Front end design

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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.

95 GHz LO
112.5 GHz LO
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Receiver has two dual polarized beams with a
beamswitch. One beam always on source.
Beams separated in azimuth with spacing of 3 HPBW.
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• 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 lt10K, switching time lt10 ?sec.

Out
In
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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.