A gain/phase mismatch calibration procedure for RF I/Q downconverters

Abstract

We propose a calibration procedure to compensate for gain and phase mismatch errors in RF I/Q downconversion stages requiring neither external reference signals nor adaptive techniques. The proposed indirect compensation technique is based on the use of the local oscillator (LO) signal as the reference for error measurements. A number of mismatch parameters are first estimated by an algorithm running in the DSP after the analog-to-digital (A/D) converter and then used to correct the downconverted signal digitally during normal operation. A test circuit has been designed in ¼ ½¿ m CMOS technology and it is under fabrication. Circuit simulations exhibit an imagerejection ratio ÁÊÊ ¼ dB for a LO ½± amplitude and ¿ AE phase mismatch.

Interpretation of MOS transistor mismatch signature through statistical device simulations

“…Therefore, besides well-known consequences of temperature changes such as mechanical strain due to material expansion and nominal performance changes, the mismatch behavior should be considered as well. In particular, some high-precision circuits such as, bandgap and frequency references or operational amplifiers, will suffer from a possible mismatch drift even after trimming techniques [91,92,93]. Despite the fact that this concern is widely spread among circuit designers the subject has been scarcely discussed in open literature in the past.…”