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Last Modified: Monday, 31-July-00 1:05:31 PM EDT



This material is based on work supported by the National Science Foundation under Grant AST-0096854.

Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation.

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Second IF Converter

  • Breaks up the 1.5-20 GHz band into three equal bands of 1.5-8.0 GHz to drive the autocorrelator


Second IF Converter System

Analog Autocorrelator

  • Delay lines sampled at λ/4 spacing at 8 GHz bandwidth
  • Typical line coupling is –30 dB per tap using a resistive tap
  • Tap signals are detected with biased silicon diodes, which make very accurate square law detectors
  • The frequency response is relatively flat to 8 GHz
  • Many taps are practical on a single line with weak coupling; 64 taps are used per line
  • VSWR does not increase with number of taps except near DC and twice the sample frequency,

Delay Line Schematic


Why an analog autocorrelator?

  • Analog correlation requires no high speed signal sampler
  • Dynamic range is much larger than for few bit samplers
  • No noise degradation due to sampling noise
  • Bandwidth for a single correlator is much larger
  • High accuracy analog autocorrelation is practical with low cost


Autocorrelator continued, next page...



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