268 results about "IQ imbalance" patented technology

The present invention discloses a method and apparatus of IQ imbalance compensation for a receiver. The repetitive attribute of the preamble in a signal received by the receiver is used to estimate the IQ imbalance parameters. The data carried by the preamble repeats itself every N sampling intervals. A MSE equation is derived based on assuming the ratios between any two sampling points separated by N samples are identical, and the IQ imbalance parameters can be estimated by solving the MSE equation using the LS algorithm. Consequently, the IQ mismatch offset of the signal is compensated according to the estimated parameters.

The invention provides an all-digital satellite signal simulated source. The all-digital satellite signal simulated source comprises a double-port storage, the double-port storage is a FPGA which provides interfaces for various rate conversions between coding and modulation, is connected with a digital to analog converter through a high-speed serial interface to form a core hardware framework of the satellite signal simulated source, and is connected with a broadband filter directly through a simulation output end to produce multimode high and moderate frequency broadband satellite signal simulated signals with code rates which can vary continuously, a digital signal processor serves as a main control device of the simulated source and performs analysis of various parameters issued by a monitor and parameter configuration of the FPGA, a 32-channel parallel modulation system is arranged inside the FPGA, for example, a 32-channel direct digital synthesizer (DDS) performs parallel output and composition of the central frequency, the FPGA determines the overturn of the carrier phase according to a symbol rate and a main frequency of parallel calculation, IQ two-channel signals, signal coding, code conversion and quadrature modulation are produced through a logical algorithm, a Q channel uniformization coefficient is calculated according to an IQ unbalanced parameter, Q channel uniformization coefficient and the Q channel signal amplitude are subjected to multiply-add arithmetic to calculate the Q channel amplitude, IQ is added, and a unbalanced quadrature phase shift keying (UQPSK) modulation method is simulated.

The invention discloses a method for jointly estimating carrier wave frequency deviation and sampling deviation of an MIMO-OFDM system under the influence of imbalanced IQ, which is applied to the MIMO-OFDM system which is provided with transmitting antennas with the quantity of Q, receiving antennas with the quantity of P, subcarrier waves with the quantity of N and pilot frequency subcarrier waves with the quantity of M; the method comprises the following steps: at a transmitting terminal, pilot frequency is inserted at a position on the identical subcarrier wave aimed at each transmitting antenna; the pilot frequencies are symmetrically distributed at two sides of a central subcarrier wave; at a receiving terminal, first an IQ imbalance parameter is estimated by utilizing two pilot frequencies in an OFDM symbol and mirror pilot frequencies thereof, the influence on the system of IQ imbalance is compensated, and then the joint estimation of the carrier wave frequency deviation and the sampling deviation is accomplished according to a maximum likelihood estimation principle; and the method for jointly estimating the carrier wave frequency deviation and sampling deviation of the MIMO-OFDM system under the influence of imbalanced IQ makes the most of designed OFDM symbolic structure to accomplish the estimation of the IQ imbalance, carrier wave frequency deviation and sampling deviation, and has the advantages of flexible method, simple realization, and the like.

A wireless communications device, e.g., a mobile node supporting direct peer to peer communications, performs a self-calibration of one or more of: receiver IQ imbalance, transmitter IQ imbalance, receiver DC offset, and transmitter DC offset. The wireless communications device, operating in calibration mode, intentionally sets the oscillator frequency used for downconversion in its receiver module to a different frequency than the oscillator frequency used for upconversion in its transmitter module. A first baseband signal, e.g., a single tone test signal, is input to the transmitter module and an upconverted transmit signal is generated. The transmit signal is routed via a feedback loop to the receiver, which performs a downconversion operation. Power and / or phase measurements of the signals output from the downcoversion are used to determine IQ imbalance compensation information and DC offset compensation information. The determined compensation information is used subsequently when operating in a communications mode of operation.

The present invention relates to methods for demodulating orthogonal frequency division multiplexing (OFDM) modulated signals. In particular, this invention relates to methods for in-phase (I) and quadrature phase (Q) imbalance compensation in OFDM systems. For example, the present invention relates to methods for calculating an IQ imbalance compensated signal from a received signal, comprising the steps of: removing DC from the received signal; calculating an autocorrelation matrix of IQ signal vector of the received signal; estimating IQ imbalance compensation values, K1 and K2, as a function of an amplitude imbalance, g, and a phase imbalance, θ; and calculating an IQ compensated signal as a function of the estimated K1 and K2.