Deconvolution of target signature for a scene with bistatic impulse radiating antennas and a sphere
A model for an impulse radiating antenna (IRA) has been developed in WIPL-D. A scene using a bistatic pair of these IRAs is modeled with a sphere target and is simulated in the frequency domain. The input to the antenna is a Gaussian pulse, and the current on the receive antenna is plotted vs. frequency. This receiver response is proportional to the scattered field from the sphere. The frequency domain data are processed to give the time domain response. The objective of this work is to deconvolve the signature of the scatterer from the receiver transient response. Additional separate simulations for each scene component and electromagnetic interaction were needed and were performed using WIPL-D. The process is successful for this scene, which does not include a ground plane. The analysis of the simulated data and deconvolution of the target signature are done in Matlab.
Sensor and Simulation Notes Note 474 3 June 2003 Numerical Analysis of the Impulse-Radiating Antenna
Two reflector-type impulse-radiating antennas with focal length to diameter ratios of 0.25 and 0.5 are numerically analyzed. The numerical model is developed using the method of moments code in the EIGER code suite. The performance of the numerical model is validated by comparing the radiated field measured on boresight and the reflected voltage measured in the transmission line with the results from the numerical model. Using the numerical model, the contribution of each part of the antenna to the radiated field and the reflected voltage is identified. The reflected voltage waveform in the transmission line and the electric field waveforms both in the nearand far-zones are presented. The impulse and prepulse amplitudes, spot sizes, and power budgets are also presented.
Optimizing the Feed Impedance of Impulse Radiating Antennas Part I : Reflector IIUs
, When designing a reflector Impulse Radiating Antenna, one must choose an appropriate feed impedance. Using the simplest approximations valid for high feed impedances, one finds that lower feed impedances are always prcfcrablc. However, low feed impedances imply thick feed arms, which incrcasc feed blockage for many designs, thus reducing the radiated field. Low feed impedances also lead to a breakdown of the approximation that the cffcctivc aperture height is equal to the radius of an aperture for circular apertures. Thus, even when there is no feed blockage , there is a reduced aperture height at low feed impedances. We calculate here the radiated field based on a contour integration technique that takes into account feed blockage. With these calculations, one can find the optimal feed impedance for a given configuration of feed arms. The analysis is valid in the limit of fast risetimes, and is carried out for three different feed structures. ..