RF I/Q Downconverter With Gain/Phase Calibration

We propose an RF I/Q downconverter including a calibration procedure to compensate for gain and phase mismatch errors. The indirect compensation technique is based on the use of the local oscillator (LO) signal as reference for error measurements. A number of mismatch parameters are first estimated by an algorithm running in the digital signal processing processor following the analog-to-digital converter and then used to correct the downconverted I/Q signals digitally during normal operation. The downconverter has been designed in 0.13-mum CMOS technology. The analog part of the system for calibration adds a negligible area and power consumption with respect to the front-end building blocks. Test results exhibit an image-rejection ratio IRRges48.8 dB for I/Q phase errors up to 15deg and for LO I/Q amplitude and mixer gain mismatch errors up to 10%