The self-calibration method of IR mixer with low IF
This paper describes a new self-calibration method of phase shifters providing better suppression of image component in the signal path of a receiver for ISM 2.4 GHz band. The method has been applied to Hartley architecture of image-reject mixers that are used in low IF RF receivers. The method relies on measuring the amplitude differences and phase errors between the I/Q mixer signals and iterative tuning of digitally controlled capacitance arrays, which are located inside the phase shifters. Circuit implementation of the proposed method in 0.35 mu m BiCMOS provided IRR (Image Rejection Ratio) = 45 dB what is about 20 dB better than IRR obtainable without self-calibration. The range of amplitude compensation is 20% and the phase correction operates correctly in the range of initial phase error +/- 4.
self-calibration of ir mixer low if receiver rf circuit