JPH04268802A - Wavegiude directional coupler - Google Patents

Abstract

PURPOSE:To enable the coupling of E-plane to E-plane, and to facilitate working by making the intube lengthes of a first waveguide to be main line of the trans mission of an electromagnetic wave and a second waveguide to be coupled with the first waveguide different values. CONSTITUTION:The intube length lambdag of a rectanguladr waveguide can be set by size of the major side of the waveguide. Namely, in the case that the size of the major sides of the waveguides #1 and #2 are not equal, if, providing distance between coupling ports C1 and C2 is L, the intube length lambda1 of the first waveguide is made L=lambdag1(2n+1)/4, and the intube length lambdag2 of the second waveguide is made L=lambdag2(2n+1)/4, the phase difference of pi is caused between the electromagnetic wave of p1 C1 p4 and the electromagnetic wave of p1 C2 p4, and both electromagnetic waves cancel each other. On the other hand, the phase difference of 2npi is caused between the electromagnetic wave of p1 C1 p3 and the electromagnetic wave of p1 C3 p3, and since it is the same as the phase difference of '0', a coupled electromagnetic wave appears to a port p3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide directional coupler, and more particularly to a so-called reverse coupling type waveguide directional coupler.

0002

[Prior Art] A waveguide directional coupler is used in the microwave band.
Although directional couplers in the millimeter wave band are widely used and have various configurations, conventional techniques for two types directly related to the present invention will be described below.

FIG. 3 shows the commonly used E-plane 1/4
This is a perspective view of a wavelength type directional coupler. In the figure, #1 is the first waveguide, #2 is the second waveguide, p1, p2, p3,
p4 is a port, c1 and c2 are coupling ports, and waveguides #1 and #2 have the same inner wavelength λg.
The distance between c1 and c2 is set to be equal to λg/4, or 3/4·λg if the wavelength in the tube is very short. If an electromagnetic wave is transmitted from port p1 to port p2, the electromagnetic wave that enters waveguide #2 from c1 and travels toward p4 is in phase with the electromagnetic wave that enters waveguide #2 from c2 and travels toward p4. overlap.

On the other hand, p enters waveguide #2 from c1.
The electromagnetic wave that travels toward p3 and the electromagnetic wave that enters waveguide #2 from c2 and travels toward p3 are π/
The phase is delayed by 2, and after entering waveguide #2, c2 → c1
In the meantime, the phase is further delayed by π/2, and they overlap with a total phase delay of π. If the degrees of coupling of c1 and c2 are equal to each other, the electromagnetic wave traveling toward p3 becomes 0. FIG. 5 is a diagram showing the frequency characteristics of the degree of coupling of the directional coupler shown in FIG. 3. However, in this case, the distance between the coupling ports is 3λg/4. In FIG. 5, S31 represents the bond from p1 to p3, S
41 indicates the bond from p1 to p4. S41 is -20d
Although B is kept at a constant value, S31 exhibits extremely large attenuation near the tuning frequency, exhibiting the characteristics of directional coupling.

Similar to the attenuation of S31, even if there is reflected power from p2 toward p1 in waveguide #1, its influence does not appear on p4. in this way,
Although the directional coupler shown in FIG. 3 is commonly used, the problem remains that the coupled power cannot be output to p3. However, in terms of the overall configuration of the device, there are cases where it is more convenient to extract the coupled power to the p3 side, and in such cases, a reverse coupling type directional coupler is used.

FIG. 4 is a perspective view showing the configuration of a conventional reverse coupling type directional coupler. In the figure, the same reference numerals as in FIG. The E plane of waveguide #1 is coupled to the H plane of waveguide #2. p1→c1
The paths →p4 and p1→c2→p4 have the same length, but since c2 is coupled to the opposite side of the H plane to c1, the phase is delayed by π/2 due to this coupling, and the path toward p4 The electromagnetic waves traveling in the opposite direction cancel each other out and attenuate. On the other hand, the electromagnetic wave traveling toward p3 has a phase difference of π/2 on its path (a round trip of λg/4), and further π/2 due to coupling.
A phase difference of 2 occurs, resulting in the same phase, and the combined electromagnetic wave is output to p3.

[0007]

[Problems to be Solved by the Invention] The problem to be solved is that in the configuration of a conventional reverse coupling type directional coupler as shown in FIG. The problem is that it is difficult to process in some cases.

In other words, there are waveguides whose wall surfaces of the grooves in the metal block are E-plane and waveguides whose wall surfaces are H-plane. There is a problem in that a bend must be used. It is an object of the present invention to solve the above-mentioned problems in conventional waveguide directional couplers and to construct an inversely coupled directional coupler using E-plane to E-plane coupling.

[0009]

[Means for Solving the Problems] The present invention provides a first waveguide serving as a main line for electromagnetic wave transmission, and a second waveguide coupled to the first waveguide. The most important feature is that the values are different from each other.

0010

[Operation] The internal wavelength λg of the rectangular waveguide can be arbitrarily set depending on the dimension of the long side of the waveguide, with the free space wavelength as the lower limit. Therefore, assuming that the long sides of waveguides #1 and #2 are not the same in the configuration of FIG. 3, the distance L between c1 and c2 is
, the inner wavelength λg1 of the first waveguide is L=λg1(2
n+1)/4, and the inner wavelength λg2 of the second waveguide is L.
=λg2(2n-1)/4, then p1→c1→p4
There is a phase difference of π between the electromagnetic waves of p1→c2→p4 and they cancel each other out, and there is a phase difference of 2nπ between the electromagnetic waves of p1→c1→p3 and the electromagnetic waves of p1→c2→p3. Since a phase difference of 2nπ is the same as a phase difference of 0, the combined power comes out to port p3.

[0011]

[Embodiment] FIG. 1 is a sectional view showing one embodiment of the present invention, and assuming the perspective view of FIG. 3, it shows a cross section taken by a plane parallel to the H-plane of the waveguide and including coupling ports c1 and c2. . In FIG. 1, the same symbols as in FIG. 3 indicate the same or corresponding parts, and λg
1 is the internal wavelength of waveguide #1, and λg2 is the internal wavelength of waveguide #2. While the electromagnetic wave travels through waveguide #1 from c1 to c2, the phase is delayed by (2n+1)π/2 and c
2 to waveguide #2, connects to waveguide #2 at c1, and travels through waveguide #2 to c2.
The phase is delayed by /2. That is, the electromagnetic waves heading toward p4 are delayed in phase by π at c2, overlap, and are sufficiently attenuated.

On the other hand, considering the electromagnetic wave heading toward p3, the electromagnetic wave that travels in waveguide #1 from c1 to c2, couples to waveguide #2 at c2, and returns to c1 is (2n+1)π/
The phase is delayed by 2+(2n-1)π/4=2nπ, and this phase lag is equal to 0 phase lag, so it overlaps with the electromagnetic wave directly coupled to waveguide #2 at c1 in the same phase and passes through port p.
It appears in 4.

FIG. 2 is a diagram showing frequency characteristics of coupling by the circuit shown in FIG. 1, and is indicated using the same reference numerals as in FIG. 5. However, the long side dimension of waveguide #1 is 5.7 mm, c1,
Distance L between c2 = 9.78 mm, long side dimension of waveguide #2 3.71 mm, λg1 = 4L/5, λg2 = 4L/3
This is the characteristic when set to . Coupling S31 inputting from port p1 and outputting to port p3 is maintained at approximately -20 dB, whereas coupling S41 outputting to port p4 exhibits extremely large attenuation at the center frequency, making it difficult to use an inversely coupled directional coupler. Configure. Note that the width of the long side of the waveguide #2 may be made to be the same as the width of the long side of the waveguide #1 after passing through the tapered portion on the outside after passing through the coupling portion, as shown in FIG.

[0014] In the above-mentioned embodiment, the case where there are two connection ports is explained, but just as the structure shown in FIG. 3 has three or more connection ports, the structure shown in FIG. The configuration may include three or more coupling ports. In addition, in order to change the wavelength within a waveguide, there are other methods such as inserting a dielectric material in addition to changing the dimensions of the long side, and the present invention uses such a method to adjust the wavelength inside the waveguide. It can also be applied in cases.

[0015]

As described above, the present invention has the advantage that an inverse directional coupler can be realized with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing the frequency characteristics of the coupling of the circuit shown in FIG. 1;

FIG. 3 is a perspective view showing an E-plane quarter-wave directional coupler.

FIG. 4 is a perspective view showing a conventional reverse coupling type directional coupler.

FIG. 5 is a diagram showing the frequency characteristics of the coupling of the circuit shown in FIG. 3;

[Explanation of symbols]

#1 First waveguide #2 Second waveguide p1, p2, p3, p4 Ports c1, c2, respectively
connection port respectively

Claims (1)

[Claims] Claim 1: The electromagnetic waves to be transmitted are connected to the electromagnetic waves to be transmitted through coupling ports provided at a predetermined interval on the wall surface parallel to the TE10 mode electric field of the first waveguide, which has an input port and an output port and serves as the main line for electromagnetic wave transmission. In a waveguide directional coupler having a second waveguide to be coupled, the dimension of the long side of the second waveguide is smaller than the dimension of the long side of the first waveguide, and the The inner wavelength of the first waveguide is λg1, and the wavelength of the second waveguide is λg1.
When the internal wavelength of the waveguide is λg2, the spacing between the coupling ports should be equal to (2n+1)λg1/4 (n is any positive integer) and equal to (2n-1)λg2/4. A waveguide directional coupler characterized in that it is set to