Implementation of Polarization Diversity Pulse Pair mode on the NRC Airborne W-band Radar

As part of an ESA Doppler Wind Radar Demonstrator Project, the NRC Airborne W-band (NAW) radar was recently upgraded with a new power supply modulator and a radar control card that allow operating the NAW radar in Polarization Diversity Pulse Pair (PDPP) mode. Although the PDPP technique was demonstrated successfully in ground based systems, the NAW radar is the first airborne system with successful implementation of the PDPP mode. The NAW radar antennae sub-system consists of three fixed Gaussian Optics Lens antennae and a two-axis reflector housed in an external radome. For the PDPP demonstration, a dual-pol side-looking antenna and a dual-pol aft-looking antenna and reflector combinations are used. With a careful selection of aircraft maneuvers, extensive PDPP dataset being collected at various radar beam angles using the two fixed dual-pol antennae. 

For the NAW PDPP upgrade, a hybrid PDPP and conventional pulse-pair operating mode was implemented using the previously available NAW PP10 pulsing mode. In this new PDPP mode, sequence of H/V and V/H polarization diversity pulse-pairs are transmitted interleaved with conventional staggered PRT H/H and V/V pulse-pairs. The radar control board (RCB) does not trigger the data system at the second PDPP pulses, so the data system real-time processes the measured data using the currently available PP8 algorithm. The main NAW upgraded features include, the ability to transmit double pulsing with short spacing as low as 6 µs and recording of the raw IQ radar data in PDPP mode. The PDPP mode is also tested at 12, 20 and 40 µs separations.

In this paper, we present details of the PDPP implementation on the NAW radar with details of the hardware modifications, ground tests results on polarization switching and analysis of the accuracy of high velocity (up to 80 m/s) measurements from an airborne platform.