JPH09275304A - Band filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a band filter of a rectangular waveguide shape with a simple configuration by automatically compensating the frequency fluctuation attending a temperature change. SOLUTION: A threaded support block 13 is fixed on a drive member 14 fixed on an outer wall of a waveguide 31 and an adjustment pin 11 is inserted to the threads of the support block 13. An insert amount (x) of the adjustment pin 11 to the waveguide 31 is adjustable by adjusting one end. The drive member 14 has a prescribed thermal expansion coefficient to change the insert amount (x) depending on a temperature change thereby compensating a change in the frequency characteristic caused by the temperature change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band pass filter used in a high frequency band, and more particularly to a technique for compensating a change in frequency characteristic due to a temperature change.

[0002]

2. Description of the Related Art As a bandpass filter used in a high frequency band, there is known a bandpass filter configured to change a pass frequency in a waveguide by adjusting an insertion amount of a piston or a pin inserted in the waveguide. There is.

FIG. 3 is an external perspective view of a conventional band-pass filter 1 of this type. In the band-pass filter 1, a plurality of supports 30 are arranged at appropriate intervals on the long side outer wall surface of a waveguide 31 having a rectangular cross section. Each support 30 has an adjustment pin, and the insertion amount of the tip of the support 30 in the inside direction of the waveguide can be adjusted arbitrarily.

4 (a), (b) and (c) are a left side view, a front view and a right side view of a bandpass filter 1 of this type.
In FIG. 4B, the support 3 inserted into the bandpass filter 1 is shown.
A partial cross-section diagram of 0 is shown. Referring to FIG. 4 (b), the adjustment pin 32 is inserted into the tap on the long side outer wall surface of the bandpass filter 1, and the adjustment pin 32 is fixed by being tightened by the fixing nut 33. ing.

In the bandpass filter 1, since the characteristics of the electromagnetic wave passing through the bandpass filter 1 change depending on the insertion amount of the adjustment pin 32, various resonance frequencies can be obtained by adjusting the insertion amount of the adjustment pin 32. . Usually, the adjustment amount of the adjustment pin 32 is adjusted at room temperature, and the adjustment pin 32 is fixed by the nut 33 after the adjustment.

[0006]

The temperature of the waveguide 31 itself forming the bandpass filter 1 may change due to changes in the ambient temperature environment. When the temperature of the waveguide 31 changes, the waveguide 31 expands or contracts, so that the passing frequency in the tube shifts. Conventionally, the adjustment pin 32
Is fixed on the outer wall surface of the long side of the waveguide 31, there is a problem that the deviation of the passing frequency cannot be corrected when the waveguide 31 expands and contracts.

An object of the present invention is to provide a bandpass filter that can automatically compensate for frequency fluctuations due to ambient temperature changes and maintain a predetermined frequency characteristic.

[0008]

In order to solve the above-mentioned problems, the present invention has an adjusting pin whose tip end position in the waveguide inner wall direction is regulated by a support body arranged at a predetermined portion of the waveguide outer wall. In the bandpass filter that changes the pass frequency of the electromagnetic wave in the waveguide according to the protrusion amount of the adjustment pin protruding from the inner wall of the waveguide, the support has the adjustment pin in the waveguide according to the cycle temperature. It is characterized in that it comprises an elastic member for changing the amount of protrusion. As a preferred embodiment of the present invention, the support is provided with a support block of a mechanism that reduces or increases the protrusion amount of the adjustment pin when the elastic member extends.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. (First Embodiment) A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a configuration example of a support body in which the amount of adjustment pins inserted is reduced with an increase in temperature. In FIG. 1, the same parts as those of the conventional product are designated by the same reference numerals.

Referring to FIG. 1, this form of support 10
The drive member 14 is fixed to the outer wall of the long side of the short waveguide 31, and the support block 13 whose center is tapped is fixed on the drive member 14. further,
The adjustment pin 11 is inserted into the tapped portion of the support block 13, and the amount x of insertion of the other end into the waveguide 31 is adjusted by adjusting an external adjustment mechanism formed at one end thereof. It is adjustable. As a material of the driving member 14, a material having a large thermal expansion coefficient (for example, 0.000125 for Teflon) or a shape memory alloy such as Teflon can be used.

In the band-pass filter 1 having such a configuration, first, the external adjusting mechanism of the adjusting pin 11 is adjusted to adjust the frequency characteristic at room temperature. Specifically, the insertion amount x of the adjustment pin 11 is adjusted to select a desired pass frequency,
After the adjustment is completed, the nut 12 is attached and fixed to the adjustment pin 11.

Next, in the band-pass filter 1, when the material of the waveguide 31 expands and contracts due to a temperature change and the frequency characteristic changes, this change is automatically compensated to maintain a constant frequency characteristic. The function will be described. When the ambient temperature of the bandpass filter 1 rises, the driving material 14 expands as the temperature rises, pushing the support block 13 upward. Along with this, the adjustment pin 11 is also pushed up in the same direction, and the amount of insertion into the waveguide 31 is relatively reduced. The expansion coefficient with respect to the temperature rise of the driving member 14 at this time is known in advance, and based on this, the insertion amount x that cancels the change of the frequency characteristic due to the temperature change of the bandpass filter 1 is realized. . Therefore, the frequency characteristic is automatically compensated even if the temperature changes.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view showing a configuration example in which the amount of adjustment pins inserted in the support increases with an increase in temperature.

In the support 20 of this embodiment, a bottomed cylindrical body 25 having an open central portion is fixed on the outer wall of the waveguide 31, and further, between the bottomed cylindrical body 25 and the waveguide 31, A support block 23, which holds the drive member 24 and is tapped, is provided. The adjustment pin 21 is inserted into the tapped portion of the support block 24, and one end of the adjustment pin 21 projects from the central opening of the bottomed tubular body 25 to form an external adjustment mechanism. By adjusting this external adjustment mechanism, the insertion amount x into the inside of the waveguide 31 at the other end can be adjusted.

In the band-pass filter 1 having such a configuration, first, the external adjusting mechanism of the adjusting pin 21 is adjusted to adjust the frequency characteristic at room temperature. Specifically, the insertion amount x of the adjustment pin 21 is adjusted to select a desired pass frequency,
After the adjustment is completed, the nut 22 is attached and fixed to the back surface of the support block 23.

When the ambient temperature of the bandpass filter 1 rises, the driving member 24 expands as the temperature rises and pushes the support block 23 downward. Along with this, the adjustment pin 2
1 is pushed down, and the insertion amount x into the waveguide 31 relatively increases. Similar to the aspect of the first embodiment, the bandpass filter 1 in the second embodiment is also configured to realize the insertion amount x that cancels the change in the frequency characteristic due to the temperature change. Therefore, the frequency characteristic is automatically compensated even if the temperature changes.

[0017]

As is apparent from the above description, according to the bandpass filter of the present invention, the change in the frequency characteristic in the waveguide is automatically canceled even in the environment where the temperature changes drastically, so that the stable passage is achieved. The frequency can be obtained. Further, since the driving material made of a material having a predetermined coefficient of thermal expansion is arranged on the support, the structure for realizing the compensation of the frequency characteristic due to the temperature change is simple and the required space is reduced. There is also a practical effect that the minimum is sufficient.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a support body according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a support according to a second embodiment of the present invention.

FIG. 3 is an external perspective view of a conventional bandpass filter.

FIG. 4A is a left side view of a prior art bandpass filter,
(B) is the front view, (c) is the right side view.

[Explanation of symbols]

 1 bandpass filter 10,20,30 support body 11,21,32 adjustment pin 12,22,33 nut 13,23 support block 14,24 drive material 25 bottomed cylinder 31 short waveguide

Claims (3)

[Claims] 1. An amount of protrusion of the adjustment pin projecting from the inner wall of the waveguide is provided with an adjustment pin whose tip position in the inner wall direction of the waveguide is regulated by a support body arranged at a predetermined portion of the outer wall of the waveguide. In the bandpass filter that changes the passing frequency of the electromagnetic wave in the waveguide according to, the support includes an elastic member that changes the protrusion amount of the adjustment pin in the waveguide according to the cycle temperature. And the bandpass filter. 2. The bandpass filter according to claim 1, wherein the support body includes a support block of a mechanism that reduces a protrusion amount of the adjustment pin when the elastic member extends. 3. The bandpass filter according to claim 1, wherein the support body includes a support block of a mechanism that increases the protrusion amount of the adjustment pin when the elastic member extends.