JPS58129802A - Distribution coupled circuit - Google Patents

Abstract

PURPOSE:To increase the band of a filter which uses a distribution coupled circuit and to obtain a large impedance ratio by empolying the same photoetching technique and increasing the degree of coupling of a parallel coupled line greatly. CONSTITUTION:One input/output line (i.e. part of a resonator) 31 is divided into projecting parts 33 and 34 having narrow line width. The other line 32 is divided into projecting parts 35 and 36. They are set in parallel and adjacent projecting parts 33 and 35, and 34 and 36 form parallel coupling part consitution which has coupling length lambdag/4 and coupling intervals S1 and S2. When S1= S2<S3 where S3 is the interval between the projecting parts 35 and 36, the design of the coupling part is facilitated. Consequently, two parallel coupling parts are obtained and the line width is decreased, so the couplig is reinforced and the size of the coupling part is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distributed coupling circuit using a TEM line in the VHF-8HF band.

2.: Figure 1 shows an example of a bandpass filter using a microstrip line that has been put into practical use. (The line structures explained here are all based on microstrip lines. The same applies to strip lines, so we will not specifically explain the line structures separately.) In the figure, 11 is a dielectric substrate, and 12 is a conductor. The ground conductors 13 to 17 formed of a film are conductors formed into a predetermined pattern using techniques such as photoetching.

Of these, 13 and 14 are input and output lines, 15 and 16 degrees, and the coupling between the input and output and the resonator are parallel to each other, and the section between the resonators (for example, the resonance line 15 and the resonance line 16) is Since the line spacing is small, the spacing between the lines is wide, and the coupling degree of input/output coupling (for example, the input line 13 and the resonant line 16) is about an order of magnitude larger than that of the inter-resonator coupling, so the line spacing is narrow and the impedance There are three pages in which the width of the line must be narrowed for connection purposes. FIG. 2 shows details of the input coupling section. The same numbers as in FIG. 1 represent exactly the same things. As can be seen in the figure, the spacing between the parallel couplings between the input line 13 and the resonant line 16 is designated by S. The equivalent circuit of the distributed coupling circuit shown in FIG. 2 is as shown in FIG. 41 and 42 represent input/output terminals, 43 and 44 lines, and 46 an admittance inverter (parameter Jo). (The relationship between Figures 2 and 3 is M, Makimoto et, aj2 B
andpass FiltersUsing Para
llel Coupled 5tripline St
eppedImpedance Re5onators
, IEEE M,T, TVoL, MTT-28,
h112. Dec 1980. PP1413-141
It has been derived completely.

Letting 1 matrix of the circuit in Fig. 3 be [Fa], 1 is an imaginary number.In the conventional distributed coupling circuit shown in Fig. 2, the input line 1
The gap 20 formed by the distance S between the parallel coupling portion of the resonant line 16 and the parallel coupling portion of the resonant line 16 is the thickness H of the substrate 11 (as shown in FIG. 1).

) is constant, it becomes narrower as the degree of coupling increases. Since the degree of coupling increases in proportion to the passband width C2 of the filter, the gap interval S is inversely proportional to the passband width of the filter. However, the gap distance S cannot be set below a certain value because there is a limit to the accuracy of photoetching. Therefore, once the thickness H of the substrate 11 is specified, the upper limit of the bandwidth of the filter that can be realized is determined by the accuracy of photoetching. In order to realize a filter with a wider bandwidth than this, it is necessary to increase the thickness H of the substrate 11 and increase S (the degree of coupling is the same value if S/H is constant). The circuit pattern itself also becomes larger, leading to an increase in cost.

The present invention provides a 6-page coupling circuit which can greatly increase the degree of coupling of parallel coupling lines using the same photo-etching technique, and its basic configuration is shown in FIG. In the figure, reference numerals 31 and 32 are input/output lines (or they may be considered as part of the resonator), and the line 31 is divided into narrow protrusions 33 and 34. Similarly, the line 32 is divided into protrusions 35 and 36. divided into Then, a parallel connecting portion structure is adopted in which the parallel connecting portions are connected at mutually parallel and adjacent protrusions 33°S2. In addition, in the figure, the interval between the protrusions 35 and 36 is 83
If 5l-82<S3 is used, the design of the joint becomes easy. Also, as is clear from the figure, the parallel joint part is
Since there are only two locations and the line width can be reduced, it is possible to increase the coupling and also to reduce the size of the coupling portion.

The equivalent circuit of the coupling section according to the present invention can be expressed as shown in FIG.

Here, 51.52 are input/output terminals, and 63 to 66 are special terminals 57.
58 is an admittance inverter having a parameter of 1p.

6 -・ It can be expressed as

Therefore, if the value of (Fb) is selected to be the same as the 0 equation, that is, each value is selected so that the relationship of the 0 equation holds, then the combination method of the present invention is shown in FIG. Since it can be replaced in exactly the same manner as the conventional coupling method, except for the coupling method part, the other parts can be done in the same way as the conventional circuit design.
This has the advantage that the design itself is extremely easy.

Although the above example has been described with reference to the case where there are two branching parallel coupling parts, the present invention is applied to a case where there are two or more branching parallel coupling parts.

Further, even if the branch parallel joint part has a shape as shown in FIG. 6 and there are 7 pages, it functions in exactly the same way as in FIG. 4.

Each reference numeral shown in FIG. 6 corresponds to the same reference numeral in FIG.

FIG. 7 shows an example implemented in a three-stage bandpass filter. Here, 61 and 62 indicate a distributed coupling part with input and output 67. By the way, a comparison with the conventional example shown in FIG. 1 will be made. The band of the filter is 30% to 40%, the number of stages is 3, and the relative dielectric constant ε is 2.5.

Consider a case in which a dielectric with a thickness of 1 and orrrln is used and a microstrip line is constructed.

At this time, in the conventional configuration shown in Fig. 1, the line spacing of the input/output coupling part is 38 to 40μ, but when using the method of the present invention, zp is selected to be 80 to 90Ω, and the minimum line spacing (input and output The bonding portion) is 120 to 150μ. In other words, the gap is enlarged by 3 to 4 times, which greatly improves the ease of manufacturing and the yield of products. Conversely, if the minimum value of the input/output line spacing is 1150μ, the conventional example shown in FIG. If there are production restrictions, increase the bandwidth to 3~
It has the advantage of being able to be expanded four times.

FIG. 8 shows another embodiment of the present invention, which is an example in which the present invention is applied to an impedance transformer.

Here, 71 and 72 are the input/output terminals of the transformer, 73 is the distributed coupling circuit according to the present invention, and 74 is the load impedance connected to the output terminal.

Now, the 1 matrix of the coupling part is 0 formula, and the load impedance is ZI
, the input impedance Zi seen from the input terminal 71 is equal to . Therefore, it can be used as an impedance transformer.

With this configuration, it is possible to increase the degree of coupling and improve the impedance transformation ratio (Zi/ZL).

In addition, in the conventional system, the line impedance is uniquely determined when the impedance ratio is given, whereas the present invention
Since it is determined by two parameters, p and J, it has the advantage of increasing the degree of freedom in circuit configuration.

As described above, the present invention has the following advantages: (1) A resonant line with both ends open using an IJ tube line or a microstrip line
In a distributed coupling circuit in which two or more lines are arranged, each of the two lines is open, and the lines are branched into at least two near the open end, and the open ends of the branched lines are arranged in opposite positions. It is characterized by having two or more parallel coupling parts, and by applying it to filters, impedance transformers, etc., it is possible to achieve wide bands or large impedance ratios that could not be achieved with conventional methods. can be easily realized and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 1a is a plan view of a distributed coupling bandpass filter using a conventional microstrip line resonator; 3 is a block diagram showing an equivalent circuit of the conventional distributed coupling circuit shown in FIG. 1, FIG. 4 is a plan view showing an embodiment of the distributed coupling circuit of the present invention, and FIG. A block diagram showing an equivalent circuit of a distributed coupling circuit in one embodiment of the invention, FIG. 6 is a plan view showing another embodiment of the distributed coupling circuit of the invention, and FIG. FIG. 8 is a plan view showing an example of the configuration of a band-pass filter, and FIG. 8 is a plan view showing an example in which the present invention is applied to an impedance transformer. 11...Dielectric substrate, 13.14...
Input/output line device, 66.67... Distributed coupling circuit section of the present invention. Name of agent: Patent attorney Toshio Nakao and 1 other person11
41 Figure (a)
t), Nol? 2nd Figure 3 13511 4th Figure JII51!1 a6 Figure 0--3 car → Figure I7

Claims (3)

[Claims] (1) It is constructed by arranging a plurality of resonant lines with both ends open using strip lines or microstrip lines, and at least one of the coupling regions formed by the two resonant lines is engaged with each other by a protrusion. 1. A distributed coupling circuit comprising two or more parallel coupling parts. (2) The distributed coupling circuit according to claim 1, wherein in the parallel coupling portion, each of the protrusions has the same width and the gaps between the protrusions are also equal. (3) The distributed coupling circuit according to claim 1, wherein the coupling length of the parallel coupling portion is one quarter of the wavelength of the center frequency of the frequency band used.