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Microwave band-pass filter

  • US 4,761,624 A
  • Filed: 03/20/1987
  • Issued: 08/02/1988
  • Est. Priority Date: 08/08/1986
  • Status: Expired due to Fees
First Claim
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1. A microwave band pass filter for obtaining a sharp skirting characteristic on a low frequency side of a passing band, such as obtained in a coaxial type band pass filter (BPF), as well as on a high frequency side of the passing band, such as obtained in a combline type BPF, comprising in series at least the following:

  • a first dielectric block having a resonator providing a coaxial type BPF having a characteristic of lower cutoff frequencies which is formed by a hole lined with an inner conductor and a pair of leading and trailing electrodes on a face of said block in one direction spaced on each side of an end of said hole;

    a second dielectric block having a plurality of resonators providing a combline type BPF having a characteristic of higher cutoff frequencies which is formed by respective holes spaced apart in parallel and in series, each lined with an inner conductor, and a pair of leading and trailing electrodes on a face of said block in the one direction spaced on each side of the series of holes; and

    a third dielectric block having a resonator providing a coaxial type BPF having a characteristic of lower cutoff frequencies which is formed by a hole lined with an inner conductor and a pair of leading and trailing electrodes on one face of said block in the one direction spaced on each side of an end of said hole,wherein the lower cutoff frequencies for said coaxial type BPF are included in a passing band for the combline type BPF, and the higher cutoff frequency for the combline type BPF are included in a pass band for the coaxial type BPF, andwherein the trailing electrode of said first block is connected to the leading electrode of said second block, and the trailing electrode of said second block is connected to the leading electrode of said third block, whereby the low frequency side skirting characteristic of a coaxial type BPF is obtained by the resonators of said first and third blocks being connected through said second block in series through equivalent capacitances formed by the connection of the leading and trailing electrodes, and the high frequency side skirting characteristic of a combline type BPF is obtained by the resonators of said second block connected in series through equivalent coaxial lines formed by their parallel arrangement in said second block.

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