Study and Experimentation of RF Pulse Generating And Amplifying Techniques for Improving Radar Emission Characteristics

摘要

The report concerns techniques for generating shaped pulses having very narrow frequency spectra. Promising results were previously obtained by driving a single klystron with a pulse shaped at low-level. The shaping scheme was quite complex hence this investigation was undertaken to produce similar pulses with less hardware. Two techniques were tried. Both use a crystal oscillator, broad-band multipliers and an up-converter to produce an output in the frequency range 2.7 to 2.9 GHz. Shaped pulses were produced at 30-MHz and linearly mixed with an appropriate S-band signal to give the desired output. A tunable filter was constructed to dispose of unwanted components from the up-converter. The first technique used a 9-pole band-pass Bessel filter through which a 30-MHz pulse was passed to produce the shaped pulse. The second employed a 9-pole low-pass Bessel filter which was used to modulate a gated 30-MHz signal to produce the shaped pulse. Since preliminary tests showed the band-pass technique to be inferior to the low-pass technique, emphasis was concentrated on the latter. Output pulse shape and spectra were measured for various amounts of shaping by varying the gate to the Bessel filter in either technique. The output pulse shape can be varied between a Gaussian-like and a nearly-rectangular pulse. Data were taken for four pulse shapes covering the range of interest. (Author)