Resonance suppression in interdigital capacitors useful as dc bias breaks in diode oscillator circuits

Claim 2

An interdigital capacitor comprising, a stripline having a first and second section of conductive material, each section having a set of fingers protruding from one end, said sections being positioned to interdigitate the fingers of one section with the fingers of the other so that a continuous gap is created between the conductive sections, the gap forming a resonant transmission line, at least one slot cut into one of the conductive sections and coupling into the gap, said slot being dimensioned and positioned to shift the frEquency of resonance of the transmission line out of a selected frequency band, and a resistive film positioned across said slot for dissipating the energy of the shifted resonance.

Claim 3

An interdigital capacitor comprising: a stripline having a first and second section of conductive material, each section having a set of fingers protruding from one end, said sections being positioned to interdigitate the fingers of one section with the fingers of the other so that a continuous gap is created by the conductive sections, the gap forming a resonant transmission line, means for reactively loading the transmission line formed by the gap to shift its frequency of resonance, said reactive loading means including at least one slot cut into one of the conductive sections and coupling into the gap, CHARACTERIZED IN THAT, a resistive film is positioned across said slot for dissipating the energy of the shifted resonance.

Claim 4

An interdigital capacitor comprising: a stripline having a first and second section of conductive material, each section having a set of fingers protruding from one end, said sections being positioned to interdigitate the fingers of one section with the fingers of the other so that a continuous gap is created by the conductive sections, the gap forming a resonant transmission line, means for reactively loading the transmission line formed by the gap to shift its frequency of resonance, said reactive loading means including at least one slot cut into one of the conductive sections and coupling into the gap, CHARACTERIZED IN THAT, a resistive film is positioned across said slot for dissipating the energy of the shifted resonance.

Claim 5

An interdigital capacitor as claimed in claim 2 wherein said conductive material is affixed to a substrate and said resistive film is applied to the substrate and lies essentially in the plane of the conductive material.

Claim 6

An interdigital capacitor as claimed in claim 2 wherein said conductive material is affixed to a substrate and said resistive film is positioned on a sheet of intermediate material, said sheet being applied to the substrate.

Claim 7

An interdigital capacitor as claimed in claim 2 wherein said slot is coupled to the gap substantially at the voltage null point of the standing wave pattern of the resonance being shifted.

Claim 8

An interdigital capacitor as claimed in claim 5 wherein said slot is coupled into the center of the gap to shift a half-wave resonant frequency.

Claim 9

An interdigital capacitor as claimed in claim 5 wherein said slot is coupled to the gap at a point off the center of the gap to shift a full-wave resonant frequency.

Claim 10

An interdigital capacitor as claimed in claim 2 wherein said means for reactively loading the transmission line includes a pair of slots cut into one conductive section and symmetrically displaced from the center line of that section to shift a full-wave resonant frequency, and said resistive film is positioned across both of said slots.

Claim 11

A circuit for operating in a selected frequency band comprising: a circulator having an input port, output port and a diode port, a diode oscillator coupled to the diode port; bias means for applying a dc bias to the diode oscillator; means for blocking the dc bias from the input and output ports including at least one stripline interdigital capacitor as claimed in claim 2.

Claim 12

A circuit for operating in a selected frequency band comprising; an oscillator having an input port, output port and a diode port, a diode oscillator coupled to the diode port; bias means for applying a dc bias to the diode oscillator; means for blocking the dc bias from the input and output ports including at least one stripline interdigital capacitor coupled to one of the ports; said one capacitor including a conductor having two sets of interconnected conductive fingers intedigitated to form a gap between the fingers of the two sets, said gap having a length such that it is capable of supporting resonance at a first frequency, and at least one slot within said conductor being coupled to the gap and dimensioned to extend the effective length of the gap so that the capacitor''s resonance is shifted to a second frequency outside the selected frequency band; CHARACTERIZED IN THAT a resistive film is positioned across said slot parallel to the plane of the conductor to damp the energy of the shifted resonance.

Claim 13

A circuit for operating in a selected frequency band comprising; an oscillator having an input port, output port and a diode port, a diode oscillator coupled to the diode port; bias means for applying a dc bias to the diode oscillator; means for blocking the dc bias from the input and output ports including at least one stripline interdigital capacitor coupled to one of the ports; said one capacitor including a conductor having two sets of interconnected conductive fingers intedigitated to form a gap between the fingers of the two sets, said gap having a length such that it is capable of supporting resonance at a first frequency, and at least one slot within said conductor being coupled to the gap and dimensioned to extend the effective length of the gap so that the capacitor''s resonance is shifted to a second frequency outside the selected frequency band; CHARACTERIZED IN THAT a resistive film is positioned across said slot parallel to the plane of the conductor to damp the energy of the shifted resonance.

Claim 14

An oscillator circuit as claimed in claim 10 wherein said means for blocking dc bias includes a single interdigital capacitor coupled to the diode port.