JP3472822B2 - Variable polarization system, polarization diversity system, and polarization modulation system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization variable system, a polarization diversity system and a polarization modulation system using an array antenna provided with a C-shaped slot pair.

Since the Ku band has been used mainly in fixed satellite communication such as VSAT, the frequency is shared by linearly polarized waves. Recently, the use of this frequency band in automobiles and moving bodies such as helicopters has been examined, but in order to prevent interference with existing systems,
The use of linear polarization is desired. In order to secure communication in a mobile unit, polarization tracking according to the movement of the mobile unit is necessary, and a polarization variable function for that purpose is desired.

[0003]

2. Description of the Related Art Conventionally, the Ku band has been used in fixed satellite communication. In that case, the frequency was shared by the horizontal polarization and the vertical polarization of the linear polarization, and the frequency was effectively used. recent years,
The use of Ku band in mobile communication is under study. In that case, it is desirable to use the linearly polarized wave by extending the conventional fixed satellite communication technology, but since the attitude changes due to the roll and pitch of the moving body, tracking for beam capture is naturally performed. However, there is a problem that the transmission / reception level decreases unless the linear polarization of transmission / reception of the moving body is tracked in the vibration direction of the propagating radio wave. To compensate for this, polarization tracking according to the movement of the mobile body is required.

On the other hand, the inventors of the present invention previously proposed a slot array antenna in which a C-shaped slot pair is divided and arranged (Japanese Patent Application No. 2000-119158).

The C-shaped slot pair used in the proposed slot array antenna is shown in FIG. The V-shaped slot pair 4 is arranged in the propagation direction by a length of 1/4 of the wavelength λg of the radio wave propagating inside the dielectric by feeding, and the inclination is with respect to the propagation direction of the radio wave (feeding direction). It is composed of a first slot 41 and a second slot 42 that have an angle of −45 degrees and 45 degrees. In order to obtain circularly polarized waves, the first slot 41 and the second slot 42 are paired with their directions orthogonal to each other and separated by a quarter of the guide wavelength λg.

FIG. 10 shows the types of C-shaped slot pairs. As shown in the figure, the combination of the slot 41 and the slot 42 is the pair A of (1), the pair B of (2), the pair C of (3),
There are four types of pair D in (4), and the feed wave is in the waveguide.
When propagating from the negative direction (lower side) of (axial direction), pair A and pair B shown in FIG. 9 generate right-handed circularly polarized waves, and pair C and pair D generate left-handed circularly polarized waves. When viewed from the inside of the waveguide, the slot intervals in the axial direction are all λg / 4, so that the reflected wave is canceled out. The radiated power is also the same. Therefore, even if these pairs are combined as an array element, the axially symmetric mode in the waveguide is maintained, and a slot pair that generates right-handed circular polarization and a slot pair that generates left-handed circular polarization are combined and polarized. Waves and directivity can be changed depending on the direction around the cylinder axis.

FIG. 11 is an explanatory view of the slot array antenna in which the slot pairs are divided in the circumferential direction in the proposed slot array antenna, FIG. 12 is an external view of the proposed slot array antenna 1, and FIG. 13 is the proposed slot array antenna. Two
FIG.

FIG. 11 (a) is a region formed by dividing a slot pair 4 having a V-shape for generating circularly polarized waves having mutually different rotation directions in the circumferential direction of the coaxial cylinder (two in this example). Shows the arrangement of. There are four types of combinations of slot pairs in which the rotation directions of circularly polarized waves are different: AC, AD, BC, and BD (A, B, C, and D are shown in (1) to (4) of FIG. 10). By feeding power from the coaxial line 8 at the lower end of the coaxial cylindrical slot array antenna shown in FIG. 11 (a), the rotation direction of the circularly polarized wave transmitted according to the azimuth angle is changed. In the example shown in (b), the boundary line 12 is φ = 0 degrees, and the boundary line 13 is φ =
180 degrees.

In the configuration of the slot array antenna 1 shown in FIG. 12, the same slot pairs A are arrayed over the entire surface, and a transmission / reception port (coaxial line) is provided at both the upper end and the lower end.
8 and 9 are provided. The right-handed circularly polarized signal S1 input to this antenna regardless of the azimuth direction is output to the coaxial line 8 side because the slot pair 4 is the pair A. However, the left-handed circularly polarized signal S2 is not output to the coaxial line 8 side because the slot pair 4 is the pair A. On the other hand, the pair A viewed from the coaxial line 9 becomes equivalent to the pair D that transmits and receives the left-handed circularly polarized wave, and outputs the left-handed circularly polarized signal S2 to the coaxial line 9 regardless of the azimuth direction. That is, if the incoming wave is circularly polarized and its rotation direction is known, the receiving port can be switched depending on the rotation direction.

Further, the slot array antenna 2 shown in FIG. 13 is a combination of the above-mentioned FIG. 11 and FIG. 12, in which the array of slot pairs is divided in the circumferential direction, and the transmission / reception indicated by symbols 8 and 9 at the lower and upper ends. Port (port P1, port P
2) is provided. As a result, when power is supplied from one of the ports, a circularly polarized wave with different rotation directions is output depending on the azimuth angle, and the output port changes according to the rotation direction of the received circularly polarized wave. In order not to disturb the coaxial mode of the feed wave, symmetrical C-shaped slot pairs are arranged in the circumferential direction. In addition, since the coaxial cylindrical slot array antenna with this C-shaped slot pair transmits and receives circularly polarized waves, the signal level is not affected by rotation in the polarization direction.

[0011]

As described above, the proposed coaxial cylindrical slot array antenna using the C-shaped slot pair was suitable for transmitting and receiving circularly polarized waves.
There is a problem that the polarization efficiency is reduced to ½ if the linear polarized wave transmission / reception is performed without assuming the linear polarized wave transmission / reception.

Further, as described above, the Ku band is mainly used for fixed satellite communication such as VSAT and is shared (multiplexed) with linear polarization depending on the polarization direction. This frequency band is also used for mobile communication. It is under consideration. However, there is a problem that the attitude of the mobile body changes, but it is difficult to track the polarization direction with a normal fixed linear polarization antenna.

The present invention provides a polarization variable system, a polarization diversity system, and a polarization modulation system using an array antenna having a square-shaped slot pair capable of tracking a change in the polarization direction of a linearly polarized wave. The purpose is to provide.

[0014]

FIG. 1 is a diagram for explaining the principle of the present invention, showing the direction of a magnetic current excited in a C-shaped slot pair during reception. Is circular polarization, B.
Shows four typical examples of the case of linear polarization. In the figure, 41 and 42 are slots forming a square-shaped slot pair.

In the V-shaped slot pair, the slot component perpendicular to the propagation direction of the waveguide serves as an excitation source, and the magnetic currents excited in the slots have the same horizontal magnetic current direction and opposite vertical magnetic current directions. Therefore, in FIG. As shown in, the direction of propagation in the waveguide changes according to the direction of circularly polarized wave of transmission and reception. In the case of reception, the left-handed polarized wave propagates upward and the right-handed polarized wave propagates downward.

On the other hand, since the linearly polarized wave corresponds to a superposition of left-handed polarized wave and right-handed polarized wave, if the array antenna provided with the C-shaped slot pair has a symmetric structure with respect to the ports, two ports are provided. However, the phase of the vibration differs depending on the direction of polarization. It can be understood that this is because the equivalent receiving position in the waveguide changes depending on the direction of the polarized wave, and the receiving phase difference changes due to the change in the position.

In the case of vertically polarized waves, the B.D. As shown in, the equivalent receiving position is understood to be the middle position of the C-shaped slot pair, but since the propagation direction is opposite, an opposite phase signal is output. The direction of the vertical magnetic current component of the slot excited by the horizontal polarization is B.I. As shown in (1), since it is in the opposite direction, it is considered that the equivalent receiving position is separated from the intermediate position of the slot pair by λg / 4, and is excited in the opposite phase. However, since the transmission directions are opposite, the signals propagated up and down eventually become in phase. Further, since the linearly polarized wave of 45 degrees at an angle is excited only on one side of each slot as shown in B of FIG. 1, each slot position is defined as a reception position (position λg / 8 apart from the intermediate position). It is considered that the phase difference between the output signals of the two ports is 90 degrees.

FIG. 2 is a diagram showing the waveforms of the propagating wave generated in each slot in the waveguide in the linearly polarized wave reception, the waveform of the composite wave, and the mathematical formulas of the upward and downward composite waves. Figure 2 (a) is a square-shaped 2 in the case of vertical polarization reception in Figure 1B above.
The wave propagating in the waveguide of the signal received in one slot is shown by the broken line, and the composite wave is shown by the solid line. From the equations for the upward and downward waves, it can be seen that the upward and downward waves have opposite phases from the polarities of the equation. ± λg from the center of the pair
The position of / 8 is the position of the slot, which is the receiving point of each slot. Figure 2 (b) shows the propagating wave (dotted line) and the composite wave (solid line) of the received signal of each slot in the waveguide in the case of horizontal polarization reception in Figure 1B above. It is a mathematical expression for waves, and in this case, it can be seen that the upward wave and the downward wave are in phase. The equivalent receiving point in this case can be regarded as a position λg / 4 from the center of the pair. Furthermore, when the vibration direction of the generalized polarization is at an angle α from the horizontal direction, the upward and downward combined waves can be expressed by a mathematical expression as shown in Fig. 2 (c). According to this, it can be seen that the phase difference β between the upward wave and the downward wave is 2α in total.

As described above, the present invention makes use of the characteristic that the circularly polarized wave that can be transmitted and received changes the direction of rotation of the circularly polarized wave depending on the direction of propagation in the feed waveguide. Polarization tracking is performed using the principle that the equivalent receiving position changes and the receiving phase difference also changes.

In the present invention, a phase shifter is provided at the output of the two ports of the array antenna having a symmetrical structure with respect to the port provided with the V-shaped slot pair, and the direction of the linearly polarized wave is changed in the direction of the antenna. Can also be configured to keep the vibration direction of linearly polarized waves constant.

In the present invention, it is also conceivable to use a parallel plate slot array antenna as the antenna having two symmetrical ports, in addition to the coaxial cylindrical slot array antenna. This antenna is flat and can be applied to the surface of a moving object.

Further, in the case of receiving the circularly polarized wave, the present invention can select the turning direction of the received circularly polarized wave by providing a switch between the output ports. Furthermore, when receiving general elliptically polarized waves, the axial ratio and long axis direction of the elliptically polarized waves being received can be measured from the ratio of the magnitudes of the received power at both ports and the phase difference. It is also possible to improve the S / N ratio of the received signal by performing maximum ratio combination.

According to the present invention, it is possible to construct a polarization diversity antenna sharing the antenna part or a polarization modulation antenna by giving the phase shifter a modulation function.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be implemented by using the above-mentioned proposed coaxial cylindrical slot array antenna (see FIG. 8) having the above-mentioned V-shaped slot pair. It can also be implemented using a flat array antenna.

FIG. 3 shows a parallel plate array antenna according to the present invention. Is a front view, B. Is a sectional view. In the figure, 10 is a parallel plate waveguide composed of conductors arranged on the front and back surfaces, 11 is a parabolic reflection wall formed at both upper and lower ends of the parallel plate waveguide 10, and 12 is a microstrip line 13. Power supply slot to connect, 13
Is a microstrip line connecting the power feeding slot and the port, 14 is a port 1 provided above and below, and ports 2 and 18 are semicircular reflecting walls. In addition, B. In the cross-sectional view of the figure, a dielectric 1 made of glass cloth Teflon, etc.
Two copper plates are attached to both surfaces of No. 5 to form a parallel plate waveguide. A large number of C-shaped slot pairs shown in FIG. 1 are arranged on the copper plate.

In this parallel plate array antenna, the transmission wave propagates in the direction including the two ports, and the radio wave in the direction perpendicular to it is collected at the focal point by the parabolic reflection wall. Such an operation extends the waveguide of the proposed coaxial cylindrical slot array antenna to a plane, and the function of collecting light in the same phase is achieved by the parabolic reflection wall instead of the radial waveguide. A slot is provided at the focal point, and it is guided to the microstrip line on the back surface by electromagnetic coupling. Further, as shown in FIG. 3, a reflection wall 18 is provided on the opposite side of the slot 12 from the parabolic reflection wall 11 so as to block a radio wave that directly goes to the C-shaped slot for radiation. The propagating wave is not in the TEM mode in the case of the coaxial cylindrical slot array antenna.

FIG. 4 is a diagram showing a configuration of connection between ports and polarization selection. 1 is a parallel plate array antenna with two ports whose structure of the antenna with a square-shaped slot pair is symmetrical with respect to the port, 16 is an adjustable phase shifter, or (c) of FIG. In, it is a fixed phase shifter due to line length.

The case of reception will be described. In the case of left-handed polarized light, A. As explained in Section 4, the output is only to the upper port as shown in Fig. 4 (a), and in the case of right-handed polarization, it is output only to the lower port as shown in Fig. 4 (b). In addition, the linearly polarized wave is output to both ports at the same level, but the horizontally polarized wave is received in the opposite phase as explained in B of Fig. 1 above, so the phase shift is performed as shown in Fig. 4 (c). Bowl 1
The output can be obtained by setting the phase shift at 180 in 180 degrees. Thus, when the direction of the linearly polarized wave to be received is an oblique angle α between the horizontally polarized wave and the vertically polarized wave, the phase shifter 16 shown in (e) of FIG.
The maximum output can be obtained by setting the phase shift amount β of 2α (rad).

On the contrary, from the relationship of FIG. 4 (e), the inclination angle α of the polarized wave can be detected from the angle β of the phase shifter that maximizes or minimizes the combined power.

An example of actual fabrication of the parallel plate slot array antenna according to the present invention will be described. The parallel-plate array antenna shown in FIG. 3 is formed by etching technology in which an array of square-shaped slot pairs 4 is formed on the front surface of a printed circuit board on which copper foil is laminated on both sides, and a feeding slot 12 is formed on the central axis of the rear surface. Then, both ends of the substrate are cut so that the parabolic reflection wall 11 is formed so that the power feeding slot is at the focal position. Next, a conductive tape was attached to all the formed outer peripheries, and the microstrip line 13 was overlapped on the power feeding slot 12 to prepare the device.

The parallel plate dielectric 15 has a relative permittivity of 2.17, a thickness of 1.5 mm, a uniform element slot size of 4.725 mm × 0.45 mm, and 31 array elements in the axial direction. , Element spacing is 10.18m which is the designed guide wavelength
m, 24 pieces in the horizontal direction, the spacing is 6.1 mm, the size of the feeding slot is 5.1 mm × 0.9 mm, the microstrip substrate thickness is 1.5 mm, which is the same as the dielectric 15, and the line width is 50Ω. It was made to be about 5 mm. 25.5 dBi at a design frequency of 20 GHz, including a loss of MSL (abbreviation of Microstrip Line) of about 10 cm
A circularly polarized antenna with a gain of 1 has been realized.

The in-phase composite output pattern of the antenna thus created is shown in FIG. This is a pattern in a plane (vertical plane) containing two ports at a frequency of 19 GHz in which the beam faces the broadside direction, and according to FIG.
The horizontal polarization component indicated by the solid line in the front direction (0 ° direction) has a higher gain than the vertical polarization component indicated by the broken line, and operates in the beam direction as a linear (horizontal) polarization antenna instead of a circular polarization. I understand.

The parallel plate array antenna according to the present invention is
Since it can be constructed from a single substrate and can be shaped into various curved shapes due to its thin shape, it can be applied, for example, to a vehicle body of a moving body.

FIG. 6 shows a configuration that enables polarization selection of circular polarization. In FIG. 6, reference numeral 10 'is a parallel plate array antenna provided with a V-shaped slot pair, and has the configuration shown in FIG. Reference numeral 5 is a switch, and 6 is a terminal for outputting a reception signal (in the case of transmission, a transmission signal is input).

This configuration is the same as the A. When the switch 5 is connected to the upper side,
Two ports 1 provided on the antenna according to the above principle
The left-handed polarized wave received signal is selected from the upper port 1 of 4 (port 1 and port 2), and the right-handed polarized wave received signal is selected from the lower port 2 when the switch 5 is connected to the lower side. To be done.

In addition to polarization tracking and polarization selection, the present invention is applied to an antenna capable of polarization diversity and polarization modulation by applying the combination of symmetrical input / output ports using the V-shaped slot pair of the present invention as a radiating element. FIG. 7 shows a configuration of polarization diversity and polarization modulation according to the present invention.

FIG. 7A. Polarization diversity, B. Shows the configuration of polarization modulation. In the figure, 10 'is a parallel plate array antenna provided with a V-shaped slot pair, and 16 is a phase shifter.

FIG. 7A. Is the polarization diversity in the case of circular polarization and uses the output of two ports. A. of FIG. Is the polarization diversity in the case of linear polarization,
The output of the terminal to which the outputs of the two ports are directly connected and the output of which the terminal is the connection point of the lower output and the upper output shifted by 180 degrees by the phase shifter 16 are used. In addition, in FIG. Shows the configuration of polarization modulation, and B. In the case of transmission, one of the two ports is connected to the other port via the phase shifter 16 to transmit the carrier wave,
The modulation signal is input to the phase shifter 16 to change the amount of phase shift.
As a result, the vibration direction (polarized wave) of the radio wave output from the antenna changes according to the modulation signal. B. of FIG. In the case of reception, one of the two ports is connected to the other port directly or via the phase shifter 16 and the output is combined to obtain the received signal due to fluctuations in the vibration direction (polarization) of the radio wave. The level fluctuation is obtained as a modulation signal. This makes it possible to efficiently receive the polarization-modulated radio waves.

The array antenna provided with the V-shaped slot pair of the present invention can be used for transmitting and receiving an arbitrary elliptically polarized signal.

FIG. 8 is a diagram showing the configuration of the elliptically polarized wave according to the present invention. In the figure, 16 is a phase shifter and 17 is a maximum ratio combiner.

Similar to the antenna shown in FIG. 7, it is a slot array antenna having a C-shaped slot pair and having a symmetrical structure with respect to the ports. One of the signals from one of the two ports is supplied to the phase shifter 16. The phase difference between the left-handed circularly polarized wave and the right-handed circularly polarized wave forming the elliptical polarized wave is eliminated, and their outputs are supplied to the maximum ratio combiner 17. The maximum ratio combiner 17 combines the circularly polarized signals from the other port of the antenna and the phase shifter 16 so that the S / N ratio becomes maximum corresponding to the ratio of the levels of both signals. And output an elliptically polarized signal. In this way, arbitrary elliptically polarized waves can be transmitted and received.

Using the elliptical polarization configuration shown in FIG. 8, the ratio of the received power magnitudes and the phase difference of both ports of the array antenna having a symmetrical structure with respect to the port provided with the V-shaped slot pair. Therefore, it is also possible to measure the axial ratio of the elliptically polarized wave being received and the long axis direction.

[0043]

According to the present invention, an array antenna having a C-shaped slot pair and having a symmetrical structure with respect to ports is used to set the polarization direction of a linearly polarized wave to horizontal, vertical, or between horizontal and vertical. It is possible to change the direction to any direction, and thus to follow the direction of any linearly polarized wave.
In addition, by switching between the two ports, it is possible to select right-handed circular polarization and left-handed circular polarization.

Further, by forming the array antenna provided with the V-shaped slot pair by the parallel plate array made of a thin material, the mounting on the moving body becomes easy.

Furthermore, according to the present invention, it is possible to realize transmission / reception of diversity of circular polarization and linear polarization, and transmission / reception of elliptical polarization.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing a waveform of a propagating wave generated from each slot in a waveguide in linearly polarized wave reception, a waveform of its combined wave, and mathematical expressions of upward and downward combined waves.

FIG. 3 is a diagram showing a parallel plate array antenna in which the present invention is implemented.

FIG. 4 is a diagram showing a configuration of connection between ports and polarization selection.

FIG. 5 is a diagram showing an in-phase combined output pattern of the created antenna.

FIG. 6 is a diagram showing a configuration that enables circular polarization selection.

FIG. 7 is a diagram showing a configuration of polarization diversity and polarization modulation according to the present invention.

FIG. 8 is a diagram showing a configuration of elliptical polarization according to the present invention.

FIG. 9 is an explanatory diagram of a C-shaped slot pair.

FIG. 10 is a diagram showing types of C-shaped slot pairs.

FIG. 11 is an explanatory diagram in which slot pairs are arranged by being divided in the circumferential direction by the proposed slot array antenna.

FIG. 12 is an external view of a slot array antenna 1 having a proposed C-shaped slot pair.

FIG. 13 is an external view of a slot array antenna 2 having a proposed C-shaped slot pair.

[Explanation of symbols]

4 C-shaped slot pair 41,42 slots

Claims (8)

(57) [Claims] 1. A polarization variable system using an array antenna having a V-shaped slot pair, wherein the array antenna is provided with a large number of C-shaped slot pair arrays in a waveguide and a slot having a symmetrical structure with respect to a port. Consists of an array antenna, and the output of one of the two ports of the antenna is passed through an adjustable phase shifter and is connected to the other port to combine the outputs and respond to fluctuations in the polarization direction of the transmitted and received linearly polarized waves. Then, the phase shift angle of the phase shifter is adjusted so that the sum of the output passing through the phase shifter and the output at the connection point of the other port produces the maximum output. . 2. The polarization variable antenna having a symmetric structure with respect to a port, wherein the array of the C-shaped slot pairs is provided in a waveguide according to claim 1, and the polarization variable antenna comprises a coaxial cylindrical slot array antenna. Variable polarization method. 3. The polarization variable antenna according to claim 1, wherein the array of the C-shaped slot pairs is provided in a waveguide and has a structure symmetrical with respect to a port, and the polarization variable antenna is constituted by a parallel plate array antenna. Variable polarization method. 4. A polarization tunable system using an array antenna having a V-shaped slot pair, wherein the array antenna is provided with a large number of C-shaped slot pair arrays in a waveguide and has a symmetric structure with respect to a port. A slot array antenna with two ports is provided with a switch that is selectively switched and connected to one of the outputs of the two ports of the antenna, and the circularly polarized right-handed polarization is connected to one port. Polarization variable method characterized by transmitting and receiving wave signals and transmitting and receiving left-handed circularly polarized signals while connected to the other port. 5. A polarization tunable system using an array antenna having a C-shaped slot pair, wherein the array antenna is provided with a large number of C-shaped slot pair arrays in a waveguide and has a structure symmetrical with respect to a port. A slot array antenna with one port, the output of one of the two ports of the antenna is supplied to the phase shifter to adjust the phase, and the output of the other port and the output of the phase shifter Polarization characterized in that a maximum ratio combiner for inputting two signals and combining so as to maximize the S / N ratio is provided, and an arbitrary elliptical polarization signal is received through the maximum ratio combiner. Variable method. 6. A polarization diversity system using an array antenna having a V-shaped slot pair, wherein the array antenna is provided with a large number of C-shaped slot pair arrays in a waveguide and has a symmetric structure with respect to a port. It consists of a slot array antenna with two ports,
A polarization diversity system characterized by performing polarization diversity by circular polarization using outputs from two ports of the antenna. 7. A polarization diversity system using an array antenna having a V-shaped slot pair, wherein the array antenna is provided with a large number of C-shaped slot pair arrays in a waveguide and has a structure symmetrical with respect to a port. It consists of a slot array antenna with two ports,
The output at the point where the outputs of the two ports of the antenna are connected and the output at the point where the output of one port of the antenna is connected to the other port with a phase difference of 180 degrees depending on the phase shifter or line length. Polarization diversity method characterized by performing polarization diversity by linearly polarized waves using and. 8. A polarization modulation system using an array antenna having a V-shaped slot pair, wherein the array antenna has a large number of C-shaped slot pair arrays in a waveguide and has a symmetrical structure with respect to a port. By configuring a slot array antenna with two ports, one port of the antenna is connected to the other port via a phase shifter as an input port, and by varying the phase shift amount of the phase shifter, A polarization modulation method characterized by varying the vibration direction (polarization) of linearly polarized waves transmitted and received from an antenna and propagating in the space with the modulation signal as the polarization direction for communication.