267 results about "IQ imbalance" patented technology

An arrangement (600) and method for frequency domain compensation of OFDM signals with IQ imbalance by converting IQ signals to the frequency domain (610); and providing imbalance compensation and channel equalization means (620) and therewith, in the frequency domain, compensating for IQ imbalance in the IQ signals and providing channel equalization thereto. Adaptive equalization is used to adapt filter coefficients, allowing IQ imbalance compensation and channel equalization to be achieved simultaneously in a simple and elegant manner. This allows complexity in analog circuitry and associated costs to be reduced at the expense of additional digital signal processing, yielding an overall economic system solution. The invention can be easily applied to existing systems, such as the DVB-T standard, without requiring changes to installed broadcasting infrastructure in order use receivers incorporating the invention.

A transceiver includes a switching unit configurable for isolating an input of a receiver from an output of a transmitter during a local calibration mode. A known signal present at the output at a first power level during the calibration mode will also be present at the input at a second power level lower than the first power level and will be converted by the quadrature demodulator. A compensation factor is estimated for compensating the receiver section for imbalances in the in-phase and quadrature phase signals resulting from conversion of the known signal. Remote calibration is implemented using a method for remotely compensating for I-Q imbalance wherein a data packet having a known signal is transmitted to a receiver for conversion by a quadrature demodulator and compensation factors are estimated for compensating for imbalances in the in-phase and quadrature phase signals resulting from conversion of the known signal.

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.

An OFDM transceiver has a transmitter, a receiver, and a loopback switch. The loopback switch configured is for selectively establishing a physical connection between an output terminal of the transmitter and an input terminal of the receiver. The transmitter is configured for outputting to the output terminal an OFDM signal generated based on a local oscillator signal. The receiver is configured for demodulating the OFDM signal, received via the physical connection, using the local oscillator signal and determining amplitude and phase imbalance parameters based on performing frequency-domain estimation of amplitude and phase imbalances. Hence, the receiver is configured for performing imbalance compensation on a received wireless OFDM signal based on the determined amplitude and phase imbalance parameters. Hence, amplitude and phase imbalances can be estimated accurately despite channel fading and frequency variations encountered between the transmitter of the wireless OFDM signal and the receiver.

Digital IQ imbalance estimation and compensation is facilitated by shaping the frequency response of receiver branches. In particular, in a multi-carrier receiver, the frequency response of signal processing elements in at least one receiver branch is set to not fully attenuate received signals in a frequency band of interest. The frequency band of interest is greater than the carrier bandwidth of the received signal processed by that receiver branch. In some embodiments, the received signal is not attenuated, and adjacent interfering signals are partially attenuated. This allows information regarding the interfering signals to appear in an IQ imbalance-induced, inter-carrier image of the signals in anther receiver branch, facilitating digital estimation and compensation of IQ imbalance.

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 relates to a method for adjusting IQ-imbalance of a direct conversion receiver (200). In the method a radio frequency training signal is locally generating and conveyed to an in-phase branch and a quadrature-phase branch of the receiver (200). The method comprises mixing, in the analogue domain, the radio frequency training signal of the in-phase branch with a first mixing signal to form a baseband in-phase component (I) of the training signal and mixing, in the analogue domain, the radio frequency training signal of the quadrature-phase branch with a second mixing signal to form a phase shifted component (Q) of the training signal. The baseband in-phase component (I) and phase shifted component (Q) are analogue-to-digital converted to form a digital baseband in-phase component and a digital baseband phase shifted component of the training signal. In the method the digital baseband in-phase and phase shifted components of the training signal are analyzed, in a digital demodulator (210), so as to detect the IQ-imbalance of the direct conversion receiver (200). The IQ-imbalance is corrected, based on the analysis, in the analogue domain.

The invention discloses an ultra wide band hopping frequency synthesizer based on digital up-conversion. The ultra wide band hopping frequency synthesizer based on digital up-conversion comprises a PC, a field-programmable gate array ( FPGA ), a clock generator, a DA converter and a low-pass filter, wherein a hopping frequency sequence storer, a hopping frequency carrier signal generating unit, a modulation base band interpolation filtering unit and an up-conversion unit are arranged in the FPGA, the hopping frequency sequence storer is connected with the hopping frequency carrier signal generating unit through a signal line, and the hopping frequency carrier signal generating unit and the modulation base band interpolation filtering unit are connected with the up-conversion unit through two signal lines respectively. According to the ultra wide band hopping frequency synthesizer based on digital up-conversion, a digital base band is directly modulated onto a carrier wave by means of digital up-conversion, and then hopping frequency signals modulated by any digits are generated, hopping frequency bandwidth reaches 800MHz, modulation bandwidth is larger than 100MHz, and carrier wave leakage and IQ imbalance are avoided.

Embodiments of an adaptive in-phase (I) and/or quadrature-phase (O) imbalance correction for multicarrier wireless communication systems is generally described.

A calibration device for use in a radio receiver enables receiver self-calibration and self-correction of inbound RF signals. The calibration device includes an estimation module for receiving a sample digital packet and calculating imbalance parameters as a function of a portion of the sample digital packet. The calibration device further includes a correction module for applying the imbalance parameters to a received digital packet of an inbound RF signal to produce a corrected digital packet. The received digital packet may be a portion of the sample digital packet, the complete sample digital packet or a new packet.

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.

An apparatus and method for correcting IQ imbalance are presented. An exemplary receiver for processing I and Q signals from a tuner includes: a non-decision directed (NDD) imbalance canceller coupled to receive the I and Q signals, and a decision directed (DD) imbalance canceller coupled to the non-decision directed imbalance canceller. The DD imbalance canceller converges after the NDD imbalance canceller converges, so as to correct IQ imbalances in the receiver. An exemplary method for processing I and Q signals from a tuner includes: (a) converging a NDD imbalance canceller to correct a majority of IQ imbalances, and (b) subsequently converging a DD imbalance canceller to correct a remainder of IQ imbalances not corrected in step (a). The apparatus and method correct frequency-dependent and frequency-independent IQ imbalances.

The invention provides an IQ imbalance compensation method and device in a transmitter. A long training sequence and a short training sequence which are received by the OFDM transmitter are used for estimating and compensating the phase difference and the amplitude difference between a channel I and a channel Q which are generated by IQ imbalance. According to the IQ imbalance compensation method and device, the channels are allowed to have frequency selectivity, and the method and device are suitable for the condition where the channel environment is poor. With the increasing of signal bandwidths, the frequency selectivity of the channels is gradually embodied. According to the method and device, the advantage of joint estimation of the frequency domain multi-tap channels and the IQ imbalance is more and more obvious. In addition, the IQ imbalance compensation method and device are high in both practicability and transferability.

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 general inventive concept relates to apparatuses and/or methods for measuring an in-phase and quadrature (IQ) imbalance. In one embodiment, a detector can measure an error caused by an IQ imbalance using a first IQ signal including a desired signal and a corresponding image signal by the IQ imbalance. The detector can include a derotator to derotate the first IQ signal by a first angular frequency to obtain a second IQ signal and derotate the first IQ signal by a second angular frequency to obtain a third IQ signal, a DC estimator to obtain a fourth IQ signal corresponding to a DC component of the second IQ signal and a fifth IQ signal corresponding to a DC component of the third IQ signal and a controller can determine a gain error or a phase error from the fourth IQ signal and the fifth IQ signal.

The invention belongs to the technical field of wireless communication and particularly relates to a channel estimation and IQ (In-phase Quadrature) imbalance united compensation method in a wireless communication system which is influenced by in-phase orthogonal two-way imbalanced interferences. The channel estimation and IQ imbalance united compensation method comprises the following steps of performing constraint on ranges of IQ imbalanced parameters; constructing objective functions; obtaining coordinate values of an optimal solution; working out an optimal parameter for IQ imbalance; recovering ideal CFR (Channel Frequency Response); and performing compensation on the IQ imbalance and achieving the channel estimation and correction of the IQ imbalance.

The invention belongs to the technical field of wireless communication and particularly relates to an IQ imbalance compensation method based on the Golay complementary sequences, wherein the IQ imbalance compensation method is applied to a wireless communication system which is disturbed by IQ imbalance. The IQ imbalance compensation method based on the Golay complementary sequences comprises the steps that S1 a training sequence pair is established and sent; S2 a receiving terminal receives the training sequence pair established in the step S1 and conducts circular correlation processing on each training sequence which is received; S3 the influence of the IQ imbalance of a received signal is compensated. According to the IQ imbalance compensation method based on the Golay complementary sequence, under the condition that channel information does not need to be known, complex parameters of IQ imbalance are estimated and then IQ imbalance is compensated.

A wireless communication apparatus generates transmission signal including first and second pilot signal sequences allocated to first and second frequencies symmetrically located in relation to a center frequency, and third and fourth pilot signal sequences allocated to third and fourth frequencies symmetrically located in relation to the center frequency, quadrature-modulates the transmission signal, to obtain a quadrature modulation signal, quadrature-demodulates the quadrature modulation signal, to obtain a reception signal, extracts first to fourth pilot signal sequences from the reception signal, estimates a first transfer characteristic concerning first and second frequency by using first and second pilot signal sequences, estimates a second transfer characteristic concerning third and fourth frequencies using third and the fourth pilot signal sequences, generates a third transfer characteristic from which an influence of transmission IQ imbalance is removed by using first and second transfer characteristic, and estimates, from the third transfer characteristic, reception IQ imbalance characteristic.

A distortion compensating apparatus has an IQ imbalance compensation coefficient arithmetic circuit 31 for calculating, from correlation values of a transmission signal and a feedback signal, IQ imbalance compensation coefficients for compensating for IQ imbalance in a quadrature modulator 23; and an IQ imbalance compensator 21 for compensating for the IQ imbalance with respect to a distortion compensated signal output from a distortion compensator 11 according to the IQ imbalance compensation coefficients, and for outputting to the quadrature demodulator 23.

The invention provides IQ imbalance estimation and correction equipment, system and method. Quadrature demodulation of a received training sequence sent by a sending terminal is performed; a frequency offset estimate value of the training sequence is determined according to a reception signal in the demodulated training sequence; an IQ imbalance correction parameter of a receiving terminal is obtained through calculation according to the frequency offset estimate value; influences of carrier frequency offset are taken into consideration during estimation of the IQ imbalance correction parameter of the receiving terminal; an IQ imbalance correction parameter of the sending terminal is obtained according to the training sequence subjected to frequency offset compensation and the IQ imbalance correction by the receiving end; and influences of carrier frequency offset are also taken into consideration during estimation of the IQ imbalance correction parameter of the sending terminal. Therefore, IQ imbalance estimation and correction of the sending terminal is achieved. The IQ imbalance estimation and correction of the receiving terminal is achieved through a remote loopback mode, and the accuracy of IQ imbalance correction of a sending terminal and a receiving terminal of a system is improved.

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.