Salient Features of the CSU-CHILL radar X-band channel upgrade

The CSU-CHILL radar has recently gone through a major transformation to add support for simultaneous dual-wavelength (S and X), dual polarization (H and V) radar operation, as well as high polarization purity S and X band stand alone operations. This process started with the installation of a low-sidelobe dual-offset Gregorian antenna capable of supporting three different feeds (S, X and simultaneous S and X all with dual-polarization capability), and culminated with the the development and installation of a separate X-band channel dual-polarization radar system. The X-band channel dual-polarization radar system uses a magnetron transmitter that is split to create a simultaneous H and V polarization signal. A low-noise, high dynamic range dual-channel parallel receiver is used to down-convert the analog signal to the system IF centered around 150 MHz. A high-speed digitizer is employed to sample and digitally down-convert the IF signal to base band. The entire radar system hardware is mounted directly on the CSU-CHILL radar antenna, and all control and data communication is done through a gigabit capable slip ring mounted on the antenna pedestal. The signal processor for the X-band channel radar system allows operation of the system both at single PRF and dual PRF, and the use of the different signal processing algorithms. The small antenna beam-width at X-band (0.3 deg) and simultaneous availability of dual-polarization, dual-wavelength (S and X-band) make the CSU-CHILL radar a unique platform for meteorological observations supporting both research and education. Furthermore, the radar also contributes to the development of processing techniques for higher frequency radars that can be verified with the collocated low-frequency observations at S-band. Figure 1 below shows one such example where an attenuation correction algorithm for X-band data is investigated and compared to the collocated S-band data. This paper presents the multi-frequency radar architecture as well as evaluation of the performance of the dual-frequency radar system.