JPS6365908B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an angle error detection device that uses an antenna that receives radio waves emitted by a target to detect a pointing angle error between the pointing direction of the antenna and the direction of the target.

Conventionally, such angular error detection devices have relatively simple methods when the polarization emitted by the target is fixed, such as in the case of circular polarization or linear polarization, and many have already been put into practical use. It is being However, when the polarization emitted by the target is arbitrary polarization and its circular polarization rate and polarization slope change over time, angular error detection devices have recently been developed for frequency reuse communication using two orthogonal polarizations. This has become necessary along with the practical application of cross-polarization compensation methods for propagation paths during rain, which has been an obstacle in the practical application of such methods.

FIG. 1 shows an example of a conventional angle error detection device of this type. In Fig. 1, the signal from the target is received by antenna 1, and antenna 2 is used to detect the angle error.
Only the high-order mode components excited in the circular waveguide are extracted by the two high-order mode couplers 2 and 3. At this time, the two higher-order mode couplers 2 and 3 are higher-order mode couplers that are orthogonal to each other, and for example, a TE° ₀₁ mode coupler 2 and a TM° ₀₁ mode coupler 3 are used.
Note that the fundamental mode component passes through the higher-order mode couplers 2 and 3 and is converted into a polarized wave shape by the polarization converters 4 and 5.
Convert polarization plane. In this example, as a polarization converter
A 90° retardation plate 4 and a 180° retardation plate 5 are used. The polarization-converted signal is passed through a polarization demultiplexer 6 into two orthogonal signals.
It is separated into two polarization components E _XC and E _YC . E _XC here
is the main polarization component, and E _YC is the orthogonal polarization component. E _XC is a phase detector (hereinafter called PSD) 7 a loop filter 8 and a voltage controlled oscillator (hereinafter called VCO) 9
This forms a so-called phase-locked loop (hereinafter referred to as PLL), so that the output of the VCO 9 is maintained at a phase difference of 90° from that of _EXC . On the other hand E _YC
is detected by the output of VCO 9 using PSD 17 and sent to amplifier 18.
The polarization converter 5 is driven by the motor 19 via the motor 19, and at the same time, the polarization converter 4 is
to drive.

On the other hand, the higher-order mode components from the higher-order mode couplers 2 and 3 are combined by an orthogonal polarization combiner 33, passed through polarization converters 34 and 35 equivalent to the phase difference plates 4 and 5, and then 36 with two orthogonal components E _XD and E _YD
These are split into PSD37 and PSD47,
Synchronous detection is performed using the output of the VCO 9 or its phase shifted by 90° by the 90° phase shifter 10, and only the DC component is extracted by the low-pass filters 38 and 48, thereby producing two angular error voltages ΔX. , ΔY is obtained.

The above operation will be explained below using formulas.

Figure 2 is a diagram showing the relationship between the target, the tracking antenna equipped with this device, and polarization when using such an angular error detection device. In the figure, E indicates the tracking antenna equipped with this device, and T indicates the target. Assume a coordinate system XY whose origin is the intersection O of this plane and the center direction of the beam of the tracking antenna E in a plane including T. In addition
The angle Δθ between EO→ and ET→ is the angular error of the tracking antenna, φ is the angle indicating the direction of the angular error and the inclination with the X-axis direction, and when the shape of the arriving polarized wave is as shown in the figure.
Emax is the long axis electric field of the elliptical polarization, Emin is the coaxial short axis electric field, and angle α is the inclination angle of the direction of Emax from the X axis.

When the tracking antenna is equipped with the angular error detection device shown in FIG. 1 in the state shown in FIG. 2, the electric fields E _XA and E _YA at the input section of the polarization converter 4 _shown in FIG. It is expressed as jEminsinγ E _YA = Emaxcosγ + jEmincosγ ... [1]. Here, E _XA and E _YA are X and Y in Figure 2.
This is the electric field of the X and Y components at the point that determines E _XA and E _YA when the coordinates are translated in parallel in the EO direction. The same applies to E _XB , E _YB , E _XC , E _YC , and E _YD below. The angles of polarization converters 4 and 5 are α
By calculating E _XC and E _YC as and β, the formula [2] is obtained.

_E -γ) E _YC = −Emaxcos(α-2β)sin(α-γ) −Eminsin(α-2β)sin(α-γ) −jEmaxsin(α-2β)cos(α-γ) +jEmincos(α-2β )cos(α-γ) [2] When using Fig. 1 for linear polarization reception, by providing the relationship α=2β using the gear box 20,
The PSD 17 amplifier 18 and motor 19 automatically control α=γ. In this case, E _XC = −jEmax E _YC = jEmin [3].

On the other hand, the angular error signals taken out by the higher-order mode couplers 2 and 3 are combined by the orthogonal polarization combiner 33, and _E
E _{YB ,} but when Δθ _is small, E } [4]. However, k is a proportionality constant.

Polarization converters 34 and 35 have the same angle as 4 and 5, α and β respectively, so α=2β
When the condition α=γ is given, the outputs E _XD and E _YD of the polarization splitter 36 are expressed by equation [5].

_{E _ _ _ _} Then, as ΔX, we obtain ΔX=Re(E _XD /E _XC )=kΔθcosψ ... [6].

Similarly, only the orthogonal component to E _XC of E _YD is set to PSD4.
7, we obtain ΔY as ΔY=Im(−E _YD /E _XC )=kΔθsinψ ...[7].

ΔX, ΔY given by formulas [6] and [7]
As can be seen from FIG. 2, represents the components of the angular error Δθ in the X direction and the Y direction.

Next, when FIG. 1 is used for circularly polarized wave reception, the polarization converters 4, 5, 34, and 35 are not driven but fixed, and α=-π/4 and β=0.

At this time becomes.

Therefore, E _XD /E _XC =kΔθe ^-j 〓=kΔθ(cosψ−jsinψ)
10], _and PSD37 and 4 with E _XD as standard
7, it is possible to obtain as ΔX and ΔY ΔX=ReE _XD /E _XC =kΔθcosψ [11 _] ΔY=Im− _E

At this time, the switch 41 in FIG. 1 is connected as shown in the figure, and in the case of linear polarization, it is connected to the E _YD side.

As described above, in the method shown in FIG. 1, the angular error voltages ΔX and ΔY can be obtained by appropriately switching the angular error detection circuit depending on the state of the arriving polarized wave. In the system shown in Figure 1, it is necessary to switch the configuration of the device for circularly polarized waves and linearly polarized waves, which makes the operation complicated when the arriving polarized wave changes drastically. Another drawback was that it was not possible to maintain good reception at all times.

In other words, _E For example, if a left-handed circularly polarized wave arrives while a right-handed circularly polarized wave is being received, a case will occur where E _XC = 0, and in equation [8]
(Emax = -Emin) There is a possibility that reception will be impossible.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is possible to appropriately control a polarization converter for any incoming polarized wave and at the same time reduce the effect on the angle error signal caused by it. It is an object of the present invention to provide an angular error detection device that obtains a stable angular error voltage while always maintaining a good reception condition by removing the angular error voltage.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 3, the parts with the same numbers as in Fig. 1 have the same functions; the fundamental mode component is taken out to E _XC , a PLL is configured for it, and it is synchronized with _E A signal with a phase difference of
Obtained as the output of VCO9.

In this invention, the arriving wave having arbitrary polarization is transferred to the lag surfaces (hereinafter referred to as lag surfaces) of the 90° retardation plate 4 and the 180° retardation plate 5 by the cross-polarization terminal output E _YC of the polarization demultiplexer. By independently controlling the rotation of the outputs of the PSDs 17 and 27 by motors 19 and 20 via amplifiers 18 and 28 so as to minimize the polarization loss, a reference signal E _XC with little polarization loss is obtained.

The operating principle shown in FIG. 3 will be explained in detail below.

To simplify the above general formula [2] for E _XC and E _YC , let Emax=Ecosδ [12] Emin=Esinδ, _then E 2β-δ) −jcos(α-γ)cos(α-2β+δ)} E _YC =E{−sin(α-γ)cos(α-2β-δ) +jcos(α-γ)sin(α- 2β-δ)} [13] is obtained.

In formula [13], E _YC is calculated using E _XC as a reference, and formula [14] is obtained.

E _YC /E _XC = −cos2(α−2β) sin2δ−sin2(α−2β
)cos2δcos2(α−γ)−jsin2(α−γ)cos2δ/2
{sin ² (α−γ) sin ² (α−2β−δ)−cos ² (α−γ
) cos ² (α−2β+δ)} [14] In equation [14], one of the conditions for setting the imaginary part to 0 is α=γ, and in Fig. 3, the VCO 9 with a 90° phase difference with _E This condition is satisfied if E _YC is detected by the output of , and the polarization converter 4 is driven by the motor 19 so that this output becomes zero. When α=γ, equation [14] becomes E _YC /E _XC = −sin2 (α−2β+δ)/2{sin ² (α−
γ) sin ² (α−2β−δ)+cos2(α−γ)−cos ² (α
−2β+δ)[15] Therefore, VCP by PSD27
_{E _}
If the polarization converter 5 is driven by the motor 29 so that the detected wave becomes 0, the condition α-2β+δ=0 is obtained, which makes the equation [15] 0.

When the two conditions α = γ and α-2β + δ = ₀ are satisfied, E _XC = -jE, and all the fundamental mode components of the arriving wave are obtained at the terminal of _E . Therefore, for arriving waves of arbitrary polarization, the full power of the fundamental mode component is basically always obtained in E _XC , eliminating the drawbacks of the conventional system.

On the other hand, the 90° retardation plate 34 and 180° retardation plate 35 used in the angular error signal circuit for tracking the target are the same as the reference signal circuit 90° retardation plate 4 and 180° retardation plate 5, respectively. If the angle is set to , it is not easy to extract the angular error signal for the arbitrary polarization target. Therefore, by setting the 90° retardation plate 34 and the 180° retardation plate 35 in a specific angular relationship as shown below, automatic tracking of arbitrary polarized waves is made possible.

The arriving polarized wave shown in FIG. 2 maintains the same state at point a in FIG. 3. Figure 4 shows the circularly polarized wave at point a, a circularly polarized wave 71 with CCW rotation and a circularly polarized wave 7 with CW rotation.
It is broken down into two parts.

In Figure 4, the CCW circularly polarized wave 71 electric field is E ₁ a,
If the electric field 72 of the CW circularly polarized wave 72 is E ₂ a, at the angle γ from the X axis, E ₁ a=E ₁ E ₂ a=E ₂ (16) where E ₁ = (Emax + Emin)/2 E ₂ = (Emax−Emin)/2 (17) If the setting angle (slow plane) α of the 90° retardation plate 4 is α = γ + 90° (18), the polarization state at point b is 71 is 73. Linearly polarized wave E ₁ b as shown, 72 is linearly polarized wave shown as 74
Converted to E ₂ b.

E ₁ b=√2 ^E1 E ₂ b=√2 ^E2 (19) Therefore, since 73 and 74 are in phase, their combined wave 75 becomes a linearly polarized wave. If 75 is E〓 _b , then E〓 _b = √2 ( ² ₁ + ² ₂ (20), and its inclination angle γ from the X axis is γ = γ - 45° + ρ (21) where ρ = tan ^-1 (E ₂ /E ₁ ) (22) If the setting angle β of the 180° retardation plate 5 is β = 1/2γ + 90° (23), the polarization at point C will be 76 and the polarization will be on the X axis. The result is a matched linearly polarized wave.Figure 5 shows a CCW rotating circularly polarized wave 7.
This is a drawing of the polarization state of 1 and CW rotating circularly polarized wave 72 shown at point C. 71 becomes 77, 72 becomes 78, and 7.
It is shown that the composite wave 76 of 7 and 78 becomes a linearly polarized wave that coincides with the X axis. 76 as E〓, E〓 = √2 ( ² ₁ + ² ₂ = √ ² _nax + ² _nio (24). E〓 is the angle reference signal and is equal to E _XC .

Next, mutually orthogonal higher-order modes are detected at 2 and 3, respectively, and the orthogonal polarizations are synthesized by the orthogonal polarization combiner 33, resulting in a CCW circular polarization E ₁ d shown at 81 in FIG. 6 and a CW circular wave shown at 82. It becomes a polarized wave decomposed into polarized waves E ₂ d. In FIG. 6, 81 and 82 are polarized waves at point d, and at an angle γ-ψ inclined from the X axis, E ₁ d=kΔθE ₁ E ₂ d=kΔθE ₂ (25).

If the setting angle α' of the 90° phase difference plate 34 is α'=α+ρ (26), then at point e, 81 becomes the linearly polarized wave of 83 E ₁ e,
82 is converted into 84 linearly polarized wave E ₂ e. E ₁ e and
E ₂ e is It has the phase and amplitude shown by . A 180° retardation plate 35 with these 83 and 84 set at an angle of β' from the X axis.
Pass through.

If β'=β at this time, the polarization state at point f will be as shown in FIG. In FIG. 7, 87 is 83, and 88 is 84 converted by the 180° retardation plate 35. If 87 is E ₁ f and 88 is E ₂ f, then E ₁ f = E ₁ d=√2kΔθE ₁ e ^-j( 〓 ⁺ 〓 ⁾ (28) E ₂ f=E ₂ d=√2kΔθE ₂ e ^j( 〓 ⁺ 〓 ⁾ (29).

For example, if the 90° retardation plate 50 is installed (fixed) at 90°, at point g E ₁ g=E ₁ f=√2kΔθE ₁ e ^-j( 〓 ⁺ 〓 ⁾ (30) E ₂ g=E ₂ fe− ^- 〓 ^/2 =√2kΔθE ₂ e ^j( 〓 ⁺ 〓 ^- 〓 ^/2) (3
1) Since E ₁ g and E ₂ g are linearly polarized waves that coincide with the X and Y axes, respectively, tilt the polarization splitter 36 by 45 degrees. If we divide the waves so that becomes.

From equation (34), when _the real part of _E From Equation (35), when the imaginary part of E _Y ′ _D is detected by PSD 47 and passed through low-pass filter 48, we get can be obtained. In other words, for the antenna's angular pointing error direction ψ, equation (36) is proportional to cooψ, and equation (37) is an amplitude proportional to sinψ, that is, the control signal has an amplitude proportional to the error in the X direction and Y direction, respectively. It becomes a signal.

Here, ρ in equation (26) is ρ = 2β − γ − 135° (38), α is from equation (18), and β is from equation (23) and equation (21).
Therefore, the setting angle α' of the 90° retardation plate 34 is α'=2β−45° (39). That is, the angle of the 90° retardation plate 34 is twice the angle of the 180° retardation plate 5, and the angle of the 180° retardation plate 35 is twice the angle of the 180° retardation plate 5.
By controlling the rotation angle in a one-to-one relationship with 5, the signals shown in equations (36) and 37) can be obtained.

The fixed 90° retardation plate 50 and polarization splitter 36 shown in FIG. 3 operate as a so-called circularly polarized wave generator because their relative positions are inclined at 45°. Therefore, instead of this, it is possible to achieve the same purpose as shown above by using a configuration as shown in FIG. In FIG. 8, 36 is a polarization splitter, 51 is a so-called 180° hybrid represented by Magic T, and 52 is a 90° phase shifter.

Furthermore, in one embodiment of the present invention shown in FIG.
If the 90° retardation plate 34 and the 180° retardation plate 35 of the angle error signal circuit are set to the angles shown in the following relationship, the fixed 90° retardation plate 50 can be removed.
This is because the fixed 90° retardation plate 50 has the function of delaying 78 by 90° out of the polarization components 77 and 78 shown in FIG. Therefore, if the 90° retardation plate 34 in FIG. 3 is rotated by 45° more than the angle shown by equation (26) or equation (39),
That is, if α′=2β (40), the components E ₁ e and E ₂ e at point e are becomes. Next, if the 180° retardation plate 35 is set at an angle such that β' = β + 22.5° (42), the component E ₁ f at point f
and E ₂ f is the phase of E ₁ f=√2kΔθE ₁ e ^-j( 〓 ⁺ 〓 ⁺ 〓 ^/4) (43) E ₂ f=√2kΔθE ₂ e ^j( 〓 ⁺ 〓 ⁺ 〓 ^/4) (44) It becomes a linearly polarized wave as shown at 87 and 88 in FIG. 7, with an amplitude of . This signal is passed through a polarization splitter 36 tilted at 45°. If we divide the waves so that That is, it is possible to obtain ΔX and ΔY by applying the processing of equations (36) and (37) to E〓 of equation (24) as a signal passed through a (−π/4) phase circuit.

In the above-described embodiment of the present invention, a 90° retardation plate is provided on the side closer to the mode coupler and a 180° retardation plate is provided in the subsequent stage as a polarization conversion circuit for dealing with arbitrary polarization reception of the reference signal circuit. However, even if this relationship is reversed as shown in FIG. 9, arbitrary polarization reception can be handled in the same manner as above. Figure 9 shows a configuration in which the installation positions of the 90° retardation plate 4 and _the 180° retardation plate 5 in Figure 3 are swapped. Board 4
If the setting angle of is α″ and the setting angle of 80° retardation plate 5 is β″, then the conditions for minimizing E _YC are α″=ρ+45° (48) β″=1/2γ+90° (49) Become. From equation (49) and equation (23), β=β″ (50) Therefore, the 90° retardation plate 34 of the error circuit in Fig. 3
and 180° Since the setting angle of the retardation plate 35 is a quantity related only to β in any of the above embodiments, 34 and 35 in FIG. 9 may be the same setting angle as 34 and 35 in FIG. 3. it is obvious.

Furthermore, even in the method of configuring 50 and 36 in FIG. 9 as shown in FIG. 8, 50 is omitted and 3
It is clear that the same function can be obtained even if 4 and 35 are set as in the relational expressions of equation (40) and equation (42), respectively.

In the above embodiment, both the 90° retardation plate 34 and the 180° retardation plate 35 of the angle error circuit are one-to-one or one-to-one with the rotation angle of the 180° retardation plate of the reference signal circuit.
A rotation ratio of 2:2 may also be used. Such a control operation can be easily carried out by a mechanical connection such as gears or an electrical connection using a synchronizer and a motor. Furthermore, although the explanation explains that the slow planes of the 90° retardation plate and the 180° retardation plate are both rotated by a motor, it is possible to control the slow phase plane using an electric signal using a retardation plate using a ferrite element. The control method can also be implemented in the same way.

As described above, according to the present invention, the 90° phase difference plate of the angle error signal circuit is controlled at a rotation ratio of 1:2 with respect to the 180° phase difference plate of the reference signal circuit, and the 90° phase difference plate of the angle error signal circuit is controlled at a rotation ratio of 1:2. Since the retardation plate is controlled with a rotation ratio of 1:1 with the 180° retardation plate of the reference signal circuit, it is possible to efficiently receive arbitrary polarized waves and to obtain accurate angle error signal detection. Because you can
It is effective when used as an angular error detection device for automatically tracking rockets, satellites, etc. whose polarization variation of arriving waves is large.

A similar effect can also be obtained when used in a high frequency band where the polarization state in the propagation path is easily affected by rain or the like.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of a conventional angle error detection device, Fig. 2 is a conceptual diagram showing the positional relationship between a target and an antenna equipped with this device for explaining the operation of the present invention, and Fig. 3 is a system diagram showing an example of a conventional angle error detection device. A system diagram showing an embodiment of the present invention, FIGS. 4 and 5 are conceptual diagrams of the polarization relationship of the reference signal for explaining the operation of the present invention, and FIGS. 6 and 7 are also polarization diagrams of the error signal. 8 and 9 are system diagrams showing other embodiments of the present invention. In the figure, 1 is a radiator, 2 and 3 are higher-order mode couplers,
4, 34 are 90° retardation plates, 5, 35 are 180° retardation plates, 6, 36 are polarization demultiplexers, 7, 17, 27, 37
8 is a phase detector, 8 is a loop filter, 9 is a voltage controlled oscillator, 10 is a 90° phase shifter, and 33 is an orthogonal polarization synthesizer. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 At least one first 180° retardation plate whose slow phase is controlled so that the reception polarization loss of the device that receives the radio waves emitted by the target is minimized;
A reference signal is extracted by the fundamental mode in the waveguide that has passed through the 90° phase difference plate, and an angular error signal is extracted using two higher-order modes having an orthogonal relationship with each other, and the local oscillator output is synchronized with the reference signal. In the angular error detection device that detects two angular errors that are orthogonal to each other by synchronously detecting the angular error signal using a high-order mode detector for extracting the output of the high-order mode, a circuit for composing the two high-order mode outputs so as to maintain an orthogonal relationship, and at least one second 90° phase difference plate whose slow phase plane is rotatable at 180°. It comprises a circuit in which a retardation plate is continuously connected and a fixed 90° retardation plate connected to this circuit, and the second 90° retardation plate is provided on the circuit side to be synthesized, and its slow phase face is 2 of the slow phase surface of the first 180° retardation plate
The slow surface of the second 180° retardation plate is controlled in a one-to-one angular relationship with the slow surface of the first 180° retardation plate.
After passing the output of the 180° phase difference plate through the fixed 90° phase difference plate, the output is split into mutually orthogonal polarized components.
The branch output of is synchronously detected using a local oscillator output synchronized with the reference signal to produce a first angular error output, and the second branch output is used as a first angular error output by the local oscillator output. An angular error detection device characterized by performing synchronous detection with a phase difference of 90° to produce a second angular error output orthogonal to the first angular error output.