JPH05299901A - Circularly polarized wave device - Google Patents

Abstract

PURPOSE:To maintain an excellent circularly polarized wave characteristic at a required band with simple configuration by connecting circularly polarized waveguides side by side so that a direction of a polarized wave giving a long guide wavelength of one waveguide and a direction of a polarized wave giving a short guide wavelength of other waveguide are coincident with each other. CONSTITUTION:Parts of axial lengths L1, L2 of a circular waveguide are decreased by h1, h2 respectively in the direction X. A step difference is provided in the inside of the circular waveguide to differentiate a propagation speed of a radio wave in the X polarized wave component in the direction X and in the Y polarized wave component in the direction Y. Two waveguides whose guide wavelength for orthogonal polarized waves is changed are employed and they are connected so that the direction of the polarized wave with longer guide wavelength of one waveguide and the direction of the polarized wave with shorter guide wavelength of the other waveguide are coincident with each other, then the two circular polarized wave devices are connected together in which the frequency characteristics of a phase difference of two polarized waves are opposite to each other. Thus, the phase difference between the two orthogonal polarized waves caused when a radio wave passes through the two circular polarized wave devices has a flat characteristic with respect to the frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circular polarizer having good circular polarization characteristics in a wide band or two different frequency bands.

[0002]

2. Description of the Related Art When a circularly polarized wave is generated in a horn antenna used as a primary radiator of a reflector antenna or an element antenna of an array antenna, the phase difference between two orthogonal polarized waves is just 90 degrees. A circular polarizer is used in which the shape of the waveguide is changed or a dielectric or the like is inserted inside the waveguide. Specific examples are shown below.

FIG. 11 is a diagram showing a circular polarizer which generates a circular polarized wave by the phase difference between two orthogonal polarized waves.
(A) is a view seen from the waveguide opening, and (b) is a cross-sectional view taken along the waveguide axis. In FIG.
Since the circular waveguide of a circular polarizer has a part of the inner diameter that is different in the x-direction and the y-direction, the polarization component that has an electric field in the y direction that is greater than the guide wavelength of the polarization component that has the electric field in the x direction. The in-tube wavelength of becomes larger, and the phase of the y-polarized wave appears to be delayed compared with the x-polarized wave when the radio wave passes. Where distance L
Is set so that the phase difference between the two polarized waves is 90 degrees, the P direction or the Q direction (45 degrees with respect to the x and y directions) is set.
Circularly polarized waves can be generated when an electric field having a polarized wave (in a tilted direction) is input. In this case, the circularly polarized waves generated when the polarized waves in the P direction and the polarized waves in the Q direction are input have a relationship of mutually opposite polarized waves.

As a method for making the phase difference between two orthogonal polarized waves 90 degrees in this way, in addition to the above-mentioned example, a method of inserting a dielectric into the waveguide or a waveguide of metal screws is used. There is a method of projecting inward, but these methods can set the frequency characteristics optimally at a certain specific frequency, but maintain good circular polarization characteristics in a wide band because the wavelength inside the tube has frequency characteristics. Hard to do. For example, it is important from the standpoint of cost, etc. to share transmission / reception for antennas for satellites and for earth stations, but it is common that the transmission frequency and the reception frequency are relatively far apart, so that a wideband circular polarization is used. In some cases, wave instruments cannot be configured.

Therefore, a method is known in which circularly polarized waves are generated by connecting two waveguides having different phase characteristics (Japanese Patent Laid-Open No. 3-220901). That is,
As shown in FIG. 12, in the first waveguide 91a, the circular waveguide is contracted in the x direction, and in the second waveguide 91b, metal screws are arranged in the xz plane, and these two waveguides are arranged. A broadband circular polariser is constructed by connecting the tubes. FIG. 13 shows the phase difference of the y polarization when the x polarization is used as a reference in this case. The first waveguide has a characteristic that it becomes α at the frequency f0 and the phase difference decreases as the frequency increases. The second waveguide has a frequency characteristic opposite to that of the first waveguide, and the phase difference that was γ at the frequency f0 has the characteristic of increasing as the frequency increases. The sum of the phase characteristics becomes flat.

Circular polarizers having different phase characteristics are
The first waveguide is formed by deforming the waveguide shape, or the second waveguide is formed by using a tuning screw made of a dielectric material or a metal screw. However, a waveguide using a dielectric is not preferable for use in a place where the environment changes drastically or when transmitting and receiving high-power electromagnetic waves, because the characteristics of the dielectric easily deteriorate.
Further, a waveguide using a tuning screw has difficulty in tuning, and if tuning is incomplete, there are disadvantages such as power loss, leakage, and spark generation. Further, in such a circular polarizer, since two different waveguides are connected, it is difficult to design and manufacture.

[0007]

As described above, in the conventional circular polarizer having a combination of different phase characteristics, the dielectric and the metal screw are used, so that the environmental resistance and the adjustment are troublesome. Met. Moreover, since different circular polarisers were combined, the effort of designing and manufacturing was complicated.

The present invention solves the above problems,
It is an object of the present invention to provide a circular polarizer having a simple structure capable of maintaining a good circular polarization characteristic even in the antenna for both transmission and reception.

[0009]

In order to solve the above-mentioned conventional problems, the present invention has, in the first invention, means for changing the guide wavelength for one of the orthogonal polarizations. A circular polarizer in which at least two waveguides are connected to each other, wherein a direction of a long-wavelength polarization in one of the waveguides and a direction of a short-wavelength polarization in the other waveguide are set. They are connected so that they match.

According to the second aspect of the invention, a waveguide having a means for changing the guide wavelength for one polarization of the orthogonal polarizations and an orthogonal polarization separation connected to the waveguide. A circular polarizer having a demultiplexer, wherein the means for changing the in-tube wavelength has a pass phase difference of 270 degrees in a lower frequency band and a pass phase difference of a higher frequency band in two different frequency bands. The demultiplexer for orthogonal polarization separation is set to 90 degrees, and the circular polarization components of the two different frequency bands are separately input and output as orthogonal polarizations.

[0011]

According to the first aspect of the present invention, by using two waveguides in which the waveguide wavelengths of the orthogonal polarizations are changed, the direction of the polarization with the longer waveguide wavelength of one waveguide and the waveguide of the other waveguide are used. By connecting the waveguides so that the directions of polarized waves with short wavelengths in the waveguide match,
It seems that two circular polarizers are connected in which the frequency characteristics of the phase difference of one polarization are opposite to each other. Therefore, the phase difference between the two orthogonally polarized waves generated when the radio waves pass through the two circular polarisers can be set to have a flat characteristic with respect to frequency. Here, the phase difference between the two polarized waves can be maintained at 90 degrees in the wide band, and good circular polarization characteristics can be maintained in the wide band.

Further, in the second invention, in the waveguide in which the guide wavelengths of the orthogonal polarizations are changed, the fact that the phase difference between the two orthogonal polarizations decreases with the frequency is utilized, and The phase difference is set to 270 degrees at a low frequency fa and 90 degrees at a high frequency fb. An orthogonal polarization demultiplexer (OMT) is connected to this circular polarizer, and f
Circular polarization components in the same direction can be generated by inputting and outputting polarization components orthogonal to each other at a and fb.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a horn antenna according to an embodiment of the first invention. The horn antenna 1 is
The horn 2, the waveguide 3, and the waveguide converter 4 are sequentially connected. The horn antenna 1 is made of a conductive metal, or a conductive material is used inside the waveguide. The waveguide converter 4 converts, for example, a circular waveguide into a rectangular waveguide.

In the waveguide 3, the first waveguide 3a and the second waveguide 3b face each other and are connected by an opening face, and a step is provided in one direction inside the circular waveguide. FIG. 2 is a diagram showing the first waveguide 3a and the second waveguide 3b. here,
Assuming that the axial direction of the waveguide is the z-axis, the vertical direction is the x-axis, and the direction orthogonal thereto is the y-axis (the same applies below), x-
y is a front view, (b) is an xz vertical sectional view, and (c) is a yz horizontal sectional view. In the region of the axial lengths L1 and L2 of the circular waveguide 3, the x direction is h1, h2.
Just shorten it. By providing the step inside the circular waveguide in this way, the propagation speeds of two orthogonal polarization components, that is, the x polarization component in the x direction and the y polarization component in the y direction, are different. Come on. FIG. 3 shows h of two polarization components in the fundamental mode (TE11 mode) in this case.
It is a figure which shows the cutoff wavelength (lambda) c characteristic with respect to / r. As is clear from FIG. 3, as h / r increases, the cutoff wavelength becomes longer in the x polarization and becomes shorter in the y polarization. Therefore, the in-tube wavelength at a certain frequency is larger in the y-polarized wave than in the x-polarized wave, and when two orthogonal polarized waves pass through this waveguide, the x-polarized wave is more phase-shifted than the y-polarized wave. , The phase difference between the x polarization and the y polarization can be set to a desired value by arbitrarily setting the lengths L1 and L2 in FIG. The reason why the inside diameter of the region of length L2 is different from that of the region of length L1 is to improve the matching as a transmission line by adjusting the characteristic impedance of the two regions, as shown in FIG. Thus, a taper may be provided.

The first waveguide 3a and the second waveguide 3b configured as described above are rotated 90 degrees about the z-axis and are connected to each other at their opening surfaces. Specifically, as shown in FIG. 5, the first waveguide 3a is provided with a step in the x direction, whereas the second waveguide 3b is provided with a step in the y direction orthogonal thereto. Are connected in a positional relationship.

FIG. 6 is a diagram showing the phase difference between the radio waves of the y polarization and the phase of the x polarization when the radio waves pass through the first waveguide 3a and the second waveguide 3b. In FIG. 6, in the first waveguide 3a, since the y-polarized wave advances later than the x-polarized wave,
At a certain frequency f0, the difference in the amount of phase becomes α (a positive value). Further, in the second waveguide, the y-polarized wave is advanced compared to the x-polarized wave, so that the difference in the phase amount is β (negative value) at a certain frequency f0. First waveguide 3a and second waveguide 3
Both b have frequency characteristics, and the phase difference becomes smaller as the frequency increases. That is, y compared to x polarization
The absolute value of the phase difference between polarized waves becomes smaller. The phase difference when radio waves pass through both of these two waveguides has the characteristic shown in FIG. 6 by taking the sum of the phase differences of these two waveguides. At frequency f0, the phase difference is α
It becomes + β, and the frequency characteristic is relatively flat as compared with the case of individual waveguides. If the inclination of the phase difference depending on the frequencies of the first waveguide 3a and the second waveguide 3b is set to a value that is exactly positive and negative, the phase difference that does not depend on the frequency can be set. By setting this phase difference to 90 degrees, a circular polarizer having a good axial ratio characteristic in a very wide band can be realized. By setting the step h that shortens the inner diameter of the circular waveguides of the first waveguide 3a and the second waveguide 3b and the length L of the region, the first waveguide 3a and the second waveguide 3a It is possible to make the inclination of the phase difference depending on the frequency of the wave tube 3b close to a value having the same absolute value by reversing positive and negative. With the above configuration, it is possible to realize a circular polarizer having a wide band and good circular polarization characteristics. Therefore, it is very effective as a circular polarizer used for an antenna for both transmission and reception, an antenna for a wide band, and the like. Further, since a region for improving the matching property can be provided, it is possible to realize the one having excellent reflection characteristics. The circular polarizer of the present invention can be easily manufactured with high precision by a die-cast molding method in which a molten metal is attached to a mold and the mold is pulled out after the metal is solidified.
Furthermore, since it can be composed entirely of metal without the use of dielectrics, etc., even for high-power antennas where heat generation is a problem, there is no deterioration of the characteristics due to heat, so the effect is great, and the projection inside the waveguide is large. Since there is no part to do, it is also excellent in strength.
Therefore, it is effective for feeding power to a satellite-mounted antenna in which environmental resistance is a problem.

As the first waveguide and the second waveguide, a method of changing the waveguide wavelength of orthogonal polarization by providing a step in the inner diameter of a circular waveguide in one direction was used. Therefore, even if the in-tube wavelength of the orthogonal polarization is changed, the same effect can be obtained. For example, as shown in FIG. 7, a step may be provided only on one side inside the circular waveguide. Further, instead of the circular waveguide, a rectangular waveguide or an elliptic waveguide having different vertical and horizontal sizes of the waveguide cross section may be used.

Next, an embodiment of the second invention will be described. FIG. 8 is a diagram showing the configuration of the horn antenna according to the embodiment of the second invention. As shown in FIG. 11, the horn antenna 1 is composed of a waveguide 3, an OMT (orthogonal polarization separation duplexer) 5, and waveguide converters 4 and 4'connected to each other.

The circular waveguide 3 is provided with a step inside the waveguide as in the first invention. The propagation velocity of the radio wave passing through this waveguide is as described above, but in the present embodiment, by selecting any value for h1, h2, L1, and L2, the y-polarized wave with respect to the x-polarized wave is selected. As shown in FIG. 9, the phase difference is set to φa at the frequency fa and to φb at the frequency fb. Here, for example, φa = 270 degrees and φb = 90 degrees are set, and the frequency fa
When the input or output polarization direction is the P direction (direction rotated by 45 degrees from the x direction to the y direction), the input or output polarization direction is the Q direction when the frequency is fb (the x direction is the negative y direction). This antenna can transmit (or receive) circularly polarized waves of the same polarization at two frequencies fa and fb. φa and φb are 450
.Degree. And 270.degree., 630.degree. And 450.degree., Etc. are possible, but φa = 270 when considering to widen the band where the circular polarization characteristic can be obtained.
It is desirable that φb = 90 °. By connecting the OMT 5 to the waveguide 3 having such a configuration, P and Q
Input and output of polarized waves in any direction. FIG. 10 is a diagram showing the configuration of the OMT 5. The opening surface of the OMT 5 is connected to the opening surface of the waveguide 3 so that the P axis of the waveguide 3 is aligned with the u axis of the OMT 5 and the Q axis is aligned with the v axis. As a result, the radio wave polarized in the P direction is directly output (input) to the port A, and the radio wave polarized in the Q direction is propagated to the port A direction due to the cut-off frequency or less by the conductor plate 6. Instead, they are coupled by the coupling slot 7 and input (output) to the port B. Therefore, port A has frequency fa and port B
If the input and output of the frequency fb is performed, the entire antenna can transmit and receive circularly polarized waves of the same polarization at these two frequencies, and good circularly polarized wave characteristics can be realized at either frequency.

The circular polarizer shown above is particularly effective when the transmitting and receiving frequencies are widely separated and it is difficult to realize a broadband circular polarizer over the entire band between transmitting and receiving. Is. The present invention is also effective when the transmission output of a satellite antenna or the like is very large. The reason is,
Since the transmission and reception radio waves are orthogonal to each other at the time of input / output, the coupling is small, and OMT can provide a considerable isolation between transmission and reception. Therefore, it is possible to reduce the size of the filter for blocking the power flowing from the transmitter side to the receiver side, reduce the size and weight of the entire antenna, and reduce the power loss, which is very convenient. ..
Further, according to the present invention, it is possible to realize both the right-handed circular polarization and the left-handed circularly polarized wave at two frequencies with the same configuration, which is very effective.

In the above description of the embodiment,
As a waveguide, the circular waveguide is described as an example in which the size of a part of the circular waveguide is reduced. However, if a phase difference occurs between two orthogonal polarizations and the phase difference changes with frequency, Other than this may be used. For example, a rectangular waveguide whose vertical and horizontal sizes are changed or an elliptical waveguide can be used.

Furthermore, when the polarization directions of the circularly polarized waves are opposite at two different frequencies, the OMT is not necessary and the structure is simple. In this case, the phase difference φ at the low frequency fa is set by setting the shape of the waveguide appropriately.
a = 270 degrees, phase difference φb = 9 at high frequency fb
It may be 0 degree.

[0024]

According to the first aspect of the present invention, a circular polarizer having good circular polarization characteristics in two different frequency bands such as a wide band and transmission and reception can be realized with a simple structure. Furthermore, it is easy to provide a region for improving matching, and a circular polarizer having good reflection characteristics and small power loss can be configured. Its production is easy by a method such as die casting. Since it can be made entirely of metal, it is effective as a component of a high-power antenna such as a satellite-borne antenna where heat generation is a problem.

Further, according to the second aspect of the present invention, since the radio waves for transmission and reception can be separated by the orthogonal polarization by connecting the OMT, a filter for preventing the transmission power from sneaking into the receiver side is provided. It can be made small, and it is very effective for a satellite-mounted antenna or the like, which is important in terms of cost, etc., because the size and weight of the whole antenna are small.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a configuration of a horn antenna according to the first invention.

FIG. 2 is a diagram showing a circular waveguide in FIG.

3 is a diagram showing a cutoff wavelength λc characteristic with respect to a cross-sectional shape of the circular waveguide in FIG.

FIG. 4 is a view showing another embodiment of the circular waveguide according to the first invention.

5 is a diagram showing a positional relationship when two circular waveguides in FIG. 1 are connected.

FIG. 6 is a diagram showing a phase difference of orthogonal polarization when a radio wave passes through a circular waveguide according to the first invention.

FIG. 7 is a view showing another embodiment of the circular waveguide according to the first invention.

FIG. 8 is a diagram showing an embodiment of a configuration of a horn antenna according to the second invention.

9 is a diagram showing a phase difference of orthogonal polarized waves when passing through the circular waveguide in FIG.

10 is a diagram showing OMT in FIG. 11. FIG.

FIG. 11 is a diagram showing a circular polarizer in a conventional antenna.

FIG. 12 is a diagram showing a conventional circular polarizer in which two waveguides are connected.

13 is a diagram showing a phase difference of orthogonal polarization when passing through the waveguide in FIG.

[Explanation of symbols]

 1 Horn Antenna 2 Horn 3 Circular Waveguide 3a First Waveguide 3b Second Waveguide 4, 4'Waveguide Converter 5 OMT 6 Conductor Plate 7 Coupling Slot A, B Port

Claims (2)

[Claims] 1. A circular polarizer in which at least two waveguides having means for changing the guide wavelength for one of the orthogonal polarizations are connected to each other, wherein one of the waveguides is a circular polarizer. A circular polarizer characterized in that a polarization direction having a long guide wavelength and a polarization direction having a short guide wavelength in the other waveguide are connected so as to coincide with each other. 2. A circular polarization having a waveguide having a means for changing the in-tube wavelength with respect to one of polarizations orthogonal to each other and a demultiplexer for orthogonal polarization separation connected to the waveguide. In the wave filter, the means for changing the guide wavelength changes the pass phase difference of the lower frequency band of two different frequency bands by 270 degrees,
The pass phase difference of the higher frequency band is set to 90 degrees, and the orthogonal polarization separation duplexer separately inputs and outputs the circular polarization components of the two different frequency bands as orthogonal polarizations. A circular polarizer characterized in that