Target Visualization Approach Based on Phased-Array Effect in Antennas with Transient Excitation

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Introduction
Target visualisation is main goal of the practical radargram recovering procedure. There are a lot of visualisation algorithms (2D-filtering. migration. FFT etc.) that is mainly based on final images processing. Existent methods are not frequently allowed to get adequate results due to considerably complex properties of the surrounding target environment.

In this work an approach to target visualisation based on phased-array effect in antennas with transient excitation is proposed and discussed. This reconstruction method uses initial information about properties of the used for radargram getting antennas. Preliminary results of this approach, its applicability and sensitivity are presented.

An Approach of Target Visualisation
In contrast to antennas behaviour with sinusoidal or narrow frequency band excitation such one with transient excitation has some differences [1]. As a matter of fact transient radiation of an antenna depends on its geometry. If pulse generator impedance and input antenna impedance is matched in the antenna is observed so-called double-passing excitation mode [2]. hi this case temporary structure of the antenna radiation field consists of three impulses sequence. Note that time delays between neighbouring impulses are associated to antenna length and the second impulse polarity is inverse one to the first and third pulses.

Let's consider monopole linear antenna with impulse excitation in Cartesian coordinates as it is shown in Fig. 1. Assume that the antenna length is L and a target coordinates is (X0. Y0). Distances from target to excitation point and antenna edges are Rl and R2. accordingly.

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