Design and implementation of a high efficiency RF power amplifier for S-band telemetry subsystems

In this paper we present design, implementation and characterization of a high efficiency radio frequency (RF) power amplifier (PA) for S-band telemetry subsystems. The proposed RF PA has been implemented using an AlGaN/GaN Hot Electron Mobility Transistor (HEMT) die and shows 50 W output power with a highly linear power gain in required bandwidth. Central frequency of the proposed telemetry can be tuned from 2200 to 2290 MHZ. It works in E class with 28 V power supply voltage and achieves more than 63% efficiency in working bandwidth. Considering the tradeoff between power efficiency and linearity, to achieve the required linearity of π/4-DQPSK modulation, we have tried to implement our structure near to EB-class instead of E-class. Two tone Intermodulation Distortion Third Harmonic (IMD3) in this condition is better than −26 dBc in-band. Also, AM to AM conversion is better than 0.3 dB/dB and AM to PM conversion is less than 3.5 Deg/dB. For the proposed PA design a Rogers printed circuit board (PCB) on a Cu hot plate for better thermal transferring has been used. All of the pads are bonded to PCB with 25 μm gold bonding wires directly.