Antenna system requirement for dual polarization radar design in hybrid mode of operation

For dual polarization radar design, the hybrid mode of operation (simultaneous transmission simultaneous reception) is becoming popular due to simplicity of the system compared to the polarization switching methodology. Alternating transmission mode of operation between horizontal (H) and vertical (V) polarization states can measure the full covariance matrix whereas the hybrid mode can only measure the co-polar subset of the covariance matrix. The estimation of co-polar radar parameters from hybrid mode measurements will be biased when cross polarization coupling occurs. The cross polarization coupling can be introduced either by the backscattering properties of hydrometeors, as represented by the linear depolarization ratio (LDR), or the system limitations such as cross-polar isolation or both. In this paper the impact of system polarization isolation is emphasized and investigated. It is shown that the measurement accuracy in the hybrid mode is more sensitive to the isolation between channels. Various scenarios are analyzed in the presence of inadequate polarization isolation. These studies are converted to the system requirements for the dual-polarization weather radar design in the hybrid mode of operation.