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Front end design Front end like SEQUOIA, except that both signal polarizations combined with ortho-mode transition. Entire signal band down-converted at once to two 18.5 GHz wide IF bands. Four receivers with 8 outputs in total. 112.5 GHz LO 95 GHz LO
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Beams separated in azimuth with spacing of 3 HPBW. Receiver has two dual polarized beams with a beamswitch. One beam always on source.
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In Out Faraday Rotation Switch Beamswitch developed for this work improves enormously on any previous device. Dual polarized beam is rotated by 45 using a switched magnetic field in a ferrite. Added noise <10K, switching time <10 sec.
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Analog autocorrelator vs digital Analog correlation requires no high speed signal sampler-digitizer. Analog requires no signal quantization: Very wide dynamic range. No noise degradation. Analog bandwidth is much larger -- 8.0 GHz. High accuracy analog autocorrelation is practical with low cost, ~$10/lag.
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Analog Autocorrelator Basics Delay lines Nyquist sampled ( /4) for 8 GHz bandwidth with weak coupling using a resistive tap. Many taps are practical, we use 64 on each line. Tap signals are detected with silicon diodes which act as multipliers.
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Correlator board presently in test, everything works. Delay lines with 256 taps, detectors, AC amplifiers, A/D converters, FPGA for digital signal processing all on one board. 31 MHz resolution.
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