Cavity resonator with thermal compensation

Patent metadata

Field	Value
Publication number	US-9865909-B2
Application number	US-201615045356-A
Country	US
Kind code	B2
Filing date	Feb 17, 2016
Priority date	Feb 17, 2016
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

An exemplary cavity resonator has a resonant frequency and includes a conductive body containing a cavity and a plate attached to the body enclosing the cavity. The position of a conductive tuning mechanism that protrudes into the cavity affects the tuning of the resonant frequency of the cavity resonator. A portion of the enclosed cavity is made of a shape memory alloy (SMA) material that has been trained to have a coefficient of thermal expansion that results in dimensional changes of the portion as the temperature varies so that the dimensional changes produce changes in the resonant frequency that counteract the combined change in the resonant frequency due to dimensional changes with temperature associated with the other portions of the enclosed cavity made of materials other than SMA material. This results in a stable resonant frequency versus temperature characteristic.

First claim

The invention claimed is:

1. A cavity resonator having a resonant frequency comprising:
a conductive body containing a cavity;
a conductive plate attached to the body and enclosing the cavity;
a mechanical tuning mechanism that protrudes into the cavity, a position of the tuning mechanism in the cavity affecting a tuning of the resonant frequency of the cavity resonator;
a portion of the enclosed cavity being made of a shape memory alloy (SMA) material that has been trained to have a coefficient of thermal expansion that causes dimensional changes of the portion as a temperature of the cavity resonator varies so that the dimensional changes counteract other dimensional changes due to other parts of the enclosed cavity that are made of materials other than the SMA material to stabilize the resonant frequency of the cavity resonator as the temperature changes, said portion made of the SMA material comprising a resonator rod attached to the body within the enclosed cavity.

2. The cavity resonator of claim 1 wherein the SMA material is nickel titanium.

3. The cavity resonator of claim 1 wherein the mechanical tuning mechanism has an end and the resonator rod is located adjacent the end.

4. A filter for electronic signals, where the filter contains a plurality of coupled resonant cavities and produces a signal transfer characteristic, each resonant cavity comprising:
a conductive body containing a cavity,
a conductive plate attached to the body and enclosing the cavity,
a mechanical tuning mechanism that protrudes into the cavity, a position of the tuning mechanism in the cavity affecting a tuning of a resonant frequency of the cavity resonator,
a portion of the enclosed cavity being made of a shape memory alloy (SMA) material that has been trained to have a coefficient of thermal expansion that causes dimensional changes of the portion as a temperature of the cavity resonator varies so that the dimensional changes counteract other dimensional changes due to other parts of the enclosed cavity that are made of materials other than SMA material to stabilize the resonant frequency of the resonant cavity as the temperature changes;
each of the resonant cavities having a stabilized resonant frequency versus temperature characteristic which produces a stabilization of the signal transfer characteristic during the temperature changes, said portion made of the SMA material comprises a resonator rod attached to the body within the enclosed cavity.

5. The filter of claim 4 wherein the mechanical tuning mechanism has an end and the resonator rod is located adjacent the end.

6. The filter of claim 4 wherein the SMA material is nickel titanium.

7. A method for stabilizing a resonant frequency of a cavity resonator during temperature changes comprising the steps of:
making a portion of an enclosed cavity of the cavity resonator of a shape memory alloy (SMA) material;
training the SMA material to have a predetermined coefficient of thermal expansion (CTE) that causes dimensional changes of the portion as a temperature of the cavity resonator varies so that the dimensional changes counteract other dimensional changes due to other parts of the enclosed cavity that are made of materials other than the SMA material to stabilize the resonant frequency of the cavity resonator as the temperature changes;
the training including:
starting with a first length of the SMA material at one end of a temperature range;
stretching or compressing the first length of the SMA material while at the one end of the temperature range to a second length that equals a length of the SMA material based on the predetermined CTE: (a) when not being stretched or compressed and (b) while at the other end of the temperature range;
maintaining the SMA material at the second length while the SMA material is cycled back and forth between the ends of the temperature range until a strain versus temperature characteristic of the SMA material is stabilized.

8. The method of claim 7 wherein the SMA material is nickel titanium.

9. A method for stabilizing a resonant frequency of a cavity resonator during temperature changes comprising the steps of:
making a portion of an enclosed cavity of the cavity resonator of a shape memory alloy (SMA) material;
training the SMA material to have a predetermined coefficient of thermal expansion (CTE) that causes dimensional changes of the portion as a temperature of the cavity resonator varies so that the dimensional changes counteract other dimensional changes due to other parts of the enclosed cavity that are made of materials other than the SMA material to stabilize the resonant frequency of the cavity resonator as the temperature changes;
forming said portion made of the SMA material into a resonator rod and attaching the resonator rod within the enclosed cavity.

10. The method of claim 9 further comprising attaching said resonator rod adjacent an adjustable tuning mechanism within the enclosed cavity.

11. The method of claim 9 wherein the SMA material is nickel titanium.

Assignees

• Northrop Grumman Systems Corp

Inventors

• Chan Edward

Classifications

• H01P1/208 Primary

  Cascaded cavities; Cascaded resonators inside a hollow waveguide structure (H01P1/205 takes precedence) · CPC title

• H01P7/06

  Cavity resonators · CPC title

• H01P1/30

  for compensation of, or protection against, temperature or moisture effects {; for improving power handling capability (H01P1/04, H01P1/08 take precedence)} · CPC title

• H01P1/2053 Primary

  the coaxial cavity resonators being disposed parall to each other · CPC title

• H01P7/04

  Coaxial resonators · CPC title