I - Q BALANCE METHOD FOR DIRECT CONVERSION RECEIVERS
Original Publication Date: 2001-Mar-16
Included in the Prior Art Database: 2001-Mar-16
This paper describes a method for balancing the intermediate frequency (IF) signals for use in a direct conversion receiver where the incoming signal is converted to an in-phase and quadrature (I and Q) IF signal at a very low frequency (near DC). The IF signals in the direct conversion receiver are then demodulated to recover the base-band information. The demodulators can be implemented with conventional analog circuits or the IF can be converted to digital signals and demodulated using software algorithms in a digital signal processor (DSP) or other micro-processor. In either case the amplitude and phase balance of the I and Q IF signals is important to properly carry out the demodulation process and minimize distortion of the base-band signal. Good amplitude and phase tracking are difficult to achieve across the frequency band in a wide band receiver. This is a method of calibration that matches the I and Q amplitude and tracks the phase across a wide RF frequency band.