JP3084398B2 - Polarization adaptive phased array antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phased optical system capable of identifying the polarization state of an incoming radio wave whose polarization is unknown, changing the polarization state in accordance with the identified polarization, and operating the elliptically polarized beam. It relates to an array antenna.

[0002]

2. Description of the Related Art In general, it is difficult to identify the polarization state of an incoming radio wave whose polarization is unknown, and to configure an antenna capable of changing the polarization state in accordance with the identified polarization. For example, in a millimeter-wave intra-premises communication antenna, in millimeter-wave intra-premises communication, radio waves that arrive directly from a master station to a slave station are used. Alternatively, it is conceivable to use radio waves reflected by walls or the like.

[0003] However, when a circularly polarized wave hits a wall or the like and is reflected, it generally becomes a counter-rotating elliptically polarized wave, and the elliptical polarization rate depends on the material of the wall and the incident angle of the radio wave. And
If an attempt is made to use radio waves reflected from a wall or the like, an antenna suitable for uncertain polarization is required, but conventional antennas could not easily receive this.

[0004]

However, in order to identify the polarization state of the arriving radio wave, three parameters, ie, an elliptic polarization rate, an elliptic tilt angle (Tilte angle), and a polarization rotation direction are required. is there. Generally, by measuring the amplitude and phase of the electric field of an incoming radio wave in two directions orthogonal to each other, the above three parameters of the elliptical polarization can be obtained. However, an accurate apparatus requires an expensive apparatus.

When an elliptical polarized beam is to be scanned according to the identified polarization, a phased array antenna as shown in FIG. 12 is constructed using a two-point feeding microstrip antenna shown in FIG. A simple phased array antenna is conceivable. In this phased array, in addition to the phase shifter for beam scanning, a phase shifter for changing the polarization of the element antenna is attached to each element antenna, so that the polarization of the element antenna itself can be changed. , And can scan an elliptically polarized beam.

However, the phased array antenna having the configuration shown in FIG. 12 requires a phase shifter for an element antenna in addition to a phase shifter for beam scanning, and a two-point power splitter because it is a two-point feed microstrip antenna. Is required for each element antenna, and there is a problem that the cost increases.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional disadvantages, and is a phased array comprising linearly polarized element antennas. Value) and the received power (or the amplitude of the received voltage) when the direction of rotation of the circularly polarized wave is switched to left or right by the phased array antenna, so that the polarization of the arriving radio wave can be measured without measuring the phase. A phased array antenna capable of identifying a wave state is provided.

It is another object of the present invention to provide a phased array antenna capable of scanning a beam having a polarization suitable for the identified polarization state.

This phased array switches the polarization in the beam scanning direction to left-handed circularly polarized light or right-handed circularly polarized light without adding an active device such as a switch to the phased array and using a feed phase amount. It can be set just by changing. Further, the polarization in the beam scanning direction can be set to a desired elliptical polarization only by changing the feed phase amount.

More specifically, the present invention is an array antenna comprising a plurality of linearly polarized element antennas, wherein each element antenna is rotated about a boresight axis by p (n-1) π / N radians (N is Total number of elements, n is element number, P is 1 ≦ P ≦ N
And each element antenna is coupled to a power divider via a phase shifter, and the reception power (or the amplitude of the reception voltage ) of each element antenna is given.
Detecting retrieve the values), among the above-mentioned antenna elements
Elements in three or more directions with different rotation directions for incoming elliptical polarization
Based on the child antenna received power (amplitude value or the received voltage)
Then, the elliptical polarization rate of the arriving radio wave and the inclination angle of the ellipse are obtained, and the received power (or the amplitude value of the received voltage) when the polarization of the combined wave of the array antenna is switched to the left-handed circular polarization and the right-handed circular polarization. )
Rotation of elliptical polarization based on comparing the magnitude of
The Rukoto seek direction, to provide a phased array antenna and identifying the polarization state of the incoming radio wave without phase measurements.

Further, the present invention is an array antenna comprising a plurality of linearly polarized element antennas, wherein each element antenna is rotated around a boresight axis by p (n-1) π / N radians (N is the total number of elements). , n represents the element number, with P is placed giving 1 ≦ P ≦ n-1 integer), further binds power divider through respective each element antenna phase shifter, each containing
Take the received power (or received voltage amplitude value) of the
Detected out, incoming elliptically polarized among the respective antenna elements
Based on the reception power (or the amplitude value of the reception voltage) of the element antennas in three or more directions different in the rotation direction with respect to the wave ,
The elliptical polarization rate of the radio wave and the inclination angle of the ellipse are obtained, and the magnitude of the received power (or the amplitude value of the received voltage) when the polarization of the composite wave of the array antenna is switched to the left-handed circular polarization and the right-handed circular polarization. To
Formed based on the comparing, by Rukoto determined the direction of rotation of elliptical polarization, to identify the polarization state of the incoming radio wave without measurement of the phase, the antenna beam polarization adapted to its polarization state The present invention provides a polarization adaptive phased array antenna.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, in an array antenna using linearly polarized element antennas, each element antenna is rotated around a boresight axis by p (n-1) π / N radians (N is the total number of elements, n is An element number and p are given by giving 1 ≦ p ≦ N−1), a phase shifter is attached to each element antenna, and a phased array capable of extracting the reception power (voltage amplitude value) of each element antenna is provided. 1 is a basic configuration according to an embodiment of the present invention. The linearly polarized element antenna includes a microstrip antenna shown in FIG.

In order to identify an unknown polarization, the elliptical polarization ratio (axial ratio), the tilt angle, and the direction of rotation of the polarization need only be known. Therefore, the elliptical polarization ratio (axial ratio) and the tilt angle can be determined by monitoring the reception power (or the amplitude value of the reception voltage) of at least three elements among the outputs of the element antennas.

Next, by operating the present array antenna as a circularly polarized wave switching antenna, the direction of polarization rotation can be determined. That is, when the received power of the array (or the amplitude value of the received voltage) when the right-handed polarization operation is performed is compared with the received power (or the amplitude value of the received voltage) of the array when the left-handed polarization operation is performed, the value becomes The larger polarization rotation is the rotation direction of the elliptical polarization. Also, the elliptical polarization ratio (axial ratio) can be obtained by using the reception power (or the amplitude value of the reception voltage) of the right-handed polarization and the reception power (or the amplitude value of the reception voltage) of the left-handed polarization.

Switching between left-handed and right-handed circularly polarized waves is performed as follows. Each element antenna of the above-described phased array is arranged on the XY plane in FIG. 3 and the polarization in the direction of beam scanning in the (θ ₀ , φ ₀ ) direction is switched to left-handed or right-handed circularly polarized light. phase U _n (θ ₀ to be supplied to the antenna, φ
₀ ) is defined as Equation 1 below.

[0016]

(Equation 1)

In the equation 1, the variables are defined as follows. n: element number d _n : position vector indicating the position of the element antenna r (θ ₀ , φ ₀ ): unit vector in the beam scanning direction (θ ₀ , φ ₀ ) k ₀ : wave number in free space One term is a phase for beam scanning. Second
The term is a phase for circular polarization, and is represented by Expression 2.

[0018]

(Equation 2)

In equation (2), variables are defined as follows. p: Integer of p ≦ N−1 N: Number of array elements n: Element antenna number A circle is obtained by the phase of Expression 2 and the rotation angle p (n−1) π / N radian about the boresight axis of the element antenna. Polarization is obtained. Here, m is a coefficient that determines the rotation direction of the circularly polarized wave,
When m = 0, left-handed circular polarization is obtained, and when m = 1, right-handed circular polarization is obtained.

In the phased array, since the phase represented by Expression 1 is given by the phase shifter, the control of m can be easily performed. It is possible to switch to circular polarization.

In the polarization adaptive beam scanning, the polarization state of the arriving radio wave is identified, and an antenna beam having a polarization suitable for the polarization state is formed.

In order to operate as a phased array whose polarization state is variable, the phase V _n (θ ₀ ,
φ ₀ ).

[0023]

(Equation 3)

In Equation 3, n represents the element number. The first term in the equation (3) is a phase for beam scanning. The second term is a phase for circular polarization expressed by Expression 2.
Further, [Delta] [Psi] _n of the third term is the phase for the composite electric field elliptically polarized, elliptically polarized wave ratio and the ellipse tilt angle (tiltangle) is determined by how give the [Delta] [Psi] _n. The phase V _n (θ ₀ , φ ₀ ) represented by Expression 3 can be realized by a phase shifter connected to each element antenna.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below. The function of identifying the polarization state of an incoming radio wave will be described with reference to a four-element array shown in FIG.

For simplicity, it is assumed that the radio wave having unknown polarization is identified from the front of the array antenna. The radio wave format is C.I. W. And When dealing with communication waves, the same performance can be obtained by monitoring the envelope of a phase-modulated or frequency-modulated signal in which the envelope of the output voltage is constant, as in the case of the adaptive array of the CMA method.

As shown in FIG . 5 , consider the elliptical polarization rate and the tilt angle when voltage amplitudes in three directions having different elliptical polarizations are given. For simplicity, one of the three directions is defined as an S-axis direction, and the other direction is defined as a T-axis direction. The remaining directions are directions rotated by ξ from the S axis. If the amplitude values of the voltages in the three directions are a, b, and c, respectively, the elliptical polarization rate AR is given by Expression 4.

[0028]

(Equation 4)

The inclination angle τ is given by Expression 5.

[0030]

(Equation 5)

Here,

[0032]

(Equation 6)

First, the four-element array shown in FIG.
It is assumed that the elliptically polarized waves shown in FIG. 5 arrive from the boresight direction (Z-axis direction) of this four-element array. For simplicity, the directions of linear polarization of the element antennas of element numbers 1 and 3 in the four-element array coincide with the X-axis and Y-axis in FIG. It is assumed that the S axis and the T axis of the wave coincide. The direction of the linear polarization of the element antenna of element number 3 is は = π / of the elliptical polarization of FIG.
4 direction. When the amplitude value a _1, b _1, c ₁ of the received voltage of each element antenna element numbers 1, 2, 3, q is given by Equation 7.

[0034]

(Equation 7)

By substituting q, a = a ₁ , b = b ₁ , and c = c ₁ into Equations 4 and 5, the elliptical polarization rate and the tilt angle are obtained.

Next, consider a case where elliptical polarized light arrives from a direction away from the boresight direction of the four-element array of FIG. However, it is assumed that the direction of arrival is unknown.

In general, when θ departs from the boresight direction, the E-plane pattern and the H-plane pattern of the element antenna do not coincide with each other, but it can be considered that a widely used microstrip circular patch antenna or the like substantially coincides over a considerably wide range. Therefore, it can be considered that the element antenna has a substantially uniform reception gain in the azimuth direction (φ direction) for a wide range of θ.

For simplicity, it is assumed that the elliptical polarization of FIG. 5 has arrived from the (θ, 0) direction. When the element antenna has a uniform reception gain in the azimuth direction (φ direction), FIG.
The polarization element antennas has received on the XY plane, elliptically polarized wave and apparent choice value obtained by projecting the elliptically polarized in Figure 5 in the XY plane
, And the thus, the amplitude value _{a 2,} b 2, _{c 2} and a the elliptically polarized in Figure 5 of the reception voltage of each element antenna element numbers 1, 2, 3, b, the relationship between the c in Equation 8 expressed.

[0039]

(Equation 8)

By substituting Equation 8 into Equations 4 and 5, even when an unknown radio wave arrives from an oblique direction, if the arrival direction is known, the amplitude value of the reception voltage of the element antenna is detected. The polarization state can be fixed.

Next, by operating the four-element array shown in FIG. 4 as a circularly polarized wave switching antenna, the rotation direction of the polarized wave can be determined. That is, when the received power of the array (or the amplitude value of the received voltage) when the right-handed polarization operation is performed is compared with the received power (or the amplitude value of the received voltage) of the array when the left-handed polarization operation is performed, the value becomes The larger polarization rotation is the rotation direction of the elliptical polarization. As described above, the elliptical polarization rate, the tilt angle, and the rotation direction of the polarization of the incoming radio wave can be specified.

Hereinafter, the principle of operating the element array of FIG. 4 as a circularly polarized wave switching antenna will be described.

First, consider the operation of the array in the boresight direction. Rotate each element antenna around the boresight axis by (n-1) π / 4 radians (n is the element number,
The polarization of each element antenna after being arranged with p = 1) is as shown in FIG. Each element antenna is linearly polarized. The linearly polarized wave can be decomposed into a right-handed circularly polarized wave component and a left-handed circularly polarized wave component as shown in FIG. In order to scan the right-handed circularly polarized beam in the boresight direction of the array, the phase of Equation 9 is given to each element antenna.

[0044]

(Equation 9)

Equation 9 is the case where m = 1 in Equation 2. In Expression 9, n represents an element number. In this case, as shown in FIG. 7, the electric field vector of each element antenna is synthesized in the same phase for the right-handed circularly polarized wave component, but the electric field vector of each elemental antenna is synthesized for the left-handed circularly polarized wave component. It works so that it becomes zero when combined. Therefore, a right-handed circularly polarized wave is obtained for the entire array, and the left-handed circularly polarized wave component becomes zero. Conversely, to scan a left-handed circularly polarized beam in the boresight direction of the array, each element antenna is given the phase of Equation (10).

[0046]

(Equation 10)

Equation (10) is for the case where m = 0 in Equation (2). In Equation 10, n represents an element number. In this case, as shown in FIG. 8, the left-handed component is synthesized in phase, but the right-handed component becomes zero. In a phased array, the phase can be controlled by a phase shifter, so that it is easy to switch between the power supply phase for right-handed circular polarization and the power supply phase for left-handed circular polarization.

Next, consider the case where the beam is scanned in a certain direction. The direction in which the beam was scanned by the phased array (θ
₀ , φ ₀ ), the electric field of the n-th element antenna is
It is represented by 1.

[0049]

[Equation 11]

Here, E _e (θ ₀ ) and E _h (θ ₀ ) are the E-plane electric field and the H-plane electric field in the θ = θ ₀ direction, respectively, and eθ
, Eφ Are unit vectors in the θ and φ directions, respectively, j
Is an imaginary unit. The first term in Equation 11 is left-handed elliptical polarization,
The second term represents right-handed elliptical polarization. E _e (0) = E in the boresight direction of the array, that is, in the θ ₀ = 0 direction
_{Since h} (0), the first term of Equation 11 is left-handed circularly polarized light, and the second term is right-handed circularly polarized light, and linearly polarized light can be decomposed into left-handed circularly polarized light and right-handed circularly polarized light.

Generally, when θ departs from the boresight direction, E
_{Although e} (θ ₀ ) and E _h (θ ₀ ) do not coincide, it can be considered that they are almost coincident in a considerably wide range in a commonly used microstrip circular patch antenna or the like. For this reason, the operation when the beam is scanned in a certain direction is almost the same as the operation in the boresight direction of the array discussed above, and the beam can be scanned by switching between left-handed and right-handed circularly polarized waves.

A second embodiment of the present invention will be described below. A description will be given of a function of identifying the polarization state of an incoming radio wave and forming an antenna beam having a polarization suitable for the polarization state.

First, as in the first embodiment, the polarization state of the arriving radio wave is identified, and m relating to the rotation direction of the polarization is determined based on this information. 1
The polarization variable phase amount ΔΨ _n to be given to each element antenna is determined so that the axis ratio AR and the inclination angle τ given by 3 match the axis ratio and the inclination angle obtained by identifying the polarization state of the incoming radio wave. In this case, ΔΨ that can realize a certain axis ratio and a certain inclination angle
_Since there are many combinations of _n, a method of obtaining ΔΨ _n is, for example, in the case of using a digital phase shifter, creating a table of all the combinations in advance and citing the table.

The following describes that the polarization in the beam scanning direction can be set to a desired elliptical polarization. As in the case of the first embodiment, a microstrip circular patch antenna or the like is used as an element antenna, and E _e (θ ₀ ) and E
Consider a case in which _h (θ ₀ ) can be regarded as substantially coincident over a fairly wide range. In the phased array of Fig. 1,
_{(Θ 0, φ 0) (} θ 0, φ 0) when the feeding phase expressed by Equation 3 as the direction to the beam scanning elliptically polarized rate in the direction (axial ratio) AR and tilt angle τ is Formula 12, Formula 13
In expressed, depend on the polarization varying phase [Delta] [Psi] _n in Equation 3.

[0055]

(Equation 12)

[0056]

(Equation 13)

Here, Θ _n is a phase for circularly polarized waves represented by Equation 2 and is fixed for each element antenna. Thus, by choosing the polarization varying phase [Delta] [Psi] _n to be applied to each element antenna appropriately, it is possible to change the elliptically polarized ratio AR and the tilt angle tau.

[0058] Here, looks like the elliptical polarization rate AR and tilt angle τ from being a function of the polarization varying phase [Delta] [Psi] _n, varies simultaneously depending on the polarization varying phase [Delta] [Psi] _n, elliptically polarized looks like it is not possible to change the Namiritsu AR and tilt angle τ independently fact it is possible to independently varied by selection of a combination of a polarization-varying phase [Delta] [Psi] _n.
For example, a combination of a polarization-varying phase [Delta] [Psi] _n in 4 element array shown in FIG. 4, it compares the elliptically polarized ratio AR and the tilt angle τ in the case of the following two cases. In this case, the phase Θ _n for circular polarization is set to m = 1 in Expression 2 and is a right-hand circular polarization.

Case 1

[0060]

[Equation 14]

Case 2

[0062]

(Equation 15)

The state of polarization in case 1 is as shown in FIG. At this time, the elliptical polarization rate AR1 and the inclination angle τ1 are represented by Expression 16.

[0064]

(Equation 16)

The polarization state in case 2 is as shown in FIG. At this time, the elliptical polarization rate AR2 and the inclination angle τ2 are expressed by Expression 17, and the elliptical polarization rates are equal but the inclination angles are different from those in Case 1.

[0066]

[Equation 17]

[0067] Thus, by selecting a combination of a polarization-varying phase [Delta] [Psi] _n, it is possible to change the elliptically polarized ratio AR and angle of inclination τ independently.

As described above, the present invention has been described based on the embodiments shown in the drawings. However, the present invention is not limited to the above-described embodiments, but can be implemented in any manner unless the structure described in the claims is changed. can do.

[0069]

In summary, according to the present invention, the following tremendous effects can be obtained. A phased array comprising linearly polarized element antennas, wherein at least three elements of received power (or received voltage amplitude value) of received power (or received voltage amplitude value) of each element antenna and a phased array antenna are circular. By detecting the reception power (or the amplitude value of the reception voltage) when the rotation direction of the polarization is switched between the left rotation and the right rotation, the polarization state of the arriving radio wave can be identified without measuring the phase.

Further, it is possible to scan a beam having a polarization suitable for the identified polarization state.

The phased array switches the polarization in the beam scanning direction to left-handed circular polarization or right-handed circularly polarized light without adding an active device such as a switch to the phased array, and using a feed phase amount. It can be set just by changing. Further, the polarization in the beam scanning direction can be set to a desired elliptical polarization only by changing the feed phase amount.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a phased array for identifying a polarization state of an incoming radio wave.

FIG. 2 is a configuration diagram illustrating a linearly polarized element antenna.

FIG. 3 is a conceptual diagram showing a relationship between each element antenna of a phased array arranged on a plane and a coordinate system.

FIG. 4 is a block diagram showing a configuration of a four-element phased array for identifying the polarization state of an incoming radio wave.

FIG. 5 is a conceptual diagram showing a relationship between elliptical polarization and amplitudes in three directions.

FIGS. 6 (1) and (2) are conceptual diagrams showing decomposition into a right-handed circularly polarized wave component and a left-handed circularly polarized wave component.

FIG. 7 is a conceptual diagram showing a state of right-handed circularly polarized wave generation.

FIG. 8 is a conceptual diagram illustrating a state of generation of left-handed circularly polarized waves.

FIGS. 9 (1), (2), and (3) are conceptual diagrams showing Case 1 of a combination of polarization variable phases ΔΨ _{n in} a four-element array.

FIGS. 10 (1), (2), and (3) are conceptual diagrams showing Case 2 of a combination of polarization-varying phases ΔΨ _{n in} a four-element array.

FIG. 11 is a configuration diagram showing an element antenna by two-point feeding.

FIG. 12 is a block diagram illustrating a configuration of a conventional phased array for scanning an elliptically polarized beam using a polarizable element antenna.

Claims (2)

(57) [Claims] 1. An array antenna comprising a plurality of linearly polarized element antennas, wherein each element antenna is rotated around a boresight axis by p (n-1) π / N radians (N
The total number of elements, n represents the element number, with P is placed giving 1 ≦ P ≦ N-1 integer), further binds power divider through respective each element antenna phase shifters, each element
Extract the received power (or received voltage amplitude) of the antenna
And detected, incoming elliptically polarized among the respective antenna elements
Based on the received power (or the amplitude value of the received voltage) of the element antennas in three or more directions with different rotation directions.
The elliptical polarization rate of the wave and the inclination angle of the ellipse are obtained, and the magnitude of the received power (or the amplitude value of the received voltage) when the polarization of the combined wave of the array antenna is switched to the left-handed circular polarization and the right-handed circular polarization. Ratio
Based to compare, by Rukoto determined the direction of rotation of elliptical polarization, antenna arrays and identifying the polarization state of the incoming radio wave without phase measurements. 2. An array antenna comprising a plurality of linearly polarized element antennas, wherein each of said element antennas is rotated around a boresight axis by p (n-1) π / N radians (N
The total number of elements, n represents the element number, with P is placed giving 1 ≦ P ≦ N-1 integer), further binds power divider through respective each element antenna phase shifters, each element
Extract the received power (or received voltage amplitude) of the antenna
And detected, incoming elliptically polarized among the respective antenna elements
Based on the received power (or the amplitude value of the received voltage) of the element antennas in three or more directions with different rotation directions.
The elliptical polarization rate of the wave and the inclination angle of the ellipse are obtained, and the magnitude of the received power (or the amplitude value of the received voltage) when the polarization of the combined wave of the array antenna is switched to the left-handed circular polarization and the right-handed circular polarization. Ratio
Based to compare formed by Rukoto determined the direction of rotation of elliptical polarization, to identify the polarization state of the incoming radio wave without measurement of the phase, the antenna beam polarization adapted to its polarization state A polarization adaptive phased array antenna characterized in that: