The WiBEX solid state X-band radar system

Weather radars utilizing low-power solid-state transmitters are an emerging technology. Their primary benefits relative to electron-tube transmitters are increased instantaneous bandwidth, relaxed duty cycle requirements and improved reliability. At the same time, the low available peak power requires the use of pulse compression techniques to achieve sensitivity and range resolution comparable to electron tube transmitters.

Solid-state transmitters are also an essential component of active phased-array antennas, such as the ones being developed for the CASA project. The Wideband Experimental X-band (WiBEX) radar system is designed as a test-bed for the development of complex radar waveforms that are suitable for use with low peak power weather radar systems. Use of a mechanically-scanned reflector antenna allows the development of waveforms independent of beam spoiling due to electronic scanning off boresite. This paper describes the solid-state radar system that has been developed at Colorado State University.

The paper will describe the waveforms used to achieve wide bandwidth and average power. The waveforms apply tapering in both frequency and amplitude, with the aim of reducing the range sidelobe levels after pulse compression. Finally, the blind-zone mitigation scheme is outlined. The implementation of the solid-state radar, starting with a versatile Transmit Waveform Generator, capable of producing wideband waveforms is described. This subsystem makes use of FPGA technology for maximum waveform flexibility and ease of development. The RF subsystem, including the frequency reference, up-convert chain, antenna, down-convert chain and calibration subsystems are described. The FPGA based channelizing digital receiver and pulse compression hardware are also covered in this section. Again, the use of FPGA technology permits design flexibility, rapid development, and extremely high performance digital signal processing required to do pulse compression simultaneously on multiple channels. Preliminary data sets collected with the WiBEX radar system are presented. Data examples will be used to demonstrate the advanced blind-range mitigation system, showing that solid-state transmitters are a viable option for research-quality weather radar systems.