JPH06216608A - Waveguide type bandpass filter - Google Patents

Abstract

PURPOSE:To prevent the complication of the structure of a waveguide type bandpass filter where an inductive round bar is arranged within a waveguide and to facilitate the adjusting work of a frequency characteristic. CONSTITUTION:In a waveguide type bandpass filter where an inductive round bar 2 is arranged at the inside of a rectangular waveguide 1, an adjusting screw cylinder 7 of large diameter is fitted to one end part of the inductive round bar 2 coaxially and this adjusting screw cylinder 7 is constituted so that it may advance and retreat to the inside of the waveguide 1. For instance, the projecting amount of the adjusting screw cylinder 7 to the inside of the waveguide is adjusted by constituting the inductive round bar 2 by a round screw bar 3, by screwing the adjusting screw cylinder 7 onto the one end part of this round screw bar 3, screwing and advancing the adjusting screw cylinder 7 for the round screw bar 3 by performing a rotation operation for the screw cylinder. Thus, the frequency characteristic of the bandpass filter is possible to be adjusted by changing the diameter dimension of the inductive round bar 2, changing and adjusting susceptance and changing the center frequency and pass band width of a resonator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type bandpass filter used in microwave and millimeter wavebands, and more particularly to a waveguide type bandpass filter capable of adjusting frequency characteristics.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional waveguide type bandpass filter.
There is one shown in. In FIG. 1A, the rectangular waveguide 1
A partition 12 having a partly opened inside is provided in the inside 1, and the opening is configured as an inductive window 12a. Here, four inductive windows 12a are arranged, and by constructing the waveguide resonators a, b, and c in the waveguides between the inductive windows, respectively, the waveguide resonators required by these waveguide resonators are formed. It constitutes a bandpass filter for the frequency band. In addition, in the case of the same figure (b), the inductive round bar 22 is arranged in the rectangular waveguide 21, and this inductive round bar 22 is an inductive window in the bandpass filter of the same figure (a). The band pass filter is constituted by the waveguide resonators a, b, and c which have the same function as 12a and are formed in the waveguide between the inductive round bars 22.

In this type of waveguide type bandpass filter, the band is determined by the resonance frequency of the waveguide resonators a, b and c formed in the waveguide, but the resonance frequency is induced. It is determined by the opening size of the flexible window 12a, the diameter size of the inductive round bar 22, and the like. However, comparing the opening size of the inductive window and the diameter of the inductive round bar, it is easier to obtain the accuracy of the diameter of the inductive round bar from the viewpoint of manufacturing. In order to obtain a characteristic, that is, a bandpass filter having a desired center frequency and pass band width, a guided wave bandpass filter using an inductive round bar is more advantageous.

FIG. 5 is a schematic cross-sectional view for explaining the frequency characteristics of a waveguide type bandpass filter using an inductive round bar, in which the diameter dimension φD of the inductive round bar 22 and the rectangular conductor. The frequency characteristic is determined by the susceptance obtained from the internal dimension L of the wave tube 21. That is, the susceptance B is obtained from the following equation. B≈−2λg / [L·ln (4a / πD) -2] where λg is the wavelength in the waveguide. From this, in order to adjust the frequency characteristic of the waveguide bandpass filter, the susceptance B may be adjusted, and for that purpose, the substantial diameter of the inductive round bar in the waveguide may be adjusted. I understand.

However, since changing the diameter of the inductive round bar to change the frequency characteristic is not a good idea from the viewpoint of manufacturing accuracy and economical problems, in practice, as shown in FIG. It is proposed that the waveguide 21 near the round bar 22 is provided with an adjusting screw 23 for adjusting the frequency characteristic. In this waveguide type bandpass filter, the inductive round bar 22 has a screw structure to penetrate the waveguide, and is fixed with nuts 24 at both ends thereof. Further, adjusting screws 23 are provided on both sides of the inductive round bar 22, and one end of the adjusting screw 23 is fixed to the waveguide 21 by a nut 25. In this configuration, the adjusting screws 2 on both sides of the inductive round bar 22 are
The susceptance can be changed by rotating 3 to change and adjust the amount of protrusion into the waveguide 21, and the frequency characteristics can be adjusted. You can get a filter.

[0006]

In the waveguide bandpass filter provided with such an adjusting screw, the adjusting screw is arranged for each of a plurality of inductive round bars provided in the waveguide. It is necessary to dispose the adjusting screws at the left and right positions depending on the position where the inductive round bar is arranged.Therefore, the number of adjusting screws becomes large, which increases the number of parts. There is a problem that the structure becomes complicated and the adjustment work of the frequency characteristic becomes troublesome. It is an object of the present invention to provide a waveguide type bandpass filter that prevents the structure from becoming complicated and facilitates the adjustment work of the frequency characteristics.

[0007]

According to the present invention, an adjusting screw cylinder having a larger diameter than that is coaxially fitted to one end of an inductive round bar arranged inside a waveguide. Is configured to be able to move back and forth inside the waveguide. For example, an inductive round bar is composed of a round threaded rod, an adjustment screw tube is screwed onto one end of this round threaded rod, and the adjustment screw tube is rotated to screw the adjustment screw tube onto the round threaded rod. Then, the amount of protrusion of the adjusting screw cylinder into the inside of the waveguide is adjusted. In this case, it is preferable that the round screw rod is extended over the entire length of the internal dimension of the waveguide, and the adjusting screw cylinder is projected into the waveguide so as to overlap with one end of the round screw rod.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1A and 1B are views showing an embodiment of the present invention. FIG. 1A is an external view and FIG. 1B is a sectional view taken along the line AA. A plurality of inductive round rods 2 are arranged in the rectangular waveguide 1, and a plurality of inductive round rods 2, three in this case, are provided by these inductive round rods 2.
One waveguide resonator a, b, c is constructed. Then, each of the waveguide resonators a, b, and c is set to a predetermined resonance frequency by the inductive round bar 2, and the frequency band of the waveguide type bandpass filter is set by this, and the required frequency is set. Characterized.

As shown in a partially enlarged perspective view of FIG. 2, the inductive round bar 2 has a round threaded bar 3 having a thread formed on the peripheral surface thereof, and the rectangular waveguide 1 It is vertically extended inside the. The round screw rod 3 has its lower end screwed into a screw hole 4 provided on the lower surface of the rectangular waveguide 1,
Moreover, it is fixed to the lower surface of the rectangular waveguide 1 by a nut 5 screwed from the outside of the rectangular waveguide 1. Further, a through hole 6 is opened on the upper surface of the rectangular waveguide 1 so as to face the round screw rod 3, and this through hole 6 is opened to have a larger diameter than the round screw rod 3, and inside the opening. The hollow cylindrical adjustment screw cylinder 7 is inserted. The adjusting screw cylinder 7 has a thread formed on each of the outer surface and the inner surface, and the thread on the inner surface is screwed into the thread at the upper end of the round threaded rod 3 and the thread on the outer surface. A nut 8 is screwed from the outside of the rectangular waveguide 1, and the adjusting screw cylinder 7 is fixed to the upper surface of the rectangular waveguide 1 by this nut 8. The adjusting screw cylinder 7 is set to have a length necessary for adjusting the frequency characteristic as described later, and a radial slit 7a is formed at the upper end thereof, and the adjusting screw cylinder 7 is axially rotated by a tool such as a screwdriver. It is configured so that it can be rotated.

According to this structure, when the nut 8 is loosened and then the adjusting screw cylinder 7 is operated around the axis by a driver or the like using the slit 7a, the adjusting screw cylinder 7 is screwed with the round screw rod 3 to be rounded. The round screw rod 3 is screwed forward with respect to the screw rod 3 and moved back and forth in the length direction of the round screw rod 3. Therefore, as shown in FIG.
If the adjusting screw cylinder 7 is set to a position that is completely retracted from the inner surface of the rectangular waveguide 1, the inductive round bar 2 in the rectangular waveguide is in a state in which only the round thread bar 3 exists, and the round thread bar 3
The susceptance is set on the basis of the diameter dimension φD1 of, and the required frequency characteristic is set. On the other hand, as shown in FIG. 3B, when the adjusting screw cylinder 7 is operated and a part thereof is projected into the rectangular waveguide 1, the diameter dimension φD of the adjusting screw cylinder 7 is adjusted.
2 and its protruding length L1, and the diameter dimension φD1 of the round screw rod 3.
The susceptance is set on the basis of the length and the exposed length L2.

As a result, the susceptance is changed between the states shown in FIGS. 3A and 3B, the center frequency and the pass band width of the waveguide bandpass filter are changed accordingly, and the frequency is changed. The characteristics will be changed and adjusted. Therefore,
In this waveguide-type bandpass filter, since the same number of adjusting screw cylinders 7 as the round screw rods 3 provided in the rectangular waveguide 1 are provided integrally with the round screw rods 3, the structure is complicated. Not,
Moreover, the number of adjustment points is the same as that of the round screw rod, and it is possible to easily perform the adjustment.

Although the round screw rod 3 and the adjusting screw cylinder 7 are screwed into each other in the above embodiment, the structure is such that they are simply fitted so as to overlap each other in the axial direction, and the upper surface of the rectangular waveguide is used. It is also possible to configure the through hole 6 provided as a screw hole to screw the adjustment screw cylinder into the screw hole and rotate the adjustment screw cylinder so that the adjustment screw cylinder can be moved forward and backward with respect to the rectangular waveguide. In this case, the round screw rod may have a screw structure only at the lower end portion fixed to the waveguide, and the other portions may have a simple round rod shape.

[0013]

As described above, according to the present invention, a large-diameter adjusting screw cylinder is coaxially fitted to one end of an inductive round bar arranged in the waveguide, and the adjusting screw cylinder is attached to the waveguide. Since it is configured to be able to move in and out, the frequency characteristics of the bandpass filter can be adjusted arbitrarily by adjusting the same number of adjusting screw cylinders as the inductive round bar, so the number of adjusting screw cylinders is the minimum required. In addition to limiting the number to the limit, it is not necessary to arrange the adjusting screw in a position different from the position where the round screw rod is arranged in the rectangular waveguide, which simplifies the structure and facilitates the adjustment. it can. Further, since the adjusting screw cylinder is formed to have a diameter larger than that of the round screw rod, the susceptance can be largely adjusted by fine adjustment of the adjusting screw cylinder, and the wide range of frequency characteristics can be adjusted. Furthermore, since the adjusting screw cylinder has a screw structure that is screwed into the round screw rod or the waveguide, the amount of protrusion of the adjusting screw cylinder in the waveguide can be finely adjusted with respect to the rotation adjustment amount, and the frequency characteristic It is also possible to finely adjust. The round screw rod extends over the entire length of the internal dimension of the waveguide, and the adjusting screw cylinder is configured to project into the waveguide so as to overlap with one end of the round screw rod. It is possible to adjust the sesaputance in the range from the amount of protrusion of the cylinder to 0 to the maximum amount of protrusion.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, (a) is an external view,
(B) is the AA line expanded sectional view.

FIG. 2 is an enlarged perspective view showing a partially broken inductive round bar.

FIG. 3 is a diagram showing an adjustment state by an adjustment screw cylinder.

FIG. 4 is an external view showing an example of a conventional waveguide type bandpass filter having an inductive window and an inductive round bar.

FIG. 5 is a schematic cross-sectional view for explaining frequency characteristics of a waveguide type bandpass filter having an inductive round bar.

FIG. 6 is a cross-sectional view of a conventional waveguide band filter provided with an adjusting screw for adjusting the frequency characteristic.

[Explanation of symbols]

 1 Rectangular Waveguide 2 Inductive Round Bar 3 Round Screw Rod 7 Adjusting Screw Tube

Claims (3)

[Claims] 1. A waveguide type bandpass filter in which an inductive round bar is arranged inside a waveguide, and an adjusting screw cylinder having a diameter larger than this is coaxially fitted to one end of the inductive round bar. The waveguide type bandpass filter is characterized in that the adjusting screw cylinder is configured to be movable back and forth in the waveguide. 2. The inductive round rod is constituted by a round threaded rod, an adjusting screw tube is screwed into one end of the round threaded rod, and the adjusting screw tube is rotated to move the adjusting screw tube to the round threaded rod. Screw it,
2. The waveguide type bandpass filter according to claim 1, wherein the adjusting screw cylinder is configured to adjust the amount of protrusion into the waveguide. 3. The round threaded rod extends over the entire length of the internal dimension of the waveguide, and the adjusting screw cylinder is projected into the waveguide so as to overlap with one end of the round threaded rod. Waveguide bandpass filter.