(A) variable gain LNA for 60GHz beamforming receiver

Abstract

In this thesis, to achieve 25dB high gain with low NF, three stage cascaded amplifier is described. For the first stage, common source with inductive degeneration topology is selected. With NF min bias condition and choose proper size, NF is optimized. For the second stage, gain control for phase shifter gain error compensation is considered. To evaluate effect of both RMS gain error and phase error, EVM is defined. With maximum 1.5dB control of digital 2bit, rms gain error decreased from 1.24dB to 0.85 and maximum EVM is 1% decreased. For the third stage, to satisfy 30cm and 3m communication distance, 10dB dynamic range is required. But with 10dB decreased gain, linearity of VGA is degraded and can’t satisfy the target spec(-4dBm). So linearizing is required. However, VGA with linearizing technique, there is also one problem that output matching doesn’t satisfy -10dB condition. So asymmetric matching technique is proposed. Then output matching issue is solved. Totally 3 stage VGLNA simulation results show 26.3dB and .14.4GHz 3dB BW. However, measurement results show frequency down shifting(1.5-2.5GHz) and gain peaking(29.3dB). Frequency down shifting can be explained difference between blanket ground and mesh ground. Gain peaking also can be explained due to mesh ground effect. But the fluctuation in gain plot occurs more than expected. By increasing inductance, similar fluctuation in gain graph is found.