Patent ID: 6424817
Filing Date: 2002-07-23
Classification: H04B,H04H

Abstract:
A downconverter system which reduces spurious signals as it downconverts first and second polarized satellite signals that occupy a common frequency band to thereby form combined communication signals, the system comprising:first and second probes arranged to respectively detect said first and second polarized signals and process them to first and second detected signals; first and second local oscillators that respectively provide a first local oscillator (LO) signal and a second LO signal that is spectrally spaced from said first LO signal; a first low-noise block downconverter that has a first mixer which responds to said first LO signal and downconverts said first detected signals to first downconverted signals in a first frequency band that is at least two octaves below said first and second LO signals; a second low-noise block downconverter that has a second mixer which responds to said second LO signal and downconverts said second detected signals to second downconverted signals in a second frequency band that is spectrally spaced from said first frequency bald and is at least two octaves below said first and second LO signals; a diplexer that combines said first and second downconverted signals to form said combined communication signals; a first intermediate-frequency (IF) filter coupled between said first mixer and said diplexer and configured to pass said first downconverted signals in said first frequency band and attenuate said second dow converted signals in said second frequency band; a second IF filter coupled between said second mixer and said diplexer and configured to pass said second downconverted signals in said second frequency band and attenuate said first downconverted signals in said first frequency band; a first LO isolation filter set to the frequency of said second LO signal and coupled between said first mixer and said diplexer to inhibit passage of said second LO signal to said first mixer; and a second LO isolation filter set to the frequency of said first LO signal and coupled between said second mixer and said diplexer to inhibit passage of said first LO signal to said second mixer; said first and second LO isolation filters thus inhibiting crosstalk between said first and second mixers to thereby reduce spurious signals in said combined communication signals.