Yoshihiro Tsukahara

A 67% PAE, 100 W GaN power amplifier with on-chip harmonic tuning circuits for C-band space applications

This paper describes a high efficiency and high output power GaN power amplifier for C-band space applications. The amplifier uses on-chip harmonic tuned FETs to improve dc-to-rf conversion efficiency. A 2nd harmonic input tuning circuit is incorporated into each unit on-chip FET cell and realizes high precise control of 2nd harmonic input impedance. In addition, 2nd and 3rd harmonic output impedances are optimized with external output matching circuits. A 100 W power amplifier with 4-chips achieves a 67.0% PAE (72.4% drain efficiency) at 3.7 GHz under CW operating conditions. To the best of our knowledge, this is the highest efficiency of C-band power amplifiers ever reported with over 100 W output power.

60GHz High Isolation SPDT MMIC switches using shunt pHEMT resonator

This paper describes the successful development of a 60GHz high isolation SPDT MMIC switch for wireless applications. In order to improve the isolation, the shunt pHEMT resonator, which is reduced on-state resistance of FET, is proposed. The developed V-band SPDT switch shows an isolation of over 45 dB and an insertion loss of 1.4 dB at 60 GHz. Input and output return losses are better than 18 dB in ON-state. Moreover, the switch requires no complex off-chip bias circuitry and consumes no DC power. These performances of high isolation and low insertion loss presented here are the best among the V-band pHEMT MMIC switches.

A compact T/R switching circuit using quadrature couplers and drain-driven HPAs

A novel T/R switching circuit is proposed for microwave T/R modules. It consists of balanced high-power amplifiers with quadrature couplers, and a low-noise amplifier which is connected to the isolation port of the coupler. In RX-mode, the HPAs are switched off by controlling drain voltage of FETs. A prototype C- to Ku-band T/R switching circuit has been fabricated, and the validity of the switching method has been confirmed experimentally.