JP2005020254A - Antenna polarization angle error detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely detect the polarization angle error at a point near the zero point of the polarization angle error with a simple structure. <P>SOLUTION: A linear polarization signal received by an antenna (1) is separated into a main polarization signal and an orthogonal polarization signal in a polarization separator (2). A phase shifter (3) gives a phase-shift amount which changes in time to the orthogonal polarization signal, and a mixer (5) mixes the two polarization signals. A polarization angle error detection part (10) detects the polarization angle error of the antenna (1) based on an output signal of the mixer (5) and the phase shift amount by the phase shifter (3). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna polarization angle error detection device that detects an error in the polarization angle of an antenna with respect to a linearly polarized signal coming from the outside. In particular, in the field of satellite communication using linear polarization, a vehicle, a ship, etc. It is related with what is used suitably for the automatic polarization-tracking apparatus of the antenna mounted in the mobile body.
[0002]
[Prior art]
In satellite communication, generally, two orthogonal polarized waves are used as separate communication paths. FIG. 6 is a diagram showing the relationship between the antenna polarization angle error (hereinafter referred to as polarization angle error) and the signal levels of the main polarization signal and the cross polarization signal. In normal use, the degree of separation between the main polarization signal 101 of FIG. 6 and the cross polarization signal 102 orthogonal thereto (hereinafter referred to as cross polarization discrimination) needs to be about 30 dB. For this reason, the allowable range of the polarization angle error is a range 103 in which a cross polarization discrimination degree of 30 dB is ensured.
[0003]
When the received signal strength is P and the polarization angle error is ψ, the strength of the main polarization signal is represented by P · cos ψ, and the strength of the cross polarization signal is represented by P · sin ψ. The sensitivity to the polarization angle error of each polarization signal is obtained by differentiating each by the polarization angle error ψ. When the polarization angle error ψ is very small, the polarization angle error sensitivity of the main polarization signal is ( −P · ψ), and the polarization angle error sensitivity of the cross polarization signal is P.
[0004]
Here, when the polarization angle error ψ is very small, that is, when ψ≈0, the polarization angle error sensitivity of the main polarization signal is very low compared to the cross polarization signal. For this reason, conventionally, the reception level of the cross polarization signal is used to detect the polarization angle error. However, for example, in the case of a signal having a signal-to-noise ratio (S / N: Signal to Noise Ratio) of 10 dB, the cross polarization signal 102 is buried in the noise 104 within the required range 103. Therefore, noise is reduced by a low-pass filter.
[0005]
As this type of antenna polarization angle error detection device, for example, the one shown in FIG. 7 is known. In FIG. 7, a signal received by the antenna 201 is separated into a main polarization signal and a cross polarization signal by a polarization separator 202. Then, the cross-polarized signal is passed through the low-pass filter 203, and the signal level after passing is detected by the level detector 204. Since this signal level indicates a polarization angle error, the automatic polarization tracking device using the antenna polarization angle error detection device of FIG. 7 performs control to rotate the polarization axis so that the signal level is minimized. Do.
[0006]
Further, as seen in the method performed by the monopulse receiver, there is a method of performing synchronous detection using the main polarization signal (see, for example, Non-Patent Document 1). A typical circuit used in this method is shown in FIG. In the monopulse method, the main polarization signal and the cross polarization signal are frequency-converted by the local oscillation signal 301 and the mixers 302 and 303, and the synchronous detection circuit 304 performs synchronous detection to extract a DC component. The level of the DC component thus obtained corresponds to the magnitude of the polarization angle error. Note that the sum signal and the difference signal in Non-Patent Document 1 correspond to the main polarization signal and the cross polarization signal here.
[0007]
Further, Patent Document 1 discloses another method. A circuit used in the system disclosed in Patent Document 1 is shown in FIG. This method is different from the method shown in Non-Patent Document 1 in that a local oscillation signal having a different frequency is used, and a signal after detection is a signal having a frequency difference between the local oscillation signals. However, since it is difficult to generate local oscillation signals with slightly different frequencies, a local oscillation signal 404 with a low frequency is mixed with a local oscillation signal 404 with a low frequency by mixing a local oscillation signal 404 with a high frequency. The frequency of the signal after passing through the low-pass filter 409 is the frequency of the local oscillation signal 404.
[0008]
[Non-Patent Document 1]
IEICE, “Antenna Engineering Handbook,” p. 187, 1980.
[Patent Document 1]
Japanese Patent Laid-Open No. 10-142307
[0009]
[Problems to be solved by the invention]
However, in the method shown in FIG. 7, when the polarization angle error is small, the signal level of the cross polarization signal 102 is very small and buried in the noise 104, so that it takes time to detect the cross polarization signal, that is, the response There is a problem that is bad. Further, when the polarization angle error is detected using a modulated wave, it is difficult to detect the polarization angle error with high accuracy because the signal level constantly fluctuates. For this reason, a method of cutting out an unmodulated beacon signal with a narrow-band filter and removing a noise component is conceivable. However, the limit C / N that can be received by a narrowband receiver called a beacon receiver ₀ Is about 40 dBc / Hz. For example, when a beacon signal for general satellite communication is received by an antenna of about 1 m, it is about 55 dBc / Hz. Considering that cross-polarization leakage must be suppressed to -30 dB, C / N of cross-polarized component ₀ 55−30 = 25 dBc / Hz is not exceeded, and even in the beacon receiver, the cross-polarized component of the beacon wave is buried in noise and level information cannot be detected. Further, the beacon receiver uses a PLL loop band of about 1 kHz, and even if a 100 Hz loop band is realized in order to reduce the influence of noise, the limit C / N that can be received. ₀ Is only about 30 dBc / Hz, it is impossible to detect the cross-polarized wave component, and the lock operation due to the narrow band becomes unstable, which is difficult to realize.
[0010]
In the system shown in FIG. 8, although the influence of noise can be reduced because the DC output is taken out, the output signal after detection is weak near the zero point, so that it is necessary to use an amplifier practically. There are problems of voltage and drift, and it is difficult to detect the polarization angle error with high accuracy.
[0011]
In the system shown in FIG. 9, since the mixers 405, 406, 407, and 408 are frequently used, there is a problem that the number of parts increases and the circuit scale and power consumption increase. Further, the installation of the low frequency generator 404 increases the cost. A rectangular wave is often used as a simple local oscillation signal. In this case, since a low-frequency odd multiple wave is generated, the configuration of FIG. 9 complicates the filter.
[0012]
The present invention has been made in view of the above circumstances, and an object thereof is an antenna polarization angle error that can detect a polarization angle error with high accuracy even near the zero point of the polarization angle error with a simple configuration. It is to provide a detection device.
[0013]
[Means for Solving the Problems]
A first invention for solving the above-described problems and achieving the object includes a polarization separator that separates a linearly polarized signal received by an antenna into two orthogonally polarized signals, and the polarization separation A phase shifter that gives a phase shift amount that changes with time to one polarization signal separated by the phase shifter, and one polarization signal and the other polarization signal phase-shifted by the phase shifter A polarization angle error detection unit that detects an error in the polarization angle of the antenna with respect to the linearly polarized signal based on the output signal of the mixer and the amount of phase shift by the phase shifter; This is an antenna polarization angle error detection device.
[0014]
In a second aspect based on the first aspect, the phase shifter shifts the phase so that the phase difference between the two polarization signals is alternately switched between 0 ° and 180 °, and the polarization angle The error detection unit includes a low-pass filter that extracts a low-frequency component from the output signal of the mixer, a direct-current amplifier that amplifies the output signal of the low-pass filter, and the direct current when the phase difference is 0 ° A polarization angle error calculating unit that calculates a difference between the output signal of the amplifier and the output signal of the DC amplifier when the phase difference is 180 °.
[0015]
In a third aspect based on the first aspect, the phase shifter gives a phase shift amount that changes continuously in time, and the polarization angle error detection unit is based on an output signal of the mixer. A band pass filter for selectively extracting a signal having a phase rotation frequency by the phase shifter, an AC amplifier for amplifying an output signal of the band pass filter, and an amplitude of the output signal of the AC amplifier as the phase shifter A polarization angle error reading unit that reads in synchronization with the phase rotation of
[0016]
In a fourth aspect based on the first aspect, the phase shifter gives a phase shift amount that changes continuously in time, and the polarization angle error detection unit is based on an output signal of the mixer. A low-pass filter that extracts low-frequency components, an AC amplifier that includes a capacitor before and after amplifying the output signal of the low-pass filter, and the amplitude of the output signal of the AC amplifier is synchronized with the phase rotation by the phase shifter. A polarization angle error reading unit.
[0017]
In a fifth aspect based on the first aspect, the phase shifter gives a phase shift amount that changes continuously in time, and the polarization angle error detection unit outputs the output signal of the mixer. An amplifying amplifier, a frequency converter for converting the amplitude of a signal having a phase rotation frequency by the phase shifter included in the output signal of the ac amplifier into a dc signal, and the dc signal from the output signal of the frequency converter A low pass filter.
[0018]
In a sixth aspect based on the fifth aspect, the phase shifter rotates the phase of the one polarization signal at a constant phase rotation frequency, and the frequency converter outputs an output signal of the AC amplifier. Is rotated at the constant phase rotation frequency in the opposite direction to the phase shifter.
[0019]
According to a seventh aspect based on the fifth aspect, the phase shifter rotates the phase of the one polarization signal at a constant phase rotation frequency, and the frequency converter includes the constant phase rotation frequency. Is generated, and the AC signal and the output signal of the AC amplifier are mixed.
[0020]
Further, an eighth invention is the invention according to any one of the first to seventh inventions, wherein the polarization signal is provided in a signal path from the polarization separator to the mixer and automatically amplifies the polarization signal to a desired signal strength. Alternatively, it further includes at least one automatic gain controller for damping.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of an antenna polarization angle error detection device according to the present invention will be described below in detail from the first embodiment to the fourth embodiment with reference to the accompanying drawings.
[0022]
(First embodiment)
FIG. 1 is a block diagram showing a configuration of an antenna polarization angle error detection device according to the present embodiment. In FIG. 1, the antenna polarization angle error detection apparatus includes an antenna 1, a polarization separator 2, a phase shifter 3, an amplifier 4, a mixer 5, and a polarization angle error detection unit 10. In the present embodiment, the polarization angle error detection unit 10 includes a low-pass filter 11, a DC amplifier 12, and a polarization angle error calculation unit 13.
[0023]
Hereinafter, the flow of signals in the antenna polarization angle error detection apparatus shown in FIG. 1 and the operation of the apparatus will be described.
[0024]
A linearly polarized signal coming from the outside is received by the antenna 1 and separated into a main polarization signal and a cross polarization signal orthogonal to each other by the polarization separator 2. The cross polarization signal is supplied to the phase shifter 3, and a phase shift amount that changes with time is given by the phase shifter 3. This amount of phase shift will be described later. Since the cross-polarized signal has a low signal level, it is amplified by the amplifier 4 and then supplied to the mixer 5. In the mixer 5, the cross polarization signal output from the amplifier 4 and the main polarization signal output from the polarization separator 2 are mixed. The output signal of the mixer 5 is supplied to the polarization angle error detection unit 10, and the polarization angle error detection unit 10 performs linear polarization based on the output signal of the mixer 5 and the phase shift amount of the phase shifter 3. An error in the polarization angle of the antenna 1 with respect to the signal is detected.
[0025]
Specifically, the output signal of the mixer 5 is supplied to the low-pass filter 11, and a low-frequency component is extracted from the output signal of the mixer 5 by the low-pass filter 11. Here, when the polarization angle error is near zero, the level of the output signal of the low-pass filter 11 is very small. Therefore, the DC amplifier 12 amplifies the output signal of the low-pass filter 11. The output signal of the DC amplifier 12 is supplied to the polarization angle error calculation unit 13, and the polarization angle error calculation unit 13 is based on the output signal of the DC amplifier 12 and the phase shift amount of the phase shifter 3. Calculate the error of the polarization angle.
[0026]
Here, the output signal of the DC amplifier 12 includes an error due to the offset voltage or drift of the DC amplifier 12. Therefore, in order to remove the influence of the offset voltage and drift, the phase shifter 3 and the polarization angle error calculation unit 13 operate as follows. In the following description, the signal received by the antenna 1 is P · cos (ω ₁ t) and the polarization angle error is ψ. At this time, the main polarization signal is
P ・ cosψ ・ cos (ω ₁ t)
And the cross polarization signal is
P · sinψ · cos (ω ₁ t)
It becomes.
[0027]
The phase shifter 3 shifts the phase of the cross polarization signal so that the phase difference between the main polarization signal and the cross polarization signal supplied to the mixer 5 is alternately switched between 0 ° and 180 °. More specifically, when there is no phase difference between the two polarization signals in the mixer 5, the phase shifter 3 switches the phase shift amount between 0 ° and + 180 ° or −180 ° alternately, When there is a phase difference, the phase adjustment amount and (phase adjustment amount + 180 °) or (phase adjustment amount−180 °) are alternately switched.
[0028]
Due to the above phase shift, the mixer 5 has a cross polarization signal.
P · sinψ · cos (ω ₁ t)
And 180 ° phase-shifted cross-polarized signal
-P · sinψ · cos (ω ₁ t)
Are supplied alternately.
[0029]
When the phase difference of the output signal of the mixer 5 is 0 °,
(P ² / 4) · sin (2ψ) · {cos (2ω ₁ t) +1}
When the phase difference is 180 °,
-(P ² / 4) · sin (2ψ) · {cos (2ω ₁ t) +1}
It becomes.
[0030]
When the output signal of the low-pass filter 11 has a phase difference of 0 °,
(P ² /4).sin(2ψ)
When the phase difference is 180 °,
-(P ² /4).sin(2ψ)
It becomes.
[0031]
The gain of the DC amplifier 12 is set to G ₁ , The offset voltage is V _of Then, when the phase difference of the output signal of the DC amplifier 12 is 0 °,
S ₁ = G ₁ ・ {(P ² / 4) · sin (2ψ) + V _of }
When the phase difference is 180 °,
S ₂ = G ₁ ・ {-(P ² / 4) · sin (2ψ) + V _of }
It becomes.
[0032]
The polarization angle error calculation unit 13 outputs the output signal S of the DC amplifier 12 when the phase difference is 0 °. ₁ And the output signal S of the DC amplifier 12 when the phase difference is 180 °. ₂ And take the difference
S ₁ -S ₂ = G ₁ ・ (P ² / 2) ・ sin (2ψ)
Is calculated as a value indicating the polarization angle error. This value is V _of The effects of offset voltage and drift are eliminated.
[0033]
According to the antenna polarization angle error detection device of the present embodiment, the following effects can be obtained.
(A) It is possible to compensate for the offset voltage and drift of the DC amplifier 12, and it is possible to detect a polarization angle error that does not include an error due to these.
(B) Since two polarization signals are mixed, the influence of noise can be reduced, and even if one polarization signal is buried in noise, a polarization angle error can be detected.
(C) Since a local signal is not required, it is not affected by phase noise of the oscillator, frequency accuracy error, frequency fluctuation due to temperature change, and signal sneaking into the circuit.
(D) Since fluctuations in the reception level due to modulation can be eliminated by mixing two polarization signals, the polarization angle error can be detected stably.
(E) Cost and circuit scale can be reduced by using a simple phase shifter.
(F) Because it is possible to estimate the error of the polarization angle with high accuracy, automatic tracking of the polarization axis of the antenna mounted on the moving body should be performed with high accuracy in satellite communications using linearly polarized waves. Is possible.
[0034]
(Second Embodiment)
Hereinafter, the present embodiment will be described with reference to the drawings. However, the description of the parts common to the first embodiment is omitted, and the same reference numerals are used.
[0035]
FIG. 2 is a block diagram illustrating a configuration of the antenna polarization angle error detection device according to the present embodiment. In the present embodiment, the polarization angle error detection unit 20 includes a band-pass filter 21, an AC amplifier 22, and a polarization angle error reading unit 23.
[0036]
In the present embodiment, the phase shifter 3 gives a phase shift amount that changes continuously in time to the cross-polarized signal. As a result, the signal indicating the polarization angle error included in the output signal of the mixer 5 becomes an AC signal.
[0037]
In the polarization angle error detection unit 20, the bandpass filter 21 selectively extracts a signal having a phase rotation frequency by the phase shifter 3, that is, an AC signal indicating a polarization angle error, from the output signal of the mixer 5. . The AC signal extracted by the band pass filter 21 is amplified by the AC amplifier 22 and output to the polarization angle error reading unit 23. The polarization angle error reading unit 23 reads the amplitude of the output signal of the AC amplifier 22 in synchronization with the phase rotation by the phase shifter 3 and detects it as a value indicating the polarization angle error.
[0038]
Hereinafter, the flow of the signal and the operation of the apparatus will be described more specifically using mathematical expressions.
[0039]
The signal received by the antenna 1 is P · cos (ω ₁ t), and the polarization angle error is ψ, the main polarization signal is
P ・ cosψ ・ cos (ω ₁ t)
And the cross polarization signal is
P · sinψ · cos (ω ₁ t)
It becomes.
[0040]
The amount of phase shift of the phase shifter 3 is ω ₂ t, that is, the phase of the cross polarization signal is changed by the phase shifter 3 to the phase rotation frequency (ω ₂ / 2π), the cross polarization signal is P · sinψ · cos ((ω ₁ + Ω ₂ ) T)
It becomes.
[0041]
The output signal of the mixer 5 is
(P ² / 4) · sin (2ψ) · {cos ((2ω ₁ + Ω ₂ ) T) + cos (ω ₂ t)}
It becomes. The band pass filter 21 calculates the phase rotation frequency (ω ₂ / 2π) is an AC signal,
(P ² / 4) · sin (2ψ) · cos (ω ₂ t)
Selectively.
[0042]
The amplification factor of the AC amplifier 22 is G ₂ Then, the output signal of the AC amplifier 22 is
G ₂ ・ (P ² / 4) · sin (2ψ) · cos (ω ₂ t)
It becomes.
[0043]
The polarization angle error reading unit 23 reads the amplitude of the output signal of the AC amplifier 22 in synchronization with the phase rotation,
G ₂ ・ (P ² /4).sin(2ψ)
Is detected as a value indicating a polarization angle error.
[0044]
According to the antenna polarization angle error detection device according to the present embodiment, in addition to the effects (b) to (f), the following effects can be obtained.
(G) Since a signal indicating a polarization angle error included in the output signal of the mixer 5 is used as an AC signal by giving a phase shift amount that changes continuously in time to the polarization signal, an error due to an offset voltage or drift The signal indicating the polarization angle error can be amplified by the AC amplifier that does not cause the polarization angle error, and the polarization angle error can be detected with high accuracy.
(H) Since the phase speed of the phase shifter 3 is easily variable, the output frequency of the mixer 5 can be easily changed.
(I) Since the amount of phase shift of the phase shifter 3 is continuously changed in time, generation of a multiplied wave and an image is suppressed, so that a filter for extracting a signal indicating a polarization angle error is simplified. .
[0045]
In the present embodiment, the same effect can be obtained by inserting a low-pass filter instead of the band-pass filter 21 and inserting capacitors before and after the AC amplifier 22. In this case, the DC component included in the output signal of the low pass device is removed by the capacitor.
[0046]
(Third embodiment)
Hereinafter, the present embodiment will be described with reference to the drawings. However, the description of the parts common to the first embodiment is omitted, and the same reference numerals are used.
[0047]
FIG. 3 is a block diagram showing the configuration of the antenna polarization angle error detection device according to this embodiment. In the present embodiment, the polarization angle error detection unit 30 includes an AC amplifier 31, a frequency converter 32, and a low-pass filter 33.
[0048]
In the present embodiment, the phase shifter 3 gives a phase shift amount that changes continuously in time to the cross-polarized signal. As a result, the signal indicating the polarization angle error included in the output signal of the mixer 5 becomes an AC signal.
[0049]
In the polarization angle error detection unit 30, the AC amplifier 31 amplifies the output signal of the mixer 5 and outputs it to the frequency converter 32. The frequency converter 32 converts the amplitude of the signal having the phase rotation frequency by the phase shifter 3 included in the output signal of the AC amplifier 31 into a DC signal and outputs it to the low-pass filter 33. The low-pass filter 33 takes out a DC signal included in the output signal of the frequency converter 33 and detects it as a value indicating a polarization angle error.
[0050]
Hereinafter, the flow of the signal and the operation of the apparatus will be described more specifically using mathematical expressions.
[0051]
As in the second embodiment, the signal received by the antenna 1 is P · cos (ω ₁ t), and the polarization angle error is ψ, and the phase shifter 3 converts the phase of the cross polarization signal to the phase rotation frequency (ω ₂ / 2π). At this time, the output signal of the mixer 5 is
(P ² / 4) · sin (2ψ) · {cos ((2ω ₁ + Ω ₂ ) T) + cos (ω ₂ t)}
It becomes.
[0052]
The amplification factor of the AC amplifier 31 is G ₃ Then, the output signal of the AC amplifier 31 is
G ₃ ・ (P ² / 4) · sin (2ψ) · {cos ((2ω ₁ + Ω ₂ ) T) + cos (ω ₂ t)}
It becomes.
[0053]
When the frequency converter 32 is a phase shifter, the phase of the output signal of the AC amplifier 31 is converted into the phase rotation frequency (−ω ₂ / 2π), the signal after frequency conversion is
G ₃ ・ (P ² / 4) · sin (2ψ) · {cos (2ω ₁ t) +1}
It becomes. That is, the phase rotation frequency (ω ₂ The amplitude of the signal having / 2π) is a DC signal,
G ₃ ・ (P ² /4).sin(2ψ)
Is converted to This DC signal is taken out by the low-pass filter 33 as a value indicating a polarization angle error.
[0054]
Further, the frequency converter 32 has a phase rotation frequency (ω ₂ / 2π), and when the AC signal and the output signal of the AC amplifier 31 are mixed, the signal after frequency conversion is
G ₃ ・ (P ² / 8) · sin (2ψ) · {cos ((2ω ₁ + 2ω ₂ ) T) + cos (2ω ₁ t) + cos (2ω ₂ t) +1}
It becomes. That is, the phase rotation frequency (ω ₂ The amplitude of the signal having / 2π) is a DC signal,
G ₃ ・ (P ² /8).sin(2ψ)
Is converted to This DC signal is taken out by the low-pass filter 33 as a value indicating a polarization angle error.
[0055]
According to the antenna polarization angle error detection device according to the present embodiment, the following effects can be obtained in addition to the effects (b) to (b).
(Nu) Since the output signal of the mixer 5 is frequency-converted with the phase rotation frequency of the phase shifter 3, a signal indicating the polarization angle error is obtained as a DC signal that is easy to handle.
(L) Since the frequency of the output signal of the mixer 5 is frequency-converted with the phase rotation frequency of the phase shifter 3, the signal indicating the polarization angle error and the noise signal can be easily separated, and the influence of noise can be reduced.
[0056]
(Fourth embodiment)
The antenna polarization angle error detection device according to the present embodiment is almost the same as that according to the first to third embodiments, but automatically in the signal path from the polarization separator 2 to the mixer 5. At least one automatic gain controller (also referred to as an AGC: Automatic Gain Control circuit) for amplifying or attenuating the polarization signal to a desired signal intensity is provided. Hereinafter, although this embodiment is described using drawings, explanation is omitted about the portion which is common in the 1st-3rd embodiment, and the same numerals are used.
[0057]
FIG. 4 is a block diagram illustrating a configuration of the antenna polarization angle error detection device according to the present embodiment. The antenna polarization angle error detection device shown in FIG. 4 is almost the same as that according to the first embodiment shown in FIG. 1, but differs in that automatic amplification factor controllers 41 and 42 are provided. The automatic amplification factor controllers 41 and 42 are provided in the signal path from the polarization separator 2 to the mixer 5. The automatic gain controller 41 is inserted in the path of the main polarization signal, and the automatic gain controller 42 is inserted in the path of the cross polarization signal.
[0058]
In FIG. 4, the automatic gain controllers 41 and 42 are inserted in the antenna polarization angle error detection device according to the first embodiment shown in FIG. 1, but in the second or third embodiment. May be inserted into the antenna polarization angle error detection device according to the above. Moreover, although provided in the path | route of both polarization signals, you may provide in the path | route of any one polarization signal.
[0059]
In the present embodiment, the main polarization signal and the cross polarization signal are amplified by the automatic gain controllers 41 and 42, respectively, and then supplied to the mixer 5.
[0060]
FIG. 5 shows a simulation result of the polarization angle error signal output. Here, C / N was set to 15 dB. In FIG. 5, the horizontal axis represents the polarization angle error, and the vertical axis represents the polarization angle error signal output detected by the antenna polarization angle error detection device. The output X is the output of the device according to the present embodiment, and the output Y is the output of the device according to the first embodiment. In other words, the output X is the result with AGC, and the output Y is the result without AGC.
[0061]
From FIG. 5, it can be confirmed that signal levels corresponding to polarization angle errors are obtained. It can also be seen that the polarization angle error can be detected with high accuracy even in a noisy environment. Furthermore, in the present embodiment using the automatic gain controllers 41 and 42, it can be confirmed that the sensitivity to the polarization angle error is greatly improved and the polarization angle error can be detected with high accuracy.
[0062]
According to the antenna polarization angle error detection device of the present embodiment, the following effects can be obtained in addition to the effects (A) to (L).
(E) Since the cross polarization signal is amplified by the automatic gain controller 42, the sensitivity to the cross polarization signal can be increased.
(W) When a large polarization angle error occurs, the main polarization signal becomes weak and the sensitivity is reduced, but the main polarization signal is amplified by the automatic gain controller 41, so that the sensitivity reduction is avoided. be able to.
[0063]
As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to the said 1st-4th embodiment.
[0064]
For example, in the above embodiment, the cross polarization signal is phase-shifted by the phase shifter 3, but the main polarization signal may be phase-shifted, or both polarization signals may be phase-shifted.
[0065]
In addition, an amplifier may be inserted as necessary, or a low-pass filter or a band-pass filter may be inserted as necessary in order not to saturate the amplifier in a band unnecessary for observation.
[0066]
【The invention's effect】
According to the present invention, since the two polarization signals are mixed, the influence of noise can be reduced. In addition, since a local oscillation signal and many mixers are not required, the configuration is simple. Further, since the phase shift amount that changes with time is given to one polarization signal and the polarization angle error is detected based on the phase shift amount, the influence of the offset voltage and drift of the amplifier can be avoided. As a result, the polarization angle error can be detected with high accuracy even in the vicinity of the zero point of the polarization angle error with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an antenna polarization angle error detection device according to a first embodiment.
FIG. 2 is a block diagram showing a configuration of an antenna polarization angle error detection device according to a second embodiment.
FIG. 3 is a block diagram illustrating a configuration of an antenna polarization angle error detection device according to a third embodiment.
FIG. 4 is a block diagram illustrating a configuration of an antenna polarization angle error detection device according to a fourth embodiment.
FIG. 5 is a diagram showing a simulation result of a polarization angle error signal output.
FIG. 6 is a diagram illustrating a relationship between a polarization angle error and signal levels of a main polarization signal and a cross polarization signal.
FIG. 7 is a block diagram showing a configuration of a conventional antenna polarization angle error detection device.
FIG. 8 is a block diagram showing a configuration of a typical circuit used in the method shown in Non-Patent Document 1.
9 is a block diagram showing a configuration of a circuit used in the method disclosed in Patent Document 1. FIG.
[Explanation of symbols]
1 Antenna
2 Polarization separator
3 Phase shifter
4 Amplifier
5 Mixer
10, 20, 30 Polarization angle error detector
11, 33 Low-pass filter
12 DC amplifier
13 Polarization angle error calculator
21 Band-pass filter
22, 31 AC amplifier
23 Polarization angle error reading unit
32 Frequency converter
41, 42 Automatic gain controller

Claims (8)

A polarization separator that separates the linearly polarized signal received by the antenna into two orthogonally polarized signals;
A phase shifter that gives a phase shift amount that changes with time to one polarization signal separated by the polarization separator;
A mixer for mixing one polarization signal phase-shifted by the phase shifter and the other polarization signal;
A polarization angle error detection unit that detects an error in the polarization angle of the antenna with respect to the linearly polarized signal based on the output signal of the mixer and the amount of phase shift by the phase shifter. An antenna polarization angle error detection device. The phase shifter shifts the phase so that the phase difference between the two polarization signals is alternately switched between 0 ° and 180 °,
The polarization angle error detector is
A low pass filter for extracting low frequency components from the output signal of the mixer;
A DC amplifier for amplifying the output signal of the low-pass filter;
A polarization angle error calculating unit that calculates a difference between the output signal of the DC amplifier when the phase difference is 0 ° and the output signal of the DC amplifier when the phase difference is 180 °. The antenna polarization angle error detection device according to claim 1. The phase shifter provides a phase shift amount that changes continuously in time,
The polarization angle error detector is
A band-pass filter for selectively extracting a signal having a phase rotation frequency by the phase shifter from an output signal of the mixer;
An AC amplifier that amplifies the output signal of the bandpass filter;
The antenna polarization angle error detection device according to claim 1, further comprising: a polarization angle error reading unit that reads the amplitude of the output signal of the AC amplifier in synchronization with the phase rotation by the phase shifter. The phase shifter provides a phase shift amount that changes continuously in time,
The polarization angle error detector is
A low pass filter for extracting low frequency components from the output signal of the mixer;
An AC amplifier including a capacitor before and after amplifying the output signal of the low-pass filter;
The antenna polarization angle error detection device according to claim 1, further comprising: a polarization angle error reading unit that reads the amplitude of the output signal of the AC amplifier in synchronization with the phase rotation by the phase shifter. The phase shifter provides a phase shift amount that changes continuously in time,
The polarization angle error detector is
An AC amplifier for amplifying the output signal of the mixer;
A frequency converter for converting the amplitude of a signal having a phase rotation frequency by the phase shifter included in the output signal of the AC amplifier into a DC signal;
The antenna polarization angle error detection device according to claim 1, further comprising: a low-pass filter that extracts the DC signal from the output signal of the frequency converter. The phase shifter rotates the phase of the one polarization signal at a constant phase rotation frequency,
6. The antenna polarization angle error detection device according to claim 5, wherein the frequency converter rotates the phase of the output signal of the AC amplifier at the constant phase rotation frequency opposite to the phase shifter. . The phase shifter rotates the phase of the one polarization signal at a constant phase rotation frequency,
6. The antenna polarization angle error according to claim 5, wherein the frequency converter generates an AC signal having the constant phase rotation frequency and mixes the AC signal with an output signal of the AC amplifier. Detection device. It further comprises at least one automatic gain controller provided in a signal path from the polarization separator to the mixer, and automatically amplifies or attenuates the polarization signal to a desired signal strength. The antenna polarization angle error detection device according to claim 1.

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