Research on Broadband Power Amplifiers in Ka Band
Date Issued
2012
Date
2012
Author(s)
Tsay, Chao-Hsiuan
Abstract
Most reported broadband power amplifiers in Ka band have narrowband power characteristics. A broadband power amplifier should have wideband characteristics which include not only gain and return losses but also power performance. In this dissertation, the design and analysis of broadband amplifiers is demonstrated. To verify the proposed method, two Ka-band amplifiers are designed and implemented.
A full Ka-band 20-dBm power amplifier is implemented in 0.15-um GaAs pHEMT technology. The cascode configuration is adopted to provide higher gain. Spurious oscillations are observed in measurement and can be suppressed by off-chip bypass and raising the gate bias of CG transistor. The measurement result shows a power added efficiency (PAE) at 1-dB compression point (P1dB) up to 15.5% and 19.3-dBm OP1dB. Peak PAE higher than 22.5% and saturation output power (Psat) higher than 22.7 dBm are obtained at 27 GHz. Since the measurement results differ from simulation, we find that the transistor model is not precise at the desired bias, thus a modified model is introduced. Because the amplifier suffers from oscillations, the Q factor of bypass network is analyzed to stabilize the amplifier, and the proposed amplifier is redesigned.
A 27-34 GHz buffer amplifier (BA) is fabricated in 65-nm CMOS process. The measurement results show a PAE at P1dB up to 13% while maintaining 21.8-dB gain and 7.7-dBm OP1dB at 30 GHz. The peak PAE and Psat are higher than 23.3% and 10.6 dBm, respectively. To the best of our knowledge, the 27-34 GHz BA has the highest PAE among reported Ka-band CMOS BAs.
Subjects
Power Amplifier
High PAE
Ka Band
Broadband
Type
thesis
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