Fixed and varactor-tuned bandstop filters with spurious suppression
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorAndrew C. Guyette
Life of this patent
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Abstract
A bandstop filter configured to suppress a spurious resonance frequency includes a resonator and a transmission line that is coupled to the resonator at a first junction and at a second junction with a length θ of transmission line running between the two couplings. The configuration provides two signal paths so that constructive interference occurs at the spurious resonance, and destructive interference occurs at a fundamental bandstop frequency. This provides spurious suppression by effectively cancelling out resonator couplings via the constructive interference, extending the upper passband of the bandstop filter to any degree required by the application.
Claims18
A bandstop filter configured to suppress a spurious resonance frequency, comprising:
- a resonator;
- and
- a transmission line coupled to the resonator at a first junction and at a second junction defining a length θ of transmission line therebetween, thereby defining two signal paths such that constructive interference occurs at the spurious resonance frequency and destructive interference occurs at a fundamental bandstop frequency to thereby suppress the spurious resonance frequency, ad wherein the couplings have a sign
- BW=4K2 cos2 0/2 Equation (1)
- where BW is the bandwidth and K is the coupling coefficient.
A bandstop filter configured to suppress a spurious resonance frequency, comprising:
- a resonator;
- and
- a transmission line coupled to the resonator at a first junction and at a second junction defining a length θ of transmission line therebetween, thereby defining two signal paths such that constructive interference occurs at the spurious resonance and destructive interference occurs at a fundamental bandstop frequency to thereby suppress the spurious resonance frequency, and wherein the couplings have opposite signs
- BW=4K2 sin2 0/2 Equation (2)
- where BW is the bandwidth and K is the coupling coefficient.
A second-degree bandstop filter, comprising:
- two 1st-degree bandstop sections mutually coupled in a cascade configuration and wherein each said section comprises:
- a stepped-impedance combline resonator, and
- a transmission line coupled to the resonator at a first junction and at a second junction defining a length θ of transmission line therebetween, thereby defining two signal paths such that constructive interference occurs at the spurious resonance and destructive interference occurs at a fundamental bandstop frequency to thereby suppress the spurious resonance frequency.
A second-degree bandstop filter, comprising:
- two 1st-degree bandstop sections mutually coupled in a cascade configuration and wherein each said section comprises:
- a varactor-loaded combline resonator, and
- a transmission line coupled to the resonator at a first junction and at a second junction defining a length θ of transmission line therebetween, thereby defining two signal paths such that constructive interference occurs at the spurious resonance and destructive interference occurs at a fundamental bandstop frequency to thereby suppress the spurious resonance frequency.
Dependencies are inferred from the claim text.