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.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.