A Ka- Band Dual Circularly Polarized CMOS Transmitter with Adaptive Scan Impedance Tuner and Active XPD Calibration Technique for Satellite Terminal

An adaptive scan impedance tuner for varying impedance of array antenna along with the beam scan and calibration circuits for deteriorated cross-polarization are proposed for the low earth orbit (LEO) satellite terminal for earth observation application. With the proposed load tuner, TX power efficiency is improved to 11.7 % from 6.5 % at a VSWR=1:3 load condition where the same load point as the 50° scan angle. Furthermore, 18.1 dB and 16.4 dB of the cross-polarization discrimination (XPD) is recovered for the right-handed circular polarization (RHPC) and left-handed circular polarization (LHPC), respectively, by the proposed circular polarization calibration circuit with the modulated signal. Accordingly, the error vector magnitudes (EVM) are also improved by 12.2 dB and 14.8dB at the RHCP and the LHCP, respectively. To the best of the authors' knowledge, the proposed TX is the first reported work with the dual circular polarization transmitting mode measurement results in Ka-band for satellites.