Ground-based validation

The HCR transceiver was configured in a ground-based dual-antenna mode in order to verify the design and performance. Two coplanar 12-inch antennas were mounted on the top plate of a sea container. Both antennas had a matched beamwidth of 0.68° and gains of 46.21 dB. Custom designed antenna shrouds with millimeter-wave absorber were added to provide additional isolation between the transmit and receive antenna.

Signal was transmitted from one antenna and received simultaneously by the other. A reflector mounted on top of both antennas (shown in left figure) was used to aim the transmit beam to the desired near-horizontal angle.

The figure below shows the original CAD model for the ground-base configuration. Initially, it was designed with a 18-inch transmission and a 12-inch reception antenna due to antenna availability. The configuration was soon modified to two identical, matched-beamwidth, 12-inch antenna for the entire ground validation. 

Comparison with NEXRAD

In order to compare measurements from ground-based HCR with the NEXRAD (KFTG) radar, measurements from clouds with low reflectivity values were selected. This criterion ensured Rayleigh scattering for which reflectivity is independent of radar wavelength. HCR collected vertical profiles while the NEXRAD was operated in clear-air mode on June 1, 2010.

Despite the minor differences in sampling volumes and times, this preliminary comparison indicates HCR reflectivity measurements are in reasonable agreement with NEXRAD observation.

Comparison with Wyoming Cloud Radar (WCR)

The phase-A, pod-based HCR was brought to the University of Wyoming for the collaborated engineering assessment. By comparing the HCR with the well-calibrated, mature Wyoming Cloud Radar (WCR), the deficiencies and performance of the HCR can be easily verified.

A 30-minute stratoform rain event was observed by both radars on September 27, 2012. To accurately evaluate the performance, minimum time and range interpolation was performed on the WCR data. The preliminary, aligned signal-to-noise ratio (SNR) from both systems are shown to the left. Similar patterns are recorded in both systems. Patterns in far ranges seem more skewed than close ranges. This suggests the two systems may not be perfectly aligned in the azimuth direction. The scatterer correlation was plotted and is shown to the right. The HCR shows good correlation with the WCR with approximately 0.5 dB offset in SNR.