TEMPERATURE COMPENSATED TUNEABLE TEM MODE RESONATOR
A TEM mode resonator ( 12 ) comprising a tuneable cavity ( 13 ) defined by an electrically conducting cavity wall ( 14 ), the cavity wall comprising a grounding face ( 15 ), a capacitor face ( 16 ) and a surrounding wall ( 17 ) extending therebetween; an electrically conducting resonator member ( 18 ) within the cavity extending from the grounding face ( 15 ) part way to the capacitor face; a tuning member ( 19 ) within the cavity between the resonator member and capacitor face adapted to be displaced towards and away from the capacitor face along a displacement axis to tune the resonator; the capacitor face ( 16 ) further comprising an electrically conducting temperature compensation plate ( 25 ), the temperature compensation plate being connected to the capacitor face at two spaced apart points ( 23, 24 ) and forming a bowed surface therebetween; the temperature compensation plate having a smaller coefficient of thermal expansivity than the capacitor face. The temperature compensation plate comprises an aperture ( 26 ) being arranged such that on displacement of the tuning member towards the capacitor face the tuning member is displaced towards the aperture.
1 . A TEM mode resonator comprising
a tuneable cavity defined by an electrically conducting cavity wall, the cavity wall comprising a grounding face, a capacitor face and a surrounding wall extending therebetween;
an electrically conducting resonator member within the cavity extending from the grounding face part way to the capacitor face; and
a tuning member within the cavity between the resonator member and capacitor face adapted to be displaced towards and away from the capacitor face along a displacement axis to tune the resonator;
the capacitor face further comprising an electrically conducting temperature compensation plate, the temperature compensation plate being connected to the capacitor face at two spaced apart points and forming a bowed surface therebetween;
the temperature compensation plate having a smaller coefficient of thermal expansivity than the capacitor face; and wherein
the temperature compensation plate comprises an aperture being arranged such that on displacement of the tuning member towards the capacitor face the tuning member is displaced towards the aperture.
2 . A TEM mode resonator as claimed in claim 1 , wherein the displacement axis passes through the aperture.
3 . A TEM mode resonator as claimed in claim 2 , wherein the displacement axis passes through the center of the aperture.
4 . A TEM mode resonator as claimed in claim 1 , wherein the displacement axis is orthogonal to the capacitor plate.
5 . A TEM mode resonator as claimed in claim 4 , wherein the displacement axis extends through the center of the capacitor plate.
6 . A TEM mode resonator as claimed in claim 5 , wherein the resonator member is symmetrically arranged about the displacement axis.
7 . A TEM mode resonator as claimed in claim 1 , wherein the aperture and face of the tuning member facing the aperture are the same shape.
8 . A TEM mode resonator as claimed in claim 7 , wherein the aperture is circular and the tuning member is cylindrical.
9 . A TEM mode resonator as claimed in claim 1 , wherein an area of the aperture is larger than an area of the face of the tuning member facing the aperture.
10 . A TEM mode resonator as claimed in claim 1 , wherein the tuning member is connected to a displacement mechanism by a tuning arm, the displacement mechanism being adapted to displace the tuning member along the displacement axis.
11 . A TEM mode resonator as claimed in claim 10 , wherein the tuning arm extends through an aperture in the capacitor plate.
12 . A TEM mode resonator as claimed in claim 10 , wherein the tuning arm extends through an aperture in the resonator member.
13 . A TEM mode resonator as claimed in claim 12 , wherein the resonator member comprises an end face at least a portion of which is parallel to the capacitor face.
14 . A TEM mode resonator as claimed in claim 13 , the end face comprising a recess, the tuning arm extending through an aperture in the recess.
15 . A TEM mode resonator as claimed in claim 14 , wherein the displacement mechanism is adapted to displace the tuning member from a retracted position at least partially within the recess towards the capacitor plate to an extended position.
16 . A TEM mode resonator as claimed in claim 1 , wherein the resonator member is an integral portion of the grounding face.
17 . A TEM mode resonator as claimed in claim 1 , wherein the capacitor face is aluminium.
18 . A TEM mode resonator as claimed in claim 1 , wherein the temperature compensation plate is copper.
19 . A TEM mode resonator as claimed in claim 1 , wherein the tuning member is a metal
20 . A TEM mode resonator as claimed in claim 1 , wherein the tuning member is a dielectric.
21 . (canceled)