Unperturbed ring resonator with an odd overtone vibration mode

Details Unperturbed ring resonator with an odd overtone vibration mode Unperturbed ring resonator with an odd overtone vibration mode

1998-10-23

2001-05-01

Pascal, Robert (Department: 2817)

Wave transmission lines and networks

Resonators

C333S235000, C333S205000

Reexamination Certificate

active

06225879

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ring resonator comprising a planar conducting ring arranged on a substrate beside a planar conductor of a microwave circuit. This type of ring resonator is also used in a microwave circuit in order to, e.g., tune an oscillator to a desired resonance frequency or in order to filter out a predetermined small frequency band from a larger frequency range.
2. Prior Art
A ring resonator whose conducting ring is dimensioned in regard to its width and its diameter so that it is driven at its fundamental frequency is described in the article, “Varactor Tuned Ring Resonator Microwave Oscillator”, Electronics Letters, Vol. 32, No. 1, 1996, pp. 46 to 48, by Shih-Lin Lu and A. M. Ferendeci. Two closely neighboring modes occur at this fundamental frequency, one of which must be suppressed. That happens by means of a slot provided in the conducting ring. The ring resonator has a higher radiation of electromagnetic radiation because of this slot and thus the Q-factor of the resonator is disadvantageously reduced. The resonance frequency depends strongly on the spacing of the ring resonator from the cover of the housing in which the microwave circuit with the ring resonator is mounted because of the high radiation from the resonator. The resonance frequency is subjected to undesirable changes because of variations of the spacing of the housing cover from the ring resonator—originating from the thermal expansion of the housing or from mechanical vibrations.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a ring resonator of the above-described type that has as high a resonator Q-factor as possible and which can be provided with a minimum expense.
These objects, and others that will be made more apparent hereinafter, are attained in a ring resonator comprising a planar conducting ring arranged on a substrate beside a planar conductor of a microwave circuit.
According to the invention the conducting ring has a conductor width and diameter dimensioned so that it resonates with an odd overtone vibration mode.
Because the ring resonator is not operated in its fundamental mode but instead in an odd overtone mode, its diameter is greater than in fundamental mode operation. That means that the curvature of the conducting ring is less so that the radiation of electromagnetic energy is substantially reduced so that the resonance Q-factor is clearly increased. In overtone operation then many modes no longer occur next to each other so that the slot in the conducting ring for suppression of modes can be dispensed with and because of that a further increase in the Q-factor can be obtained. The spacing between the ring resonator and the housing cover less strongly effects the resonance frequency because of the reduced radiation of the electromagnetic energy. The larger size of the conducting ring also has the advantage that it is insensitive to manufacturing tolerances.
According to a preferred embodiment of the invention a coupler can be arranged beside the conducting ring for tuning the resonance frequency. A Varactor diode can be connected to it for the purpose of variable tuning of the resonance frequency.


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