JPS6029205Y2 - high frequency coaxial resonator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency coaxial resonator suitable for simple and economical high frequency radio equipment that can perform highly selective tuning over a narrow range.

For example, in order to tune within a narrow range, for example within a deviation of about 7 MHz, in the high frequency band of 150 to 1.500 MHz, the resonant circuit must have a sharp resonance characteristic with a selectivity of 400 to 1.50 degrees. must not.

Conventionally, there is a resonator employed for this purpose as shown in Fig. 1. In Fig. 1, a coil 3 is directly connected to a piston trimmer 2 in a space of a metal casing 1 forming a resonant path. The fixed electrode 2 of this trimmer and the movable electrode 1 are moved by turning a screw D to adjust the capacitance by moving them closer to each other or separating them from each other.

This resonator is a capacitor-terminated type in which the trimmer is made by soldering a porcelain J-cylindrical body to a metal part M, so it has an electrical contact part, and is particularly precise in order to smoothly move the movable electrode of the capacitor in and out. Not only is it inevitable that it will be large and difficult to mass-produce, but if the movable electrode has any contact failure, it will cause slight vibrations in the coil, resulting in undesirable results. The drawback is that only stable resonance characteristics can be obtained.

In addition, there is usually a device that inserts and removes a dust core to adjust the inductance of the coil, but the practical frequency band is 1.
Up to about 50 MHz, and the selectivity is at most 20 (X
The problem is that you can only get up to I.

The present invention focuses on the above-mentioned drawbacks and aims to provide an inexpensive, highly selective resonator in which the variable capacitance for tuning is adjusted depending solely on changes in dielectric constant.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2A is a partially cutaway side view of the resonator of the present invention, B is a sectional view of the inner wall of the bobbin 12, FIG. 3 is a partially cutaway top view of FIG. 2A, and FIG. 4 is an equivalent model diagram thereof. .

First, 11 is a metal casing whose bottom is closed by a printed circuit board P, and 12 is a metal casing having a plurality of ribs L on its inner wall surface, screwed into the threaded portion of a non-magnetic metal slug 14, and a spiral groove provided on the outer periphery. This is a bobbin made of an insulating material with low dielectric loss, on which the coil 13 is wound.

One end of the bobbin is fixed by a fastener N to a printed circuit board fastened to the bottom of the casing, and the other end of the slug, which slides back and forth in the direction of the arrow, is fitted into and inscribed in an opening in the wall of the casing.

Further, one end of the coil 13 is tied to a band B or left open, and the other end is grounded by soldering S to a ground terminal of a printed circuit board.

In this embodiment, the bottom of the casing is explained using a printed circuit board, but it may be made of a metal substrate of the same quality as the metal of the casing.

The slug 14 is caused to advance by its spiral rotation, and as shown in FIG. 4, the stray capacitance O between the slug and the housing is
Similarly, the stray capacitance C2 between the slug and the coil is C
Tuning is achieved while moving the resonance point within the range of I>C2.

Here, C31, C32, C41, and C42 are stray capacitances between the coil and the housing 11, which is a resonance path, and the coil is suitable for input/4 that can shorten the line length.

In this way, the selectivity of a resonant circuit that is not capacitively terminated is maximum at the self-resonant frequency, but by adding the inductive coupling capacitance between the non-magnetic slug and the resonant path, that is, the case and the coil, it is possible to tune it slightly below the self-resonant point. It is possible to take .

In this way, the present invention provides an electric coupling method that adjusts the stray capacitance between the coil, which has a resonant path without capacitance termination, wound around the outer periphery of the bobbin and is grounded at one end, and the housing of the resonant path whose bottom is closed by a printed circuit board. Because it is a contactless configuration,
Stable resonance characteristics with high selectivity can be obtained in a limited and narrow frequency range in the mobile radio frequency band, and there are no obstacles seen in conventional capacitive termination types, and there is no need for high precision processing, expensive materials, and high manufacturing costs. It is advantageous in that it can be constructed simply and compactly without spending a lot of money, and satisfies economic efficiency and mass production.

[Brief explanation of drawings]

Fig. 1 is a side view of a conventional capacitively terminated resonator, Fig. 2 is a partially cutaway side view of an embodiment of the present invention, Fig. 3 is a top view of the main part of Fig. 2, and Fig. 4 is an explanatory diagram. This is an equivalent model diagram for. 1...Metal housing, 12...Low dielectric insulating bobbin, 13...Coil, 14...Nonmagnetic slag, P... Printed board.

Claims (1)

[Scope of utility model registration request] A coaxial resonator with a metal casing as part of the resonance path includes an insulating bobbin with low dielectric loss having an inner cylinder in which a non-magnetic metal slug can slide back and forth, and a spiral groove wound around the outer circumference of the bobbin. and a coil whose one end is short-circuited and grounded together with the casing,
One end of the bobbin is fixed onto a metal board or printed circuit board to which the bottom of the casing is fastened and closed via a ground terminal, and the outer periphery of the other end is internally fitted into an opening in the wall of the casing. A high-frequency coaxial resonator featuring