Wave transmission lines and networks – Resonators – With tuning
Reexamination Certificate
1999-10-21
2001-11-13
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Resonators
With tuning
C333S219100
Reexamination Certificate
active
06317017
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to high frequency resonator, and more particularly, to resonator whose frequencies can be broadly and rapidly varied.
BACKGROUND OF THE INVENTION
Dielectric resonator elements are used in oscillators and filters as the frequency adjustment elements for narrow-band frequencies in the microwave and millimeter wave bands. Dielectric resonator elements are small in size, and have high Q values In addition, the resonant frequency of dielectric resonators is insensitive to temperature fluctuations. Accordingly, such resonators are being used on a rapidly-increasing scale in satellite communication devices, mobile radio devices, variable-frequency oscillators, and other applications.
While a dielectric resonator having a high Q value provides a stable resonance frequency, its resonance frequency cannot be widely varied electronically. Instead, its resonance frequency is varied mechanically, such as by mechanically varying the cavity size. However, mechanical adjustments change the resonance frequency slowly, and are bulky and expensive.
In one form of communication referred to as Minimum Shift Keying (MSK), data is sent by using two different frequencies to represent the binary data values 0 and 1, respectively. This system requires an oscillator whose frequency can be rapidly changed. The rate at which data can be transmitted in this system depends on the difference in frequency used to transmit the two data states.
Systems that allow the oscillator frequency to be shifted in response to a signal are known to the art. For example, unexamined Japanese Patent Publication No. HEI 9-205324 discloses a system in which the resonance frequency of an oscillator is altered by applying a signal to a variable capacitance element in an auxiliary transmission line. The magnetic field in the resonating element is coupled to the magnetic field of the auxiliary transmission line in this system. By altering the magnetic field, this device alters the resonant frequency. Generally, the variation in the resonance frequency is limited to about 0.1% of the resonance frequency. Hence, when a resonator of this type is used to construct a voltage-controlled oscillator that oscillates in the 5 GHz band for MSK communications, the oscillation frequency can only be varied by about 5 MHz. This limits the data transmission rate to about 10 Mbps. However, speeds exceeding 20 Mbps are sought for 5 GHz band radio communications.
Broadly, it is the object of the present invention to provide an improved dielectric resonator.
It is a further object of the present invention to provide a resonator whose resonance frequency can be shifted in response to an external electrical signal.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.
SUMMARY OF THE INVENTION
The present invention is a resonator having a variable resonance frequency. The resonator includes a cavity enclosed by a conductive wall. A resonating element and a conductive plate are located within the cavity. A photoconductive element is connected between two points on the conductive plate. The photoconductive element has a first impedance when illuminated with light and a second impedance when not so illuminated, the second impedance being greater than the first impedance. The resonator also includes a light source for irradiating the photoconductive element. In the preferred embodiment of the present invention, the conductive plate is circular and includes a gap, the photoconductive element connecting two points on the gap. The preferred resonating element is a cylindrical dielectric resonator element having a TE
01&dgr;
mode electromagnetic field distribution, the cylindrical dielectric resonator having a cylindrical shape characterized by top and bottom surfaces and a diameter. The circular conductive plate is preferably placed parallel to the top surface of the cylindrical dielectric resonator substantially midway between the top surface and the inner surface of the top of the conducting wall. The diameter of the circular plate is preferably greater than that of the cylindrical dielectric resonator. In one embodiment of the present invention, the photoconductive element includes first and second photoconductive regions, the first photoconductive region connecting first and second points on the conductive plate and the second photoconductive region connecting third and fourth points on the conductive plate. In this embodiment, the light source includes first and second light emitting elements, for respectively illuminating said first and second photoconductive regions. The magnitude of the change in resonance frequency induced by illuminating the photoconductive region is altered by adjusting the relative position of the photoconductive element and the light source.
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P. R. Herczfeld et al., “Indirect Optical Injection Locking of Dielectric Resonator Oscillator for Phased Array Application” IEEE Symposium on Antennas ans Propagation, Jun. 17-21, 1985, pp. 35-39.
Nesic, Aleksandar; “A New Method for Frequency Modulation of Dielectric Resonator Oscillators”, Proceedings of 15th European Microwave Conference, 1985, vol. 15, pp. 403-406.
Herczfeld, P.R. et al. “Optically Tuned and FM Modulated X-Band Dielectric Resonator Oscillator”, 14th European Microwave Conference Liege, 1984, vol. 14, pp. 268-273.
Agilent Technologie,s Inc.
Bettendorf Justin P.
Jones Stephen E.
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