K u-Band Image Rejection Sliding-IF Transmitter in 0.13-μm CMOS Process

The insensitivity to gain and phase mismatches is investigated in a multiband double image rejection transmitter (DIRT). Although a direct in-phase/quadrature (I/Q) modulator architecture is simple, the I/Q gain and phase mismatches directly affect the image rejection ratio (IRR) over the operating frequencies. However, the DIRT has low sensitivity to a small I/Q phase mismatch, while the IRR is predominantly dependent on the IF gain mismatch. Furthermore, there is a region of insensitivity to both gain and phase mismatches in the DIRT. To characterize the mismatch effects of the DIRT, the IRR is theoretically analyzed and simulated at the system level. The proposed DIRT with sliding-IF is implemented on a 0.13-μm CMOS process to prove the insensitivity to the I/Q mismatch effects over 11―15-GHz multiband frequency ranges. For supporting the multiband functionality, frequency dividers-by-4/8/16 are utilized to generate 0.675-, 1.35-, and 2.7-GHz quadrature IF LO signals using 10.8-GHz RF local oscillator (LO) signal. The measurement results show that the in-band image rejection and LO leakage suppression are greater than 48.8 and 43.5 dBc, respectively, over the wideband frequency range. The output referred 1-dB compression point is obtained as high as ―4 dBm with a 1.5-V power supply. A multiband CMOS DIRT operating over Ku-band has not been previously reported.