JP2001244705A - Band rejection filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a band rejection filter(BRF) with a high Q, a small size and ease of frequency adjustment, where a main signal flows through its microstrip line. SOLUTION: An inner (center) conductor 1 of a channel shape, that is preferably subjected to sheet metal working is put into an outer conductor 2 of a sheet metal case shape to configure a pair of resonators, the one side of which is short-circuited with each other via a conductive support spacer 6 and the other side, of which is open with an interval S. Adjustment machine screws 3 are located at places close to the open position of the inner (center) conductor 1 in each resonator for varying the stray capacitance for frequency adjustment. Degree of coupling between the resonators is adjusted by the open position of the interval S of the inner (center) conductor 1. Furthermore, by properly setting the interval between the inner (center) conductor 1 and a MAIN signal line (microstrip line 4), the coupling between the resonators and the microstrip line 4 is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a band rejection filter,
More particularly, the present invention relates to a microstrip band rejection filter that blocks a signal of a desired predetermined band.

[0002]

2. Description of the Related Art Band Rejection Filtration
ter, hereinafter referred to as BRF) is a circuit functional element that attenuates a signal component of a selected desired frequency with a predetermined large attenuation, and passes other frequency components substantially without attenuation. In such a BRF, reducing insertion loss is an important factor.

Various BRFs have been proposed. As an example of the prior art, for example,
JP-A-215102, “Microstrip band rejection filter” (hereinafter referred to as “first prior art”)
The “band rejection filter” (hereinafter referred to as “second related art”) disclosed in Japanese Patent Application Laid-Open No. 04-035505 is generally known. In the first prior art, a quarter-wavelength resonator is constituted by a microstrip line. However, since the microstrip line itself has a large passage loss, the Q of the resonator cannot be increased, and a steep band rejection characteristic cannot be expected. Further, the frequency of each resonator cannot be easily adjusted. In particular, when steep characteristics are desired, fine adjustment of the frequency is required, so that it is very difficult to have steep characteristics.

On the other hand, in the case of the second prior art, since a dielectric resonator is used, the Q value of the resonator can be increased, but the resonator becomes large. Therefore, in order to reduce the size of the resonator, a technique such as mode degeneration is conceivable. However, this technique has problems such as difficulty in accuracy and design of the resonator. In addition, because of the dielectric resonator, it is difficult to adjust the frequency of the resonator itself.

Further, a related prior art is disclosed in
JP-A-139704, "Stripline band-stop filter", JP-A-10-322155, "Band-stop filter", JP-A-63-70601, "Microstrip band-pass filter", -47603
JP-A-63-47604 and JP-A-63-47604
Japanese Patent Application Laid-Open No. 605/605, "Microstrip Band Rejection Filter" and JP-A-59-27601 also disclose "Microstrip Band Rejection Filter".

[0006]

As described above, a BRF requiring a steep characteristic includes a resonator having a high Q value, easy adjustment, and small size. . However, the above-mentioned prior art does not sufficiently satisfy all these requirements.
In particular, the situation in which a microstrip line (substrate) to which this BRF is applied is generally used in a small size, which can be easily mounted by soldering or the like, does not require a special shield or the like, and must be realized at low cost. There is also the problem of not being.

[0007]

SUMMARY OF THE INVENTION Accordingly, one of the objects of the present invention is to provide a BRF that can be miniaturized provided that it is mounted on a microstrip line. It is another object of the present invention to provide a band rejection filter (BRF) having a high Q value, a simple configuration, which can be realized at low cost, and easy frequency adjustment.

[0008]

SUMMARY OF THE INVENTION A band rejection filter (BRF) according to the present invention is a filter for preventing transmission of a selected frequency component of a high frequency signal transmitted to a microstrip line. A substantially U-shaped inner conductor spaced apart from the plane
It is characterized by comprising a pair of resonators formed by an outer conductor substantially surrounding the inner conductor and electrically coupled to the microstrip line.

According to a preferred embodiment of the BRF according to the present invention, the above-described inner conductor and outer conductor substantially form a stripline. Further, air is used as a dielectric between the inner conductor and the outer conductor. Further, the inner conductor and the outer conductor
On the other side of the open position of the inner conductor, a short circuit is caused by the conductive support spacer. The length of the inner conductor is selected to be approximately one quarter wavelength.
The outer conductor has a sheet metal case shape, and a pair of frequency adjustment screws is provided near the open portion of the inner conductor. Further, the frequency adjusting screw is arranged in a gap between the microstrip line and the GND pattern.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of a preferred embodiment of a BRF according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a preferred embodiment of a BRF according to the present invention, and FIG.
(B) is a side sectional view. BRF of this preferred embodiment
Is composed of an inner (or center) conductor 1, an outer conductor 2, an adjusting screw 3, a microstrip line 4, a ground (GND) pattern 5, and a conductive support spacer 6. Preferably, the microstrip line 4 and the GND patterns 5 on both sides thereof are formed on a conventional printed circuit board or the like.

The inner conductor 1 has a substantially U-shape made of a conductive metal (for example, copper) plate by, for example, sheet metal processing. That is, the inner conductor 1 has a substantially rectangular shape having a portion parallel to the microstrip line 4 and a portion perpendicular to the microstrip line 4 (however, as will be described later, a gap S is formed on one side and a complete loop shape is formed). is not). The internal conductor 1 is supported by a support spacer 6 and is configured to be separated from (ie, to float in) the plane on which the microstrip line 4 and the GND pattern 5 are formed. This inside (center)
The conductor 1 and the outer conductor 2 on the side surface form a line (that is, a signal transmission line) close to a stripline line, and are short-circuited (short-circuited) with the outer conductor 2 by the conductive support spacer 6. ing. The outer conductor 2 is a sheet metal case obtained by processing a conductive metal plate such as a copper alloy or aluminum into a case shape by sheet metal processing.

The outer conductor 2 thus configured has a role of ground (ground) for a pair of resonators (or couplers) formed by the inner conductor 1 and the outer conductor 2. The sheet metal case-shaped outer conductor 2 is formed of the BR.
Since it also has a role of a shield case for F, it suppresses a radiation electromagnetic field to the outside and plays one of the roles of obtaining a high Q. On the opposite side of the resonator, by providing an interval S, both resonators are open (open). The length of the U-shaped line from this open position to the support spacer 6 is a length equal to a quarter wavelength of the desired resonance frequency of the high frequency signal transmitted through the microstrip line 4 which is the MAIN route. If so, both resonators resonate at that frequency.

Since the inner conductor 1 is hollow (that is, air is used as a dielectric), there is no substance that loses power such as a dielectric between the outer conductor 2 and the inner conductor 1. Container. Further, as described above, the BR shown in FIG.
F has a pair (two) of resonators. The coupling between these two resonators is determined by an interval S between the two resonators, and the degree of coupling can be set by this interval S. In addition, the frequency of the external conductor 2 is set at a position close to the open position of the resonator (that is, on both sides of the interval S), preferably at a position corresponding to the gap between the microstrip line 4 and the GND pattern 5. A conductive adjustment screw 3 for adjustment is provided. These adjustment screws 3 rotate to rotate the microstrip lines 4 and G
It moves in the direction perpendicular to the plane on which the ND pattern 5 is formed. In other words, the tips of the adjusting screws 3 move so as to approach or separate from the above-described plane. The adjusting screw 3 changes the stray capacitance at an open place of the resonator. By adjusting these adjusting screws 3, the band rejection frequency, which is the resonance frequency of each resonator, can be adjusted.

The coupling between the BRF and the MAIN route (that is, the microstrip line 4 through which the main signal is transmitted) according to the present invention is performed in space. Therefore, the position of the inner conductor 1 and the microstrip line (MAIN route) 4 is determined. Relationship (in FIG. 1, microstrip line 4 and GND
The amount of coupling between the MAIN route by the microstrip line 4 and the above-described resonator can be adjusted by changing the pattern 5 on which the pattern 5 is formed, for example, in the height direction from the surface of the printed circuit board.

The configuration and operation of the preferred embodiment of the BRF according to the present invention have been described above in detail. However, such an embodiment is merely an exemplification of the present invention, and does not limit the present invention in any way. It will be readily apparent to those skilled in the art that various modifications and changes can be made in accordance with the particular application without departing from the spirit of the invention.

[0017]

As is apparent from the above description, according to the BRF of the present invention, it is possible to reduce the size and to manufacture it at low cost. According to the BRF of the present invention,
An adjusting screw is provided in each resonator, and the frequency can be easily adjusted by adjusting the adjusting screw. Furthermore, since each resonator is formed in a strip line shape with air interposed therebetween, a loss of the resonator itself is small, and a resonator having an extremely high Q can be obtained. Thereby, the BRF of the present invention is:
A remarkable practical effect that a steep band rejection characteristic can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a preferred embodiment of a band rejection filter according to the present invention, wherein (A) is a plan view and (B) is a side sectional view.

[Explanation of symbols]

 Reference Signs List 1 inner (center) conductor 2 outer conductor 3 adjusting screw 4 microstrip line 5 GND (ground) pattern 6 support spacer

Claims (7)

[Claims] 1. A band rejection filter for blocking transmission of a selected frequency component of a high-frequency signal transmitted to a microstrip line, wherein the band-rejection filter is disposed substantially apart from a plane on which the microstrip line is formed. And a pair of resonators, each of which is constituted by an inner conductor and an outer conductor substantially surrounding the inner conductor, and electrically coupled to the microstrip line. 2. The band rejection filter according to claim 1, wherein said inner conductor and said outer conductor substantially form a strip line. 3. The band rejection filter according to claim 1, wherein air is used as a dielectric between said inner conductor and said outer conductor. 4. The semiconductor device according to claim 1, wherein the inner conductor and the outer conductor are short-circuited by a conductive support spacer on a side opposite to an open position of the inner conductor.
4. The band rejection filter according to 2 or 3. 5. The band rejection filter according to claim 1, wherein the length of said inner conductor is selected to be substantially a quarter wavelength. 6. The apparatus according to claim 1, wherein the outer conductor is in the form of a sheet metal case, and a pair of frequency adjusting screws are provided near the open portion of the inner conductor. Band-stop filter. 7. The band rejection filter according to claim 1, wherein said frequency adjusting screw is disposed in a gap between said microstrip line and a GND pattern.