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Interference rejection RF filters

  • US 9,685,928 B2
  • Filed: 08/01/2014
  • Issued: 06/20/2017
  • Est. Priority Date: 08/01/2013
  • Status: Active Grant
First Claim
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1. An apparatus comprising an RF filter structure, which comprises:

  • a plurality of resonators comprising a pair of weakly coupled resonators;

    a plurality of cross-coupling capacitive structures, wherein each of the plurality of cross-coupling capacitive structures is coupled between two of the plurality of resonators; and

    a plurality of egress/ingress capacitive structures, wherein a first portion of the plurality of egress/ingress capacitive structures is coupled between the plurality of resonators and a first connection node, and a second portion of the plurality of egress/ingress capacitive structures is coupled between the plurality of resonators and a second connection node, wherein;

    a corresponding coupling coefficient of each of the plurality of egress/ingress capacitive structures is adjustable;

    a first tunable RF filter comprises at least a portion of the plurality of resonators, at least a portion of the plurality of cross-coupling capacitive structures, and at least a portion of the plurality of egress/ingress capacitive structures;

    a frequency response of the first tunable RF filter is a bandpass filter response with a first notch filter response, which has a first notch frequency, such that the bandpass filter response has a center frequency; and

    the first notch frequency is equal to a first sum plus a first difference, such that the first sum is equal to a sum of the center frequency and a harmonic of a local oscillator frequency, and the first difference is equal to a difference between the center frequency and the local oscillator frequency.

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