CHARACTERISTICS OF IMPULSES REFLECTED FROM A SECH2 ELECTRON-DENSITY PROFILE AND BANDPASS FILTERED

The signal reflected from a sech2 electron-density profile and bandpass filtered was calculated for an incident plane wave with an impulsive time variation. For “wide” bandwidths, the envelope of the filter output decreases in duration with decreasing bandwidth, with some increase in peak amplitude. For “narrow” bandwidths, the envelope of the filter output decreases in peak amplitude and increases in duration with decreasing bandwidth; the envelope also oscillates about its mean value after the peak. The critical bandwidth, at which the filter output changes from the “wide-” to the ‘harrow-” band behavior, was found to be associated with a characteristic pattern of the saddle points of the Fourier-transform integrand. Copyright © 1968 by The Institute of Electrical and Electronics Engineers, Inc.