JPS60229501A - Direct current blocking circuit - Google Patents

Abstract

PURPOSE:To relax the prescribed precision of geometric size and to improve the yield of manufacture by widening the line width of a coupling part and widening a line interval. CONSTITUTION:A distribution coupled circuit is expressed by the thickness H of a substrate, specific dielectric constant Er, line width W, and line interval S in terms of structure. Then, a load (ZL) 32 is connected to the output terminal 16 of the distribution coupled circuit 21 and a power source 24 with power source impedance (ZO) 22 is connected to the input terminal 15. The distribution coupled circuit functions as an impedance transformer as shown by an equation I. Then, the distribution coupled circuit is provided with the function of the impedance transformer as well as a DC cutoff function and ZOe-ZOO is decreased. The input/output impedance of a semiconductor is normally <=50OMEGA, so the addition of the impedance transformer function is suitable for practical circuit design. When ZL=12.5OMEGA and ZO=50OMEGA, an equation II holds. When an alumina substrate is used and S=W in design, W/H=S/H=0.34, which is about three times as large as before, so the design and manufacture are extremely easy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a (1) knob line distributed coupling DC blocking circuit, which is used in an active circuit of a microwave/millimeter wave integrated circuit.

Conventional configurations and their problems Recently, microwave and millimeter wave circuits have been actively integrated into integrated circuits, and a large number of... hybrid ICs, monolithic ICs, etc.
C has been developed. 1] When using active elements such as transistors and diodes, it is necessary to supply DC voltage and current to the element, but if this is applied to the external circuit, it is often inconvenient and will always cause damage to the active circuit. It is required to provide a DC closed circuit for input and output. When the frequency is low, there is no problem if a lumped constant capacitor is used, but when the frequency reaches the microwave region, the size of the element becomes impossible to ignore compared to the wavelength, and it no longer functions as a capacitor, so a normal small capacitor cannot be used. Even tinopucapacitors cannot be used. In addition, capacitors with an interdigital structure in which lumped constant elements are miniaturized31\-7 are sometimes used by patterning them on the substrate (there is a limit to the capacitance value that can be achieved, and in order to increase the capacitance value, a fine structure is used). If so, the yield would be extremely poor and there would be a limit to the range of application.

From the above, in the microwave band where it is difficult to apply lumped constant capacitors, the open-ended distributed coupling circuit shown in FIGS. 1(&) and (b) is often used as a DC blocking circuit.

In this circuit shown in FIG. 1, a dielectric substrate 13 with a thickness H, a ground conductor 14, and two conductors 11.12i with a distance W2 in the line S.
provided and configured. One end of the two lines is open on the opposite side, and the other end is connected to the input terminal 16. Output terminal 16
This provides distributed coupling between the two lines and at the same time has a DC blocking function.

However, the coupling length is selected to be a quarter wavelength at the mid-zero frequency used.

The distributed coupling circuit shown in Fig. 1 is structurally based on the substrate thickness H.
It is expressed by 2 relative permittivity Or, line length W, and line spacing S. In addition, the interval in the line is standardized by the thickness H, W/H,
S/H (i7 is often used.

Even mode impedance Z is an electrical parameter. The oI odd mode impedance is 2°0.

Now, as shown in FIG. 2, consider the case where a load (Zb) 23' (r connection is connected to the output terminal 16 of the distributed coupling circuit 21, and a power supply 24 having a power supply impedance (Zo) 22 is connected to the input terminal 15. think.

When the electrical length of the distributed coupling circuit 21 is selected to be 900 (coupling length is a quarter wavelength), its fundamental matrix CF) becomes... (1). Connect the load ZL to the output side, and connect the input terminal 1
If the impedance seen from 6 is Z, then Zi-(ko(Zoo-Zoo)/21/lko ZLa2/[Zo
s -200)1-(ZOo-Z.0V4ZL...
・Shun).

In order to achieve matching at the input end, Z must be equal to Zo. Therefore, Zo8-Zo. - Power input = 2h evaluation ...... (
3) A normal DC element circuit is designed with Z0=zL260Ω. That is, z. ,−'Z,,. : 2Zo:100 (Ω) ,,
, (4) are the design conditions for a normal DC element circuit.

1. If an alumina substrate (relative dielectric constant Cr=9.ei), which is often used in the microwave band, is designed under the condition of S-W, W/H=S/H-0,12.

(However, in this case, Z..=154.Zoo: 54Ω) If the substrate thickness is about IMM, it becomes a W-8-0,12 sheath and can be manufactured with high precision. However, in the millimeter wave band, 0
．． Since a 2ff thick substrate is also used, in this case 5=W
= 0.02411111, and achieving it with high precision requires advanced technology, and furthermore, the production yield is poor.
It also causes high costs. Furthermore, because the lines were not spaced sufficiently apart, there was also a problem in terms of withstand voltage.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a direct current blocking circuit which widens the line rIJ of the coupling part and widens the line spacing, thereby relaxing the precision required for the geometrical -j- method and improving the manufacturing yield. It is intended to capture and provide information.

A distributed coupling line in which a strip conductor is arranged in parallel with a second strip conductor having an output terminal at one end and an open end at the other end so that the inside and length are approximately equal and the input and output are reversed. The above objective is achieved by making the difference between the even mode impedance and odd mode impedance of the input/output impedance smaller than twice the input/output impedance.

Description of examples A first embodiment of the present invention will be described below.

First, as shown in equation (3), the distributed coupled line has a function as an impedance transformer. Therefore, the 7-be-2 distributed coupling section (Z.

Make smaller. Since the input/output impedance of a semiconductor element is generally smaller than 50Ω, adding an impedance transformation function is convenient for actual circuit design. 1 In Figure 2, ZL-12, 60, zo=6oΩ
Then, zos ”oo = 2E♂ to 12.5-5o(,Q)
becomes. Using alumina substrate (Or=9.s) i, S=W
When designing with W/H=S/H=0.34 (at this time Z0
6==103, zoo=53. ), which is approximately three times as large as before, making design and production extremely easy.

A second embodiment of the present invention will be described below.

FIG. 3 is a plan view of a DC blocking circuit in a second embodiment of the present invention. As shown in FIG. 4, quarter-wavelength transformers 33 and 34 whose line impedance is ZT are provided at the input and output of the distributed coupling line 36. When transformers are configured at the input and output in this manner, the (Zoa ``oo'') of the coupling section can be lowered, so that the design of the coupling section becomes easier as described above.

In Fig. 3, if the input/output impedance is 200Ω and the transformer impedance Zt' is 2tsΩ, the input/output impedance at the coupling part is zT/60:25150;
Z because it becomes 12.5Ω. , ZOO=2V "R" and C Σ5=25 (Ω), and the difference can be made extremely small.Similarly to the above, if an alumina substrate is used and designed under the condition of W=5, W/H-S/H = 0.63, which means that the line spacing is lower than before.

It is now possible to design the inside of the track by about 6 times as large, making manufacturing even easier.

A third embodiment of the present invention will be described below, and FIG. 4 is a plan view of a DC blocking circuit in the third embodiment of the present invention.

In the embodiment shown in FIG. 3, the input and output impedances are equal to 50.
Ω, but in this embodiment, the input and output impedances are different. (However, the distributed coupling section does not have an impedance transformation function.) 9 In Fig. 4, 41 is the input terminal on the high input impedance side, 33 is the quarter wavelength transformer, 35 is the distributed coupling section,
42 is an output terminal on the low impedance side. As described above, since semiconductor elements generally have a resistance of less than 60Ω, it is desirable that the resistance of the active element side of a distributed coupling circuit having a DC blocking function be 60Ω or less. In the first embodiment, the distributed coupling circuit itself has an impedance transformation function, but as shown in Fig. 4, when widening the band, it is more advantageous to use a quarter-wavelength transformer, and the design of the distributed coupling section is also easier. It becomes easier.

Effects of the Invention As described above, the present invention enables designing with each spacing in the line several times wider, which eases the requirement for pattern accuracy and greatly contributes to product yield. The degree of freedom in design is expanded, and its industrial value is extremely large.

[Brief explanation of drawings]

Figures 1 (IL) and (b) are cross-sectional views of a conventional stripline distributed coupling DC blocking circuit, Figure 2 is a schematic diagram for determining the input and output impedance of the distributed coupling circuit, and Figure 3 is a diagram of the present invention. FIG. 4 is a plan view of the DC blocking circuit in the second embodiment of the present invention, and FIG. 4 is a plan view of the DC blocking circuit in the third embodiment of the present invention. 21.35...distributed coupling circuit, 33.34...
... Quarter wavelength impedance transformer, 15, 31
゜41... Input terminal, 18.32.42...
...Output terminal. Name of agent Patent attorney Toshio Nakao and one other person (Z
oo) Procedural amendment to 2 1986//Mon/lI [1 Indication of the case by the Commissioner of the Patent Office 1988 15'' Patent Application No. 86417rL2 Name of the invention Direct current blocking circuit 3 Relationship with the amended person case 1 ,1゛ Application Person Address 1006 Kadoma, Kadoma City, Osaka Name (5g2) Matsushita Electric Industrial Co., Ltd. 14 Representative 111 Toshihiko Shimo 4 Agent 571 Address 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 5 Target of amendment 6, Contents of amendment (1) Correct the "relative permittivity Cr" on page 3, line 19 of the specification to [relative permittivity ErJ]. (2) [w = 5 J to 1w = sj on page 8, line 9]
will be corrected. (3) Figure 1 of the drawings shall be corrected and edited as shown in the attached sheet. Figure 1 (α) 7 (ZN) (i!to) (bn-P

Claims (3)

[Claims] (1) "1" and length of the first strip conductor, which has an output terminal at one end and is open at the other end, and the second strip conductor, which has an output terminal at one end and is open at the other end. A direct current blocking circuit in which the difference between the even mode impedance and the odd mode impedance of distributed coupled lines arranged in parallel so that the input and output impedances are substantially equal and the input and output are reversed is less than twice the input and output impedance. (2) A DC blocking circuit according to claim 1, characterized in that a quarter wavelength impedance transformer is provided at each of the input and output terminals of the distributed coupling line. (3) The DC blocking circuit according to claim 1, further comprising a quarter-wavelength impedance transformer at either the input or output of the distributed coupling line. 2be