Spatial Polarization Characteristics of Radar Antenna by Huanyao Dai Xuesong Wang Hong Xie Shunping Xiao & Jia Luo

Author:Huanyao Dai, Xuesong Wang, Hong Xie, Shunping Xiao & Jia Luo
Language: eng
Format: epub
Publisher: Springer Singapore, Singapore

(4.1.7)

A resolution function for scalar quantity of the array factor can be obtained as follows:

(4.1.8)

Hence, relationship between phase scanning and beam spatial direction under the spherical coordinate system can be obtained:

(4.1.9)

It can be seen from the Eqs. (4.1.7)–(4.1.9) that any beam direction of the phased array is realized by varying the feed phase, and scanning direction of the beam corresponds to the space angle coordinate. According to multiplying principle in the antenna array theory, overall radiation field of the phased array antenna is a product obtained by multiplying a polarization vector element direction pattern by a scaled array factor function . Hence, it can be known from the above-mentioned expression that the array factor decides direction angle of electric scanning of the beam, while scanning polarization characteristic of the phased array antenna can be decided and illustrated jointly by the polarization characteristic of the center radiation unit and observation direction .

In other words, the polarization characteristic can be jointly decided by the vector polarization direction pattern of element in array in observation direction and the beam direction determined by the beam scanning; therefore, spatial polarization characterization used to describe the mechanical mechanism-scanning system antenna is still applicable for phased array system.

It is noted that, during scanning of the phased array antenna, structure of the polarization direction pattern will vary, and antenna radiation field at different beam scanning position will be different. Hence, polarization characteristic cannot be approximately described by variation law of the radiation field at several observation angle, but it is required to first consider distribution condition of the antenna radiation field at fixed scanning angle, then, spatial polarization characteristic of the phased array antenna can be described accurately only by summing up or fitting polarization characteristic of the main lobe of the radiation field at several scanning angles.

Supposing that represents space angle coordinate at measuring point, which is a two-dimensional vector of the orientation direction and elevation direction , abbreviated to , and Ω, where Ω is spatial range scanned by the antenna. It can be known from the Eq. (4.1.3) that spatial polarization ratio of the antenna radiation field is as follows:

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