JPH03162002A - Strip line filter - Google Patents

Abstract

PURPOSE:To adjust a filter characteristic by removing part of a short-circuited electrode and a guard electrode formed to the side base of a dielectric substrate whose main surface is provided with a resonance electrode and the rear surface is provided with a grounding electrode by means of trimming or the like. CONSTITUTION:A resonance electrode 2 whose one end is formed to be an open end is formed to the front side of a dielectric ceramic base 1 whose rear side is formed with a ground electrode 4 at prescribed intervals. Moreover, a short-circuited electrode 3 is formed to one side face of the base 1 and a short-circuited end of the resonance electrode 2 is connected to a ground electrode 4. Then the electrode 3 and parts 6, 6', 6'' are eliminated by trimming or the like. In such a case, the trimming position and its quantity are formed symmetrical to the left and right with respect to the prolonged direction of the resonance line. Thus, the capacitive component caused to the open end in a parasitically is reduced to adjust the filter characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a stripline filter used in the microwave band.

(b) Conventional technology Filters currently used in the microwave band include those using a coaxial resonator and those using a stripline resonator, and generally, by short-circuiting one side, the resonant frequency can be increased. A 1/wavelength filter that resonates at 18 wavelengths (f.) is well known. Among these, filters constructed using a material having a high dielectric constant (εr#90) have come to be used as compact filters. Screen printing is generally used as a method for manufacturing such filters, but there is a big problem with variations in filter characteristics. In addition, when forming a resonant electrode pattern using the screen printing method, in order to prevent variations in the resonant frequency, a ground electrode with short-circuiting side electrodes called guard electrodes extending to the main surface side is used.
It is necessary to provide it at the short-circuited end of the /4-wavelength resonator.
The influence of this portion on the open end causes variations in the in-band characteristics.

(c) Problem to be solved by the invention: To reduce the variation in filter characteristics that occurs when strip line filters are manufactured by screen printing, and the variation in center frequency that occurs due to variation in the dielectric constant of the dielectric substrate. It provides a filter for the purpose of

(2) Means for solving the problem In a stripline filter that has a resonant electrode pattern on the main surface of a dielectric substrate, a grounding electrode on the opposite surface, and a short-circuit connection electrode on the side surface of the substrate, the side surface of the substrate is The filter characteristics can be adjusted by removing part of the short-circuit side wall or guard electrode by trimming or the like.

(e) Effect In a stripline filter, typically an interdigital type, its transmission characteristics depend on the thickness of the dielectric substrate,
It is almost uniquely determined by the dimensions of the resonator (the length of the line and its width) and the line distance (the gap between the lines). In particular, in the case of a bandpass filter, the center frequency (CF), IF bandwidth (BW), etc. of the bass band are determined by the resonator length and the number of stages (number of resonant lines).
Tuple (r i p) etc. tend to be determined by the distance between lines. Therefore, when a resonant electrode pattern is formed by screen printing, its dimensional accuracy is poor and yield cannot be expected. Further, variations in the dielectric constant of the dielectric material used for the substrate cause variations in the center frequency. In order to adjust these variations, as shown in Figures 1 and 4, the side electrodes and guard electrodes facing the open end of the resonant electrode are removed by trimming, etc., and the equivalent circuit shown in Figure 2 is obtained. Open as shown in 4j: It is possible to reduce the capacitance that is parasitically occurring on the 4j side and adjust the filter characteristics.

(v) Embodiment Fig. 1 (a) shows the trimming part for adjustment in the present invention by a shaded area, and Fig. 1 (b) shows (X-X ') is a cross-sectional view. As shown in FIGS. 1(a) and 1(b), this filter consists of a dielectric ceramic substrate (1) on which a ground electrode (4) is formed on almost the entire back surface.
) has an 18-wavelength resonant electrode with one end open on the surface side (
2) is formed by forming a plurality of 1k rows at regular intervals, and
A short-circuiting electrode (3) is formed on one side of the substrate, and the short-circuiting electrode (3) connects each other end of the resonance electrode (2), which becomes the short-circuiting end, to the ground electrode (4). The structure is connected to each other.

And, with such a filter,
As described in Publication No. 41 [HO I P 1/2 0 3], the resonant frequency f. is the resonant electrode (2)
Let the length of be i and the effective dielectric constant of the substrate (1) be εe, then f,=7s,,'F! ．． It is known that it is given by π.

In Figure 1, (5) (5)' are input/output lines, (6)
(6)'(6)'' is the trimming section. Figure 2 is a diagram showing the trimming effect using an equivalent circuit, and (7
)(7)' is an input/output terminal, (8) is an input/output unit element, (9) is a resonance unit element, and (10) is an additional capacitor at the open end. FIG. 3 shows that the adjustment ratio varies depending on the trimming position and amount. Moreover, in this case, the trimming position and its amount are basically symmetrical with respect to the extending direction of the resonant line.

In Figure 3, the vertical axis is the amount of change (△
f. ) (MHz), and the horizontal axis represents the trimming location. In the figure (a), the amount of trimming is 6 mm'', (b) the amount of trimming is 0, and (c) the amount of trimming is 2 11!n''
The characteristics of the case are shown below. FIG. 4 shows an example in which disturbances in in-band ripples are adjusted by trimming, and the hatched area indicates the trimmed portion. FIG. 5 is a comparison diagram, in which the dotted line (a) shows the trimming before adjustment, and the solid line (b) shows after the adjustment. FIG. 6 shows an example of another pattern to which the present invention is applied.

(g) Effects of the Invention According to the present invention, it is possible to improve the performance yield of a stripline filter manufactured using screen printing or the like.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing a strip line filter of the present invention,
Fig. 2 is an explanatory diagram using the equivalent circuit, Fig. 3 is a comparison diagram of the characteristics of the effect, Fig. 4 is another embodiment according to the present invention, Fig. 5 is a characteristic diagram of the effect, and Fig. 6 is the characteristic diagram of the effect. Examples using other patterns are shown. (1)...Dielectric substrate, (2)...Resonance electrode, (3
)... Side electrode for short circuit, (4)... Ground electrode, (5
)...Input/output line, (6)...Trimming section, (7
)...Input/output terminal, (8)...Input/output unit element,
(9)... Unit element for resonance, (10)... Open end additional capacitance, (1l)... Guard electrode.

Claims (1)

[Claims] (1) In a quarter-wavelength strip line filter formed by printing and baking an electrode pattern on a dielectric substrate, a part of the short-circuit side electrode formed on the side surface of the substrate or the short-circuit side surface A strip line filter characterized in that filter characteristics are adjusted by removing a portion of a guard electrode extending from the electrode by a method such as trimming.