JPH098508A - Band pass filter for reactance branch circuit - Google Patents

Abstract

PURPOSE: To optimize the coupling adjustment of the band pass filter connecting to a branch device having the reactance branch circuit by avoiding the effect of a coupling amount of the reactance branch circuit. CONSTITUTION: Resonance rods 2a-2e whose length is 1/4 wavelength short- circuited at one side and open at the other side are arranged in an interdigital band pass filter built in a case 5, and the frequency is adjusted by adjustment screws 1a-1e in the center of each resonance rod. Furthermore, as input and output parts of the filter, coupling rods 3a, 3b are provided, an interval (L'1) between the branch side coupling rod 3a and the resonance rod 2a and an interval (L'2) between the resonance rods 2a and 2b are selected wider than intervals L1, L2 of the output side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bandpass filter for a reactance branch circuit, and more particularly to a bandpass filter used for a duplexer having a high-frequency reactance branch circuit for microwave communication.

[0002]

2. Description of the Related Art Conventionally, as a demultiplexer having a reactance branch circuit, there is a demultiplexing / synthesizing device described in Japanese Patent Laid-Open No. 5-29806.

The plurality of bandpass filters according to this conventional example are ones in which a plurality of bandpass filters each having an independent characteristic are connected, and each bandpass filter is adjusted as a whole after being connected to a reactance branch circuit. Had obtained the characteristics of the duplexer. In general, as a characteristic of a duplexer having a reactance branch circuit, since the coupling between the coupling rod near the branch side of each bandpass filter and the resonator is strong, the first stage of each bandpass filter and The second-stage coupling adjusting screw was adjusted in a direction to reduce the coupling amount as compared with the coupling adjusting screws having the other number of stages.

FIG. 7 is a diagram showing the structure of a conventional bandpass filter. FIG. 7A shows a top view of an interdigital type five-stage bandpass filter, and FIG. 7B shows a vertical sectional view of AA ′ in FIG. 7A.
In FIG. 7A, in the metal case 10, one is short-circuited, the other is open, and the length is 1 /
Five resonance rods 12a to 12e of four wavelengths are arranged, and frequency adjusting screws 11a to 11e are attached to these resonance rods so that the length of each resonance rod can be adjusted. Further, coupling rods 13a and 13b are provided at the input and output parts of the bandpass filter. Further, in FIG. 7B, coupling adjusting screws 14a to 14f are arranged between the resonators and between the coupling rods.

In FIG. 7 (a), connecting rods 13a, 13
Regarding the positions of b and the resonance rods 12a to 12e, for example, the distance between the coupling rod 13b and the resonance rod 12e, the coupling rod 13
The distance between a and the resonance rod 12a is L1. Further, the distance between the resonance rods 12a to 12e is L2. As described above, the positions of the coupling rods and the resonance rods are determined by the case
It is attached in a symmetrical position with respect to. This is because the structure of the bandpass filter is simplified and the manufacturing is intended to be easy.

[0006]

As described above, in the bandpass filter used in the conventional reactance branch circuit, the spacing between the coupling rod and the resonance rod is taken into consideration without considering the characteristic that each filter changes the coupling amount near the branch side. Therefore, when adjusting the duplexer, there is a problem that the adjustment adjustment of the coupling adjustment screw on the coupling side on the branch side is out of the screw adjustment range, which makes coupling adjustment difficult.

For example, the demultiplexing characteristics (return loss characteristics) when the BPF and the reactance branching circuit having the configuration of FIG. 7 are used, frequency 5 GHz band, 4-branching (40 MHz demultiplexing),
Full ripple bandwidth 31.6MHz, 5 BPF stages,
FIG. 8 shows the result obtained by simulating under the condition of Q = 4500. In this case, since the coupling amounts of the first and second stages on the branch side connected to the reactance branch circuit are large and the demultiplexing characteristic is deteriorated, the frequency adjusting screw 11
Adjustment was impossible for a and 11b.

An object of the present invention is to reduce the amount of coupling on the side connected to a reactance branch circuit in a bandpass filter connected to a duplexer having a reactance branch circuit,
It is to optimize the filter design by widening the adjustment range by the frequency adjustment screw.

[0009]

A reactance branch circuit bandpass filter according to the present invention is connected to one end branched into a plurality of reactance branch circuits, and has a plurality of coupling rods on the input and output sides and a plurality of coupling rods between the coupling rods. And the resonance rods are arranged in a line in the case, and the mutual attachment distance between the coupling rod and the resonance rod is increased toward the branch side.

[0010]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a diagram showing a configuration when the present invention is applied to an interdigital type five-stage bandpass filter. FIG. 1A is a top view and FIG. 1B is FIG. (A)
3 is a vertical cross-sectional view taken along line AA ′ of FIG. FIG. 1 (a)
The interdigital bandpass filter has five resonance rods 2a to 2 each having a short circuit (short circuit), another circuit open (open), and a length of ¼ wavelength with respect to the case 5.
e are lined up. Further, the length of the resonance rod can be adjusted by the frequency adjusting screws 1a to 1e, respectively. Also, regarding the input / output section of the filter,
Connecting rods 3a and 3b are provided. Further, FIG. 1 (b)
As shown in FIG. 3, coupling adjusting screws 4a to 4f are provided between the resonators and between the coupling rod and the resonance rod.

L1 and L2 in FIG. 1A are shown in FIG.
The distance between the coupling rods and the resonance rods near the output side of the interdigital portable pass filter is the same as that of L1 and L2 shown in FIG. The coupling rod and resonance rod intervals L'1 and L'2 are arranged in a line wider than L1 and L2 in consideration of the tight coupling by the reactance branch circuit.

For example, L'1 and L'2 are L1 and L1, respectively.
In relation to L2, L′ 1 = 1.5 × L1 (50% increase) L′ 2 = 1.3 × L2 (30% increase).

As described above, the coupling amounts of the first and second stages on the branch side of the filter are made equal by equalizing the coupling amounts of all the resonance rods by increasing the distance between the coupling rod and the resonance rod.
Adjustment screws can be set in the coupling adjustment range.

FIG. 2 is a block diagram of a 4-branch demultiplexer composed of four interdigital 5-stage bandpass filters 24 to 27 and a reactance branch circuit 22 as an embodiment to which the above-described bandpass filter of the present invention is applied. It is the figure which showed.

In the figure, the signal input from the input terminal 33 is branched into four by the reactance branching circuit 22 and then centered at four center frequencies f1 to f by four band filters.
4 frequency components are output to the output terminals 34 to 37.

FIG. 3 is a diagram showing the configuration of the 4-branch demultiplexer shown in FIG. In the figure, the output of the reactance branch circuit 22 is connected to the interdigital type five-stage bandpass filters 24 to 27.

The signals input from the input terminal 33 are respectively demultiplexed and output to the output terminals 34 to 37.

With respect to such a configuration, the conditions specifically described above, that is, the frequency of 5 GHz band, four branches (40 MHz)
Demultiplexing), full ripple bandwidth 31.6MHz, BPF5
FIG. 4 shows the demultiplexing characteristics at the stage, Q = 4500.

This figure shows that by setting the intervals between the coupling rods and the resonance rods of the band-pass filters 24 to 27 to be L'1 and L'2, the coupling amount can be made uniform in all the resonance rods, so that each frequency adjusting screw can be used. It is shown that adjustment can be easily performed using 1a to 1e, and excellent demultiplexing characteristics can be obtained.

In this embodiment, L'1 and L'2 are 1.5 times and 1.3 times as large as L1 and L2, respectively, but the present invention is not limited to this. For example, the reactance branch circuit may be changed in its ratio value according to the coupling amount, or L '
It is also effective to set 3 to a value different from L2.

In this embodiment, the method of changing the coupling amount on the branch circuit side of the bandpass filter by changing the distance between the coupling rod of L'1 and L'2 and the resonator in FIG. 1 is used. Needless to say, the same effect can be obtained by changing the diameter or diameter to reduce the amount of binding.

That is, FIG. 5 shows a second embodiment of the present invention, which is all shown in FIG. 7 except that the length of the connecting rod 50 near the branch side is shorter than that of the connecting rod 13a shown in FIG. The configuration is the same as that of. In this case, since the length of the connecting rod 50 is short and the connecting amount is small, the same effect as that of the configuration shown in FIG. 1 can be obtained. Further FIG.
FIG. 8 is a diagram showing a third embodiment of the present invention, but is all the same as the configuration of FIG. 7 except that the diameter of the coupling rod 51 near the branch side is smaller than that of the coupling rod 13a shown in FIG. Is.
Also in this case, since the diameter of the connecting rod 51 is small, the amount of connection can be reduced and the same effect as that of the configuration shown in FIG. 1 can be obtained.

Although the interdigital bandpass filter has been described in this embodiment, the type of the bandpass filter is not limited to this. For example, the present invention is applicable to all bandpass filters used in reactance branch circuits such as dielectric filters, semi-coaxial filters, and waveguide filters. That is, in the case of a bandpass filter using a dielectric filter, it is possible to easily adjust the filter characteristics by arranging a plurality of dielectric filter connection intervals so as to be widened only near the reactance branch circuit.

[0025]

As described above, in consideration of the close coupling in the vicinity of the branch side of the duplexer having the reactance branch circuit in advance, the first stage and the stage of the branch side of the band pass filter are arranged so that the branch side is coarsely coupled. By making the interval between them asymmetric with respect to the input / output unit, there is an effect that the adjustment of the filter can be performed easily and reliably.

[Brief description of drawings]

FIG. 1A is a top view of a first embodiment of a bandpass filter of the present invention. (B) It is a longitudinal cross-sectional view of the first embodiment of the bandpass filter of the present invention.

FIG. 2 is a block diagram of a 4-branching duplexer of the present invention.

FIG. 3 is a diagram showing a configuration of a 4-branch demultiplexer shown in FIG.

FIG. 4 is a diagram showing a demultiplexing characteristic of the 4-branching demultiplexer of the present invention.

5 (a) is a top view of a second embodiment of the bandpass filter of the present invention. FIG. (B) It is a longitudinal cross-sectional view of the second embodiment of the bandpass filter of the present invention.

FIG. 6 (a) is a top view of a third embodiment of the bandpass filter of the present invention. (B) It is a longitudinal cross-sectional view of a third embodiment of the bandpass filter of the present invention.

FIG. 7A is a top view of a conventional bandpass filter. (B) It is a longitudinal cross-sectional view of a conventional bandpass filter.

FIG. 8 is a diagram showing a demultiplexing characteristic of a conventional 4-branch demultiplexer.

[Explanation of symbols]

 1a-1e Frequency adjustment screw 2a-2e 1/4 wavelength resonance rod 3a, 3b Coupling rod 4a-4f Coupling adjustment screw 5 Case 6a, 6b Connection pin 10 Case 11a-11e Frequency adjustment screw 12a-12e 1/4 wavelength resonance rod 13a, 13b coupling rod 14a-14f coupling adjustment screw 16a, 16b connection pin 33 input connector 34-37 output connector 24-27 interdigital band pass filter 50,51 coupling rod

Claims (5)

[Claims] 1. A reactance branch circuit is connected to one end of a plurality of branches, and two coupling rods on the input / output side and a plurality of resonance rods between the coupling rods are arranged in a row in the case. A bandpass filter for a reactance branch circuit, characterized in that the mutual mounting intervals of the resonance rods are widened toward the branch side. 2. A reactance branch circuit is connected to one end branched into a plurality, and two coupling rods on the input / output side and a plurality of resonance rods between the coupling rods are arranged in a line in the case. A bandpass filter for a reactance branch circuit, wherein the length of only the coupling rod near the branch side is shortened. 3. A reactance branching circuit is divided into a plurality of branches, which are connected to one end, and two coupling rods and a plurality of coupling rods are lined up in the case between the coupling rods on the input / output side and the coupling rods. And a resonance rod, wherein only the coupling rod near the branch side has a smaller diameter than the resonance rod. 4. The coupling rod and the resonance rod each have a frequency adjusting screw at the center thereof.
A band filter for a reactance branch circuit according to the items 2 and 3. 5. The reactance branch circuit according to claim 1, wherein the reactance branch circuit bandpass filter is any one of an interdigital bandpass filter, a dielectric filter, and a semi-coaxial filter. Bandpass filter.