JPH09232804A - Distributed coupling narrow band elimination filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain miniaturization without, deterioration in the characteristic by arranging each short stub along a straight line in parallel with a transmission line and arranging a shield member connecting to ground to each distribution coupling between the transmission line and each short stub. SOLUTION: Three short stubs 5-7 connecting to ground are arranged not to both sides of a base transmission line 1 but to one side along a straight line in parallel with the transmission line 1 (the length of the stubs is identical to each other, λ/4, where λ is the wavelength with respect to the center frequency of an eliminated band). Furthermore, a shield member 8(9) connecting to ground is arranged between the short stubs 5 and 6 (short stubs 6 and 7). Then 3-stages of band elimination operation is conducted by a distribution coupling between the transmission line 1 and the short stub 5, between the transmission line 1 and the short stub 6, and between the transmission line 1 and the short stub 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication using microwaves or the like, for example, a distributed coupling type narrow band elimination filter used in a terminal of a personal handyphone system or the like, which is a basic transmission line. And miniaturization of a distributed coupling type narrow band elimination filter having two or more stages, which is composed of two or more short stubs arranged in parallel with this.

[0002]

2. Description of the Related Art In a microwave circuit, a multistage distributed coupling type narrow band elimination filter is often used to remove a part of the band extracted by a bandpass filter. FIG. 4 shows a structure of a three-stage distributed-coupling type narrow band elimination filter which is one of
Shown in That is, in the conventional three-stage distributed-coupling type narrow band elimination filter, it is alternately parallel to the upper and lower sides (or left and right sides) of the basic transmission line 1 (along the longitudinal direction of the transmission line 1). The short stubs 2, 3, and 4 were arranged in the meaning of being parallel in the plane including the center line, as well as elsewhere in this specification. This separates adjacent distributed couplings (for example, between the distributed coupling between the transmission line 1 and the short stub 2 and the distributed coupling between the transmission line 1 and the short stub 3), and the interaction between the two distributed couplings. This is for reducing the narrow band and realizing narrow band removal.

In a multi-stage distributed-coupling type narrow band elimination filter having three or more stages, short stubs are alternately arranged on both sides such as the upper and lower sides of the transmission line in parallel with the transmission line for the same reason as above. The number was set according to the number.

[0004]

However, in the conventional distributed coupling type narrow band elimination filter as described above, since the short stubs are arranged on both sides of the transmission line, this distributed coupling type narrow band elimination filter is inevitable. However, it was difficult to reduce the size. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-stage distributed coupling type narrow band elimination filter having a structure that can be downsized.

[0005]

A multistage distributed-coupling type narrow band elimination filter having a basic transmission line and two or more short stubs arranged in parallel with the basic transmission line is configured as follows. That is, two or more short stubs are arranged along one straight line parallel to the transmission line, and a shield member grounded is provided between each distributed coupling between the transmission line and each short stub. It is arranged to be arranged.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below based on an embodiment of the present invention shown in the drawings. FIG.
FIG. 4 shows a configuration of a three-stage distributed coupling type narrow band elimination filter according to an embodiment of the present invention. That is, in this embodiment, three ground lines are provided not on both sides of the basic transmission line 1 but only on one side (lower side in the figure) along one straight line parallel to the transmission line 1. The short stubs 5, 6 and 7 are provided (all have the same length and λ / 4, where λ is the wavelength corresponding to the center frequency of the elimination band). Further, between the short stubs 5 and 6 and between the short stubs 6 and 7, shield members 8 and 9 which are grounded are arranged. The transmission line 1 and the short stubs 5, 6, 7
Are formed by strip lines, and in FIG. 1, the thickness of the strip lines is shown thick for the sake of clarity.

FIG. 2 is a fragmentary three-dimensional view showing the actual structure of the above embodiment in an easy-to-understand manner. That is, the transmission line 1 is arranged in a grounded conductive case 10, and the short stubs 5, 6 and the like are arranged in parallel and opposed to the transmission line 1 at regular intervals. And is fixed to the case 10 by the conductor fixing members 5a and 6a at the left ends thereof. Also, the right end portions of the short stubs 5 and 6 are all insulator fixing members 5b,
It is fixed to the case 10 by 6b (not shown). The conductor shield member 8 and the like are arranged between the short stubs 5 and 6 and fixedly installed in the case 10.

In the above embodiment configured as described above, the distributed coupling between the transmission line 1 and the short stub 5 shown in FIG. 1, the distributed coupling between the transmission line 1 and the short stub 6 and the transmission line are shown. By the distributed coupling between 1 and the short stub 7, the band elimination operation of three stages is performed,
Since all of the above three distributed couplings are formed below the transmission line 1, the space occupied by this distributed coupling type narrow band elimination filter becomes smaller accordingly, and as a result, the size of this distributed coupling type narrow band elimination filter becomes smaller. Can be realized.
Moreover, even if the above three distributed couplings are close to each other as described above, the presence of the shield members 8 and 9 separates them from each other and does not affect each other, so that the narrowing of the removal band is not impaired. FIG. 3 shows the effect of the presence of the shield members 8 and 9, etc., FIG. 3A shows the filter characteristics when the shield member is arranged, and FIG. 3B shows the shield member arranged. Although the filter characteristics are shown in the case of not performing, it can be seen that (a) shows sharper and larger attenuation in the central portion of the removal band.

As described above, according to the present invention, in order to miniaturize a multistage distributed coupling type narrow band elimination filter, a plurality of distributed couplings are provided only on one side of the transmission line, not on the upper and lower sides (or left and right sides). Further, it is intended to avoid the deterioration of the filter characteristics of the narrow band elimination filter due to the formation by providing a shield member between the distributed couplings.

[0010]

As described in detail above, according to the present invention,
Without degrading the characteristics as a narrow band elimination filter,
(EN) It is possible to provide a multi-stage distributed coupling type narrow band elimination filter that can be downsized.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a partially cutaway three-dimensional view showing a partial configuration of the above embodiment.

FIG. 3 is a diagram showing a difference in filter characteristics depending on the presence or absence of a shield member.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Transmission line 2 Short stub 3 Short stub 4 Short stub 5 Short stub 6 Short stub 7 Short stub 8 Shield member 9 Shield member 5a Conductor fixing member 5b Insulator fixing member 6a Conductor fixing member 10 Case

Claims (1)

[Claims] 1. A distributed-coupling type narrow band elimination filter having two or more stages, comprising a basic transmission line and two or more short stubs arranged in parallel with each other, wherein each of the two or more short stubs is provided. It is arranged along a straight line parallel to the transmission line, and a shield member grounded is arranged between each distributed coupling between the transmission line and each short stub. Distributed-coupling narrow band elimination filter.