JP3071941B2 - Microwave slow wave circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave delay for transmitting a signal wave in a microwave band or a quasi-millimeter wave band of about 1 GHz or more and having a phase speed lower than the speed of light. Wave circuit.

[0002]

2. Description of the Related Art FIG. 12 shows a first conventional microwave slow wave circuit. As shown in FIG. 12, on the semiconductor substrate 4,
A center conductor 6 having a width Ws and a predetermined distance Wp from the center conductor 6
After a coplanar line 5L including the ground conductors 5a and 5b formed only apart from each other is formed, the dielectric layer 3 is formed on the entire surface of the coplanar line 5L. Further, on the entire surface of the dielectric layer 3, a plurality of strip ground conductors 1 each having a side in the longitudinal direction perpendicular to the longitudinal direction of the coplanar line 5L and a width La are provided at predetermined intervals in a so-called sleeper shape or lattice shape. It is formed separated by Lb.

In the region where the strip ground conductor 1 of the microwave slow wave circuit is formed, a vertical section (hereinafter, referred to as a first section) in a direction parallel to the longitudinal direction of the strip ground conductor 1 is provided.
Is called a vertical section. In (2), the capacitance between the center conductor 6 formed through the dielectric layer 3 and the strip ground conductor 1 becomes relatively large, and as a result, the capacitance having the relatively low characteristic impedance Z _L is relatively low. 1 transmission line 500. On the other hand, in a region where the strip ground conductor 1 is not formed, in the vertical section parallel to the longitudinal direction of the strip ground conductor 1 (hereinafter, referred to as a second vertical section), the center conductor 6 and the ground conductors 5a, 5a, because a relatively large interlinked magnetic force lines between 5b, the second transmission line 600 having a relatively high characteristic impedance Z _H inductive.
That is, the conventional microwave slow-wave circuit has at least one first longitudinal section, and has at least one capacitive strip having a relatively low characteristic impedance Z _L and substantially formed of a microstrip line. a first transmission line 500, at least composed of a coplanar line has a relatively high characteristic impedance Z _H of a and induced a second longitudinal section
And two second transmission lines 600, wherein the first transmission lines 500 and the second transmission lines 600 are alternately arranged and each of the transmission lines 500, 500 in a direction perpendicular to the longitudinal direction of the strip ground conductor 1. It is configured to be cascaded and connected in 600 stretching connection directions.

Here, when the period length (La + Lb) is sufficiently shorter than the guide wavelength and Z _H ≫Z _L , when a microwave signal is input to the microwave slow wave circuit,
The electrical energy is mainly stored in the first transmission line 500, while the magnetic energy is mainly stored in the second transmission line 600, so that a slow wave having a phase speed lower than the speed of light propagates. . Further, when the above-mentioned cycle length (La + Lb) approaches the guide wavelength, a standing wave is present, so that a cutoff frequency is generated. In the microwave slow wave circuit, the slow wave rate defined by the quotient obtained by dividing the free space wavelength by the guide wavelength becomes substantially equal to the square root of (Z _H / Z _L ), and the characteristic impedance becomes (Z _H · Z). _L ) is approximately equal to the square root of

Accordingly, in order to increase the slow wave ratio of the circuit, it is necessary to reduce the characteristic impedance Z _H increased and the characteristic impedance Z _L. Here, in order to decrease the characteristic impedance Z _L , the width Ws of the center conductor 6 of the coplanar line 5L may be increased, and in order to increase the characteristic impedance Z _H , the center conductor 6 and each ground conductor 5a may be increased. , 5b may be widened.

[0006]

However, these facts clearly indicate that each of the ground conductors 5 of the coplanar line 5L.
The interval between a and 5b (Ws + 2Wp) increases, and as a result,
The circuit area of the circuit increases. If it is difficult to greatly increase the characteristic impedance Z _H , only a microwave slow wave circuit having a relatively low characteristic impedance can be realized. The microwave slow-wave circuit having a relatively low characteristic impedance is effective for connection with an active element such as an FET having a relatively small input impedance, but the relatively low characteristic impedance requires that the slow-wave circuit be used. There is a problem that it becomes a limiting condition when widely applied to microwave circuits in general.

In order to solve the above-mentioned problems, the present inventor has disclosed in Japanese Patent Application No. 4-46783, FIGS.
5 has been proposed (hereinafter referred to as a second conventional example). 13 to 15,
The same components as those in FIG. 12 are denoted by the same reference numerals.

The second conventional microwave slow wave circuit includes two projecting conductors 6b projecting from the strip conductor 6a in the first longitudinal section, so that the center conductor is wider than the width Ws of the strip conductor 6a. A plurality of first transmission lines 100 shown in FIG. 14 having a first longitudinal section having a width Wst of 6 and having a relatively low capacitive characteristic impedance Z _L shown in FIG. 14; A plurality of second transmission lines 200 each including an elevated coplanar line shown in FIG. 15 having a second longitudinal section and having a relatively high inductive characteristic impedance Z _H, and Line 100 and the second
Are connected alternately and cascaded in a direction in which the transmission lines 100 and 200 extend in a direction parallel to the longitudinal direction of the central conductor 6. Hereinafter, the plane of the semiconductor substrate 4 of the microwave slow wave circuit is referred to as an XY plane, and each line 100,
The longitudinal direction of 200 is the Y-axis direction, and the direction perpendicular to the Y-axis direction is the X-axis direction. The microwave slow wave circuit of the second conventional example is formed by the following steps.

First, as shown in FIG. 13, a side having a length Lg having a longitudinal direction parallel to the X-axis direction and a side having a length Lb parallel to the Y-axis direction are formed on the entire surface of a semiconductor substrate 4 made of GaAs. A ground conductor 5 is formed in which a plurality of rectangular slots 5s having sides are spaced from each other by a predetermined distance La and juxtaposed in the Y-axis direction. Next, on the entire surface of the semiconductor substrate 4 exposed through the ground conductor 5 and the rectangular slot 5s,
After the dielectric layer 3a is formed, on the dielectric layer 3a,
A strip conductor 6a having a width Ws in the X-axis direction and extending in the Y-axis direction in the longitudinal direction and passing through the center of each rectangular slot 5s; and a strip conductor 6 located immediately above the ground conductor 5 located between the rectangular slots 5s. 6a, the width L in the Y-axis direction protruding in the X-axis direction and in the direction opposite to the X-axis direction
The center conductor 6 including the rectangular-shaped projecting conductor 6b is formed. Here, the lengths of the strip conductor 6a and the two projecting conductors 6b in the X-axis direction are indicated by Wst and Wst in FIGS. 13 and 14, respectively.

After the dielectric layer 3b is formed on the entire surface of the center conductor 6 and the exposed dielectric layer 3a, a part of the strip ground conductor 1 is formed on the dielectric layer 3b by a rectangular slot 5s. The plurality of strip ground conductors 1 located directly above the ground conductor 5 located therebetween and having the width La with the X-axis direction being the longitudinal direction are separated from each other by a predetermined Lb and positioned directly above the ground conductor 5. In other words, it is formed in a so-called sleeper shape or lattice shape so as not to be located immediately above each rectangular slot 5s.

In the first longitudinal section of the microwave slow wave circuit formed as described above, as shown in FIG. 14, the center conductor 6 composed of the strip conductor 6a and the protruding conductor 6b is connected to the ground conductor 5 and the strip ground. A first transmission line 1 composed of a triplate microstrip line formed between a conductor 1 and dielectric layers 3a and 3b, respectively.
00 is formed. This first transmission line 100 is
It has a relatively low capacitive impedance Z _L.
On the other hand, in the second longitudinal section of the microwave slow-wave circuit, as shown in FIG.
A strip conductor 6a located on the upper side by a thickness of a is formed by an elevated coplanar line formed at a predetermined same interval from each ground conductor 5 located in the left-right direction in FIG. Two transmission lines 200 are formed. The second transmission line 200 has a central conductor 6
Since the interlinked relatively large magnetic field lines chains between the grounding conductor 5, with a relatively high characteristic impedance Z _H inductive.

When a microwave signal is input to the input terminal PI of the microwave slow wave circuit configured as described above, its electric energy is mainly stored in the first transmission line 100, while its magnetic energy is Mainly accumulated in the second transmission line 200, as a result, a slow wave having a phase speed lower than the speed of light propagates.

[0013] The second conventional slow-wave circuit provides the first
When realizing the same delay rate and the same characteristic impedance as the conventional example, the delay circuit can be downsized as compared with the first conventional example, but the circuit occupies a large area. There was a problem.

An object of the present invention is to solve the above problems and to provide a smaller microwave delay circuit having a higher delay rate and a higher characteristic impedance than the conventional example.

[0015]

In the microwave slow wave circuit according to the present invention, the first center conductor is connected to the first ground conductor and the second ground conductor.
Between the first center conductor and the ground conductor through the first and second dielectric layers, respectively, so that the line width direction of the first center conductor is parallel to the longitudinal direction of the microwave slow wave circuit. And at least one first transmission line having a relatively low capacitive characteristic impedance and a second center conductor,
Between the second ground conductor and the third ground conductor, the direction of the line width of the second central conductor is the length of the microwave slow wave circuit via the third and fourth dielectric layers. At least one second transmission line, which is formed so as to be parallel to the direction and overlap a part of the first central conductor, and has a relatively low capacitive characteristic impedance; A first strip conductor having a line width smaller than the line width of the center conductor is formed in a spiral shape between the first and second dielectric layers, and has a relatively high inductive characteristic impedance. At least one third
And a second strip conductor having a line width smaller than the line width of the first and second center conductors is formed in a spiral shape between the third and fourth dielectric layers. Forming at least one fourth transmission line having a relatively high inductive characteristic impedance and penetrating the second and third dielectric layers and not contacting the second ground conductor. And at least one through-hole conductor connecting the third transmission line and the fourth transmission line, wherein the third and fourth transmission lines and the through-hole conductor are connected to the microwave slow wave circuit. The first to fourth transmission lines and the first to fourth transmission lines are formed so as to be located on one side of both sides of first and second center conductors formed so as to partially overlap each other in the longitudinal direction. The through-hole conductor is a microwave slow wave circuit Between the input terminal and the output terminal, the first transmission line, the third transmission line, the through-hole conductor, the fourth transmission line, and the second transmission line are cascaded in this order. Characterized by being connected to

[0016]

[0017]

[0018]

In the microwave slow wave circuit according to the first aspect, the line widths of the first and second transmission lines are larger than the line width of the third transmission line. while the transmission line has a relatively low characteristic impedance Z _L of the capacitive, the third transmission line has a relatively high characteristic impedance Z _H inductive. Here, when a microwave signal is input to the input terminal of the microwave slow wave circuit, its electric energy is mainly stored in the first and second transmission lines, while its magnetic energy is mainly stored in the third transmission line. As a result, a slow wave having a phase speed lower than the speed of light propagates.

In the microwave slow-wave circuit, the first and second center conductors have a line width direction of the first and second center conductors parallel to a longitudinal direction of the microwave slow-wave circuit. And the second center conductor is formed so as to overlap with a part of the first center conductor. The first center conductor and the second center conductor are connected to the second ground conductor. , The isolation between the first transmission line and the second transmission line can be increased, and the first center conductor and the second center conductor can be separated from each other. They can be formed such that a part thereof overlaps each other. Therefore, it is possible to realize a microwave slow-wave circuit that is significantly reduced in size as compared with the conventional example. The first center conductor of the first transmission line is formed between the first and second ground conductors with the first and second dielectric layers interposed therebetween. The second center conductor of the second transmission line is formed between the second and third ground conductors with the third and fourth dielectric layers interposed therebetween. The occupied area of the first or second central conductor may be relatively small as compared with the case where only one side is a ground conductor, thereby making it possible to greatly reduce the size and cut off the transmitted microwave. The frequency can be increased. Further, the third transmission line includes a first strip conductor having a line width smaller than a line width of the first and second center conductors formed in a spiral shape between the first and second dielectric layers. And the fourth transmission line includes a second strip conductor having a line width smaller than the line widths of the first and second center conductors, formed of the third and fourth dielectric layers. It is formed in a spiral shape between them. As a result, the inductance of the third and fourth transmission lines can be further increased, and as described later in detail, a larger delay wave can be obtained without lowering the characteristic impedance of the microwave slow wave circuit itself. A microwave slow wave circuit having a high efficiency can be realized.

[0020]

[0021]

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a microwave slow-wave circuit according to an embodiment of the present invention when the uppermost ground conductor 23 and the dielectric layer 14 are not formed, and FIG. C
FIG. 3 is a longitudinal sectional view taken along line C-C ′, and FIG.
It is a longitudinal cross-sectional view about the D 'line.

The microwave slow wave circuit according to the present embodiment is composed of (a)
The strip conductors 41a, 43a, parallel to the longitudinal direction of the slow wave circuit (hereinafter, referred to as the longitudinal direction of the circuit).
The line width W is larger than the line width Ws of the lines 41b and 43b.
a rectangular center conductor 40a, 40b having a st
Ground conductor 22 of layered triplate microstrip line
And a plurality of first transmission lines 700a, 7 which are formed of a triplate microstrip line having a relatively low capacitive characteristic impedance Z _L located at a higher position.
00b, and (b) the line width Ws of the strip conductors 31a, 33a, 31b, 33b parallel to the longitudinal direction of the circuit.
And a rectangular center conductor 30a, 30b formed to overlap a part of the rectangular center conductors 40a, 40b, and has a larger line width Wst than that of the ground conductor 22 of the two-layer triplate microstrip line. A plurality of second transmission lines 800a and 800b each formed of a triplate microstrip line having a relatively low characteristic impedance Z _L located at a low position; and (c) rectangular center conductors 40a, 40b and 30a. Or the first transmission lines 700a, 700b formed on the same plane as 30b.
b or the second transmission lines 800a, 800b are alternately and cascaded to form the rectangular center conductors 40a, 40b, 30
a, the strip conductor 41a with a relatively high characteristic impedance Z _H inductive has a smaller width Ws than the line width Wst of 30b, 43a, 41b, 43b, 31
a, 33a, 31b, and 33b, and (d) for connecting between strip conductors 43a and 31a formed on different planes, between strip conductors 33a and 41b, and between strip conductors 43b and 31b. It is characterized by having through-hole conductors 50a, 50b, 50c.

The microwave slow wave circuit of this embodiment is formed by the following steps.

First, as shown in FIG. 4, on a central portion of a semiconductor substrate 4 made of GaAs, a side having a longitudinal direction parallel to the longitudinal direction of a circuit and a side parallel to a direction perpendicular to the longitudinal direction of the circuit. One ground conductor 21 having a side of width Lg is formed. Next, after the dielectric layer 11 is formed on the entire surface of the ground conductor 21 and the exposed semiconductor substrate 10, as shown in FIG. , And separated from each other by a predetermined distance shorter than the line width Wst.
Rectangular conductors 30a, 30b each having a side having a line length Lg parallel to the side having a width Lg and a side having a line width Wst in a direction perpendicular to the side, and (b) the ground conductor 21. A line extending directly from the center of one side of the line width Wst of the rectangular center conductor 30a and bent in the direction toward the input end PI in a U-shape, which is located immediately above the semiconductor substrate 10 Strip conductor 31a of width Ws
(C) a rectangular conductor 32a formed at the tip of the strip conductor 31a, and (d) a line width of the rectangular center conductor 30a located immediately above the semiconductor substrate 10 where the ground conductor 21 is not formed. A strip conductor 33 having a line width Ws and extending from the center of the other side of Wst and bent in a U-shape toward the output end PO.
a) (e) a rectangular conductor 34a formed at the tip of the strip conductor 33a, and (f) a line of the rectangular center conductor 30b located directly above the semiconductor substrate 10 where the ground conductor 21 is not formed. A strip conductor 3 having a line width Ws extending from the center of one side of the width Wst and bent in a direction toward the input end PI in a U-shape.
1g, (g) a rectangular conductor 32b formed at the tip of the strip conductor 31b, and (h) a line of the rectangular center conductor 30b located immediately above the semiconductor substrate 10 where the ground conductor 21 is not formed. A strip conductor 33b having a line width Ws extending from the center of the other side of the width Wst and bent in a direction toward the output end PO in a U-shape is integrally formed.

Further, the conductors 30a, 30b, 31a, 3
1b, 32a, 32b, 33a, 33b, 34a and the dielectric layer 12 formed on the exposed dielectric layer 11, and then on the dielectric layer 12, directly on the ground conductor 21 and directly on the ground conductor 21 A ground conductor 22 having the same shape as 21 is formed. Next, the ground conductor 22 and the exposed dielectric layer 1
After the dielectric layer 13 is formed on the
As shown in FIG. 1, (a) each is located immediately above the ground conductors 21 and 22 and mutually has the line width Ws
The rectangular center conductor 40a is located immediately above a part of the rectangular center conductor 30a or the rectangular center conductor 40b is located immediately above each part of the rectangular center conductors 30a and 30b at a predetermined interval shorter than t. So that the ground conductors 21 and 22
(B) rectangular ground conductors 40a and 40b each having a side having a line length Lg parallel to the side having a width Lg and a side having a line width Wst in a direction perpendicular to the side having the line length Lg; The rectangular central conductor 40a is formed right above the semiconductor substrate 10 and bent from the center of one side of the line width Wst of the rectangular central conductor 40a in a U-shape toward the rectangular conductor 32a. (C) a rectangular ring conductor 44a located immediately above the rectangular conductor 32a and formed at the tip of the strip conductor 43a; (d) the ground conductors 21 and
2 is formed right above the semiconductor substrate 10 where the second substrate 2 is not formed, extends from the center of the other side of the line width Wst of the rectangular central conductor 40a, and is bent in the direction toward the input end PI in a U-shape. And (e) one side of the line width Wst of the line width Wst of the rectangular center conductor 40b located directly above the semiconductor substrate 10 where the ground conductors 21 and 22 are not formed. A strip conductor 4 having a line width Ws and extending from the center and bent in a direction toward the rectangular conductor 32b in a U-shape.
3f; (f) a rectangular ring conductor 44b located immediately above the rectangular conductor 32b and formed at the tip of the strip conductor 43b; and (g) the semiconductor in which the ground conductors 21 and 22 are not formed. The line width Ws of the line width Ws formed directly above the substrate 10 and extending from the center of the other side of the line width Wst of the rectangular center conductor 40b and bent in a U-shaped direction toward the rectangular conductor 34a is formed. The strip conductor 41b and (h) a rectangular ring conductor 42b located immediately above the rectangular conductor 34a and formed at the tip of the strip conductor 41b are integrally formed.

Further, as shown in FIG. 3, the dielectric layers 13 and 12 located in the rings of the rectangular ring conductors 44a, 44b and 42b are arranged in the thickness directions of the dielectric layers 13 and 12 by the respective thicknesses. That is, the rectangular conductors 32a, 32b, 34
a through hole 50ha in the shape of a rectangular truncated frustum,
After 50hb and 50hc are formed, each through hole 5
Through-hole conductors 50a, 50b, 50c are formed on the inner peripheral portions of 0ha, 50hb, 50hc, respectively. As a result, the strip conductor 43a is
0a, the strip conductor 33a is electrically connected to the strip conductor 41b via the through-hole conductor 50b, and the strip conductor 43b is electrically connected to the strip conductor 31b via the through-hole conductor 50c. Electrically connected.

Further, as shown in FIG.
40b, 43a, 44a, 41a, 43b, 44b, 4
After the dielectric layer 14 is formed on the exposed dielectric layer 13 and on the exposed dielectric layer 13, the ground conductors 23 having the same shape as the ground conductors 21 and 22 are provided immediately above the ground conductors 21 and 22.
Is formed.

In the microwave slow wave circuit formed as described above, the rectangular center conductors 40a, 40b, 30a,
30b and the ground conductors 21, 22, 23 form a two-layer triplate microstrip line. Of the two-layer triplate microstrip line, (a) a larger line width Wst located between the ground conductors 22, 23
And a grounded conductor 22 and 23, and a triplate microstrip line having a relatively low capacitive characteristic impedance Z _L.
(B) the ground conductor 22,
A first transmission line composed of a triplate microstrip line having a relatively low characteristic impedance Z _L and a relatively small capacitive impedance formed by a rectangular center conductor 40b having a larger line width Wst and ground conductors 22 and 23 located between the two. 700c are formed, and (c) a bird having a relatively low capacitive characteristic impedance Z _L is provided by the rectangular center conductor 30a and the ground conductors 21 and 22 located between the ground conductors 21 and 22 and having a larger line width Wst. A second transmission line 800a composed of a plate microstrip line is formed, and (d) the capacitance is formed by the rectangular center conductor 30b located between the ground conductors 21 and 22 and having a larger line width Wst and the ground conductors 21 and 22. the made in triplate microstrip line having a relatively low characteristic impedance Z _L of sexual Transmission line 800b of formed,
(E) Each strip conductor 41a, 43a, 41b, 43
b and ground conductors 22 and 23 form third transmission lines 900a, 900b, 900c and 900d having relatively high inductive characteristic impedance Z _H , respectively, and (f) strip conductors 31a, 33a, 31b and
The fourth transmission lines 900e, 900f, 900g, and 900h having relatively high inductive characteristic impedance Z _H are formed by the ground conductors 33b and the ground conductors 21 and 22, respectively. a line having a relatively low characteristic impedance Z _L and line having a relatively high characteristic impedance Z _H is alternately connected to and cascade to each other.

When a microwave signal is input to the input terminal PI of the microwave slow wave circuit configured as described above, its electric energy is mainly transmitted to the first transmission line 700a,
While the magnetic energy is stored in the third transmission lines 900a, 900b, 900c, 900d and the fourth transmission lines 900a, 900b,
Are accumulated in the transmission lines 900e, 900f, 900g, and 900h, and as a result, a slow wave having a phase speed lower than the speed of light propagates.

In this embodiment, (a) rectangular center conductor 4
0a, 40b, 30a, and the line length Lg of the characteristic impedance Z _L of a component to 30b, (b) between the rectangular central conductors 40a and 30a, between 30a and 40b, 40b and 3
And fourth transmission lines 900a to 900 connecting between the first and second transmission lines 0b.
00h and the respective line lengths Lg of the characteristic impedance Z _H having the through-hole conductors 50a, 50b, and 50c as constituent elements.
The a, period length (Lg + Lga) is each conductor is formed as compared to the guide wavelength is sufficiently short and Z _H >> Z _L. In a preferred embodiment, Lg = Lg
a, and at this time, the slow wave rate becomes the maximum.

As described above, in the slow wave circuit of the present embodiment, since the ground conductor 22 is formed at an intermediate position between the two-layer triplate microstrip line, it propagates through the upper and lower microstrip lines. As a result, the upper-layer rectangular center conductors 40a and 40b and the lower-layer rectangular center conductors 30a and 30b can be partially overlapped with each other as shown in FIG. . Therefore, since the line width Wst can be increased as compared with the second conventional example, the characteristic impedance Z _L can be significantly reduced, thereby increasing the delay rate of the delay circuit. In addition, the area occupied by the slow wave circuit can be significantly reduced. Moreover, this superposition, it is possible to shorten the line length Lga characteristic impedance Z _H,
It is possible to prevent the cutoff frequency from lowering. Therefore, it can operate up to a higher frequency.

FIG. 10 is a simulation result of the microwave slow-wave circuit of the first conventional example of FIG. 12 and the microwave slow-wave circuit of the second conventional example of FIG. 6 is a graph showing the characteristics of a delay rate and characteristic impedance with respect to the width of a strip conductor. As apparent from FIG. 10, in the slow-wave circuit of the periodic structure, to increase the line width W _L of the strip conductors of the transmission line having a low characteristic impedance Z _L, i.e. slow-wave by reducing the characteristic impedance Z _L Although the rate can be increased, the characteristic impedance of the slow wave circuit also decreases. This is the characteristic impedance of the slow-wave circuit of the periodic structure is approximately (Z _H · Z _L) given by the square root of and increasing the characteristic impedance of the microstrip line or coplanar waveguide is formed on a semiconductor substrate (e.g. It is difficult to set the characteristic impedance to 200Ω). On the other hand, decreasing the characteristic impedance Z _L requires, for example, MMI
It can be easily realized by using a thin dielectric film used for an MIM capacitor or the like which can be easily manufactured by the C process. From these results, the conventional slow-wave circuit having a periodic structure formed on a semiconductor substrate can realize a large slow-wave rate, but cannot avoid a decrease in the characteristic impedance of the slow-wave circuit itself.

In order to solve this problem, in this embodiment and a later-described modification, the strip conductors 31a, 3a having a small line width Ws and a relatively long line length are used.
1b, 33b, 41b, 43a, 43b, (b) spiral-shaped strip conductors 60a, 60b, 60c, 6
2a or (c) meander-shaped strip conductor 71
By using a, 71b, and 71c, a slow wave circuit having a large slow wave rate can be realized without reducing the characteristic impedance of the slow wave circuit itself. That is, the width Wst = 150 μm of the strip conductor or the rectangular center conductor in the simulation result in FIG.
(Corresponding to the slow wave rate = 10) is 0.1 in FIG.
This corresponds to an inductance of about 5 nH. Therefore, by forming the transmission line composed of the strip conductor having the high impedance Z _{H so as} to have a higher inductance, it is possible to form a slow wave circuit having a large slow wave rate without lowering the characteristic impedance of the slow wave circuit itself. Can be realized.

FIG. 6 shows a microwave slow-wave circuit according to a first modification of the present invention. That is, as shown in FIG. 6, the strip conductors 31a, 33a, 3 in FIG.
Instead of 1b, spiral strip conductors 60a, 60b, 60c may be formed. The first
In the modified example, the rectangular center conductor 40a is electrically connected to the rectangular center conductor 30a through the strip conductor 43a, the rectangular ring conductor 44a, the through-hole conductor 50a, the rectangular conductor 61a, and the spiral strip conductor 60a. The center conductor 30a includes a spiral strip conductor 60b, a rectangular conductor 61b, and a through-hole conductor 50.
b, a rectangular ring conductor 42b, and a strip conductor 41b, which are electrically connected to the rectangular center conductor 40b, and the rectangular center conductor 40b is a strip conductor 43b and a rectangular ring conductor 4
4b, the through-hole conductor 50c, the rectangular conductor 61c, and the spiral-shaped strip conductor 60c are electrically connected to the rectangular center conductor 30b. Thereby, the line length of the transmission line having the characteristic impedance Z _H having a high inductive property as compared with the above-described embodiment is increased, and a slow wave circuit having a larger delay rate without lowering the characteristic impedance is realized. be able to.

As shown in a second modification of FIG.
Instead of the strip conductors 31a, 33a and 31b in FIG.
a, 71b and 71c may be formed.

Further, as shown in a third modification of FIGS. 8 and 9, instead of strip conductors 43a and 31a, spiral strip conductors 62a are respectively opposed to each other with ground conductor 22 interposed therebetween. , 60a.

As described above, according to the present embodiment and its modifications, a microwave slow wave circuit having a large slow wave rate can be realized without lowering the characteristic impedance of the slow wave circuit itself. . Therefore, by applying the microwave slow-wave circuit of the present embodiment and its modification to various microwave circuits such as a hybrid circuit, a power combining circuit, a power branching circuit, and a delay circuit, these various circuits can be significantly reduced in size. Can be Further, since the microwave slow-wave circuit of the present embodiment does not use a semiconductor doped layer, it can be easily integrated with an active element such as an FET, and the MMI incorporating the various microwave circuits described above.
C can be formed on the same substrate. This can contribute to miniaturization and high functionality of the MMIC.

Although the semiconductor substrate 10 is used in the above embodiment, the present invention is not limited to this, and a dielectric substrate may be used instead.

In the above embodiment, a two-layer triplate microstrip line is used. However, the present invention is not limited to this, and a triplate microstrip line having three or more layers may be used.

[0042]

As described above in detail, according to the microwave slow wave circuit of the present invention, the first center conductor is provided between the first ground conductor and the second ground conductor, respectively. And the second
Through the dielectric layer, the direction of the line width of the first central conductor is formed to be parallel to the longitudinal direction of the microwave slow-wave circuit, and at least a capacitor having a relatively low characteristic impedance One first transmission line and a second center conductor are connected between the second ground conductor and the third ground conductor via the third and fourth dielectric layers, respectively.
Is formed so that the direction of the line width of the central conductor is parallel to the longitudinal direction of the microwave slow-wave circuit and overlaps a part of the first central conductor, and has a relatively low capacitive characteristic impedance. At least one second transmission line and a first strip conductor having a line width smaller than the line width of the first and second center conductors are spirally interposed between the first and second dielectric layers. At least one having a relatively high inductive characteristic impedance
A plurality of third transmission lines and a second strip conductor having a line width smaller than the line widths of the first and second center conductors in a spiral shape between the third and fourth dielectric layers. And at least one fourth transmission line having a relatively high inductive characteristic impedance and penetrating the second and third dielectric layers and not contacting the second ground conductor. And at least one through-hole conductor connecting the third transmission line and the fourth transmission line, wherein the third and fourth transmission lines and the through-hole conductor The first and fourth center conductors are formed so as to be located on one of the two sides of the first and second center conductors formed so as to partially overlap each other in the longitudinal direction of the wave slow wave circuit. The transmission line and the through-hole conductor are microwave Between the input terminal and the output terminal of the filter circuit, and said first transmission line, and the third transmission line,
The through-hole conductor, the fourth transmission line, and the second transmission line are cascaded in this order.

Therefore, according to the present invention, since the first center conductor and the second center conductor are formed via the second ground conductor, the first transmission line and the second center conductor are formed.
, The first central conductor and the second central conductor can be formed such that a part of them overlaps with the other. Therefore, it is possible to realize a microwave slow wave circuit that is significantly reduced in size as compared with the conventional example. Thereby, by applying the microwave slow-wave circuit according to the present invention to various microwave circuits such as a hybrid circuit, a power combining circuit, a power branching circuit, and a delay circuit, the various circuits can be significantly reduced in size. Can be. Further, since the microwave slow-wave circuit according to the present invention does not use a semiconductor doped layer, F
It can be easily integrated with an active element such as an ET, and the MMIC incorporating the various microwave circuits described above can be formed on the same substrate. By this, MMI
It can contribute to the downsizing and high performance of C. In particular, the first center conductor of the first transmission line is formed between the first and second ground conductors via the first and second dielectric layers, respectively. The second center conductor of the second transmission line is formed between the second and third ground conductors with the third and fourth dielectric layers interposed therebetween. The occupied area of the first or second central conductor may be relatively small as compared with the case where only one side is a ground conductor, thereby making it possible to greatly reduce the size and cut off the transmitted microwave. The frequency can be increased. Further, the third transmission line is connected to the first transmission line.
And a first strip conductor having a line width smaller than the line width of the second center conductor is formed in a spiral shape between the first and second dielectric layers, and the fourth transmission line is A second strip conductor having a line width smaller than the line width of the first and second center conductors is formed in a spiral shape between the third and fourth dielectric layers. This makes it possible to further increase the inductance of the third and fourth transmission lines, thereby reducing the microwave delay having a greater delay rate without lowering the characteristic impedance of the microwave delay circuit itself. A wave circuit can be realized.

[0044]

[Brief description of the drawings]

FIG. 1 is a plan view of a microwave slow-wave circuit when an uppermost dielectric layer and a ground conductor are not formed according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view taken along line CC ′ of FIG. 1;

FIG. 3 is a longitudinal sectional view taken along line DD ′ of FIG. 1;

FIG. 4 is a plan view showing a first step of a step of forming the microwave slow wave circuit of FIG. 1;

FIG. 5 is a plan view showing a second step of the step of forming the microwave slow wave circuit of FIG. 1;

FIG. 6 is a plan view illustrating a microwave slow-wave circuit according to a first modification of the present invention and corresponding to FIG. 1;

FIG. 7 is a plan view corresponding to FIG. 1, showing a microwave slow-wave circuit according to a second modification of the present invention.

FIG. 8 is an enlarged plan view illustrating a microwave slow-wave circuit according to a third modification of the present invention and corresponding to FIG. 1;

FIG. 9 is a longitudinal sectional view taken along line EE ′ of FIG. 8;

10 is a simulation result of the microwave slow-wave circuit of the first conventional example of FIG. 12 and the microwave slow-wave circuit of the second conventional example of FIG. 13; It is a graph which shows the characteristic of a slow wave rate and characteristic impedance with respect to width.

FIG. 11 is a graph showing a simulation result when a line having a lower characteristic impedance is replaced with an inductor, showing characteristics of a slow wave rate with respect to an inductance, a cutoff frequency, and a characteristic inductance.

FIG. 12 is a perspective view of a first conventional microwave slow wave circuit.

FIG. 13 is a perspective view of a second conventional microwave slow wave circuit.

14 is a longitudinal sectional view taken along line AA ′ of FIG.

FIG. 15 is a vertical sectional view taken along line BB ′ of FIG. 13;

[Explanation of symbols]

Reference Signs List 10: semiconductor substrate, 11, 12, 13, 14: dielectric layer, 21, 22, 23: ground conductor, 30a, 30b, 40a, 40b: rectangular center conductor, 31a, 31b, 33a, 33b, 41a, 41b, 4
3a, 43b: strip conductor, 42b, 44a, 44b: rectangular ring conductor, 32a, 34a, 32b: rectangular conductor, 50a, 50b, 50c: through-hole conductor, 50ha, 50hb, 50hc: through-hole, 60a, 60b, 60c , 62a: spiral-shaped strip conductor; 61a, 61b, 61c: rectangular conductor; 71a, 71b, 71c: meander-shaped strip conductor; PI: input end; PO: output end.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyo Ogawa 5th place Sanraya, Inaya, Seika-cho, Soraku-gun, Kyoto Pref. (JP, A) JP-A-62-114 (JP, A) JP-A-49-144144 (JP, U)

Claims (1)

(57) [Claims] 1. A line of the first center conductor, which is provided between a first ground conductor and a second ground conductor via first and second dielectric layers, respectively. The width direction is formed to be parallel to the longitudinal direction of the microwave slow wave circuit, and at least one first transmission line having a relatively low capacitive characteristic impedance and a second center conductor are formed. The direction of the line width of the second central conductor is interposed between the second ground conductor and the third ground conductor via third and fourth dielectric layers, respectively. At least one second transmission line formed parallel to the longitudinal direction and overlapping a part of the first central conductor and having a relatively low capacitive characteristic impedance; The first stream having a line width smaller than the line width of the two center conductors A loop conductor formed in a spiral shape between the first and second dielectric layers, and at least one third transmission line having a relatively high inductive characteristic impedance; A second strip conductor having a line width smaller than the line width of the second center conductor is formed in a spiral shape between the third and fourth dielectric layers to provide a relatively high inductive characteristic impedance. And at least one fourth transmission line, which is formed so as to penetrate the second and third dielectric layers and not to contact the second ground conductor. At least one through-hole conductor connecting the fourth transmission line, wherein the third and fourth transmission lines and the through-hole conductor partially overlap each other in the longitudinal direction of the microwave slow wave circuit. The first formed in The first to fourth transmission lines and the through-hole conductor are formed so as to be positioned on one of the two sides of the two center conductors, and are connected to the input terminal and the output terminal of the microwave slow wave circuit. In the meantime, the first transmission line, the third transmission line, the through-hole conductor, the fourth transmission line, and the second transmission line are cascaded in this order. And a microwave slow wave circuit.