JPS62292003A - filter circuit - Google Patents

Abstract

PURPOSE:To obtain a filter having a qualified characteristics, by connecting a micro stripline to a chip capacitor in series, and arranging stripline inductors having lengths of <=1/4 wavelength at both sides of the micro stripline. CONSTITUTION:The whole rear plane of a dielectric substrate 1 is formed by an earth conductor, and on the surface of the conductor, the input circuit 2, and the output circuit 3 of a micro stripline mu SL are provided, and a chip capacitor 4 is connected in series between the circuits 2 and 3. At the connecting point of the capacitor 4 between the circuits 2 and 3, mu SL inductors 5a and 5b having the lengths of <=1/4 wavelength, whose tips are short-circuited by through holes 6a and 6b, are connected to both sides of the mu SL. In this way, it is possible to evade coupling between both inductors 5a and 5b, and a good filtering characteristic without having a trap at a cutoff area, can be obtained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a filter circuit used in satellite broadcast receivers, microwave communication devices, and the like.

2. Prior Art Conventionally, this type of filter circuit, as shown in FIG.
It was composed of b. In FIG. 3, 1 is a dielectric substrate, the back surface of which is a ground conductor over the entire surface. 2 is input line, 3 is output line, 4 is chip capacitor, 52L
, 5b is a microstrip line inductor, 62
L and eb are through holes.

Problems to be Solved by the Invention In a filter circuit with such a conventional configuration, the microstrip line inductor 5? L.

5b is placed on one side, the two microstrip line inductors 6a and sb tend to be coupled together, causing a trap in the cutoff region and deteriorating the filter characteristics.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a filter circuit that eliminates traps in the cutoff region and has good filter characteristics.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to arrange two microstrip line inductors on both sides of the microstrip line.

action The effect of this technical means is as follows.

That is, by arranging the two microstrip line inductors on both sides of the microstrip line, coupling between the two microstrip line inductors can be avoided.

As a result, the generation of traps in the new filter is eliminated, and good filter characteristics can be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a diagram showing an embodiment of the filter circuit of the present invention. In the figure, 1 is a dielectric substrate, and in this example, the dielectric constant is 2.6. A Teflon substrate with a thickness of O or S is used, and the entire back surface is a ground conductor. 2 is the input line,
3 is the output line, 4 is the chip capacitor, esa, sb
are microstrip line inductors, ea, eb
is a through hole.

FIG. 2 shows an example of the transmission characteristics of the filter circuit with the above configuration and an example of the transmission characteristics of the filter circuit with the conventional configuration.

In FIG. 2, curve a is an example of the transmission characteristic of the filter circuit according to the embodiment of the present invention. The curved line is an example of the transmission characteristics of a filter circuit with a conventional configuration, and a trap occurs at the shashinshiro. In this way, by arranging the microstrip line inductors sa and sb on both sides of the microstrip line, traps in the shingle can be eliminated.

Effects of the Invention As described above, according to the present invention, by arranging two tip short-circuited micros I-IJ tubular line inductors each having a length of 1/4 wavelength or less on both sides of a microstrip line, The generation of traps can be eliminated, and good filter characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a filter circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of transmission characteristics of a filter circuit according to the configuration of the present invention and an example of transmission characteristics of a filter circuit with a conventional configuration, and FIG. 1 is a diagram showing an example of a conventional filter circuit. 1... Dielectric substrate, 2... Input line,
3... Output line, 4... Chip capacitor, sa, sb... Micro strip line inductor, 6a. 6b...Through hole.

Claims (1)

[Claims] A microstrip line, a chip capacitor, and a microstrip line inductor whose two tips are short-circuited and whose length is less than a quarter wavelength are provided on the surface of a dielectric substrate with the back surface as a ground conductor, and the chip capacitor is A filter circuit electrically connected in series with the microstrip line, with the stripline inductor disposed on both sides of the microstrip line, and electrically connected in parallel to the microstrip line.