Experimental Validation of the Time-Multiplexed Transmission for Cross-Polar Isolation Improvement

Polarization diversity is one of the most significant advancements in weather radar over the last two decades because it greatly enhances the ability to discriminate among different weather and non-weather returns. Implementation of dual-polarization technology poses a significant design challenge in terms of acceptable cross-polar field levels. For example, to achieve acceptable differential reflectivity (Z_DR) bias (e.g., less than 0.1 dB) using simultaneous transmission and reception of H and V polarized waves, the isolation between coaxial cross-polar and co-polar beams needs to be in excess of 50 dB. Such isolation is exceptionally difficult to achieve at an affordable price by antenna hardware in radars with patched antennas (e.g., phased array radars). Consequently, additional methods are needed to attain supplementary isolation of orthogonal channels. One such technique is the time-multiplexed or quasi-simultaneous (QSHV) back-to-back transmission of horizontal (H) and vertical (V) pulses whereby H field is radiated immediately after V or vice versa. Herein, an experimental evaluation of this technique is presented. All experiments have been performed with the Advanced Radar Research Center's (ARRC) PX-1000 radar, which is a transportable solid-state polarimetric X-band radar. Results illustrating the isolation enhancements will be demonstrated.