US 7,248,625 B2Granted

Compensation of I-Q imbalance in digital transceivers

AssigneeSilicon Storage Technology, Inc.

InventorCharles Chien

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Abstract

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.

Claims105

Dependent claims

A radio transceiver, comprising:

at least one antenna;
a receiver section having a quadrature demodulator for receiving various signals and converting the various signals into in-phase and quadrature phase signals;
a transmitter section for transmitting at least one known signal to an input of the quadrature demodulator for conversion by the quadrature demodulator;
a switching unit configurable for providing an amount of isolation between an output port of the transmitter section and an input port of the receiver section such that when the at least one known signal is nresent at the outout port at a first power level, the at least one known signal is also present at the input port at a second power level lower than the first power level and is converted by the quadrature demodulator;
and
at least one receiver compensation factor estimation unit coupled to an output of the quadrature demodulator for estimating, after conversion of the at least one known signal into in-phase and quadrature phase signals, at least one receiver compensation factor for compensating the receiver section for an imbalance in subsequently received in-phase and quadrature phase signals, the at least one receiver compensation factor estimated based upon a mean value of the subsequently received in-phase and quadrature phase signals;
wherein the transmitter section comprises a transmitter compensation factor estimation unit coupled to the output of the at least one receiver compensation factor estimation unit for determining at least one transmitter compensation factor for compensating the transmitter for an imbalance in transmitted in-phase and quadrature phase signals;
and
wherein the transmitter section further comprises an inverse Fast Fourier Transform (IFFT) unit for generating a multi-carrier signal and wherein the transmitter compensation factor estimation unit estimates, after conversion of the multi-carrier signal into in-phase and quadrature phase signals, at least one transmitter compensation factor for compensating the transmitter for an imbalance in transmitted in-phase and quadrature phase signals.

6 more elements

In a communication system comprising at least one antenna. a transmitter and a receiver having a quadrature demodulator for receiving various signals and converting the various signals into in-phase and quadrature phase signals, an output of the transmitter connectable to an input of the receiver by a controllable switching unit, a method for compensating for I-Q imbalance in the in-phase and quadrature phase signals, the method comprising:

providing at least one compensation factor estimation unit for estimating at least one compensation factor;
controlling the switching unit to provide an amount of isolation between an outout of the transmitter and an input of the receiver;
controlling the transmitter to generate at least one known signal at the output of the transmitter;
setting a gain of the communication system such that the at least one known signal is coupled from the output of the transmitter to the input of the receiver at a power level that is within an operating range of the input;
converting the at least one known signal into in-phase and quadrature phase signals at the quadrature demodulator;
estimating at least one compensation factor at the at least one compensation factor estimation unit based on an imbalance in the at least one known signal, the at least one compensation factor estimated based upon a mean value of the at least one known signal;
and
applying the at least one compensation factor to subsequently received signals, transmitted signals or both received and transmitted signals;
and
storing the at least one compensation factor in a memory;
wherein setting a gain of the communication system comprises setting an initial gain of the communication system and wherein the method further comprises:
before controlling the transmitter to generate the at least one known signal, setting a value for at least one of an initial temperature of the communication system and an initial frequency of the at least one known signal;
after estimating the at least one compensation factor, storing the at least one compensation factor in the memory;
after storing the at least one compensation factor in the memory, performing at least one of setting a new gain value of the communication system, setting a new temperature value and setting a new frequency value;
and
estimating at least one additional compensation factor based on the at least one new value.

13 more elements

Dependencies are inferred from the claim text.