JPH10173406A - Linear phase band-pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a filter at a low cost by omitting the joining work of plural waveguides. SOLUTION: The non-polar linear phase band-pass filter is sequentially combines cavity resonators 1 to 8 by conductive elements Li1, L12 to L78 and L80 being main combining paths. A 1st sub combining path sequentially combines a resonator 2, a capacitive probe C2, a coaxial cable 12, a capacitive probe C7 and a resonator 7, and conductively combines the resonator 2 and the resonator 7. A 2nd sub combining path sequentially combines a resonator 3, a capacitive probe C3, a coaxial cable 11, a capacitive probe C6 and a resonator 6, and conductively combines the resonator 3 and the resonator 6. This conductive combining causes from signal phase rotation by the adjustment of the length of coaxial cables 1 and 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-polar linear phase band-pass filter used for a radio communication device in a microwave band, and more particularly to a linear phase band-pass filter formed using a waveguide. .

[0002]

2. Description of the Related Art A conventional linear phase band-pass filter of this type is disclosed in Japanese Patent Laid-Open Publication No. Sho 51-78673 (Title of Invention:
This is shown in a conventional example (FIG. 1) of a polarized band-pass filter. FIG. 2 is a plan view corresponding to the disclosed nonpolar linear phase bandpass filter. Hereinafter, a conventional linear phase band-pass filter will be described with reference to FIG.

[0003] The linear phase band pass filtering unit are each is formed on two waveguide 10A and 10B are joined by side wall surfaces (narrow wall) to each other with rectilinear waveguide TE ₁₀ figure 8 cavity resonators (8th order)
Consists of This bandpass filter comprises eight cavity resonators 1
A,..., The inductive element L12 with a round bar between the steps of 4A,
, L34, and the stage between the resonators 4A and 5A is coupled by an inductive element L45a by a window, and the resonators 5A, 5A,.
The inductive elements L56,.
Are connected sequentially. Also, between the input end Ti of the input high frequency signal Pi such as a microwave and the resonator 1A and between the resonator 8A and the output end To of the output high frequency signal Po,
They are connected by round rod inductive elements Li1 and L8o, respectively. These inductive elements Li1, L12 to L34, L
45a, L56 to L78 and L8o form the main coupling path of this bandpass filter.

[0004] This band-pass filter includes resonators 3A to 3A between two selected cavity resonators 2A and 7A.
6A is jump-coupled with an inductive element L27 by a window,
A resonator 4A is provided between two selected resonators 3A and 6A.
And 5A are jump-coupled by an inductive element L36 by a window. Each of these inductive elements L27 and L36 forms a sub-coupling path of the band-pass filter.

As described above, a non-polar linear phase band-pass filter has a sub-coupling that couples between two selected resonators when the main coupling path coupling between the resonators is an inductive element. The coupling path must also be an inductive element. To form the inductive elements L27 and L36, as shown in the figure, a waveguide 1 incorporating the resonators 1A to 4A is used.
0A and the waveguide 10B containing the resonators 5A to 8A need to be bent, and the waveguides 10A and 10B need to be connected to each other on the side wall surface. The cavity resonator may be constituted by a dielectric resonator having a side wall surface.

[0006]

In a conventional linear phase bandpass filter including a main coupling path and a sub coupling path, when an inductive coupling element is used for the main coupling path, the inductive coupling is also applied to the sub coupling path. Although it is necessary to use a coupling element, it is necessary to accurately connect the inductive coupling windows respectively opened on the side walls of the two waveguides, and this connection processing is difficult with a commonly used brazing method, etc. There was a disadvantage that the cost was high.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a linear phase bandpass filter which can simplify the configuration of the sub-coupling path and can be manufactured at low cost.

[0008]

SUMMARY OF THE INVENTION A linear phase bandpass filter according to the present invention includes a main coupling path for sequentially coupling a plurality of resonators with an inductive element, and a selected two of the resonators. A non-polar linear phase bandpass filter comprising at least one sub-coupling path coupled with an inductive element;
The sub-coupling path includes a capacitive probe electromagnetically coupled to the coupled resonator, and a coaxial cable having both ends connected to the two capacitive probes, respectively.

In this linear phase bandpass filter, the resonators can be formed in a linear waveguide, so that all the resonators can be constituted by one waveguide. There is no need to join with high accuracy, and it can be manufactured at low cost.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a linear phase bandpass filter according to an embodiment of the present invention.

The linear phase bandpass filter of FIG.
Like the linear phase band pass filtering unit of FIG. 2, a band-pass filtering device consisting of a cavity resonator 8-stage waveguide TE ₁₀ figure. Cavity resonators 1 configured between an input terminal Ti of the high frequency signal Pi and an output terminal To of the output high frequency signal Po.
Reference numeral 8 corresponds to each of the cavity resonators 1A to 8A in FIG. However, the resonators 1 to 8 are formed in one straight waveguide 10. Inductive elements Li1, L12 to L34, L56 to L78 and L8 forming a main coupling path
o also corresponds to the components of the same reference numerals in FIG. Here, the inductive element L45 that couples the resonators 4 and 5 is
Although it has the same element value as the inductive element L45a of FIG. 2, since the resonators 4 and 5 are formed on the same straight line, they are formed of a round bar like the other main coupling paths in the present embodiment. ing. Note that each of the inductive elements may be configured using a window.

The linear phase bandpass filter of FIG.
Similar to the linear phase bandpass filter of FIG. 2, a sub-coupling path for coupling the selected two cavity resonators 2 and 7 and between the cavity resonators 3 and 6 with an inductive circuit is provided. Have. That is, the sub-coupling path between the resonators 2 and 7 is connected to the probe C2 and the coaxial cable 12 connected sequentially from the resonator 2.
And a probe C7, and a sub-coupling path between the resonators 3 and 6 is a probe C3, a coaxial cable 11, and a probe C6 sequentially connected from the resonator 3. Probe C
Reference numerals 2, C3, C6, and C7 denote capacitive probes that protrude into the corresponding resonators on the side wall surfaces of the waveguide 10 and are electromagnetically coupled to each other. Being connected,
The inner conductor pins of the coaxial connector attached to the side wall of the waveguide 10 are used.

The impedance of the sub-coupling path connecting resonators 2 and 7 must be substantially equal to the impedance of inductive element L27 in the band-pass filter of FIG. 2 at the pass frequency of the band-pass filter. There is. In order to generate the same inductive impedance as that of the inductive element L27 in the sub-coupling path including the capacitive impedance of the probes C2 and C7, the length of the coaxial cable 12 is adjusted to cause the phase rotation of the high frequency signal. It should be done. Similarly, for the sub-coupling path connecting the resonators 3 and 6,
The phase rotation of the coaxial cable 11 produces almost the same inductive impedance as the inductive element L36 in FIG.

Next, the operation of the linear phase bandpass filter according to the embodiment of FIG. 1 will be described. Cavity resonators 1 to 8 are inductive elements Li1 and L12 to main coupling paths.
L78 and L8o are sequentially linked. The first sub-coupling path connects the cavity resonator 3 and the probe C2, and has a coaxial cable 12 having both ends connected to the probes C2 and C7.
To change the signal phase and couple the probe C6 and the cavity resonator 6. Similarly, the second sub-coupling path couples the cavity resonator 2 and the probe C3, changes the signal phase with a coaxial cable 11 connected at both ends to the probes C3 and C6, and sets the probe C7 and the cavity resonator 7 together. And Coaxial cable 11
And the length of 12 determines the length at which the sub-coupling path becomes inductive coupling.

[0015]

As described above, the present invention provides a main coupling path for sequentially coupling a plurality of resonators with an inductive element, and a method for connecting a selected two of the resonators with an inductive element. In a non-polar linear phase bandpass filter comprising one and the other sub-coupling path, the sub-coupling path is coupled to the resonator and the capacitive probe respectively electromagnetically coupled, the two ends of the capacitive probe Since each resonator has a coaxial cable connected to each probe, all the resonators can be formed by a single linear waveguide, so that there is no need to join multiple waveguides with high precision, and it can be manufactured at low cost. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a linear phase bandpass filter according to the present invention.

FIG. 2 is a plan view showing a conventional linear phase bandpass filter.

[Explanation of symbols]

 1 to 8 cavity resonator 10 waveguide 11, 12 coaxial cable C2, C3, C6, C7 probe Li1, L12 to L78, L8o inductive element

Claims (3)

[Claims] 1. A main coupling path for sequentially coupling a plurality of resonators with an inductive element, and at least one sub coupling path for coupling selected two of the resonators with an inductive element. In a non-polar linear phase band-pass filter, the sub-coupling path is a capacitive probe that is electromagnetically coupled to the resonator to be coupled, and a coaxial cable having both ends respectively connected to the two capacitive probes. A linear phase bandpass filter comprising: 2. The linear phase bandpass filter according to claim 1, wherein said resonator is formed in a linear waveguide. 3. The linear phase bandpass filter according to claim 2, wherein said capacitive probe is disposed on a side wall surface of said waveguide.