Wide-band microwave signal coupler
First Claim
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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Abstract
A microwave coupler for coupling microwave energy from a first waveguide to a second waveguide disposed side by side along a propagation length includes a common coupling means, and specifically, orifices along the propagation length wherein the coupling orifices are sized to promote coupling of a favored field mode of electromagnetic energy according to a Bessel function distribution of energy along the length of the waveguide. The Bessel function distribution provides for wideband, low-loss coupling of the favored field mode and maximal isolation from non-favored field modes. The invention is particularly useful for extracting a type TE21 circular mode signal from a signal containing TE11 and TE21 circular modes wherein the TE21 mode signals are used for generating elevational and azimuthal tracking signals.
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Citations
6 Claims
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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.
- 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;
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2. An apparatus for coupling a selected favored nondominant mode of electromagnetic energy from a first waveguide into a second waveguide, said first waveguide carrying dominant mode electromagnetic energy and nondominant mode electromagnetic energy, comprising:
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a first waveguide; a second waveguide juxtaposed to said first waveguide along a propagation length; and means for promoting coupling of electromagnetic energy from said first waveguide to said second waveguide, said coupling means comprising a common wall to said first waveguide and said second waveguide, said common wall having circular holes disposed along said propagation length, said circular holes having a diameter no greater than 0.3 wavelengths of the lowest order mode of the highest frequency of said dominant mode electromagnetic energy intended to traverse through said first waveguide, each said hole having a diameter selected as a function of an electric field ratio of a desired Bessel function distribution of said selected favored nondominant mode electromagnetic energy of said first waveguide along said propagation length, the Bessel function distribution being of the first kind of the zeroeth order, centers of said holes being equally spaced from one another, the smallest diameter holes being at opposing ends along said propagation length, the largest diameter holes being centered between said opposing ends of said propagation length and having therebetween holes which decrease in diameter from the largest diameter holes to the smallest diameter holes, for coupling said selected favored nondominant mode electromagnetic energy from said first waveguide to said second waveguide with maximum bandwidth and minimum phase distortion while maximizing propagation of said dominant mode microwave electromagnetic energy of said first waveguide with maximum bandwidth and minimum phase distortion through said first waveguide. - View Dependent Claims (3, 4, 5, 6)
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Specification