Polarimetry and phased array are the two most prominent radar technologies in weather and aircraft surveillance. This is because a polarimetric radar allows for multi-parameter measurements with more information content. A phased array radar (PAR), with agile beam capability, facilitates fast data update and the observation of detailed evolution of storms/targets. It is desirable to have both the polarimetry and the agile-beam capabilities in one radar system, i.e., polarimetric phased array radar (PPAR) for (MPAR). PPAR technology has been done for NASA and military missions in earth observation and target detection with synthetic aperture radar (SAR). However, PPAR has been a big challenge to the MPAR community because it requires a wide-angle scan and high-accuracy weather measurements. Budget constraints makes it more challenging to develop a high performance PPAR system. Therefore, PPAR technology and its implementation options need to be thoroughly examined and designed.
Possible modes of operation for polarimetric radars include i) Alternate Transmission and Alternate Reception (ATAR), ii) Alternate Transmission and Simultaneous Reception (ATSR), and iii) Simultaneous Transmission and Simultaneous Reception (STSR). Each of these three modes has their own advantages and disadvantages. While the ATSR mode is mostly used in target detection radars and SAR to make fully polarimetric measurements, the STSR mode is commonly used in operational weather radars such as WSR-88D to make dual-polarization measurements which do not require a high-power switch, making the dual-polarization upgrade more cost-effective. For a polarimetric phased array radar with distributed T/R modules over a large number of radiating elements, the high power switch is not an issue. Selection of polarization mode needs to be revisited. In this work, we study the three polarization modes: ATAR, ATSR and STSR for phased array approach. Information content, measurement accuracy, and implementation complexity are examined for both weather and aircraft surveillances. Cross-polarization isolation requirements and its impact on radar antenna/system cost and timeline designation for multi-missions will be analyzed. The tradeoffs between performance and cost are summarized to provide an understanding and foundation to make an optimal selection of polarization mode of operation for MPAR.
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