Hf communication receivers have progressed towards a high level of sophistication yet a high percentage of reception failures are still due to limitations within the receiver This paper considers the role of frequency selectivity for an ideal receiver and proposes a costeffective approach which should noticeably reduce reception failure

http://ieeexplore.ieee.org/iel5/5266378/5269800/05269846.pdf

A reappraisal of h.f. receiver selectivity

The paper considers the situation of a switching-diode modulator driven by a local-oscillator signal derived from some source, typically a frequency synthetiser whose output contains both a significant level of random noise and also harmonically unrelated spurious tones at low level. The interaction of input signals to the modulator with the local-oscillator interference is considered, and expressions are derived for the output-signal levels arising from this interaction in terms of the local-oscillator signal/noise ratio. The performance is shown to be independent of local-oscillator source resistance and diode `offset? voltage. The performances of experimental Shottky-barrier modulators agree well with predictions.

A.M. Yousif

Papers

Distortion effects in switching-diode modulators arising from local-oscillator interference