An X-band Phased Array Weather Radar Testbed

The University of Massachusetts Microwave Remote Sensing Laboratory is developing a testbed for phased-array weather radar polarimetry. The testbed consists of a planar dual-polarization X-band phased-array radar deployed side-by-side with a reference radar employing a traditional parabolic reflector. The phased-array, on long-term loan to UMass by Raytheon, consists of 2560 dual-polarized microstrip patch elements. Each element is a slot-fed stacked microstrip patch antenna which may be excited in either vertical or horizontal polarization. Antenna elements are arranged in 128-element tiles in a 4x5 grid. The radar operates at 9.6 GHz and employs pulse compression with a duty cycle of up to 20%. The scan range is 90 degrees in azimuth and 30 degrees in elevation (+/-15 degrees off boresight assuming the array panel is tilted 15 degrees from the vertical). The reference radar operates at 9.4 GHz employing a 1.2 m diameter parabolic reflector.

We present predictions of the polarimetric behavior of the phased array when scanning off axis and discuss issues of comparison between the two radar systems. While the two radars operate at similar frequencies with similar sensitivities and beamwidths, the radars employ differing polarization schemes (the phased-array employs Alternate Transmit Alternate Receive (ATAR) while the parabolic antenna employs Simultaneous Transmit Simultaneous Receive (STSR)). We describe initial measurements planned for the testbed.