JP3477611B2 - Band stop filter - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a band stop filter,
In particular, the present invention relates to a microstrip band elimination filter that blocks passage of a signal in a desired predetermined band.

[0002]

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

Various BRFs have been proposed. As an example of the prior art, for example, Japanese Patent Laid-Open No. 10-
No. 215102, “Microstrip band stop filter” (hereinafter referred to as “first conventional technology”) and Japanese Patent Laid-Open No.
The "band stop filter" (hereinafter referred to as the second prior art) disclosed in Japanese Patent Publication No. 4-035505 is generally known. In the first conventional technique, the quarter-wave resonator is composed of 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 stop characteristic cannot be expected. Moreover, the frequency of each resonator cannot be easily adjusted. In particular, when a steep characteristic is desired, fine adjustment of the frequency is required, so it is very difficult to have the steep characteristic.

On the other hand, in the case of the second prior art, since the dielectric resonator is used, the Q value of the resonator can be made large, but the resonator becomes large. Therefore, in order to reduce the size of the resonator, a technique such as mode degeneration can be considered, but this technique has a problem that the precision and design of the resonator are not easy. Further, since it is a dielectric resonator, it is difficult to adjust the frequency of the resonator itself.

Further, the related prior art is, in fact, the Japanese Utility Model Laid-Open No. 58-
139704 "Strip line type band stop filter", JP-A-10-322155, "Band stop filter", JP-A-63-70601 "Microstrip band filter", actual open sho 63. -47603
No. 63-47604 and No. 63-47.
No. 605, "Microstrip band stop filter" and JP-A-59-27601, "Microstrip band stop filter".

[0006]

As described above, the BRF required to have a steep characteristic is a resonator having a high Q value, which is easy to adjust and small in size. . However, the above-mentioned conventional technique does not fully satisfy all these requirements.
In particular, the situation in which a microstrip line (substrate) to which this BRF is applied is used is generally small, can be easily mounted by soldering, does not require a special shield, etc., and must be realized at a low cost. There is also the problem of not becoming.

[0007]

OBJECTS OF THE INVENTION Therefore, one of the objects of the present invention is to provide a BRF which can be miniaturized on condition that it is mounted on a microstrip line. Another object of the present invention is to provide a band rejection filter (BRF) having a high Q value, a simple configuration, a low cost realization, and an easy frequency adjustment.

[0008]

[Means for Solving the Problems]The bandstop filter according to the present invention
The filter (BRF) has the following characteristic structure.
It (1) High frequency signal transmitted to the microstrip line
A band-stop filter that blocks the transmission of selected frequency components of
In Ruta, The microstrip line is formed
A substantially U-shaped internal conductor that is arranged apart from the flat surface,
The inner conductor is substantially surrounded and a space as a dielectric is provided inside.
And an outer conductor containing air.
A band including a pair of resonators electrically coupled to the lip line
Band stop filter. (2) High frequency signal transmitted to the microstrip line
A band-stop filter that blocks the transmission of selected frequency components of
In Ruta, The microstrip line is formed
A substantially U-shaped internal conductor that is arranged apart from the flat surface,
And an outer conductor that substantially surrounds the inner conductor.
The inner conductor and the outer conductor are the inner conductor.
On the opposite side of the open position of the conductive support spacer
Electrically shorted by the microstrip line.
A band-stop filter comprising a pair of resonators coupled to.

Here, the length of the inner conductor is approximately four minutes.
One wavelength is selected, and the outer conductor has a sheet metal case shape.
A pair in the vicinity of the open part of the inner conductor.
Frequency adjustment screws are provided. Also, the frequency adjustment
The screws are the microstrip line and the GND pattern.
It is arranged in the gap between them.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The configuration and operation of a preferred embodiment of a BRF according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a preferred embodiment of a BRF according to the present invention, FIG. 1 (A) is a plan view thereof, 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 is a substantially U-shaped conductive metal (for example, copper) plate manufactured by, for example, sheet metal working. 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 not). The inner conductor 1 is supported by a support spacer 6 and is separated from the plane on which the microstrip line 4 and the GND pattern 5 are formed (that is, so as to float in the air). 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 the stripline line, and the conductive support spacer 6 short-circuits the outer conductor 2. 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 configured as described above serves as a ground for the pair of resonators (or couplers) formed by the inner conductor 1 and the outer conductor 2. Also, the sheet metal case-shaped outer conductor 2 is
Since it also has a role of a shield case of F, it radiates an electromagnetic field to the outside and plays one of the roles of obtaining a high Q. By providing a space S on the opposite side of the resonator, both resonators are open. The length of the U-shaped line from the open position to the support spacer 6 is 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 substance), there is no substance such as a dielectric substance that loses electric power between the inner conductor 1 and the outer conductor 2, so that the resonance is very high. Become a vessel. Further, as described above, the BR shown in FIG.
F has a pair of (two) resonators. The coupling between the two resonators is determined by the spacing S between the two resonators, and the spacing S allows the degree of coupling to be set. In addition, the frequency is set on the outer conductor 2 at a position close to the open position of the resonator (that is, on both sides of the space S), preferably at a position corresponding to the gap between the microstrip line 4 and the GND pattern 5. A conductive adjusting screw 3 for adjusting is provided. These adjustment screws 3 rotate to rotate the microstrip lines 4 and G described above.
It moves in the direction perpendicular to the plane on which the ND pattern 5 is formed. In other words, the tips of these adjusting screws 3 move toward or away from the above-mentioned plane. The adjustment screw 3 is for varying the stray capacitance in the open position of the resonator. By adjusting these adjusting screws 3, the band stop 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 positions of the inner conductor 1 and the microstrip line (MAIN route) 4 are located. 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, for example, the height direction from the surface of the printed board on which the pattern 5 is formed.

The configuration and operation of the preferred embodiment of the BRF according to the present invention has been described above in detail. However, it goes without saying that such an embodiment is merely an example of the present invention and does not limit the present invention. Those skilled in the art can easily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

[0017]

As is apparent from the above description, the BRF of the present invention can be miniaturized and can be manufactured at low cost. Further, according to the BRF of the present invention,
The adjustment screw is provided in each resonator, and the frequency can be easily adjusted by adjusting the adjustment screw. Furthermore, since each resonator is formed in the shape of a strip line in which air is interposed, loss of the resonator itself is small, and a resonator having an extremely high Q can be obtained. Accordingly, the BRF of the present invention is
A practically remarkable effect that a steep band stop characteristic can be obtained is obtained.

[Brief description of drawings]

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

[Explanation of symbols]

1 Internal (center) conductor 2 outer conductor 3 adjustment screws 4 microstrip lines 5 GND (ground) pattern 6 Support spacer

Claims (5)

(57) [Claims] 1. A band-stop filter for blocking the transmission of selected frequency components of a high-frequency signal transmitted to a microstrip line, wherein the band-strip filter is arranged in a substantially U-shape spaced apart from the plane on which the microstrip line is formed. And a pair of resonators that are electrically surrounded by the internal conductor and an external conductor that substantially surrounds the internal conductor and that contains air as a dielectric inside, and that is electrically coupled to the microstrip line. Characteristic band stop filter. 2. A high frequency transmitted on a microstrip line.
A band block that blocks the transmission of selected frequency components of a wave signal.
In the stop filter, separate from the plane where the microstrip line is formed.
And the substantially U-shaped inner conductor that is placed
And an inner conductor that qualitatively surrounds the inner conductor.
The body and the outer conductor are in the open position of the inner conductor.
On the opposite side of the
And is electrically coupled to the microstrip line 1
Band stop fill characterized by comprising a pair of resonators
Ta. 3. The length of the inner conductor is approximately one-quarter wavelength.
The belt according to claim 1 or 2, which is selected.
Band stop filter. 4. The outer conductor has a sheet metal case shape, and
A pair of frequencies near the open part of the inner conductor
3. A number adjusting screw is provided, and the number adjusting screw is provided.
Or the band elimination filter according to any one of 3). 5. The frequency adjusting screw is the microst
It should be placed in the gap between the lip line and the GND pattern.
Band according to any one of claims 1 to 4, characterized in that
Blocking filter.