JPH0220101A - Mode converting circuit - Google Patents

Abstract

PURPOSE:To set a slot line and the line width of a micro-strip line in the realizable range, to reduce an occupied area and to improve a high frequency characteristic by specifying the characteristic impedance of the line to execute the impedance conversion with the relation of the characteristic impedance of two transmission lines which are signal transmission lines. CONSTITUTION:The characteristic impedance of a micro-strip line 1 is Z1. Slot lines 2 and 3 are formed on the rear surface of a dielectric substrate as first and second slot lines. For the slot line 2, the line length is 1/4 wavelength and a characteristic impedance is Z2. For the slot line 3 extended to other edge of the slot line 2, the tip (left edge in the figure) is a signal input output edge and the characteristic impedance is Z3. Respective lines are formed between characteristic impedances Z1, the same Z2 and the same Z3 so that approximately Z =Z1.Z3 can be established. Since for slot lines 2 and 3 formed so as to satisfy the relation, the characteristic impedance becomes the comparatively close value, the gap between the maximum value and the minimum value of the line width (gap width) of the slot line used becomes extremely small.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mode conversion circuit used when transmitting signals between a microstrip line and a slot line in a microwave transmission circuit.

(Prior Art) In a microwave transmission circuit using a dielectric substrate, a microstrip line is formed on one plate surface (for example, the front surface) of the dielectric substrate, and a slot line is formed on the other plate surface, the back surface. A mode conversion circuit is used to connect both lines.

Conventionally, as this type of mode conversion circuit, the one shown in FIG. 2 or FIG. 3, for example, is known.

In FIG. 2, reference numeral 41 denotes a microstrip line formed on the surface of a dielectric substrate, and one end (bottom in the figure) of this microstrip line 41 is a signal input/output end, and the other end (
The open end (upper part in the figure) has a characteristic impedance of 241. On the other hand, on the back side of the dielectric substrate, lines 42, 43, and 44 are arranged in series to the three throwers 1 having different line widths, and so as to be orthogonal to the microstrip line 41 at the electromagnetic connection point 45. At the same time, the cavity 4
6 is formed.

The electromagnetic connection point 45 is a position 1/4 wavelength away from the open end of the microstrip line 41 toward the signal input/output end, that is, a point where the microstrip line 41 is electromagnetically short-circuited. The throwers 1~! whose ends intersect orthogonally at this electromagnetic connection point 45! ! The characteristic impedance Z4□ of the line 42 is approximately equal to the characteristic impedance Z41 of the microstrip line 41 (Z42≠741).The cavity 45 makes one end of the slot line 42 equivalently regarded as open. This is provided to make this happen.

That is, the slot line 42 must be open at the electromagnetic connection point 45, but in the illustrated example, one end substantially coincides with the electromagnetic connection point 45, so the cavity 45 is provided.

One end of the slot line 44 on the left side in the figure is a signal input/output end, and its characteristic impedance is z44. and,
The slot line 43 interposed between the other end of the slot line 42 and the other end of the slot line 44 has a line length of 1/4 wavelength and a characteristic impedance of Z4B.

In the above configuration, in order to perform signal transmission between the microstrip line 41 and the slot line 44, it is necessary to equalize the characteristic impedance of both lines. Therefore, in order to impedance transform the characteristic impedance Z44 to the characteristic impedance Z42, the characteristic impedance Z43 of the slot line 43 is selected so as to satisfy Z43''Z42.Z44.

In this way, the one shown in FIG. 2 performs impedance conversion on the slot line side, whereas the one shown in FIG. 3, on the contrary, performs impedance conversion on the microstrip line side.

In FIG. 3, there are three microstrip lines 51. with different line widths on the surface of the dielectric substrate. 52 and 53 are arranged in series in the vertical direction in the figure. The microstrip line 51 has a characteristic impedance of 25□, and one end at the top in the figure is an open end, and an electromagnetic contact 54 is located 174 wavelengths away from the open end toward the other end. Further, one end (lower end in the figure) of the microstrip line 53 is a signal input/output end, and its characteristic impedance is Z53. The microstrip line 52 interposed between the other end of the microstrip line 51 and the other end of the microstrip line 53 has a line length of 1/4 wavelength and a characteristic impedance of 2.
It is 52.

On the other hand, one end of the back side of the dielectric substrate has an electromagnetic connection point 54.
One slot line 55 orthogonally intersecting the microstrip line 51 and a cavity 56 having the same purpose as described above are provided. The other end (left side in the figure) of this slot line 55 is a signal input/output end, and its characteristic impedance Z55 is approximately equal to the characteristic impedance Z51 of the microstrip line 51 (Z55ζZ51).

In this mode conversion circuit, the same idea as above is used,
Characteristic impedance Z5 of microstrip line 52
2 is selected to satisfy Z 52 = Z 53 · ZSt.

(Problems to be Solved by the Invention) However, the conventional mode conversion circuit described above has the following problems.

First, since the slot line has a small kneading path width (gap width) at which the impedance becomes low, the line width of the slot line 42 in FIG.
241″rZ42) may be so small as to be difficult to realize.

In addition, since the width of the kneading path where the microstrip line becomes high impedance is small, the line width of the microstrip line 51 in FIG. 3 is equal to the characteristic impedance Z.
Depending on the value of 55 (Z 55≠251), the value may be so small as to be difficult to realize.

Furthermore, since the number of required lines is large, the area occupied by the entire circuit increases, which adversely affects high frequency characteristics.

The present invention was made in view of these conventional problems, and its purpose is to set the line width of a slot line or microstrip line within a feasible range, and to reduce the area occupied by the entire circuit. An object of the present invention is to provide a mode conversion circuit that can improve high frequency characteristics.

(Means for Solving the Problems) In order to achieve the above object, the mode conversion circuit of the present invention has the following configuration.

That is, the mode conversion circuit of the present invention has a first plate on one plate surface of a dielectric substrate, one end of which is electromagnetically open or short-circuited, the other end is a signal input/output end, and has a characteristic impedance of 21.
or a second microstrip line whose one end is a signal input/output end and whose characteristic impedance is ZI, and which is extended to the other end of this second microstrip line and whose tip is electromagnetically open or a third microstrip line that is short-circuited and has a characteristic impedance of 72; a point at which the first microstrip line is electromagnetically short-circuited to the other plate surface of the dielectric substrate; One end is electromagnetically open or short-circuited so that it intersects orthogonally with the first microstrip line and is electromagnetically open at the intersection, and the other end is located 1/4 wavelength away from the intersection. a first slot line with an impedance of 22;
A second slot line extending to the other end of the slot line, the tip of which is a signal input/output end and having a characteristic impedance of 23: or a second slot line within the third microstrip line and having a characteristic impedance of 23; One end is electromagnetically open or short-circuited, and the other end is electromagnetically open or short-circuited so that it intersects with the third microstrip line at a position 1/4 wavelength away from the other end of the line, and is electromagnetically open at the intersection. a third slot line which is an input/output terminal and has a characteristic impedance of 73; Z2+Z is approximately Z2=Zt・Z3
It is characterized by being selected so as to satisfy the following.

(for production) Next, the operation of the mode conversion circuit of the present invention will be explained.

The mode conversion circuit of the present invention uses one microstrip line (first microstrip line) and two slot lines (first and second slot lines), or two microstrip lines (second and third slot lines). (microstrip line) and one slot line (third slot line). In either configuration, the characteristic impedance Z2 of the line (second slot line, third microstrip line) that performs impedance conversion is the same as the characteristic impedance Z2 of the line (second slot line, third microstrip line) that performs impedance conversion. ) and the third slot line (Z3) or second microstrip line (ZI)
and the characteristic impedance Z1 of the first slot line (Z3)) and the characteristic impedance Z3 of the first slot line (Z3).

Therefore, according to the mode conversion circuit of the present invention, the characteristic impedance Z2 of the second slot line must be extremely small, or the characteristic impedance Z2 of the third microstrip line must be extremely large. This situation can be avoided and the line widths can be kept within a feasible range.

In addition, since the configuration is simple with two slot lines and one microstrip line, or one slot line and two microstrip lines, the area occupied by the entire circuit can be made smaller than in the conventional example.
High frequency characteristics can be improved.

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

FIG. 1 shows various embodiments of the mode conversion circuit of the present invention. The first embodiment has one microstrip line 1 and two slot lines (1) as shown in FIG. 1(a). It is composed mainly of 2 and 3). The microstrip line 1 is formed as a first microstrip line on, for example, the surface of a dielectric substrate, the lower end in the figure is a signal input/output end, the upper end in the figure is an open end, and its characteristic impedance is Zl. It is.

On the other hand, slot lines 2 and 3 are formed on the back surface of the dielectric substrate as first and second slot lines. The slot line 2 has a line length of 1/4 wavelength and a characteristic impedance of Z2, and one end thereof is formed to intersect orthogonally with the microstrip line 1 at an electromagnetic connection point 4.

The cavity 5 is configured and functions in the same manner as the conventional example,
Further, as in the conventional example, the electromagnetic connection point 4 is located at a position 1/4 wavelength away from the open end of the microstrip line 1 toward the signal input/output end. The slot line 3 extending from the other end of the slot line 2 has a signal input/output end at its tip (the left end in the figure) and has a characteristic impedance of Zl.

Then, the characteristic impedance Z0. Same z2. Same Z.

Each line is formed so that Z2=ZhiI4 (1) approximately holds between them. That is, mutual signal transmission is performed between the microstrip line 1 and the slot line 3 without causing impedance mismatch.

Here, the slot line ii! is formed so as to satisfy the relationship of formula (1) above. 82 and 3 have relatively similar characteristic impedance values, so the difference between the maximum and minimum line width (gap width) of the slot line used in 5 is much larger than that of the conventional example (Figure 2). becomes smaller. In other words, it is easy to implement. Furthermore, since the number of slot lines used is reduced compared to the conventional example, the area occupied by the circuit is reduced, and high frequency characteristics can be improved.

Next, the second embodiment is constructed mainly of two microstrip lines (6, 7) and one slot line 8, as shown in FIG. 1(b). The (second) microstrip line 6 has a signal input/output terminal at its lower end in the figure and a characteristic impedance of 71, and a (third) microstrip line 7 extends from its upper end in the figure. The upper end of the microstrip line 7 in the figure is an open end,
The characteristic impedance is z2. Note that the electromagnetic connection point 9 is located at a position 1/4 wavelength from the open end, and the distance from this electromagnetic connection point 9 to the connection point with the microstrip line 6 is also 1/4 wavelength.

On the other hand, the (third) slot line 8 has an electromagnetic connection point 9 at its right end in the figure, and is orthogonally crossed with the microstrip line 7, and its left end in the figure is a signal input/output terminal, and its characteristic impedance is Zl. It is. Note that the cavity 10 is as described above.

These lines have a characteristic impedance Z1. Same Z2. Z is formed so as to satisfy the above formula (1), and the same effects as the first embodiment circuit can be obtained.

The above corresponds to the conventional example circuits shown in FIGS. 2 and 3, but the third embodiment circuit shown in FIG. An example of a change is shown. That is, the lower end of the (first) microstrip line 11 in the figure is the signal input/output end, but the upper end in the figure is connected to the back conductor and is short-circuited both electrically and electromagnetically. This is the electromagnetic connection point 14. The (first) slot line 12 crosses the microstrip line 11 orthogonally at one end at the electromagnetic connection point 14, but the slot line 15 is extended so that one end is open at the electromagnetic connection point 14. It is. That is, the slot line 15 is a 1/4 wavelength line with a short-circuited end. The other end of the slot line 12 is located at a position 1/4 wavelength away from the electromagnetic connection point 14, and the (second) slot line 1 is connected thereto.
3 will be extended.

Also in this third embodiment, the characteristic impedance of the microstrip line 11 is Zl, and the characteristic impedance of the slot line 12 is Z2. The characteristic impedance of the slot line 13 is 73, and each line is formed so that these characteristic impedances satisfy the above formula (1), and the same effects as in the first embodiment can be obtained.

(Effects of the Invention) As explained above, according to the mode conversion circuit of the present invention, the characteristic impedance Z2 of the line (second slot line, third microstrip line) that performs impedance conversion is the signal transmission line. Since it is determined by the relationship between the characteristic impedance Z of the two transmission lines and the same Z3, there may be a situation where the characteristic impedance Z2 of the second slot line must be made extremely small, or the characteristics of the third microstrip line. It is possible to avoid a situation in which the impedance Z2 has to be made extremely large, and to keep the width of these lines within a achievable range.6 Also, if the configuration is two slot lines and one microstrip line, or Since it is simple with one slot line and two microstrip lines, the area occupied by the entire circuit can be made smaller than the conventional example.
This has the effect of improving high frequency characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of various embodiments of the mode conversion circuit of the present invention, and FIGS. 2 and 3 are block diagrams of conventional circuits. 1.6, 7, 1.1...Microstrip line, 2.3.8, 12, 1.3, 1.5...Thrower l-line 4.9.14... ...Electromagnetic connection point, 5
, 10 cavities. Agent Patent Attorney Yoshihiro Hachiman 61

Claims (1)

[Claims] A first microstrip line with one end electromagnetically open or short-circuited and the other end serving as a signal input/output end with a characteristic impedance of Z_1; or one end serving as a signal input/output end on one plate surface of the dielectric substrate; Yes, the characteristic impedance is Z_
1 and this second microstrip line
a third microstrip line extending to the other end of the microstrip line, the tip of which is electromagnetically open or short-circuited, and has a characteristic impedance of Z_2; On the plate surface, the first
One end is electromagnetically open or short-circuited and the other end is orthogonal to the first microstrip line at the point where the microstrip line is electromagnetically short-circuited and is electromagnetically open at the intersection. A first slot line is located 1/4 wavelength away from the intersection and has a characteristic impedance of Z_2, and a first slot line is extended to the other end of the first slot line, the tip of which is a signal input/output end and has a characteristic impedance of Z_3. or a second slot line that is within the third microstrip line and is perpendicular to the third microstrip line at a position spaced 1/4 wavelength from the other end of the second microstrip line; A third slot line is formed in which one end is electromagnetically open or short-circuited so as to be electromagnetically open at the intersection, and the other end is a signal input/output end and has a characteristic impedance of Z_3. , and characteristic impedances Z_1, Z_2, and Z_3 are selected to approximately satisfy Z_2^2=Z_1・Z_3.