JPH0140523B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-high frequency coaxial resonator commonly used in the VHF to SHF band.

Figure 1 shows a conventionally used capacitive coupling circuit between a coaxial resonator and its external circuit, in which 11 is the external conductor of the resonator, 12 is the center conductor of the resonator, 1
3 indicates a coupling capacitance, and 14 indicates a connector.

Conventionally, a lumped constant type capacitor is used as the coupling capacitor 12, and is connected to the tip of a quarter wavelength resonator to achieve coupling with an external circuit.

In such a configuration, the coupling capacitance becomes a lumped constant, so the electric field at the tip of the resonator is easily disturbed.
There were problems such as deterioration of the no-load Q of the resonator and dielectric breakdown when handling large electric power due to the concentration of the electric field.

The present invention aims to provide a coaxial resonator having a capacitive coupling circuit with a new structure that solves these problems.

FIG. 2 shows the configuration of a capacitive coupling circuit used in a coaxial resonator in an embodiment of the present invention. Reference numeral 21 denotes a low-loss disc-shaped dielectric substrate, which has a hole 23 in its center for attachment to the center conductor of the resonator. Also, the board 21
A circular conductor electrode 24 is provided on the bottom surface of the holder, and a ring-shaped conductor electrode 22 is provided on the top surface.

The capacitance is determined by the electrodes 22 and 2 on the upper and lower surfaces of the dielectric substrate 21.
Formed between 4. FIG. 3 shows a configuration in which the coupling capacitor shown in FIG. 2 is attached to a resonator for coupling with an external circuit.

In FIG. 3, 11 is an outer conductor, 12 is a center conductor, 14 is a connector, and 31 is a screw for fixing the dielectric substrate to the center conductor. The electrode 22 on the top surface of the dielectric substrate 21 is connected to the connector 14, and the electrode 24 on the bottom surface is connected to the center conductor 12.

As can be understood from the figure, since the coupling capacitance is formed surrounding the center conductor 12, the electric field distribution of the resonator also has an axial symmetry, which has the extremely excellent effect of reducing Q deterioration and improving the withstand voltage. .

Further, the outer diameter of the dielectric substrate 21 may be smaller than the inner diameter of the outer conductor 11 of the resonator, but by making the dimensions of both the same as shown in the figure, the center conductor 1
It is also possible to improve the vibration resistance characteristics of the resonator by using a structure that also serves as mechanical support.

FIG. 4 shows the coupling capacitance of another embodiment of the present invention, where 41 is a low-loss cylindrical dielectric, 42 is a hole for attaching to the center conductor of the resonator, and 43 is provided on the side surface of the dielectric 41. This is the electrode that was used.

FIG. 5 shows a state in which the dielectric shown in FIG. 4 is attached to a resonator.

A coupling capacitance is formed by the electrode 43 provided on the dielectric 41 and the center conductor 12, and connected to the connector 14 as shown in the figure.

In this case as well, since the structure is axially symmetrical as in FIG. 3, the electric field distribution is also uniform, achieving a high Q and a high breakdown voltage.

6 and 7 show an embodiment of the present invention. 6th
The figure shows an embodiment in which a high-frequency band rejection filter is constructed using the three resonators described in FIG. 3.

61 to 63 are resonators whose structure is exactly the same as that shown in FIG. 3, and detailed explanation thereof will be omitted. 64 is a metal housing for mounting the resonators 61 to 63;
5 and 66 are input/output connectors, respectively.

Each resonator 61 to 63 is connected to a coaxial line 67.
and 68 are connected via a coupling capacitance.
Further, the coaxial line length is selected so as to correspond to a quarter wavelength at the center frequency of the stopband. Band-stop filters often require a high Q resonator, and a high electric field is generated inside the resonator, making the resonator according to the invention extremely useful.

FIG. 7 shows an embodiment in which the resonator of the present invention is applied to an oscillator.

71 is a resonator having the structure shown in FIG.
Reference numeral 5 denotes an active circuit made of a transistor or the like, which is designed to have a negative resistance when the active circuit 75 is viewed from the coupling terminal 72 with the resonator 71.

77 is a coupling loop for obtaining output, and terminal 7
3 to the output circuit 76. The output circuit 76 usually consists of a matching circuit and a buffer amplifier. 74 indicates an output terminal.

Since the resonator 71 is a high Q resonator, the oscillation frequency is approximately determined by the resonant frequency of the resonator, and since the loss of the resonator is small, a high output oscillator can be obtained. Furthermore, by changing the material of the dielectric material constituting the coupling circuit, temperature compensation of the oscillation frequency can be easily performed.

As described above, when the resonator of the present invention is applied to an oscillator, a high output and highly stable oscillator can be realized.

As described above, the present invention realizes the coupling capacitance of a coaxial resonator with an axially symmetrical annular electrode structure that is always equidistant from the axis of the central conductor at any position. It makes the electric field distribution at the tip uniform, prevents the deterioration of the resonator's no-load Q, and makes it possible to increase the withstand voltage, allowing it to be applied to band-stop wavers, oscillators, etc., and greatly improve performance. , is extremely useful.

[Brief explanation of drawings]

Figure 1A is a vertical cross-sectional view of a quarter-wavelength coaxial resonator with a conventional lumped-parameter coupling capacitance, and Figure 1B
2A is a plan view showing the structure of a coupling capacitor used in a resonator according to an embodiment of the present invention, FIG. 3 is a sectional view thereof, and FIG. FIG. 4A is a cross-sectional view of a coaxial resonator according to an embodiment of the present invention using a capacitance of 5 is a sectional view of a coaxial resonator according to another embodiment of the present invention using the coupling capacitance shown in FIG. 4, and FIG. 6 is a band rejection constructed using the coaxial resonator of the present invention. FIG. 7 is a partially sectional front view showing an example of a filter, and FIG. 7 is a sectional view showing an example of an oscillator. 11... Outer conductor of the resonator, 12... Center conductor of the resonator, 21... Dielectric substrate, 22, 23...
Electrode, 41...dielectric, 43...electrode.

Claims (1)

[Claims] 1. In a quarter-wavelength coaxial resonator with one end short-circuited and the other end open, an annular coupling electrode is provided on the upper surface of the dielectric substrate, and the annular coupling electrode with an upper diameter is provided on the lower surface of the dielectric substrate. Circular electrodes larger than the diameter of the electrodes are formed so that their centers coincide with each other, and the annular coupling electrode, the circular electrode, and the dielectric substrate form an annular coupling capacitance. An ultra-high frequency coaxial resonator in which the circular electrode is fixed to the center conductor so as to be in contact with the center conductor, and the circular electrode is axially symmetrical so that the center axis coincides with the center axis of the center conductor of the resonator. 2. In a quarter-wavelength coaxial resonator with one end short-circuited and the other end open, an annular coupling electrode is formed on the outer surface of the cylinder of a cylindrical dielectric, and the annular coupling electrode and the cylindrical dielectric are connected to each other. A circular coupling capacitance is formed at the center of the cylindrical dielectric, and the cylindrical dielectric is axially symmetrical so that the central axis of the cylindrical dielectric that forms the coupling capacitance coincides with the central axis of the central conductor of the resonator. An ultra-high frequency coaxial resonator inserted and fixed into a conductor.