JPH05327325A - Microwave slow-wave circuit - Google Patents

Abstract

PURPOSE:To improve isolation between first and second transmission lines and to provide the compact microwave slow-wave circuit having the much higher rate of slow-wave by forming first and second central conductors through a second ground conductor. CONSTITUTION:In this microwave slow-wave circuit, line width Wst of first and second transmission lines 700a, 700b, 800a and 800b is wider than width Ws of third transmission lines 900a-900d. Therefore, the first and second transmission lines have a characteristic impedance ZL of comparatively low capacity and on the other hand, the third transmission lines have a characteristic impedance ZH of comparatively high inductivity. When microwave signals are inputted to an input terminal PI of the slow-wave circuit, the electric energy is mainly stored in the first and second transmission lines. On the other hand, the magnetic energy is mainly stored in the third transmission lines. As a result, slow-waves at phase velocity lower than light velocity are propagated and the compact microwave slow-wave circuit having the much higher rate of slow-wave is provided.

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 propagating a slow wave having a phase velocity slower than the velocity of light, which is a signal wave in a microwave band of approximately 1 GHz or more, or a quasi-millimeter wave band. Regarding wave circuits.

[0002]

2. Description of the Related Art FIG. 12 shows a microwave delay circuit of a first conventional example. 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 the coplanar line 5L including the ground conductors 5a and 5b formed apart from each other is formed, the dielectric layer 3 is formed on the entire surface of the coplanar line 5L. Further, 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 formed on the entire surface of the dielectric layer 3 in a so-called sleeper shape or a lattice shape, and each has a predetermined interval. They are formed apart from each other by Lb.

In the region of the microwave slow-wave circuit in which the strip ground conductor 1 is formed, a vertical cross section in the direction parallel to the longitudinal direction of the strip ground conductor 1 (hereinafter referred to as the first section).
Vertical section. ), The capacitance between the center conductor 6 formed via the dielectric layer 3 and the strip ground conductor 1 becomes relatively large, and as a result, the capacitance having a relatively low characteristic impedance Z _L. It becomes one transmission line 500. On the other hand, in the region where the strip ground conductor 1 is not formed, in the vertical cross section in the direction parallel to the longitudinal direction of the strip ground conductor 1 (hereinafter referred to as the second vertical cross section), the central conductor 6 and the ground conductor 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 microwave slow-wave circuit of the conventional example has at least one first strip-shaped circuit having the first longitudinal section and having the characteristic impedance Z _L having a relatively low capacitive characteristic and being substantially composed of a microstrip line. One transmission line 500 and at least one of which is a coplanar line having a second longitudinal section and having a relatively high inductive characteristic impedance Z _H.
And two second transmission lines 600, wherein the first transmission lines 500 and the second transmission lines 600 are alternately arranged and are perpendicular to the longitudinal direction of the strip ground conductor 1. It is configured to be connected in series in the extending and connecting direction of 600.

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 delay circuit,
The electric 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 velocity slower than that of light propagates. .. Further, when the cycle length (La + Lb) approaches the in-tube wavelength, a standing wave is present, so that a cutoff frequency occurs. In the microwave delay circuit, the slow wave rate defined by the quotient obtained by dividing the free space wavelength by the guide wavelength is almost equal to the square root of (Z _H / Z _L ), and the characteristic impedance is (Z _H · Z Is approximately equal to the square root of _L ).

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

[0006]

However, these are obviously the facts that each ground conductor 5 of the coplanar line 5L is
The interval (Ws + 2Wp) between a and 5b increases, and as a result,
The circuit area of the circuit is increased. Further, if it is difficult to increase the characteristic impedance Z _H to a large extent, only a microwave delay wave circuit having a relatively low characteristic impedance can be realized. This microwave delay wave circuit having a relatively low characteristic impedance is effective for connection with an active element such as FET having a relatively low input impedance, but the fact that the characteristic impedance is relatively low makes this delay wave circuit There is a problem that it becomes a limiting condition when it is widely applied to all microwave circuits.

In order to solve the above-mentioned problems, the inventor of the present invention discloses in Japanese Patent Application No. 4-46783, FIGS.
The microwave slow wave circuit shown in FIG. 5 (hereinafter referred to as the second conventional example) was proposed. In addition, in FIG. 13 to FIG.
The same parts as those in FIG. 12 are designated by the same reference numerals.

The microwave conventional slow wave circuit of the second conventional example is provided with the two projecting conductors 6b projecting from the strip conductor 6a in the first longitudinal section, so that the central conductor wider than the width Ws of the strip conductor 6a. A plurality of first transmission lines 100 formed of triplate microstrip lines shown in FIG. 14 having a first longitudinal section with a width Wst of 6 and having a relatively low capacitive characteristic impedance Z _L ; A plurality of second transmission lines 200 each having an elevated coplanar line shown in FIG. 15 having a second longitudinal section and a relatively high inductive characteristic impedance Z _H ; Track 100 and second above
The transmission lines 200 are alternately connected to each other in the extending and connecting direction of the transmission lines 100 and 200, which is 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, on a whole surface of a semiconductor substrate 4 made of GaAs, 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. A ground conductor 5 is formed in which a plurality of rectangular slots 5s having sides are separated 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 a longitudinal direction in the Y-axis direction and passing through the center of each rectangular slot 5s, and a strip conductor located directly above the ground conductor 5 located between each rectangular slot 5s. Width L in the Y-axis direction protruding from 6a in the X-axis direction and the direction opposite to the X-axis direction
The central conductor 6 is formed of the rectangular protruding conductor 6b of a. Here, the lengths of the strip conductor 6a and the two protruding conductors 6b in the X-axis direction are indicated by Wst and Wst in FIGS. 13 and 14, respectively.

Furthermore, after the dielectric layer 3b is formed on the entire surface of the central conductor 6 and the exposed dielectric layer 3a, a part of the strip ground conductor 1 is formed on the dielectric layer 3b in each rectangular slot 5s. A plurality of strip ground conductors 1 located immediately above the ground conductor 5 and having the width La in the longitudinal direction in the X-axis direction are separated from each other by a predetermined Lb and are located directly above the ground conductor 5. In other words, it is formed in a so-called sleeper shape or a lattice shape so as not to be located right 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 consisting of the strip conductor 6a and the projecting conductor 6b is connected to the ground conductor 5 and the strip ground. A first transmission line 1 composed of a tri-plate microstrip line formed between the conductor 1 and the dielectric layers 3a and 3b, respectively.
00 is formed. This first transmission line 100 is
It has a relatively low characteristic impedance Z _L.
On the other hand, in the second vertical cross section of the microwave slow wave circuit, as shown in FIG.
The strip conductor 6a located on the upper side by the thickness of a is composed of an elevated coplanar line formed by being separated from each ground conductor 5 located in the left-right direction in FIG. Two transmission lines 200 are formed. The second transmission line 200 includes the center conductor 6
Since a relatively large number of magnetic force lines interlink between the ground conductor 5 and the ground conductor 5, it has a relatively high inductive characteristic impedance Z _H.

When a microwave signal is input to the input terminal PI of the microwave delaying circuit configured as described above, its electrical energy is mainly accumulated in the first transmission line 100, while its magnetic energy is stored. A slow wave having a phase velocity slower than that of light propagates mainly as a result of being accumulated in the second transmission line 200.

The first conventional slow-wave circuit of the second conventional example
When realizing the same slow wave rate and the same characteristic impedance as the conventional example, the slow wave circuit can be miniaturized as compared with the first conventional example, but the area occupied by the circuit is still large. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a microwave delay wave circuit which has a higher slow wave rate and a higher characteristic impedance as compared with the conventional example and which is smaller in size.

[0015]

According to a first aspect of the present invention, there is provided a microwave slow-wave circuit according to the first aspect of the present invention, wherein the first center conductor is disposed below the ground conductor and the first dielectric layer is interposed therebetween. At least one first transmission line formed so that the line width direction of the first central conductor is parallel to the longitudinal direction of the microwave slow-wave circuit, and the second central conductor are connected to the ground conductor. On the top
It is formed such that the line width direction of the second central conductor is parallel to the longitudinal direction of the microwave slow-wave circuit through the second dielectric layer and overlaps a part of the first central conductor. And at least one second transmission line having a line width smaller than the line widths of the first and second center conductors, and alternately and the first transmission line and the second transmission line At least one third transmission line formed of strip conductors for connecting in cascade is provided.

A microwave delay circuit according to a second aspect of the present invention is the microwave delay circuit according to the first aspect, wherein the strip conductor is formed in a meander shape or a spiral shape.

Further, the microwave slow-wave circuit according to claim 3 is the microwave slow-wave circuit according to claim 1, wherein the strip conductor further comprises a meander-shaped or spiral-shaped strip conductor. To do.

[0018]

In the microwave delay wave circuit according to claim 1, since the line widths of the first and second transmission lines are larger than the line width of the third transmission line, the first and second transmission lines are formed. The transmission line has a relatively low characteristic impedance Z _L , while the third transmission line has a relatively high inductive characteristic impedance Z _H. Here, when a microwave signal is input to the input terminal of the microwave delaying 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. Of the slow wave having a phase velocity slower than that of light is accumulated.

In the microwave slow wave circuit, the line width direction of the first and second center conductors of the first and second center conductors is parallel to the longitudinal direction of the microwave slow wave circuit. And the second central conductor is formed so as to overlap a part of the first central conductor, the first central conductor and the second central conductor being the second ground conductor. Since the first central conductor and the second central conductor are separated from each other, the isolation between the first transmission line and the second transmission line can be increased, and the first central conductor and the second central conductor can be separated from each other. It can be formed such that some of them overlap each other. Therefore, it is possible to realize a microwave delay circuit that is significantly smaller than the conventional example.

Further, in the microwave slow-wave circuit according to the second aspect, preferably, the strip conductor is formed in a meander shape or a spiral shape. This makes it possible to further increase the inductance of the third transmission line, which, as will be described later in detail,
A microwave slow wave circuit having a larger slow wave rate can be realized without lowering the characteristic impedance of the microwave slow wave circuit itself.

Further, in the microwave slow wave circuit according to the present invention, preferably, the second strip conductor further includes a meander-shaped or spiral-shaped strip conductor. As a result, the inductance of the third transmission line can be further increased, and as a result, as will be described later in detail, the microwave delay wave circuit itself has a larger delay rate without lowering the characteristic impedance of the microwave delay wave circuit itself. A microwave slow wave circuit can be realized.

[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. 2 is shown in FIG. C
FIG. 3 is a vertical cross-sectional view taken along the line C ′, and FIG.
It is a longitudinal cross-sectional view about a D'line.

The microwave slow-wave circuit of this embodiment is (a)
Strip conductors 41a, 43a, which are parallel to the longitudinal direction of the slow wave circuit (hereinafter referred to as the longitudinal direction of the circuit),
Large track width W compared to track widths Ws of 41b and 43b
two rectangular center conductors 40a, 40b having st and 2
Ground conductor 22 of layered triplate microstrip line
First transmission line of the plurality configured in triplate microstrip line having a relatively low characteristic impedance Z _L of the capacitive located at a position higher than 700a, 7
00b and (b) the line width Ws of the strip conductors 31a, 33a, 31b, 33b parallel to the longitudinal direction of the circuit.
The rectangular center conductors 30a and 30b are formed so as to have a larger line width Wst and overlap a part of the rectangular center conductors 40a and 40b, and more than the ground conductor 22 of the two-layer triplate microstrip line. A plurality of second transmission lines 800a and 800b formed of triplate microstrip lines which are located at a low position and have a relatively low characteristic impedance Z _L , and (c) rectangular center conductors 40a, 40b and 30a Alternatively, the first transmission lines 700a and 700 are formed on the same plane as 30b.
b or the second transmission lines 800a and 800b are alternately and cascaded to form rectangular center conductors 40a, 40b and 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, 33b, and (d) for connecting between the strip conductors 43a and 31a formed on different planes, between the strip conductors 33a and 41b, and between the strip conductors 43b and 31b. The through-hole conductors 50a, 50b, 50c are provided.

The microwave delay 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 the circuit and a direction parallel to the longitudinal direction of the circuit are parallel. One ground conductor 21 having a side with a width Lg is formed. Next, after the dielectric layer 11 is formed on the ground conductor 21 and the entire surface of the exposed semiconductor substrate 10, as shown in FIG. 5, (a) each of the ground conductors 21 is formed on the dielectric layer 11. Located directly above the ground conductor 21 and separated from each other by a predetermined distance shorter than the line width Wst.
Rectangular center conductors 30a and 30b having a side having a line length Lg parallel to the side having a line 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 formed directly above the semiconductor substrate 10 and extending from the central portion of one side of the line width Wst of the rectangular center conductor 30a and being bent in a U-shape toward the input end PI. Strip conductor 31a with width Ws
And (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 directly above the semiconductor substrate 10 on which the ground conductor 21 is not formed. A strip conductor 33 having a line width Ws, which extends from the center of the other side of Wst and is bent in a direction toward the output end PO in a U shape.
a, (e) a rectangular conductor 34a formed at the tip of the strip conductor 33a, and (f) a line of a rectangular central conductor 30b located directly above the semiconductor substrate 10 on which the ground conductor 21 is not formed. A strip conductor 3 having a line width Ws, which extends from the center of one side of the width Wst and is bent in the direction toward the input end PI in a U-shape.
1b, (g) a rectangular conductor 32b formed at the tip of the strip conductor 31b, and (h) a line of a rectangular central conductor 30b located immediately above the semiconductor substrate 10 on which the ground conductor 21 is not formed. A strip conductor 33b having a line width Ws, which extends from the center of the other side of the width Wst and is bent in the 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 11 is formed on the exposed dielectric layer 11, and then the ground conductor is formed on the dielectric layer 12 and directly above the ground conductor 21. A ground conductor 22 having the same shape as 21 is formed. Then, the ground conductor 22 and the exposed dielectric layer 1
After the dielectric layer 13 is formed on the second dielectric layer 13,
As shown in FIG. 1, (a) the line widths Ws are located directly above the ground conductors 21 and 22, respectively.
The rectangular central conductor 40a is located directly above a part of the rectangular central conductor 30a, or the rectangular central conductor 40b is located directly above a part of each of the rectangular central conductors 30a and 30b at a predetermined distance shorter than t. So that the ground conductors 21, 22
Rectangular center conductors 40a, 40b having a side having a line length Lg parallel to the side having the line width Lg and a side having a line width Wst in a direction perpendicular to the side, and (b) the ground conductors 21 and 22 are formed. It is formed directly above the semiconductor substrate 10 which is not formed, extends from the center of one side of the line width Wst of the rectangular central conductor 40a, and is bent in a U-shape toward the rectangular conductor 32a. A strip conductor 43a having a line width Ws, (c) a rectangular ring conductor 44a located immediately above the rectangular conductor 32a and formed at the tip of the strip conductor 43a, and (d) the ground conductors 21, 2.
2 is located directly above the semiconductor substrate 10 on which the rectangular center conductor 40a 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 a U-shape toward the input end PI. The strip conductor 41a having a line width Ws formed by: (e) one side of the line width Wst of the rectangular central 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, which extends from the central portion and is bent in a direction toward the rectangular conductor 32b in a U shape.
3b, (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. A line width Ws that is formed immediately above the substrate 10 and extends from the center of the other side of the line width Wst of the rectangular center conductor 40b and is bent in a U-shape toward the rectangular conductor 34a. The strip conductor 41b and (h) the rectangular ring conductor 42b located directly above the rectangular conductor 34a and formed at the tip of the strip conductor 41b are integrally formed.

Further, as shown in FIG. 3, in the dielectric layers 13 and 12 located in the ring of the rectangular ring conductors 44a, 44b and 42b, only the thicknesses of the dielectric layers 13 and 12 in the respective thickness directions are provided. , That is, rectangular conductors 32a, 32b, 34
rectangular frustum-shaped through hole 50ha until reaching a,
After forming 50hb and 50hc, 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 becomes the through-hole conductor 5
0a is electrically connected to the strip conductor 31a, the strip conductor 33a is electrically connected to the strip conductor 41b via the through-hole conductor 50b, and the strip conductor 43b is connected to the strip conductor 31b via the through-hole conductor 50c. It is electrically connected.

Further, as shown in FIG. 2, the conductors 40a,
40b, 43a, 44a, 41a, 43b, 44b, 4
After the dielectric layer 14 is formed on the exposed layers 1b and 42b and on the exposed dielectric layer 13, the ground conductor 23 having the same shape as the ground conductors 21 and 22 is formed 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,
A two-layer triplate microstrip line is formed by 30b and the ground conductors 21, 22 and 23. Among the two-layer triplate microstrip line, (a) is located between the ground conductors 22 and 23 and has a larger line width Wst.
A rectangular center conductor 40a having grounds and grounding conductors 22 and 23, which are triplate microstrip lines having a characteristic impedance Z _L having a relatively low capacitance.
Transmission line 700a is formed, and (b) ground conductor 22,
A first transmission line formed of a triplate microstrip line having a relatively low characteristic impedance Z _L by means of a rectangular center conductor 40b having a larger line width Wst and grounding conductors 22 and 23, which is located between 23. 700b is formed, and (c) the rectangular center conductor 30a having a larger line width Wst and located between the ground conductors 21 and 22 and the ground conductors 21 and 22 have a characteristic impedance Z _L having a relatively low capacitance. A second transmission line 800a formed of a plate microstrip line is formed, and (d) a rectangular central conductor 30b located between the ground conductors 21 and 22 and having a larger line width Wst and the ground conductors 21 and 22 cause capacitance. 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 the ground conductors 22 and 23 form the third transmission lines 900a, 900b, 900c and 900d each having a relatively high inductive characteristic impedance Z _H , and (f) each strip conductor 31a, 33a, 31b,
33b and the ground conductors 21 and 22 form fourth transmission lines 900e, 900f, 900g, and 900h each having a relatively high inductive characteristic impedance Z _H , and between the input end PI and the output end PO, Lines having a relatively high characteristic impedance Z _H and lines having a relatively low characteristic impedance Z _L are connected to each other alternately and in cascade.

When a microwave signal is input to the input terminal PI of the microwave delaying circuit configured as described above, its electric energy is mainly the first transmission line 700a,
700b and the second transmission lines 800a, 800b are stored, while the magnetic energy is mainly stored in the third transmission lines 900a, 900b, 900c, 900d and the fourth transmission line 900a, 900b, 900c, 900d.
Are accumulated in the transmission lines 900e, 900f, 900g, and 900h, and as a result, a slow wave having a phase velocity slower than the velocity of light propagates.

In this embodiment, (a) rectangular center conductor 4
0a, 40b, 30a and 30b as component elements, the line length Lg of the characteristic impedance Z _L , and (b) the rectangular center conductors 40a and 30a, 30a and 40b, 40b and 3 respectively.
The third and fourth transmission lines 900a to 9 for connecting between 0b
00h and through-hole conductors 50a, 50b, 50c as constituent elements, each line length Lg of characteristic impedance Z _H
“A” means that each of the conductors is formed so that the cycle length (Lg + Lga) is sufficiently shorter than the guide wavelength and Z _H >> Z _L. Note that in the preferred embodiment, Lg = Lg
It is set to be a, and the slow wave rate becomes maximum at this time.

As described above, in the slow wave circuit of this embodiment, since the ground conductor 22 is formed at an intermediate position of the two-layer triplate microstrip line, it propagates through the upper and lower microstrip lines. It is possible to increase the isolation of the electromagnetic waves to be generated, whereby the upper rectangular center conductors 40a and 40b and the lower 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, and thereby the slow wave rate of the slow wave circuit can be increased. In addition, the occupied area of the slow wave circuit can be significantly reduced. Moreover, since the line length Lga of the characteristic impedance Z _H can be shortened by this superposition,
It is possible to prevent the cutoff frequency from decreasing. Therefore, it is possible to 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. 13, showing a line having a lower characteristic impedance. It is a graph which shows the characteristic of a slow wave 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 The rate can be increased, but the characteristic impedance of the slow wave circuit is also reduced. This increases the characteristic impedance of the microstrip line or the coplanar line formed on the semiconductor substrate, in which the characteristic impedance of the slow wave circuit of the periodic structure is approximately given by the square root of (Z _H · Z _L ). It is difficult to set the characteristic impedance of 200Ω). In exchange for this, reducing the characteristic impedance Z _L is, for example, an MMI.
This can be easily realized by using a thin dielectric film used for an MIM capacitor or the like that can be easily manufactured by the C process. From these results, a conventional slow wave circuit having a periodic structure formed on a semiconductor substrate can realize a large slow wave rate, but on the other hand, a decrease in the characteristic impedance of the slow wave circuit itself cannot be avoided.

In order to solve this problem, in the present embodiment and the modifications described later, the strip conductors 31a, 3 having a small line width Ws and a relatively long line length (a).
1b, 33b, 41b, 43a, 43b, (b) spiral-shaped strip conductors 60a, 60b, 60c, 6
2a or (c) a meander-shaped strip conductor 71
By using a, 71b, and 71c, it is possible to realize a slow wave circuit having a large slow wave rate without lowering 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 a transmission line made of a strip conductor having a high impedance Z _{H so as} to have an inductance larger than this, a delay wave circuit having a large delay wave ratio can be obtained without lowering the characteristic impedance of the delay wave circuit itself. Can be realized.

FIG. 6 shows a microwave delaying 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 central conductor 40a is electrically connected to the rectangular central 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, and the rectangular central conductor 40a. The center conductor 30a is a spiral strip conductor 60b, a rectangular conductor 61b, and a through-hole conductor 50.
b, the rectangular ring conductor 42b, and the strip conductor 41b are electrically connected to the rectangular center conductor 40b. The rectangular center conductor 40b includes the strip conductor 43b and the rectangular ring conductor 4.
4b, the through-hole conductor 50c, the rectangular conductor 61c, and the spiral strip conductor 60c are electrically connected to the rectangular center conductor 30b. As a result, the line length of the transmission line having the characteristic impedance Z _H having a high inductive property is increased as compared with the above-described embodiment, and a slow wave circuit having a larger slow wave rate is realized without lowering the characteristic impedance. be able to.

Further, as shown in the second modification of FIG. 7,
Instead of the strip conductors 31a, 33a, 31b in FIG. 1, strip conductors 71 each having a meander shape are provided.
You may form a, 71b, 71c.

Further, as shown in the third modification of FIGS. 8 and 9, instead of the strip conductors 43a and 31a, spiral strip conductors 62a are provided so as to face each other with the ground conductor 22 interposed therebetween. , 60a may be formed.

As described above, according to this embodiment and its modification, it is possible to realize a microwave slow wave circuit having a large slow wave rate without lowering the characteristic impedance of the slow wave circuit itself. .. Therefore, by applying the microwave delay circuit of this embodiment and its modification to various microwave circuits such as a hybrid circuit, a power combiner circuit, a power branch circuit, and a delay circuit, these various circuits can be significantly reduced in size. Can be converted. Further, since the microwave slow-wave circuit of this embodiment does not use the semiconductor-doped layer, it can be easily integrated with active elements such as FETs, and the MMI incorporating the various microwave circuits described above.
C can be formed on the same substrate. This can contribute to miniaturization and higher functionality of the MMIC.

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

Although the two-layer triplate microstrip line is used in the above embodiment, the present invention is not limited to this, and three or more triplate microstrip lines may be used.

[0042]

As described in detail above, according to the microwave delay circuit of the present invention, the first central conductor is provided below the ground conductor with the first dielectric layer interposed therebetween. At least one first transmission line 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 the second central conductor is provided above the ground conductor. Second
Via the dielectric layer, the line width direction of the second central conductor is parallel to the longitudinal direction of the microwave slow-wave circuit, and at least partially overlaps with the first central conductor. One second transmission line and a line width smaller than the line widths of the first and second center conductors, and the first transmission line and the second transmission line are alternately and cascaded. And at least one third transmission line formed of a strip conductor for connection.

Therefore, since the first center conductor and the second center conductor are formed via the second ground conductor, the space between the first transmission line and the second transmission line is increased. The isolation of the
The center conductor and the second center conductor can be formed so that they partially overlap each other. Therefore, it is possible to realize a microwave delay wave circuit that is significantly smaller than the conventional example. Accordingly, by applying the microwave slow-wave circuit according to the present invention to various microwave circuits such as a hybrid circuit, a power combiner circuit, a power branch circuit, and a delay circuit, the various circuits can be significantly downsized. You can Further, since the microwave slow-wave circuit according to the present invention does not use the semiconductor-doped layer, it can be easily integrated with an active element such as FET, and the same MMIC incorporating the above-mentioned various microwave circuits can be used. It can be formed on a substrate. This can contribute to miniaturization and higher functionality of the MMIC.

Further, in the microwave slow-wave circuit according to claim 2 or 3, the strip conductor is formed in a meander shape or a spiral shape, or the strip conductor further includes a meander shape or a spiral shape strip conductor. Therefore, it is possible to further increase the inductance of the third transmission line, thereby realizing a microwave slow wave circuit having a larger slow wave rate without lowering the characteristic impedance of the microwave slow wave circuit itself. it can.

[Brief description of 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, which is an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view taken along the line CC ′ of FIG.

FIG. 3 is a vertical cross-sectional view taken along the line DD ′ of FIG.

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

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

FIG. 6 is a plan view corresponding to FIG. 1, showing a microwave delaying circuit according to a first modification of the present invention.

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

8 is an enlarged plan view corresponding to FIG. 1, showing a microwave delaying circuit according to a third modification of the present invention.

9 is a vertical cross-sectional view taken along the line EE ′ of FIG.

10 is a simulation result of the first conventional microwave delay circuit of FIG. 12 and the second conventional microwave delay circuit of FIG. 13, showing a strip conductor of a line having a lower characteristic impedance. It is a graph which shows the characteristic of the slow wave rate and characteristic impedance with respect to width.

FIG. 11 is a graph showing simulation results when a line having a lower characteristic impedance is replaced with an inductor, and 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 microwave slow-wave circuit of a first conventional example.

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

14 is a vertical cross-sectional view taken along the line AA ′ in FIG.

FIG. 15 is a vertical cross-sectional view taken along the line BB ′ of FIG.

[Explanation of symbols]

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, Four
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 strip conductors, 61a, 61b, 61c ... Rectangular conductors, 71a, 71b, 71c ... Meander strip conductors, PI ... Input end, PO ... Output end.

Claims (3)

[Claims] 1. A first center conductor is provided below a ground conductor,
At least one first transmission line formed so that the direction of the line width of the first central conductor is parallel to the longitudinal direction of the microwave slow-wave circuit through the first dielectric layer; The second center conductor is arranged above the ground conductor with the line width direction of the second center conductor being parallel to the longitudinal direction of the microwave slow wave circuit via the second dielectric layer and At least one second transmission line formed so as to overlap a part of the first central conductor; and a line width smaller than the line widths of the first and second central conductors. A microwave delay wave circuit comprising: a transmission line and at least one third transmission line formed of a strip conductor for connecting the second transmission line alternately and in cascade. 2. The strip conductor is formed in a meander shape or a spiral shape.
The described microwave slow wave circuit. 3. The microwave slow-wave circuit according to claim 1, wherein the strip conductor further comprises a meander-shaped or spiral-shaped strip conductor.