JPS62160801A - Bandwidth cut filter - Google Patents

Abstract

PURPOSE:To make a cut-off center frequency variable by constituting an input/ output extracting line so that its line length difference is made variable. CONSTITUTION:Microstrip circuits 1a, 1b are formed by two ground conductor disks 2a, 2b arranged oppositely and two dielectric disks 3a, 3b fixed to the conductors 2a, 2b. A distribution coupler 5 is fixed on the dielectric 3b on the same central position. Further, input/output lines 6a, 6b are held freely movably in the circumferential direction so as to adjust line lengths l1, l2 in the circumferential direction between the lines 6a and 6b. Since the band stop filter is structured as above, the cut-off center frequency of the coupler 5 is decided by the line length difference l2-l1 of the input/output lines 6a, 6b. Thus, the cut-off frequency is changed properly by changing the dividing ratio of the coupler 5 by the lines 6a, 6b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a strip band cutoff filter, and particularly to a band cutoff filter suitable for making the cutoff center frequency variable.

[Background of the invention]

Conventional band cutoff filters include, for example, IEICE Microwave Research Bulletin MW79-84 (1979) No. 15.
It is introduced in "Example of amplifier circuit pattern on page 20, Figure 13" in "MIC implementation of UHF transistor amplifier using high dielectric constant substrate" on pages 22 to 22, and its main part is shown in Figure 5. -F is the main waveguide 1, B-E is the sub waveguide 2,
When these grooved wave tubes 1 and 2 are coupled through two coupling holes B and E at an interval of 2t/4, the signal λ2 flowing from A in the main wave tube 1 becomes the main wave at one coupling hole B. As a result, the distance traveled by the signal flowing through the main waveguide 1 is different, and this causes a phase difference between the two signals. will not flow to F.

Therefore, the band cutoff filter shown in Fig. 5 is an example of applying a bias to the transistor so as not to affect the signal path, and since it cuts off the signal frequency and the bias frequency is direct current. , OH2 is configured so that it does not pass through.

Moreover, in the above case, since it is a fixed pattern, the design
When there are characteristic errors due to manufacturing errors, it is difficult to make adjustments, so we redesign the product.

There are problems that require remanufacturing.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a band cutoff filter which solves the above-mentioned conventional problems and whose cutoff center frequency can be varied.

[Summary of the invention]

In order to achieve the above object, the present invention consists of a ring-shaped distribution coupler which is held in a microstrip circuit and whose line length difference is an integral multiple of 1/2 of the wavelength, and its input/output extraction line. This band cutoff filter is characterized in that the input/output extraction lines are configured so that the line length difference is variable, thereby making the cutoff center frequency variable.

[Embodiments of the invention]

1 to 4 showing one embodiment of the present invention will be described below. FIG. 1 is an exploded perspective view of the band cut filter according to the present invention, FIG. 2 is a plan view showing the input/output passage and distribution coupler of the band cut filter shown in FIG. 1, and FIG. An equivalent circuit diagram of an output path and a distribution coupler, and FIG. 4 is a theoretical characteristic curve diagram of the cutoff center frequency.

In FIGS. 1 and 2, 1α and IA are microstrip circuits with two disc-shaped ground conductors 2α and 2b placed so as to face each other, and two ground conductors 2α and 2b stacked on the opposing surfaces of the ground conductors 2α and 2b. It is formed from two disc-shaped dielectrics 3α, 3b fixed as shown in FIG.
Through holes 4α and 4A are formed in the center of the dielectric bodies 3a and 3b.
is installed. A distribution coupler 5 is formed in the shape of a ring with a small diameter, and is fixed on the lower dielectric body 3b so as to be in the same central position. 6α and 6A are two input/output lines (terminals) formed thicker than the distribution coupler 5, and the input line 6α is located on the lower dielectric 3h at a position spaced apart from the outer peripheral surface of the distribution coupler 5. The output line 6h is supported in the radial direction between the upper dielectric member 3b and the outer circumferential portion of the lower dielectric member 3b, and the output line 6h is held in a position opposite to the input line 6α across the distribution coupler 5 of the upper dielectric member 3h. . Also, the input/output line 6α.

6h are held movably in the circumferential direction, respectively, so that the line length jIh in the circumferential direction between the two input/output lines 6α and 6h can be adjusted as shown in FIG.

Numeral 7 is a fixing screw, which is inserted into the through holes 4α and 4A of both the distributors 1α and 1h, and its tip is tightened to the nut 8.
This brings the two input/output lines 6α, 6b into contact with the opposing dielectrics 6α, 54, respectively, and also connects the distribution coupler 5.
A gap is formed between the upper surface of the dielectric member 3α and the upper dielectric member 3α.

Next, in FIG. 3, 9 is the coupling capacitance due to the gap between the upper surface of the distribution coupler 5 and the upper dielectric 3α, 10α, 1
0h is the line length 1.0 between the two input/output lines 6α and 6h.
, A! It is a microstrip line having .

Since the band cutoff filter according to the present invention is constructed as described above, the ring-shaped distribution coupler 5 as shown in FIG.
is the line length difference it, -t, between the input and output lines 6α and 6b,
The center frequency of cutoff is determined by In other words, the line length difference is 12-1. is cut off at a frequency that appears to be an integer multiple of the phase inversion. Now, the difference in track length is h-! , where 11 ) 11 * is an integer, λ? is the effective wavelength.

However, ε, f is the effective dielectric constant, C is the speed of light, f is the frequency, and λ0 is the spatial wavelength.

Then, from the above formula (11 (21), the line length difference of 1.-1° is as follows. Therefore, the frequency f is: where L-1, +12. l, = -1,.

(A>1), the above formula (4) becomes f″″″d’J
It is expressed as 'L' h1.

This is because once the total length of the ring-shaped distribution coupler 5 is determined, the cutoff frequency is determined by the distribution ratio k as shown in FIG.

Therefore, the input/output lines 6a, 6 shown in FIG.
By changing the distribution ratio h, the cutoff frequency can be changed as appropriate.

〔Effect of the invention〕

As described above, the present invention is a band-cut filter whose center frequency can be easily varied with a simple configuration, which improves work efficiency when changing and adjusting patterns of strip circuits, and when creating new patterns. This has the effect of reducing time and costs.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a band-cut filter showing an embodiment of the present invention, FIG. 2 is a plan view showing an input/output path and a distribution coupler of the band-cut filter shown in FIG. 1, and FIG. FIG. 2 is an equivalent circuit diagram of the input/output path and distribution coupler shown in FIG. 4, a theoretical characteristic curve diagram of the cutoff center frequency, and FIG. 5 is a circuit diagram showing a conventional band cutoff filter.゛1α, IA...Microstrip circuit 2α,
2k...Grounding conductor 5a, Sh...Dielectric 4a, 4h...Through hole 5...- Distribution coupler 6α ,6k
...Input/output line (terminal) 7...
...Fixing screw 8 ...... Nut 9 ...... The upper surface of the distribution coupler and the dielectric above it Coupling capacity due to the gap between 10 g, 10 A...Katsuo Ogawa, patent attorney representing microstrip line - Closed 1 Figure 8-0 ■ 5p Child 5 Figure 10

Claims (1)

[Claims] 1. In a band cutoff filter consisting of a ring-shaped distribution coupler which is held in a microstrip circuit and whose line length difference is an integer multiple of 1/2 of the wavelength, and its input/output extraction line, the above input/output A band cutoff filter characterized in that a take-out line is configured such that the line length difference is variable.