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Wide-band microwave signal coupler

  • US 4,566,012 A
  • Filed: 12/30/1982
  • Issued: 01/21/1986
  • Est. Priority Date: 12/30/1982
  • Status: Expired due to Term
First Claim
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1. An apparatus for extracting tracking signals from a received microwave signal for directing an antenna, said apparatus operative to pass dominant mode information-containing microwave signals with minimum attenuation through a signal path of a first waveguide while extracting from said signal path selected favored nondominant mode microwave signals for use in developing error signals to control directional orientation of said antenna, said apparatus comprising a first waveguide, a second waveguide, a third waveguide, a fourth waveguide, a fifth waveguide, a sixth waveguide, a seventh waveguide, an eigth waveguide and a ninth waveguide, said first waveguide being circular and said second through ninth waveguides being rectangular, said second through ninth waveguides being disposed at angular separations of 45°

  • juxtaposed to said first waveguide and oriented along a central axis of said first waveguide, said first waveguide forming a common wall with one wall of each said second through ninth waveguides, said common wall defining a coupling structure having the following characteristics between said first waveguide and each one of said second through ninth waveguides;

    a row of holes whose centers are spaced equidistant along said central axis, each said hole being of a diameter no greater than 0.3 wavelengths of the wavelength of the highest frequency intended to be conveyed through said first waveguide in its characteristic dominant TE11 mode, said holes being circular, said holes being of a diameter selected to produce a distribution of coupling strengths of a preselected nondominant mode of said first waveguide for coupling to each of said second through ninth waveguides, and specifically a nondominant TE21 circular mode in said circular first waveguide which is manifest as a TE10 rectangular mode in each one of said second through ninth waveguides, said distribution of coupling strengths being characterized by a Bessel function distribution of coupling strength along said central axis, said Bessel function distribution of coupling strength being established at a certain coupling strength level at each one of said holes to minimize reverse coupling from said second through ninth waveguides into said first waveguide by the size of said holes, said second through ninth waveguides having output ports being coupled in preselected pairs to extract from said first waveguide two balanced and orthogonal signals representative of energy contained in the TE21 nondominant circular signal of said first waveguide for use in developing a tracking signal based on phase and amplitude information contained in the carrier of said TE21 mode signal.

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