel transmission function H (omega) are obtained. The method has the advantages that the computational complexity can be effectively reduced, the hardware realization is simple, and the method is suitable for matching related system by using by using the periodic PN sequence, for example, the receiving system of DMB-T digital terrestrial broadcasting.

An echo cancellation circuit for an RFID reader and the method thereof are provided. The echo cancellation circuit includes a gain calculator, a gain adjustment circuit, and a subtraction circuit. The gain calculator provides a complex gain value according to a carrier signal and a received signal through an adaptive algorithm. The gain adjustment circuit is coupled to the gain calculator. The gain adjustment circuit multiplies the carrier signal by the complex gain value, and outputs the result of the multiplication. The subtraction circuit is coupled to the gain adjustment circuit. The subtraction circuit subtracts the output of the gain adjustment circuit from the received signal, and then provides the result of the subtraction as the output signal of the echo cancellation circuit.

The embodiment of the invention provides a predistortion feedback method, an apparatus and a system, relating to the communication field, which reduces bandwidth of an AD converter in a predistorter and further reduces cost of the predistortion technology. The predistortion feedback method of the embodiment comprises: acquiring original signals from a base band; adopting preset strategy, acquiring values of time delay and complex gain demanded for processing the original signals; according to the values of time delay and complex gain, performing time delay and complex gain on the original signals; converting the original signals through time delay and complex gain into the simulation signals; substracting the feedback signals through down-conversion from the simulation signals to obtain the error signals; transmitting the values of the time delay and the complex gain to the predistorter, transmitting the error signals to the AD converter in the predistorter, to cause the predistorter to generate the predistortion signals according to the values of the time delay and the complex gain.

An equalizer equalizes a received orthogonal frequency division multiplex (OFDM) signal which includes periodic pilot symbols. The equalizer includes a channel estimation unit which estimates a frequency response the received OFDM signal, and an equalization circuit which equalizes the received OFDM signal in accordance with the frequency response estimated by the channel estimation circuit so as to output a resultant equalized OFDM signal. The channel estimation circuit determines complex gain amounts of respective propagation channels of the OFDM signal based on the pilot symbols, applies the complex gain amounts to a window function circuit which passes given complex gain amounts among the complex gain amounts which are contained within a predetermined time region window, and computes the frequency response based on the given complex gain amounts which are contained within the predetermined time region window.

In an equalizer, an scattered pilot (SP) extractor in a channel estimator extracts an SP symbol from an input signal, an IDFT circuit calculates from the SP a complex gain of each path, and a threshold comparator and a “0” addition circuit extract signals of paths. An FFT circuit Fourier-transforms signals of the paths. A multiplier in an operational equalizer multiplies a complex conjugate signal of a transmission line estimation in the path on which the Fourier-transform was made and the input signal to output the product to the coordinate corrector. A coordinate threshold generator multiplies the transmission line estimation by the complex conjugate signal to generate power of a coordinate threshold to output the power to a window function circuit, which corrects the power value to supply the value to the coordinate corrector. The corrector corrects the amplitude of the modulation coordinate in the product to output the amplitude.

Antenna system having an antenna array with multiple sub-arrays, each having one or more antenna elements, is calibrated using a distributed calibration antenna element, such as a leaky coaxial cable, that spans across at least two and possibly all of the sub-arrays. To calibrate the transmit (TX) paths of the sub-arrays, TX calibration test signals are transmitted by the sub-arrays, captured by the distributed calibration element, and processed by a corresponding calibration radio. To calibrate the receive (RX) paths of the sub-arrays, an RX calibration test signal is generated by the calibration radio, transmitted by the distributed calibration element, captured by the sub-arrays, and processed by their corresponding radios. Cross-correlation between the calibration and captured signals is performed to derive the complex gain of each sub-array transmitter and receiver, which provides information for aligning the gain, phase, and delay of the different TX and RX paths of the antenna array.

An adaptive predistorter for applying a predistortion gain to an input signal to be amplified by a power amplifier having a variable supply voltage, the predistorter including: a predistortion gain block adapted to apply a complex gain to a complex input signal; a first table implemented in a first memory and comprising a 2-dimensional array of cells storing complex gain values, the first table adapted to output the complex gain values based on an amplitude of the input signal and the value of the variable supply voltage of the power amplifier; and a second table implemented in a second memory and including a 2-dimensional array of cells storing gain update values for updating the complex gain values of the first table, the gain update values being generated based on an output signal of said power amplifier.

The invention provides a light-emitting material and a preparation method thereof. The light-emitting material includes an organic complex; the organic complex is composed of tetrapyrrole macrocyclicligand A, rare-earth ion Ln and deuterated or halogenated tripodal ligand B. The organic complex gains increased external quantum dot efficiency and improved light emergence stability; near-infrared light (800-1600 nm) can be emitted efficiently under purple and blue light excitation; external quantum efficiency is high, light emission life is long, wherein the external quantum efficiency may reach 0.63 and above. In addition, emitting peak position and width can be regulated and controlled through different rare-earth ion or rear-earth ion combinations so as to improve the light-emitting performance of the light-emitting material. The light-emitting material has a promising application prospect in fiber-optic communication, biological imaging, signal conversion and amplification and component analysis fields.

The invention belongs to the technical field of non-linear distortion of traveling-wave tubes, particularly relates to a fast three-order intermodulation calculation method of a traveling-wave tube and is used for overcoming the defect that three-order intermodulation calculation of an existing traveling-wave tube is low. The method includes the steps that firstly, the center frequency of two input frequencies serves as input signal frequency, input power scanning is conducted, gain curve and phase shift curve data are obtained, and thereby complex gain curve data are obtained; then, the data are introduced into a calculation formula, rapid calculation is conducted, and output power of the two input frequencies and the three-order intermodulation output power are obtained under a specific field magnitude value; finally, the field magnitude value is scanned, and the fundamental wave output power under all input power and the three-order intermodulation output power can be obtained. According to the fast three-order intermodulation calculation method, power scanning needs to be conducted once under a single frequency, then, the three-order intermodulation under all input power can be fast solved through the formula, a one-dimension model only needs several seconds, and a three-dimension model only needs several minutes; three-order intermodulation optimization calculation efficiency is greatly improved.

In an equalizer circuit of one aspect, a first Fourier transform circuit Fourier-transforms an input signal and outputs a corresponding first Fourier-transformed signal, and a first extracting circuit extracts a plurality of pilot symbols from the first Fourier-transformed signal. An inverse Fourier transform circuit calculates a complex gain of each path of the input signal by inverse-transforming the plurality of pilot symbols extracted by the first extracting circuit. A detecting circuit detects at least one of a power value and a mean amplitude of the input signal, and a coefficient determining circuit determines a coefficient corresponding to the at least one of the power value and the mean amplitude detected by the detecting circuit. A second extracting circuit extracts complex gains having a power larger than a threshold obtained by multiplying the coefficient determined by the coefficient determining circuit by a value obtained by integrating the power for a period of time, wherein the power is obtained from the complex gains of each path of the input signal calculated by the inverse Fourier transform circuit. A second Fourier transform circuit Fourier-transforms the extracted complex gains from the second extracting circuit to obtain a corresponding second Fourier-transformed signal, and an equalizing calculation circuit equalizes the input signal using the second Fourier-transformed signal.

Provided are an equalizer and an equalization method. There is provided an equalizer that includes: a first extracting circuit extracting a plurality of pilot symbols from an inputted signal; an inverse Fourier transform circuit inversely Fourier transforming the extracted plurality of pilot symbols, and computing a complex gain per path; a second extracting circuit extracting a plurality of paths by using the complex gains; a Fourier transform circuit Fourier transforming the extracted paths; and an equalization computing circuit extracting phase components of the Fourier-transformed paths, and carrying out multiplication by using the inputted signal and the extracted phase components.

A feedforward amplifier is disclosed in which either the main amplifier or the auxiliary amplifier includes at least three parallel signal paths. Each of the signal paths includes a complex gain adjuster. In addition, a feedforward amplifier is disclosed in which a plurality of control linearizers compensate for nonlinearities in the response of signal adjusters to control inputs.