QUASI-LINEAR INTERFERENCE SUPPRESSOR
STANFORD UNIV CA STANFORD ELECTRONICS LABS
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The purpose of the research was to devise and test new interference suppression techniques. A major motivation was the desire to minimize the deleterious effects of HF radio-station interference to an ionosphere sounder. Previous research has shown that the FM-CW waveform is particularly attractive for ionosphere sounding because of the ability to generate waveforms having very large time bandwidth products using electronically controlled frequency synthesizers. In studying interference problems during this research it was appreciated for the first time that simple nonlinear processing e.g., clipping in the FM-CW sounder is directly analogous to the much more complicated nonlinear processing e.g., frequency-by-frequency limiting necessary in the corresponding simple-pulse or coded-pulse sounding systems. A new interference suppression method was devised and shown to be effective in removing pulse or FM-CW interference from narrow-band signals. Interference energy at frequencies outside the desired-signal bandwidth is processed and used to balance out the interference energy included with the desired signal. The balancing action is intermittent and the principle of operation is to switch from one linear mode to another, hence the name quasi-linear suppressor.
- Atmospheric Physics
- Electrical and Electronic Equipment