JPH0134482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave integrated circuit in which the characteristics of a bent portion of a coplanar line having two parallel slits made of a dielectric substrate and a metal film are improved.

FIG. 1 shows an example of a conventional circuit of this type, and FIG. 2 shows a lateral cross-section thereof. In the figure, 1 is a dielectric substrate such as alumina or Teflon (registered trademark), 2 and 3 are ground conductors, 4 is a center conductor, 5 is a metal wire connecting ground conductors 2 and 3, and 1, 2, 3 are ground conductors. And two parallel slits 6a, 6b are formed from 4.

The operation of this microwave integrated circuit as a mode filter will be briefly explained using FIG.

There are two types of modes that propagate easily through these two parallel slits 6a and 6b. One of them is an odd mode whose electric field is shown by a solid arrow in the figure, and the other is an even mode whose electric field is shown by a broken line arrow in the figure.
Since it is a TEM wave and the even mode radio wave is a TE wave, a magnetic field component exists in the traveling direction in the even mode.

Assuming that the radio waves in the two modes described above propagate from the left in Figure 1, first, the odd mode radio wave is a TEM wave, so the metal wire 5 stretched perpendicular to the direction of travel and the magnetic field become parallel. Therefore, the odd mode radio waves are not affected by the metal wire 5 and propagate rightward. On the other hand, since even mode radio waves are TE waves, the magnetic field component is
Since it is perpendicular to the metal wire, current flows through the metal wire and the impedance becomes close to a short circuit at the metal wire location. Therefore, most of the even mode radio waves are reflected by the metal wire 5 and do not propagate to the right.

As described above, among the odd mode radio waves and even mode radio waves coexisting in the two parallel slits, only the even mode radio waves are reflected by the metal wire, and the circuit shown in Figure 1 operates as a mode filter. .

However, in conventional microwave integrated circuits like the one shown in Figure 1, work such as bonding or soldering is required to install metal wires, so short-circuit surfaces must be fabricated with high precision and reproducibility. There were some drawbacks that made it difficult. In addition, there was a drawback that the work time was long and the cost was high. Furthermore, when using semiconductors such as mixers and switches, it may be desirable for the ground conductor 2 and the ground conductor 3 to be separated in terms of direct current, and in such cases there is a drawback that they cannot be used. .

On the other hand, FIG. 3 shows a general circuit in which two parallel slits have a bend, and 9 is the bend. In the bent portion 9, the curvature of the inner slit and the outer slit are different, and the slit lengths of the bent portion are different, resulting in a phase difference. Therefore, if a near-mode radio wave is applied from the left side of Figure 3 and propagated to the lower right of Figure 3,
A part of the input power as an odd mode is converted to an even mode, and as a result, reflection increases at the bend, which lowers the so-called power passing efficiency, and also changes the frequency characteristics of the passing efficiency. However, there were drawbacks such as ripples.

In order to eliminate these drawbacks, this invention
The total length is approximately 1/2 on the back side of the board with two parallel slits.
A metal strip with two wavelengths is placed perpendicularly across two parallel slits at both ends of the curved portion to reflect only even-mode radio waves.The drawings will be described in detail below.

FIG. 4 shows an embodiment of this invention, and FIG.
-A cross section is shown. In the figure, reference numeral 7 denotes metal strips provided at one end and the other end of the bent portion 9 on the back side of the substrate.

The total length of this metal strip 7 is set to approximately 1/2 wavelength at the center frequency at which even modes are desired to be suppressed.

As in FIG. 1, it is assumed that even mode and odd mode radio waves propagate from the left direction. Since the odd mode is a TEM wave as described above, by making the width W of the metal strip 7 narrow, the odd mode radio wave propagates rightward without being significantly coupled to the metal strip. However, at the bent portion 9, the even mode radio waves generated due to the different curvatures of the two slits have a magnetic field component as described above, and thus are coupled to the metal strip. At this time, by setting the total length of the metal strip 7 to 1/2 wavelength and leaving both ends open, the metal strip operates as a band rejection filter.
The even mode radio waves generated by the mode conversion at
It is reflected by one metal strip 7b, and the fourth
It does not propagate toward the lower right of the figure. further reflected,
The even mode radio wave that tries to return to the left in Figure 4 is
Since it is reflected by the other metal strip 7a, it does not go out to the left in FIG. In this way, the metal strips 7a and 7b temporarily confine the even mode generated by the mode conversion of the bent portion 9, and then the even mode is converted into an odd mode and then propagated as an odd mode. It is now possible to use two metal strips 7
If the interval between a and 7b is set so that resonance does not occur, reflections due to mode conversion from odd mode to even mode at the bend 9 will not increase.

Furthermore, although the above description does not limit the case surrounding the dielectric substrate having two parallel slits,
In particular, the invention may also be used in the case of providing a dielectric substrate with two parallel slits in the waveguide, an example of which is shown in FIGS. 6 and 7. FIG. 6 is a diagram seen from the top of the dielectric substrate, and FIG. 7 is a diagram showing a cross section of the dielectric substrate.
In the figure, 8 indicates the tube wall of the waveguide. In the figure, the tip of the metal strip 7 on the back side of the two parallel slits is bent because of the size limitations of the waveguide.
This is to make it the wavelength.

As described above, in the microwave integrated circuit according to the present invention, the metal strip provided on the back side of the two parallel slits can suppress the reflection caused by the even mode occurring at the bent portion.

Also, if this metal strip is made using normal photo-etching like the two slits on the back side, it has the advantage of being able to position with better precision and reproducibility than conventional metal wire bonding.
Furthermore, since it is made by etching, it has the advantage of being low cost and suitable for mass production.

In addition, by avoiding direct connection to the ground conductors that make up the two slits, it is possible to apply bias voltage to semiconductor devices such as mixers and switches without creating a direct current short circuit between the two ground conductors as in the past. It also has the advantage of being possible.

[Brief explanation of drawings]

1 to 3 are diagrams showing an example of a conventional microwave integrated circuit of this type, FIGS. 4 and 5 are diagrams showing an embodiment of the present invention, and FIGS. 6 and 7 are diagrams showing an example of a conventional microwave integrated circuit of this type. FIG. 3 is a diagram showing another embodiment according to the present invention. In the figure, 1 is a dielectric substrate, 5 is a metal wire, 6 is two parallel slits, 7 is a metal strip, and 9 is a metal wire.
is a bend. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. A metal film is provided on one surface of a dielectric substrate, and two slits parallel to each other are provided on this metal film, and a curved part is formed to form a coplanar line, and a coplanar line is formed by the above two slits. A microwave integrated circuit is used as a transmission line by exciting an odd-mode electromagnetic field in a coplanar line, in which a metal whose total length is approximately half a wavelength is placed on the other surface of the dielectric substrate at both ends of the bent portion. A microwave integrated circuit characterized in that a strip is provided so as to straddle the two slits perpendicularly.