A Plasma-Switch Impedance Tuner for Real-Time, Frequency-Agile, High-Power Radar Transmitter Reconfiguration

Recent policy changes to the United States radar S-band allocation requires that radar transmitters share the 3.45 to 3.7 GHz range with fifth-generation (5G) wireless communication systems. As more radar spectrum is designated for sharing, reconfigurable high-power radar transmitters are needed that can maintain performance while quickly adjusting operating frequency. At the heart of a frequency-agile radar transmitter is a reconfigurable matching network, placed between the power amplifier and the antenna, that can maintain optimal range performance in real time by adaptively matching the antenna to the amplifier. Our impedance tuner consists of laser diodes illuminating semiconductor-plasma switches to selectively expose six microstrip stubs and has an octave tuning range from 2-4 GHz. Using an advanced tuning algorithm, the tuner can optimize output power in approximately 260 mu s under control of a software-defined radio platform, an improvement of three orders of magnitude over presently available high-power tuning technologies.