Zenith/Nadir Pointing mm-Wave Radars: Linear or Circular Polarization?

Abstract

We consider zenith/nadir pointing atmospheric radars and explore the effects of different dual-polarization architectures on the retrieved variables: reflectivity, depolarization ratio, cross-polar coherence, and degree of polarization. Under the assumption of azimuthal symmetry, when the linear depolarization ratio (LDR) and circular depolarization ratio (CDR) modes are compared, it is found that for most atmospheric scatterers reflectivity is comparable, whereas the depolarization ratio dynamic range is maximized at CDR mode by at least 3 dB. In the presence of anisotropic (aligned) scatterers, that is, when azimuthal symmetry is broken, polarimetric variables at CDR mode do have the desirable property of rotational invariance and, further, the dynamic range of CDR can be significantly larger than the dynamic range of LDR. The physical meaning of the cross-polar coherence is revisited in terms of scattering symmetries, that is, departure from reflection symmetry for the LDR mode and departure from rotation symmetry for the CDR mode. The Simultaneous Transmission and Simultaneous Reception mode (STSR mode or hybrid mode or Z DR mode) is also theoretically analyzed for the case of zenith/nadir pointing radars and, under the assumption of azimuthal symmetry, relations are given to compare measurements obtained at hybrid mode with measurements obtained from orthogonal (LDR and CDR) modes.

Variability of Circular Depolarization Ratio in Radar Sensing of the Medium Filled with Hydrometeors

“…The prerequisite to the use for displaying and interpreting the measurements results of the ircular depolarization ratio (CDR) [1] is pronounced dependence of the circularly polarized eceived signals amplitude on the shape of the water droplets. The ratio, as it shown in [2][3][4], is ndependent of the orientation of the hydrometeors and is less subject to the influence of third party oises. The higher intensity of the rain (in other words, the more water droplets shape differs from he spherical shape), the more differences of a signal received with right and left circular olarizations [5] in the case when the probe signal polarization has one of the pointed above circular olarization states.…”

Catalyzing satellite communication: A 20W Ku-Band RF front-end power amplifier design and deployment

“…The Ku-Band satellite transmission signal proposed in this paper is a linearly polarized electromagnetic wave, with a specific polarization angle. It is based on the principle of vector signal synthesis decomposition [ 51 , 52 ]. This allows the decomposition of the phase and amplitude of the Ku linearly polarized electromagnetic wave into vertical and horizontal linear-polarization channels.…”

Estimation of the Hydrometeors’ Anisotropic Properties Based on the Use of Circular Depolarization Ratio

“…Однако существенным недостатком Z CDR является его сильная зависимость от эффектов рас-пространения электромагнитной волны, в частности, от дифференциального фазового сдвига, вносимо-го между ее ортогональными компонентами. Работы [5][6][7][8] посвящены оценке анизотропных свойств ги-дрометеоров для разных условий наблюдения, а так-же сравнению эффективности разных поляриметриче-ских методов. В частности, результаты работы [8, с.…”