242 results about "Phase imbalance" patented technology

The present invention provides a digital (computational) branch calibrator which uses a feedback signal sensed from an RF transmit signal path following the combining stage of LINC circuitry of a transmitter to compensate for gain and phase imbalances occurring between branch fragment signals leading to the combiner. The calibrator feeds a quiet (zero) base band signal through the transmit path during the calibration sequence (i.e. a period when data is not transmitted) and adjusts the phase and gain of the phasor fragment signals input thereto by driving the sensed output power to zero. The calibration is performed by alternating phase and gain adjustments with predetermined (programmable) and multiple update parameters stages (speeds). A baseband modulation is preferably used to distinguish false leakage (e.g. due to local oscillator, LO, feed through and DC offset in the base band Tx) from imbalance leakage.

A system for compensating for in-phase and quadrature (I / Q) imbalances for multiple antenna systems (MAS) with multi-user (MU) transmissions (defined with the acronym MU-MAS), such as distributed-input distributed-output (DIDO) communication systems, comprising multicarrier modulation, such as orthogonal frequency division multiplexing (OFDM). For example, one embodiment of the system comprises one or more coding modulation units to encode and modulate information bits for each of a plurality of wireless client devices to produce encoded and modulated information bits; one or more mapping units to map the encoded and modulated information bits to complex symbols; and a MU-MAS or DIDO IQ-aware precoding unit to exploit channel state information obtained through feedback from the wireless client devices to compute MU-MAS or DIDO IQ-aware precoding weights, the MU-MAS or DIDO IQ-aware preceding unit precoding the complex symbols obtained from the mapping units using the weights to pre-cancel interference due to I / Q gain and phase imbalances and / or inter-user interference.

A system for compensating for in-phase and quadrature (I / Q) imbalances for multiple antenna systems (MAS) with multi-user (MU) transmissions (defined with the acronym MU-MAS), such as distributed-input distributed-output (DIDO) communication systems, comprising multicarrier modulation, such as orthogonal frequency division multiplexing (OFDM). For example, one embodiment of the system comprises one or more coding modulation units to encode and modulate information bits for each of a plurality of wireless client devices to produce encoded and modulated information bits; one or more mapping units to map the encoded and modulated information bits to complex symbols; and a MU-MAS or DIDO IQ-aware precoding unit to exploit channel state information obtained through feedback from the wireless client devices to compute MU-MAS or DIDO IQ-aware precoding weights, the MU-MAS or DIDO IQ-aware preceding unit precoding the complex symbols obtained from the mapping units using the weights to pre-cancel interference due to I / Q gain and phase imbalances and / or inter-user interference.

A receiver (50) includes a self-calibrating receive path correction system for correction of I / Q gain and phase imbalances in a radio frequency signal. The system includes a signal-processing block (53), an I / Q phase imbalance detection and correction circuit (98), an I / Q gain imbalance detection and correction circuit (96), and an adaptive loop bandwidth control circuit (102). The I / Q phase imbalance detection and correction circuit (98) equalizes for the relative phase imbalance and the I / Q gain imbalance detection and correction circuit (96) equalizes for the relative gain imbalance between the I and Q channels created by the analog portion of a quadrature receiver. The adaptive loop bandwidth control circuit (102) dynamically adjusts at least one loop bandwidth for the I / Q gain imbalance detection and correction circuit (96) and the I / Q phase imbalance detection and correction circuit (98) on a slot boundary.

Methods and apparatus for performing amplitude and phase imbalance correction operations on in-phase and quadrature phase signal components corresponding to a received signal are described. The imbalance correction operations relay on the use of relatively simple to implement feedback loops. The phase imbalance feedback loop relies on the tendency of transmitted symbols to be distributed uniformly around the origin of the I / Q plane if proper phase balance is present in the processed signal. Phase correction coefficients are generated over time as a function of the negated product of the processed in-phase and quadrature phase signal components. Amplitude correction coefficients are generated over time as a function of the difference in the squared values of the I and Q processed signal components.

Most modern integrated circuit transceivers, especially wireless LAN, utilize a direct conversion radio architecture, which is highly advantageous from the perspectives of cost and flexibility, there exist several performance impairments, including gain and phase imbalances between the in-phase (I) and quadrature (Q) of a transmitter or receiver. Disclosed herein is a signal processing methodology and system for compensation of I / Q imbalance for a direct conversion packet-switched OFDM communications system. The imbalance, which accounts for transmitter I / Q imbalance, RX I / Q imbalance, phase / frequency error, and dispersive multipath fading. Both frequency dependent I / Q imbalance and frequency independent cases are considered, covering both wideband and narrowband modulation. The proposed estimation algorithms operate within the fully compliant framework of existing multi-user OFDM radio standards (WLAN, LTE, WimAX). These algorithms accurately estimate and correct transceiver I / Q imbalance on a packet-by-packet basis, all within the receiver's digital baseband.

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.

A radio frequency transceiver for off-line transmit and receive calibrations includes: a transmit pre-distortion module configured to receive a transmit calibration signal during a transmit calibration mode, a transmit communication signal during a transmit communication operation mode, and one or more transmit calibration adjustment signals; a transmit channel frequency converter; and a transmit calibration module configured to provide the one or more transmit calibration adjustment signals and the transmit calibration signal to the transmit pre-distortion module. It may also include a receive channel frequency converter; a receive pre-distortion module configured to receive a receive calibration signal during the receive calibration mode, a receive communication signal during a receive communication operation mode, and one or more receive calibration adjustment signals; and a receive calibration module configured to provide the one or more receive calibration adjustment signals to the receive pre-distortion module and a receive calibration signal to the transmit pre-distortion module.

A DC offset estimator and removal circuit removes the DC offsets for each of the I and Q signal components in a received signal. A gain imbalance estimator and compensator circuit estimates and compensates for gain imbalances within the I and Q signal components. A phase imbalance estimator and compensator circuit estimates and compensates for phase imbalances within the I and Q signal components to produce a communications signal that is compensated for received DC offsets and gain and phase imbalances within the I and Q signal components.

A quadrature transceiving system for compensating a direct current (CD) offset, a gain imbalance and a phase imbalance between an I-channel signal and a Q-channel in a quadrature transmitting system is disclosed. The quadrature transceiving system includes a transmitter for detecting a DC offset, a gain imbalance and a phase imbalance by using an average of a data aided signals included in a RF transmitting signal and compensating one of the I-channel and the Q-channel based on the detected imbalances and DC offset; and a receiver for detecting a DC offset, a gain imbalance and a phase imbalance by varying loop filter gain and compensating one of the I-channel and the Q-channel based on the detected imbalances and DC offset.

A radio frequency transceiver for off-line transmit and receive calibrations includes: a transmit pre-distortion module configured to receive a transmit calibration signal during a transmit calibration mode, a transmit communication signal during a transmit communication operation mode, and one or more transmit calibration adjustment signals; a transmit channel frequency converter; and a transmit calibration module configured to provide the one or more transmit calibration adjustment signals and the transmit calibration signal to the transmit pre-distortion module. It may also include a receive channel frequency converter; a receive pre-distortion module configured to receive a receive calibration signal during the receive calibration mode, a receive communication signal during a receive communication operation mode, and one or more receive calibration adjustment signals; and a receive calibration module configured to provide the one or more receive calibration adjustment signals to the receive pre-distortion module and a receive calibration signal to the transmit pre-distortion module.

The present invention includes methods and devices to compensate for gain and phase imbalance for OFDM and other multi-carrier symbol transmission systems. More particularly, methods and devices for determining compensation parameters are provided. This invention may be applied to a variety of standards utilizing OFDM technology, including IEEE 802.11a, Hiperlan / 2 and MMAC. Further description of the invention and its embodiments are found in the figures, specification and claims that follow.

Disclosed is a quadrature demodulator for high-speed wireless communication, which comprises: an A / D converter for converting received signals into digital signals; a signal recovery unit for recovering carriers and symbol timing from the signals converted by the A / D converter; a decision unit for detecting recovered signals output by the signal recovery unit, and performing a decision process on them; an I / Q gain imbalance detector for detecting gain imbalances of the I and Q-phase components from the recovered signals, and outputting an I / Q gain compensation value for compensating for the gain imbalances; and an I / Q gain compensator, provided between the A / D converter and the signal recovery unit, for reflecting the I / Q gain compensation value output by the I / Q gain imbalance detector to the received signals.

An uninterruptible power supply (UPS) system that includes a multiphase AC output configured to be coupled to a load, an inverter having an output coupled to the AC output and a control circuit operatively associated with the inverter and configured to cause the inverter to compensate for a phase imbalance of a load coupled to the AC output while power is being delivered to the load from an AC power source independently of the inverter.

The present invention utilizes circuitry, already present in receivers, to calibrate and correct for gain and phase errors in a transceiver device. The present invention employs a digital signal processor along with multiple phase shifters and all pass networks to ensure proper levels of quadrature signals within the transceiver. An internally generated double sideband suppressed carrier signal is created to produce the calibration signals used by the digital signal processor.

The invention provides an IQ unbalanced calibration method and equipment of baseband signals in a wireless communication receiving machine. The method comprises the following steps that: the receiving machine receives radio frequency signals, and generates identical phase component path I signals and orthogonal component path Q signals through signal processing; a self correlation valve E(|I|2) of the path I signals, a self correlation value E(|Q|2) of the current path Q signals and a mutual correlation value E(IQ) of the path I signals and the path Q signals are obtained through calculation; carrying out four arithmetic operation on E(|I|2), E(|Q|2) and E(IQ); an estimated value of the current magnitude unbalanced calibration factor and an estimated value of the current phase unbalanced calibration factor are obtained through calculation; and the current path Q signals are calibrated according to the estimated values. The embodiment of the invention can reduce the operation quantity.

Methods and apparatus for performing amplitude and phase imbalance correction operations on in-phase and quadrature phase signal components corresponding to a received signal are described. The imbalance correction operations relay on the use of relatively simple to implement feedback loops. The phase imbalance feedback loop relies on the tendency of transmitted symbols to be distributed uniformly around the origin of the I / Q plane if proper phase balance is present in the processed signal. Phase correction coefficients are generated over time as a function of the negated product of the processed in-phase and quadrature phase signal components. Amplitude correction coefficients are generated over time as a function of the difference in the squared values of the I and Q processed signal components.

A transmit path correction system (34) for compensating for digital DC offsets, I / Q gain imbalances and I / Q phase imbalances includes a mixed signal forward path (36) and a mixed signal feedback path (38). The forward pat (36), which is operable to process input data symbols to produce at least one analog output signal, preferably includes a digital DC offset correction circuit (86) for compensating for digital DC offsets in the forward path (36) using at least one digital feedback signal (82, 84), an I / Q phase equalization circuit (90) for compensating for the I / Q phase imbalances in the forward path (36), and an I / Q gain equalization circuit (88) for compensating for the I / Q gain imbalances in the forward path (36) using the digital feedback signal(s) (82, 84). The feedback pat (38) processes the analog output of the forward path (36) to produce the digital feedback signal(s) (82, 84).

The present invention provides apparatus and method for calibrating I / Q imbalance in a direct conversion transmitter-receiver, including generating a complex sinusoidal signal with a center frequency at ωi, sending the sinusoidal signal to the receiver and using FFT to estimate the I / Q the phase φ, the gain imbalance ε, and phase imbalance θ. The input signal is calibrated according to the estimated I / Q amplitude and phase imbalance.

Methods and systems to calibrating a transmitter for I / Q imbalance and local oscillator feed-through include generating a test tone, frequency up-converting the test tone, monitoring one or more features of the up-converted test tone, and adjusting one or more features of the transmitter in response to the monitoring. The monitoring optionally includes monitoring a beating of the envelope of the up-converted test tone. In an embodiment, a first harmonic of the up-converted test tone is monitored for local oscillator feed-through (LOFT). Alternatively, baseband data inputs to the transmitter are disabled, and LOFT is measured by measuring power at the transmitter output. A second harmonic of the up-converted test tone is monitored for gain and phase imbalances. The adjusting optionally includes adjusting a gain imbalance, adjusting a phase imbalance, and / or adjusting DC offsets. The adjusting optionally includes an iterative refinement process. Such a refinement process optionally includes performing a first monitoring, applying a set of relatively coarse settings to the one or more features in the transmitter, monitoring the beating resulting from each of the coarse settings, selecting the coarse setting corresponding the smallest beating, applying a set of relatively fine settings centered around the selected coarse setting, wherein the fine settings are more closely related to one another than are the coarse settings, monitoring the beating resulting from each of the fine settings, and selecting the fine setting corresponding the smallest beating.

Disclosed is a method for detecting and correcting amplitude and phase imbalances between in-phase (I) and quadrature-phase (Q) components in a high-speed wireless communication quadrature demodulator, which comprises: a) comparing an input signal with a signal determined by a quadrant to which the input signal belongs, and detecting imbalances between I and Q components with respect to the input signal; and b) using the imbalances detected in a) to correct the input signal. The present invention prevents distorting of the demodulator's performance caused by the imbalances to between I and Q components and increases application to high-speed wireless communication.

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

Systems and methods are described for a sideband suppression technique for quadrature modulation using magnitude measurements. Gain imbalance, phase imbalance, or both gain and phase imbalance are corrected in a quadrature modulator. Predetermined voltage levels are applied to one or both of the quadrature modulator input channels and resultant output magnitudes are measured. Then, a gain correction factor, a phase correction factor or both gain and a phase correction factors are determined as a function of the measured output magnitudes. Gain imbalance, phase imbalance or both gain and imbalance are then corrected using the gain and phase correction factors.

An apparatus and method for compensating an imbalance of phase and gain between I-channel and Q-channel by using variable loop gains is disclosed. The apparatus includes: a phase error generator for generating a phase error signal by using the I-channel signal and the Q-channel signal; an average value calculator for calculating an average value of the phase error signal; a comparator for comparing the average value with a predetermined threshold; a selector for selecting a loop gain value among a set of loop gains based on the comparison result; a phase imbalance generator for generating a phase imbalance by using the selected loop gain value; and a compensator for compensating the Q-channel signal based on the phase imbalance.

A neural network demodulator is used within a receiver to provide Inter Symbol Interference (ISI) channel equalization and to correct for I / Q / phase imbalance. The neural network is trained with a single integrated training step to simultaneously handle the channel impairments of ISI equalization and I / Q phase imbalance as opposed to prior art methods of separately addressing each channel impairment in sequence.

The invention puts forward an IQ unbalance correcting technology based on a digital pre-distortion system and belongs to the field of wireless communication. After quadrature modulation, signals enter the digital pre-distortion system by two paths, channel estimation is firstly conducted to obtain corresponding estimation parameters and data initialization is carried out; then based on input in-phase signals and orthogonal signals, direct current offset factors of the in-phase signals and the orthogonal signals are calculated and direct current compensation is conducted; based on the input in-phase signals and orthogonal signals, gain unbalance factors and phase unbalance factors of the in-phase signals and the orthogonal signals are calculated; according to a mirror image correction model, corresponding factors are substituted to carry out the mirror image correction; finally, the compensated gain factors and the phase factors are updated and the IQ unbalance correcting process is completed. By means of the digital pre-distortion correcting method against the IQ unbalance distortion, system hardware complexity and the cost can be reduced, and meanwhile error estimation precision and compensation precisions are improved.

A transceiver includes a transmitter, a receiver, and an electrical feedback line. The transmitter has a quadrature-modulator and is configurable to compensate inphase / quadrature phase imbalances produced by hardware of the transmitter. The quadrature-modulator is configured to quadrature-modulate a carrier wave. The receiver has a quadrature-demodulator and is configurable to compensate for inphase / quadrature phase imbalances produced by hardware in the receiver. The quadrature-demodulator is configured to demodulate a quadrature-demodulated carrier. The electrical feedback line connects an output of the transmitter to an input of the receiver.