Patent ID: 8330562

Claim:
A variable resonator, comprising: a single loop conductor line provided on one surface of a dielectric substrate; a ground conductor provided on either said one surface or an other surface opposite to said one surface of said dielectric substrate; at least two switches; and M variable reactance blocks each being configured to permit a change of a reactance value, where M is an even number of 4 or larger, wherein each of said at least two switches has one end electrically connected to said single loop conductor line and an other end electrically connected to said ground conductor, and each of said at least two switches is configured to select interchangeably electrical connection or electrical non-connection between said ground conductor and said single loop conductor line; connection positions on said single loop conductor line where said at least two switches are connected are different from each other; said single loop conductor line has a resonance frequency whose one wavelength or an integral multiple thereof corresponds to a circumference length of the single loop conductor line; the reactance values set to said M variable reactance blocks are equal to each other; M/2−1 variable reactance blocks of said M variable reactance blocks, which are referred to as first variable reactance blocks, are connected to said single loop conductor line at connection points along a clockwise part of said single loop conductor line between a position K 1 arbitrarily set on said single loop conductor line and a position K 2 apart from the position K 1 by half an electrical length of one circumference of said single loop conductor line except said position K 1 and said position K 2 so as to divide said clockwise part at an equal electrical length interval based on said resonance frequency; M/2−1 variable reactance blocks of said M variable reactance blocks except said first variable reactance blocks are connected to said single loop conductor line at connection points along a counter-clockwise part of said single loop conductor line between said position K 1 and said position K 2 except said position K 1 and said position K 2 so as to divide said counter-clockwise part at said equal electrical length interval based on said resonance frequency; two remaining variable reactance blocks of said M variable reactance blocks are connected to said single loop conductor line at said position K 2 ; a working resonance frequency at which said variable resonator resonates changes in response to the change of said reactance value of each of said M variable reactance blocks; only one of said at least two switches is selected to be rendered in a conducting state; and a bandwidth at the working resonance frequency changes in response to a change of said selection of said only one of said at least two switches with the working resonance frequency being constant.