JPS59128801A - Control method of dielectric filter - Google Patents

Abstract

PURPOSE:To attain a filter control method which can be automated easily with excellent airtightness by storing plural resonators consisting of dielectric cores surrounding inner conductors into a metallic case and deleting properly the free terminal of the inner conductor or the metallic film on the dielectric core to perform the control of frequency. CONSTITUTION:An inner conductor 99 of a prescribed length which is formed into such a shape that the free terminal of one side can be slightly deleted with the other terminal short-circuited to a case 6. Then a core 3 encloses the conductor 99. Thus plural resonators are obtained. A conductor film 5 is formed to the case 6, and a mask plate 4 is attached at the upper part of the case 6. An input terminal 7a is attached to the case 6. The conductor 99 is formed by plating copper or silver of low resistance to a metal like brass, iron, etc. An inner conductor 99a is formed into a staircase shape, for example, at its upper edge part, and projected parts are successively trimmed by a laser, etc. to obtain a desired electric characteristic standard. Thus it is possible to attain a filter control method which can be automated easily with excellent airtightness. It is also possible to constitute a resonator with an outer conductor and a dielectric core which is metallized into such a shape that can be deleted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a simple frequency adjustment method for a dielectric filter used from the VHF band to the relatively low frequency microwave band.

(Prior Art) A conventional frequency adjustment force method for a dielectric filter will be explained with reference to FIGS. 1 and 2. Figure 1 shows a cross-sectional view of a dielectric filter, and Figure 2 shows a cross-section of one resonator, where 1 is an inner conductor that also serves as a frequency adjustment screw attachment part, 2, 2a, 2b,
2c is a frequency adjustment screw, 3 is a dielectric, 4 is a shielding plate, 5
is a conductive film formed on the case side, 6 is a case, 7 is an input terminal, 8 is a nand for fixing an adjustment screw, 9 is a nut 8
It is an adhesive for fixing. When considering frequency adjustment of a dielectric filter, the following points are important.

In other words, the allowable tolerance of the resonance frequency in filter design is within 0.03%, and the resonance frequency is mainly determined by the height of the inner conductor 1, which also serves as the frequency adjustment screw attachment part, and the dielectric 3 and the inner part. It is determined by the distance between the conductor 1 and the air gap. In experimental values, the element sensitivity per inner conductor height is approximately 5.
0 MHz/mm) The element sensitivity at the gap distance is approximately I
MHz/μm. Also, the resonance frequency is set to 800 MHz.
In this case, in order to keep the design tolerance within 0.03%, it must be within 0.24 MHz. Therefore, in order to make the adjustment process unnecessary for the above-mentioned element sensitivity, it is necessary to reduce the variation in the height of the inner conductor to 4. M ttm
The gap distance must be within 0.24 μm. This tolerance becomes extremely strict when considering manufacturing technology and cost. Therefore, Figures 1 and 2
In the conventional filter shown in the figure, there are 6 dielectrics and 3
After loading, by changing the frequency adjustment screw 2, the resonant frequency of each resonator is adjusted to a predetermined value, and characteristics satisfying the standards are obtained.

Next, the adjustment procedure will be explained using FIGS. 3(a) to 3(d). In the same figure, the X axis is the frequency (MH2), and the Y axis is the frequency (MH2).
The axis represents the loss, the curve A represents the reflection characteristic, the end of the curve represents the pass characteristic, and i represents the number of resonators to be adjusted. For example, a network analyzer is used as the adjustment measuring instrument, and the frequency is adjusted to a predetermined frequency by changing the frequency adjustment screw 2. By turning the frequency adjustment screw 2 to the right and protruding it beyond the height of the inner conductor portion, the frequency To is lowered, and by lowering the screw 2, the frequency fo is raised. 1. Only one resonator is enabled, the others are short-circuited, and the reflection characteristics (curve A) and transmission characteristics (curve opening) are obtained as shown in FIG. 3(a)"K.

Next, the adjacent resonators are adjusted in the same manner, and the two resonators have the characteristics shown in FIG. 3(b). Thereafter, the number of resonators is increased in the same manner, and the frequency adjustment is repeated n times to obtain a predetermined filter characteristic as shown in FIG. 3(d). After adjustment with the frequency adjustment screws 2, each frequency adjustment screw 2 is fixed with a nut 8 as shown in FIG. Furthermore, in order to satisfy the electrical characteristics of a dielectric filter, it is essential that it be hermetically sealed. Therefore, after fixing the frequency adjustment screw 2 with a nut 8, it was hermetically sealed with an adhesive 9.

The problems with the conventional dielectric filter adjustment method described above are listed as follows: (1) Screw insertion;
The adjustment, fixing, and sealing processes are complex and require a lot of man-hours.

(2) It requires skill and is largely manual, making it difficult to automate adjustments.

(3) Since the adjustment screw method is used, problems arise in terms of fixing and airtight sealing, which causes a decrease in reliability.

(Object of the Invention) The object of the present invention was made to solve these drawbacks, and it is an object of the present invention to provide a filter adjustment method that is easy to automate and has excellent airtightness.

(Structure of the Invention) The present invention provides a metal coating (
By finely removing the conductive pattern (conductor pattern) and changing the surface area of the metal film, it is possible to perform coarse to fine adjustment of the frequency, which will be described in detail below.

(Embodiment) FIGS. 4, 5, and 6 illustrate a first embodiment of the dielectric filter adjustment method according to the present invention.
The figure is a sectional view of a dielectric filter, and FIGS. 5 and 6 show resonators in which the shape of the inner conductor is changed. 99,99a
, 99b indicates the inner conductor joined to the case 6, and the other symbols are the same as in FIGS. 1 and 2. In this case, the inner conductors 99.99a and 99b are made of metal such as brass or iron plated with low resistance copper or silver. The frequency fo of the dielectric filter is basically determined by the following equation.

fo=-4tV'' Here, C is the speed of light, fo is a predetermined frequency, t is the height of the inner conductor 99, and ε1 is the dielectric constant of the dielectric 3.

Therefore, by decreasing the height t of the inner conductor 99, the frequency fo can be increased. Also, actually the inner conductor 9
The frequency fo can be increased not only by reducing the height t of 9 but also by reducing the surface area of the inner conductor. In FIG. 5, the upper end of the inner conductor 99ts is shaped like a step, and the height of the inner conductor 99a is changed by sequentially trimming and adjusting the protrusions using means such as laser, sandblasting, chemical etching, or grinding. At the very least, a filter that satisfies electrical property standards is formed. Fig. 6 shows another shape of the inner conductor 99b. In the case of the figure, the height is constant, but the horizontally protruding part at the upper end is processed by laser, sandblasting, chemical etching, or grinding. By performing trimming adjustment using appropriate means such as the above, the surface area of the inner conductor is changed to form a filter that satisfies electrical characteristic standards.

As explained above, in the first embodiment of the present invention, the inner conductor is shaped so that it can be removed minutely, and then it is sequentially removed using a laser or the like. ) This is a method of forming a filter that satisfies the electrical characteristics standard by changing the height or surface area of the inner conductor by rimming, so it is not a foolproof method that can eliminate the above-mentioned drawbacks, but it also eliminates the need for frequency adjustment screws. There is no need to thread the conductor 99, and there is no need to drill holes on the bottom of the case, so the reliability of hermetic sealing is excellent.

FIG. 7 is for explaining a second embodiment of the present invention, and shows a sectional view of a dielectric filter. In the same figure, 100
is a conductive pattern (Ag or C) formed on the surface of the dielectric 3.
10 is an inner conductor, 11 is an outer conductor, and other symbols are the same as in FIG. 4.

8 shows a cross section of one resonator of the dielectric filter shown in FIG. 7, and FIG. 9 is a plan view of the resonator shown in FIG. It mainly shows conductor patterns with various shapes of metal coatings formed on the top surface. The symbols shown in FIG. 9 are the same as those in FIG. 7, and FIG. 9(a) shows the case where the conductor pattern 100 is not short-circuited to either the inner conductor 10 or the outer conductor 1, and FIG. 9(b)
9(C) shows the case where the conductor pattern 100 is short-circuited only to the outer conductor 11, and FIG. 9(C) shows the case where the conductor pattern 100 is short-circuited only to the inner conductor 10. In each of these cases, conductor i? Turn 100 laser sandplast,
Ken! The filter is removed using appropriate means such as processing and frequency adjustment is performed to form a filter that satisfies electrical characteristics standards. FIG. 9(a) shows a case where the same area of the conductor pattern 100 is trimmed.

(b) y (c) each result in a difference in sensitivity to frequency changes.

In other words, in the case of Fig. 9(a), the change in frequency is the smallest when trimming the same area, and therefore fine adjustment is possible; ), the sensitivity is good, and the frequency change is slightly large for the same amount of trimming area, making it possible to make intermediate adjustments, and in the case of Fig. 9(c), the frequency change is the most for the same trimming area. big. Further, in this case, if the part marked ■ is trimmed and the connection with the inner conductor is cut off, the amount of frequency change becomes smaller, and if the part marked @ and the part marked θ are trimmed, the amount of frequency change becomes smaller in order. -For example, in experiments, when trimming the part marked ■, the frequency increases by about 12 MHz, when trimming the part marked ■, the frequency increases by about 5 MI (z), and when trimming the part marked θ, the frequency increases by about 12 MHz. It became clear that the frequency increased by 0.1 MHz.

The case where the dielectric body 3 is cylindrical is shown in FIG. 9, and next, the case where the dielectric body 3 is rectangular is shown in FIG. 10. Figure 10 (
a) y (b) = (c) Each corresponds to FIG. 9, when the conductor pattern 1oo does not short to either the inner conductor or the outer conductor 11, when it shorts only to the outer conductor 11, or when the conductor pattern 10 The case where only 10 is short-circuited is shown. In each of these cases, the removal of the conductive pattern 100 and the effect are the same as in the case of FIG.

FIG. 11 shows a comparison between the conventional method and the method according to the present invention regarding frequency adjustment. Figure 1.1 (a) shows the amount of frequency adjustment per amount of screw movement in the conventional method.

The element sensitivity of the indicator screw is about 3 MH.
It is constant with z. On the other hand, Fig. 11 (b) shows a case using the adjustment method of the present invention.
Trimming (trimming of 1g area) 0, IMH
Fine adjustment, intermediate adjustment, and coarse adjustment from z to 12*2 are possible. Therefore, by changing the trimming position, area, etc., it is possible to easily realize a filter that satisfies the electrical characteristic standards.

As explained above, in the second embodiment, since the frequency 1 adjustment screw 2 is not used, the drawbacks of the conventional method can be solved, and the trimming of the metal coating can be used for everything from coarse adjustment to fine adjustment. It is possible. The amount of adjustment man-hours can be drastically reduced.

(Effects of the Invention) The present invention provides a shape in which the inner conductor is shaped so that it can be successively removed minutely, or a metal coating is formed on the top of the dielectric so that it can be removed minutely, and the inner conductor or the metal coating is trimmed using a laser or the like at a frequency. Since this is an adjustment method, it is easy to automate the adjustment, is suitable for mass production, and has the advantage that a highly reliable filter with good airtightness can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a dielectric filter for explaining the conventional adjustment method, Fig. 2 is a cross-sectional view of one resonator constituting Fig. 1, and Fig. 3 (a) to (W are An explanatory diagram for explaining the conventional adjustment method, FIG. 4 is a sectional view of a dielectric filter for explaining the first embodiment of the adjustment method of the present invention, and FIGS. 5 and 6 are diagrams of the inner conductor. 7 is a sectional view of a dielectric filter for explaining the second embodiment of the tuning method of the present invention, and FIG. 8 is a configuration of FIG. 7. 9(a) to 9(c) are cross-sectional views of one resonator.
10A to 10C are plan views of the resonator shown in FIG. Explanatory diagram,
FIG. 11 is a false explanatory diagram showing the difference in adjustment sensitivity between the conventional frequency adjustment method and the present invention. 3... Dielectric material, 4... Shielding plate, 5... Conductor coating formed on the case 6 side, 6... Case, 7... Long sword terminal, 99.99a, 99b, 10...・Inner conductor, 11
...outer conductor, 10θ...conductor pattern. Patent Applicant: Satoshi Suzuki, Agent for Oki Electric Industry Co., Ltd. Movable range amount + mm) ■ Rimi', 711 [ralmm) 1-7-12 Toranomon, Minato-ku, Tokyo, Oki Electric Industry Co., Ltd. Amendment of procedures (voluntary) 0 hair, 4 hair, 15B Commissioner of the Japan Patent Office Tono 1 Display of case 1981 Patent Application No. 003563 2, Name of Invention Method for Adjusting Dielectric Filter 3 Relationship with the Amendment Person Case Patent Application Office (
105) 1-7-12 Toranomon, Minato-ku, Tokyo 4 Agent

Claims (2)

[Claims] (1) A closed metal case, one free end of which is shaped to be microscopically removable, the other end of which is an inner conductor of a predetermined length that is short-circuited to the case, and a dielectric core that surrounds the inner conductor. 1. A method for adjusting a dielectric filter comprising a plurality of resonators, input and output terminals, and excitation means. A method for adjusting a dielectric filter, characterized in that the frequency is adjusted by appropriately removing the free end of the inner conductor and changing the height and surface area of the inner conductor. (2) A hollow inner conductor in a closed metal case, a dielectric core that surrounds the inner conductor, and has a dielectric core formed directly with metallization on the upper surface in a shape that allows fine removal of the metal film, and the outside of the dielectric core. A method for adjusting a dielectric filter comprising a plurality of resonators formed of external conductors provided in the dielectric core, input and output terminals, and excitation means, the method comprising appropriately removing a metal film on the dielectric core; A method for adjusting a dielectric filter, characterized in that the frequency is adjusted by changing the area of the metal film.