Shinichi Miwa

A 68% efficiency, C-band 100W GaN power amplifier for space applications

This paper describes a high efficiency (68%), high output power (100W), high reliability GaN HEMT amplifier for C-band space applications. The high efficiency is achieved by 2nd-harmonic frequency (2fo) tuning circuits in the input and output matching circuits. The input circuit uses open-ended stubs located nearby FET gate terminals for setting the 2fo reflection-phase at the optimum phase. In the output circuit, the optimum 2fo reflection phase is realized using three transmission-line transformers while matching loss is kept low at fundamental frequency. In addition, a 3000 hours RF overdrive life test reveals that an estimated mean time to failure (MTTF) is 1×107 hours at 150°C channel temperature, proving that the amplifier has sufficient reliability for space applications. To the best of our knowledge, the efficiency of 68% is the highest of 100-W class C-band amplifiers ever reported, and is also comparable to that of commercially available traveling wave tube amplifiers.

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.

3.0–3.6 GHz wideband, over 46% average efficiency GaN Doherty power amplifier with frequency dependency compensating circuits

A wideband GaN Doherty power amplifier (DPA) for 4G/LTE-Advanced base stations is presented. To break the inherent narrow band limitation of conventional DPA, a frequency dependency compensating circuit and a modified λ/4 inverter incorporating package parasitic elements are proposed. Measured DPA achieves 45.9–50.2 % drain efficiency with −50 dBc ACLR at 3.0–3.6 GHz under 20 MHz LTE signal after digital pre-distortion (DPD), which is very suitable for multiband radio and carrier aggregation in 4G. The use of the wideband efficient GaN DPA can reduce the complexity and energy consumption of radio, which further helps reducing the total cost of ownership (TCO) of base stations.