Fast in-phase and quadrature imbalance calibration

Abstract

An embodiment of the present invention includes a technique to calibrate receiver and transmitter in a communication system. N digitized samples I(n) and Q(n) are stored. The N digitized samples represent in-phase and quadrature (I-Q) components, respectively, of a down-converted signal from a receiver. The I-Q components are generated from a quadrature demodulator or modulator having I-Q imbalance. Phase and gain adjustment constants are computed from the N digitized samples to compensate for the I-Q imbalance using a closed form solution. Another embodiment of the present invention includes a technique to calibrate a transceiver in a communication system without using a calibrated reference receiver. A first test signal at a first frequency is injected to a transmitter having a quadrature modulator with I-Q imbalance. The quadrature modulator has a carrier frequency. The transmitter generates a transmitter signal. The transmitter signal is detected to generate a composite signal having the first test signal and a second test signal at a second frequency twice the first frequency. The composite signal is digitized. I-Q direct current (DC) offset, phase, and gain corrections are computed from the digitized composite signal to correct the I-Q imbalance using a closed form solution.