JP5721467B2 - Tracking receiver - Google Patents

Description

  The present invention relates to a monopulse tracking receiver that detects an antenna pointing direction and an angle error of a moving body and tracks the angle error to an antenna control system when tracking a moving body such as a satellite. It is.

The role of the tracking receiver in the satellite communication system that automatically tracks the satellite by receiving the signal arriving from the satellite is based on the sum signal (SUM signal) and difference signal (ERR signal) of the signals arriving from the satellite. The angle error of the azimuth angle AZ and the angle error of the elevation angle EL of the antenna with respect to the satellite is calculated, and the angle error of the azimuth angle AZ and the angle error of the elevation angle EL are supplied to the antenna control system.
In the antenna control system, by receiving the angle error from the tracking receiver, the antenna directivity direction can be directed to the satellite, and automatic tracking of the satellite can be realized.

FIG. 5 is a block diagram showing a tracking receiver disclosed in Patent Document 1 below.
Hereinafter, the operation of the tracking receiver of FIG. 5 will be briefly described.
The antenna 101 includes a plurality of horns, and the plurality of horns receive signals coming from satellites.
When a plurality of horns in the antenna 101 receive a signal, the reception circuit 102 converts the frequency of the signals received by the plurality of horns, and calculates the sum of the plurality of signals after the frequency conversion, thereby obtaining a sum signal SUM. Generate a signal.
Further, an ERR signal that is a difference signal is generated by taking a difference between the plurality of signals after frequency conversion.

The bandpass filter 103A (denoted as “BPF” in the figure) of the tracking receiver limits the band of the SUM signal in order to remove unnecessary bands in the SUM signal generated by the receiving circuit 102. Do.
The band-pass filter 103B (denoted as “BPF” in the figure) limits the band of the ERR signal in order to remove an unnecessary band in the ERR signal generated by the receiving circuit 102.

In the tracking receiver of FIG. 5, since the angle error between the azimuth angle AZ and the elevation angle EL of the antenna is detected by detecting the ERR signal with the SUM signal, the signal level of the reference SUM signal needs to be constant.
Therefore, the automatic control gain amplifier 104A (denoted as “AGC” in the figure) has a bandwidth according to the AGC control voltage output from the AGC circuit 111 (denoted as “AGC CTRL” in the figure). The SUM signal output from the pass filter 103A is amplified.
The automatic control gain amplifier 104B (denoted as “AGC” in the figure) also amplifies the ERR signal output from the band pass filter 103B in accordance with the AGC control voltage output from the AGC circuit 111.

The analog-to-digital converter 105A (denoted as “A / D” in the figure) converts the SUM signal amplified by the automatic control gain amplifier 104A from an analog signal to a digital signal, and converts the SUM signal, which is a digital signal, into a digital signal. It outputs to the detectors 108A and 108B.
The analog-to-digital converter 105B (indicated as “A / D” in the figure) converts the ERR signal amplified by the automatic control gain amplifier 104B from an analog signal to a digital signal, and converts the ERR signal, which is a digital signal, into a digital signal. It outputs to the detectors 108C and 108D.

A clock oscillation source 106 that oscillates a quasi-synchronous detection clock, a 90-degree phase shifter 107A that shifts the phase of the quasi-synchronous detection clock by 90 degrees (denoted as “π / 2” in the figure), and a detector 108A and 108B constitute quasi-synchronous detection of the SUM signal, and a signal conversion means for converting the SUM signal into a baseband I signal and a Q signal is configured. The I signal is output from the detector 108A. The Q signal is output from the detector 108B.
Further, the ERR signal is subjected to quasi-synchronous detection from the clock oscillation source 106, the 90-degree phase shifter 107B (denoted as “π / 2” in the figure) and the detectors 108C and 108D, and the ERR signal Is converted into a baseband I signal and Q signal, the I signal is output from the detector 108C, and the Q signal is output from the detector 108D.

The low-pass filters 109A to 109D (denoted as “LPF” in the figure) are signals of higher frequencies than a predetermined band among the I signals or Q signals output from the detectors 108A to 108D. Block the passage and pass only the low-frequency signal.
The power calculator 110 (denoted as “x ² + y ² ” in the figure) outputs an I signal (a signal converted from a SUM signal) output from the low-pass filter 109A and a low-pass filter 109B. The signal level of the SUM signal is calculated by calculating the sum of squares of the Q signal (signal converted from the SUM signal) output from the SUM.
The AGC circuit 111 sets the AGC control voltage to be output to the automatic control gain amplifiers 104A and 104B based on the signal level of the SUM signal calculated by the power calculation unit 110 in order to make the signal level of the reference SUM signal constant. adjust.

  The multiplication processing unit 112A includes an I signal (signal converted from the SUM signal) output from the low-pass filter 109A and an I signal (signal converted from the ERR signal) output from the low-pass filter 109C. The multiplication processing unit 112B multiplies the Q signal output from the low-pass filter 109B (signal converted from the SUM signal) and the Q signal output from the low-pass filter 109D (converted from the ERR signal). 113A, the addition processing unit 113A adds the multiplication result of the multiplication processing unit 112A and the multiplication result of the multiplication processing unit 112B.

  The multiplication processing unit 112C includes an I signal (signal converted from the SUM signal) output from the low-pass filter 109A and a Q signal (signal converted from the ERR signal) output from the low-pass filter 109D. The multiplication processing unit 112D multiplies the Q signal (signal converted from the SUM signal) output from the low-pass filter 109B and the I signal (converted from the ERR signal) output from the low-pass filter 109C. The addition processing unit 113B subtracts the multiplication result of the multiplication processing unit 112D from the multiplication result of the multiplication processing unit 112C.

The reciprocal arithmetic processing unit 114 (denoted as “1 / x” in the figure) calculates the reciprocal of the signal level of the SUM signal calculated by the power calculation unit 110.
The multiplication processing unit 115A calculates the angle error of the azimuth angle AZ by multiplying the addition result of the addition processing unit 113A by the reciprocal number calculated by the reciprocal calculation processing unit 114, and the angle error of the azimuth angle AZ is calculated by the antenna control system. To supply.
The multiplication processing unit 115B calculates the angle error of the elevation angle EL by multiplying the subtraction result of the addition processing unit 113B by the reciprocal calculated by the reciprocal calculation processing unit 114, and supplies the angle error of the elevation angle EL to the antenna control system. To do.

  As a result, in the antenna control system, control is performed to direct the antenna pointing direction toward the satellite according to the angle error of the azimuth angle AZ and the elevation angle EL output from the tracking receiver. As long as it is desirable to maintain communication with the satellite as long as possible, an accurate angle error is generated in the antenna control system even in an environment where the signal level coming from the satellite is low, such as in an environment where the satellite is rising from the horizon. It is desired to be supplied.

Incidentally, when C / N (Carrier to Noise ratio), which is a carrier-to-noise ratio, is low, the calculation accuracy of the signal level of the SUM signal appears in the operation of the tracking receiver.
That is, since the signal level of the SUM signal calculated by the power calculation unit 110 is the signal level of the SUM signal including the system noise, the influence of the system noise is small and accurate when the C / N is high. An angular error can be calculated.
However, when C / N is low, the influence of system noise cannot be ignored, and the calculation result of the signal level of the SUM signal is higher than the signal level of the actual SUM signal.

  As described above, when the calculation result of the signal level of the SUM signal becomes high, the AGC control voltage output from the AGC circuit 111 becomes low. Therefore, the amount of amplification of the SUM signal and the ERR signal in the automatic control gain amplifiers 104A and 104B. Is suppressed, and the detection amount of the angle error of the azimuth angle AZ and the elevation angle EL decreases. In particular, when C / N is lower than 10 dB, the angle error of the azimuth angle AZ and the elevation angle EL calculated by the multiplication processing units 115A and 115B is reduced by 1 dB or more from the actual angle error.

Japanese Unexamined Patent Publication No. 7-22879 (paragraph numbers [0011] to [0012], FIG. 1)

  Since the conventional tracking receiver is configured as described above, the angle error of the azimuth angle AZ and the elevation angle EL can be accurately calculated in an environment where the C / N is high, but the environment where the C / N is low. Below, the angle error of the azimuth angle AZ and the elevation angle EL cannot be accurately calculated, and there is a problem that tracking of the satellite may be difficult.

  The present invention has been made to solve the above-described problems, and provides a tracking receiver that can suppress a decrease in the amount of detection of the angle error of the azimuth angle AZ and the elevation angle EL in an environment where the C / N is low. The purpose is to obtain.

The tracking receiver according to the present invention includes signal conversion means for converting a sum signal and a difference signal of signals arriving from a mobile body into baseband I and Q signals, and I converted from the sum signal by the signal conversion means. A signal amplifying means for amplifying a sum signal and a difference signal based on the signal and the Q signal, and an angle error of an azimuth angle and an elevation angle angle from the baseband I signal and Q signal converted by the signal converting means An angle error calculating means for calculating an error, and an angle error amplifying means for multiplying the angle error of the azimuth angle and the angle error of the elevation angle calculated by the angle error calculating means by an angle error amplification coefficient corresponding to the ratio of the sum signal and noise. The angle error amplifying means previously stores, as an angle error amplification coefficient, for each ratio of the sum signal and noise, an inverse of the ratio between the signal level of the sum signal excluding noise and the signal level of the sum signal including noise. The signal level of the sum signal is calculated by summing the squares of the I signal and the Q signal converted from the sum signal by the signal conversion means, and the noise is obtained in advance from the signal level of the sum signal. The angle error amplification coefficient corresponding to the signal level and noise ratio of the sum signal excluding the noise is obtained from the table, and the angle error amplification coefficient is calculated by the angle error calculation means. And the angle error of the elevation angle is multiplied.

According to the present invention, the signal conversion means for converting the sum signal and the difference signal of the signals arriving from the mobile body into the baseband I signal and Q signal, and the I signal and Q converted from the sum signal by the signal conversion means. Calculates azimuth angle angle error and elevation angle error relative to the moving object from signal amplification means that amplifies the sum and difference signals based on the signal and baseband I and Q signals converted by the signal conversion means An angle error calculating means for multiplying the angle error amplification coefficient corresponding to the ratio of the sum signal and the noise by the angle error calculating means for multiplying the angle error of the azimuth and the angle error of the elevation angle calculated by the angle error calculating means, The angle error amplifying means stores in advance a reciprocal of the ratio between the signal level of the sum signal excluding noise and the signal level of the sum signal including noise as an angle error amplification coefficient for each ratio of the sum signal and noise. The signal level of the sum signal is calculated by summing the squares of the I signal and the Q signal converted from the sum signal by the signal conversion means, and the noise previously obtained by calculation is removed from the signal level of the sum signal. The angle error amplification coefficient corresponding to the ratio of the signal level of the sum signal excluding the noise to the noise is obtained from the table, and the angle error amplification coefficient calculated by the angle error calculation means is used as the angle error amplification coefficient. Therefore, it is possible to suppress a decrease in the detected amount of the azimuth angle error and the elevation angle error in an environment where the C / N is low.

It is a block diagram which shows the tracking receiver by Embodiment 1 of this invention. FIG. 2 is an explanatory diagram showing an image of the baseband I signal and Q signal. It is a characteristic view which shows ratio _RERR corresponding to C / N of a SUM signal. It is a block diagram which shows the tracking receiver by Embodiment 2 of this invention. It is a block diagram which shows the tracking receiver currently disclosed by patent document 1. FIG.

Embodiment 1 FIG.
1 is a block diagram showing a tracking receiver according to Embodiment 1 of the present invention.
In FIG. 1, an antenna 1 includes a plurality of horns, and the plurality of horns receive signals coming from satellites.
When a plurality of horns in the antenna 1 receive a signal, the receiving circuit 2 converts the frequency of the signals received by the plurality of horns, and sums the plurality of signals after the frequency conversion, so that a SUM signal that is a sum signal is obtained. The process to generate is performed. Moreover, the process which produces | generates the ERR signal which is a difference signal is implemented by taking the difference of the some signal after frequency conversion.

The bandpass filter 3A (denoted as “BPF” in the figure) of the tracking receiver limits the band of the SUM signal in order to remove an unnecessary band in the SUM signal generated by the receiving circuit 2. It is a filter.
The band-pass filter 3B (denoted as “BPF” in the figure) is a filter that limits the band of the ERR signal in order to remove an unnecessary band in the ERR signal generated by the receiving circuit 2.

The automatic control gain amplifier 4A (denoted as “AGC” in the figure) performs a process of amplifying the SUM signal output from the band-pass filter 3A according to the AGC control voltage output from the AGC circuit 11. .
The automatic control gain amplifier 4B (denoted as “AGC” in the figure) performs a process of amplifying the ERR signal output from the band-pass filter 3B according to the AGC control voltage output from the AGC circuit 11. .

The analog / digital converter 5A (denoted as “A / D” in the figure) converts the SUM signal amplified by the automatic control gain amplifier 4A from an analog signal to a digital signal, and detects the SUM signal which is a digital signal. Processing to output to the devices 8A and 8B is performed.
The analog / digital converter 5B (denoted as “A / D” in the figure) converts the ERR signal amplified by the automatic control gain amplifier 4B from an analog signal to a digital signal, and detects the ERR signal which is a digital signal. Processing to output to the devices 8C and 8D is performed.

The clock oscillation source 6 is an oscillator that oscillates a quasi-synchronous detection clock.
The 90-degree phase shifter 7A (denoted as “π / 2” in the figure) shifts the phase of the quasi-synchronous detection clock oscillated from the clock oscillation source 6 by 90 degrees, and after 90-degree phase shift The process for outputting the quasi-synchronous detection clock to the detector 8B is performed.
The 90-degree phase shifter 7B (indicated as “π / 2” in the figure) shifts the phase of the quasi-synchronous detection clock oscillated from the clock oscillation source 6 by 90 degrees, and after the 90-degree phase shift The process for outputting the quasi-synchronous detection clock to the detector 8D is performed.

The detector 8A uses the quasi-synchronous detection clock oscillated from the clock oscillation source 6 to convert the SUM signal output from the analog / digital converter 5A into a baseband I signal.
The detector 8B converts the SUM signal output from the analog / digital converter 5A into a Q signal in the baseband using the quasi-synchronous detection clock after the 90-degree phase shift output from the 90-degree phase shifter 7A. Perform the process.

The detector 8C uses the quasi-synchronous detection clock oscillated from the clock oscillation source 6 to convert the ERR signal output from the analog / digital converter 5B into a baseband I signal.
The detector 8D converts the ERR signal output from the analog / digital converter 5B into a Q signal in the baseband using the quasi-synchronous detection clock after the 90-degree phase shift output from the 90-degree phase shifter 7B. Perform the process.
The analog / digital converters 5A and 5B, the clock oscillation source 6, the 90-degree phase shifters 7A and 7B, and the detectors 8A to 8D constitute signal conversion means.

The low-pass filters 9A to 9D (denoted as “LPF” in the drawing) pass signals in a higher band than a predetermined band among the I signals or Q signals output from the detectors 8A to 8D. This is a filter that passes only a low-frequency signal.
The power calculation unit 10 (denoted as “x ² + y ² ” in the figure) outputs an I signal (a signal converted from a SUM signal) output from the low-pass filter 9A and a low-pass filter 9B. A process for calculating the signal level of the SUM signal is performed by calculating the sum of squares of the output Q signal (signal converted from the SUM signal).

The AGC circuit 11 (denoted as “AGC CTRL” in the figure) automatically sets the signal level of the reference SUM signal to be constant based on the signal level of the SUM signal calculated by the power calculation unit 10. Processing for adjusting the AGC control voltage output to the control gain amplifiers 4A and 4B is performed.
The automatic control gain amplifiers 4A and 4B, the power calculation unit 10 and the AGC circuit 11 constitute signal amplification means.

The multiplication processor 12A uses the I signal (signal converted from the SUM signal) output from the low-pass filter 9A and the I signal (signal converted from the ERR signal) output from the low-pass filter 9C. Multiplication is performed, and the multiplication result is output to the addition processing unit 13A.
The multiplication processor 12B uses the Q signal (signal converted from the SUM signal) output from the low-pass filter 9B and the Q signal (signal converted from the ERR signal) output from the low-pass filter 9D. Multiplication is performed, and the multiplication result is output to the addition processing unit 13A.

The multiplication processor 12C uses the I signal (signal converted from the SUM signal) output from the low-pass filter 9A and the Q signal (signal converted from the ERR signal) output from the low-pass filter 9D. A process of multiplying and outputting the multiplication result to the addition processing unit 13B is performed.
The multiplication processing unit 12D outputs the Q signal (signal converted from the SUM signal) output from the low-pass filter 9B and the I signal (signal converted from the ERR signal) output from the low-pass filter 9C. A process of multiplying and outputting the multiplication result to the addition processing unit 13B is performed.

The addition processing unit 13A performs a process of adding the multiplication result of the multiplication processing unit 12A and the multiplication result of the multiplication processing unit 12B and outputting the addition result to the multiplication processing unit 15A.
The addition processing unit 13B performs processing of subtracting the multiplication result of the multiplication processing unit 12D from the multiplication result of the multiplication processing unit 12C and outputting the subtraction result to the multiplication processing unit 15B.
The reciprocal arithmetic processing unit 14 (denoted as “1 / x” in the figure) performs a process of calculating the reciprocal of the signal level of the SUM signal calculated by the power calculation unit 10.

The multiplication processing unit 15A performs a process of calculating the angle error of the azimuth angle AZ by multiplying the addition result of the addition processing unit 13A by the reciprocal calculated by the reciprocal calculation processing unit 14.
The multiplication processing unit 15B performs a process of calculating the angle error of the elevation angle EL by multiplying the reciprocal calculated by the reciprocal calculation processing unit 14 by the subtraction result of the addition processing unit 13B.
The power calculation unit 10, the multiplication processing units 12A to 12D, the addition processing units 13A and 13B, the reciprocal calculation processing unit 14, and the multiplication processing units 15A and 15B constitute angle error calculation means.

The angle error amplification coefficient table 16 is composed of a recording medium such as a RAM, for example, and stores an angle error amplification coefficient α corresponding to the C / N (SUM signal to noise ratio) of the SUM signal.
The angle error amplification coefficient acquisition unit 17 acquires an angle error amplification coefficient α corresponding to C / N of the SUM signal from the angle error amplification coefficient table 16, and outputs the angle error amplification coefficient α to the multiplication processing units 18A and 18B. Perform the process.

The multiplication processing unit 18A performs a process of multiplying the angular error of the azimuth angle AZ calculated by the multiplication processing unit 15A by the angular error amplification coefficient α output from the angular error amplification coefficient acquisition unit 17.
The multiplication processing unit 18B performs processing of multiplying the angle error amplification coefficient α output from the angle error amplification coefficient acquisition unit 17 by the angle error of the elevation angle EL calculated by the multiplication processing unit 15B.
The angle error amplification coefficient table 16, the angle error amplification coefficient acquisition unit 17, and the multiplication processing units 18 </ b> A and 18 </ b> B constitute angle error amplification means.

Next, the operation will be described.
The antenna 1 includes a plurality of horns, and the plurality of horns receive signals coming from satellites.
When a plurality of horns in the antenna 1 receive a signal, the receiving circuit 2 converts the frequency of the signals received by the plurality of horns, and calculates the sum of the plurality of signals after the frequency conversion, thereby obtaining a sum signal SUM. A signal is generated, and an ERR signal that is a difference signal is generated by taking a difference between the plurality of signals after frequency conversion.

ここで、ｒ_ｓはＳＵＭ信号の振幅、θ_sはＳＵＭ信号の位相、ｒ_eはＥＲＲ信号の振幅、θ_eはＥＲＲ信号の位相、ｆ_ｃは中間周波数である。 The SUM signal and the ERR signal are input to a tracking receiver that employs a monopulse system. When the SUM signal at time t is S _SUM (t) and the ERR signal at time t is S _ERR (t), S _SUM (t) and S _ERR (t) are generally given by the following formulas (1) and (2).

Here, _{r s} amplitude of the SUM signal, theta _s the SUM signal phase, the r _e the amplitude of ERR signal, theta _e is ERR signal of the phase, the _{f c} is the intermediate frequency.

The bandpass filter 3A of the tracking receiver performs band limitation of the SUM signal in order to remove an unnecessary band in the SUM signal generated by the receiving circuit 2, and automatically controls the band-limited SUM signal for the SUM signal. Output to 4A.
The band-pass filter 3B limits the band of the ERR signal in order to remove an unnecessary band in the ERR signal generated by the receiving circuit 2, and outputs the band-limited ERR signal to the automatic control gain amplifier 4B. .

In the tracking receiver of FIG. 1, the angle error between the azimuth angle AZ and the elevation angle EL of the antenna is detected by detecting the ERR signal with the SUM signal, so the signal level of the reference SUM signal needs to be constant.
Therefore, the automatic control gain amplifier 4A amplifies the SUM signal output from the band-pass filter 3A according to the AGC control voltage output from the AGC circuit 11 described later, and converts the amplified SUM signal to the analog / digital converter 5A. Output to.
The automatic control gain amplifier 4B also amplifies the ERR signal output from the band pass filter 3B according to the AGC control voltage output from the AGC circuit 11, and outputs the amplified ERR signal to the analog / digital converter 5B. .

When the signal conversion means including the analog / digital converter 5A, the clock oscillation source 6, the 90-degree phase shifter 7A, and the detectors 8A and 8B receives the amplified SUM signal from the automatic control gain amplifier 4A, the SUM The signal is converted into baseband I and Q signals.
That is, when the analog / digital converter 5A receives the amplified SUM signal from the automatic control gain amplifier 4A, the analog / digital converter 5A converts the SUM signal from an analog signal to a digital signal, and converts the SUM signal, which is a digital signal, to the detectors 8A and 8B. Output.
The 90-degree phase shifter 7A shifts the phase of the quasi-synchronous detection clock oscillated from the clock oscillation source 6 by 90 degrees, and outputs the quasi-synchronous detection clock after the 90-degree phase shift to the detector 8B.

The detector 8A uses the quasi-synchronous detection clock oscillated from the clock oscillation source 6 to convert the SUM signal output from the analog / digital converter 5A into a baseband I signal.
The detector 8B converts the SUM signal output from the analog / digital converter 5A into a baseband Q signal using the quasi-synchronous detection clock output from the 90-degree phase shifter 7A after the 90-degree phase shift. To do.

Further, when the signal conversion means composed of the analog / digital converter 5B, the clock oscillation source 6, the 90-degree phase shifter 7B, and the detectors 8C and 8D receives the amplified ERR signal from the automatic control gain amplifier 4B, The ERR signal is converted into a baseband I signal and Q signal.
That is, when the analog / digital converter 5B receives the amplified ERR signal from the automatic control gain amplifier 4B, the analog / digital converter 5B converts the ERR signal from an analog signal to a digital signal, and converts the ERR signal, which is a digital signal, to the detectors 8C and 8D. Output.
The 90-degree phase shifter 7B shifts the phase of the quasi-synchronous detection clock oscillated from the clock oscillation source 6 by 90 degrees, and outputs the quasi-synchronous detection clock after the 90-degree phase shift to the detector 8D.

The detector 8C uses the quasi-synchronous detection clock oscillated from the clock oscillation source 6 to convert the ERR signal output from the analog / digital converter 5B into an I signal in the baseband.
The detector 8D converts the ERR signal output from the analog / digital converter 5B into a baseband Q signal using the 90 ° phase-shifted quasi-synchronous detection clock output from the 90 ° phase shifter 7B. To do.

ここで、Ｉ_ｓはＳＵＭ信号から変換されたベースバンド帯のＩ信号、Ｑ_ｓはＳＵＭ信号から変換されたベースバンド帯のＱ信号、Ｉ_ｅはＥＲＲ信号から変換されたベースバンド帯のＩ信号、Ｑ_ｅはＥＲＲ信号から変換されたベースバンド帯のＱ信号である。 Here, the baseband I and Q signals output from the detectors 8A to 8D and passed through the low-pass filters 9A to 9D are expressed by the following equations (3) to (6). FIG. 2 is an explanatory diagram showing an image of the baseband I signal and Q signal.

Here, I _s is the baseband I signal converted from the SUM signal, Q _s is the baseband Q signal converted from the SUM signal, and I _e is the baseband I signal converted from the ERR signal. , Q _e are baseband Q signals converted from ERR signals.

ここで、θはＳＵＭ信号の位相を基準にしたときのＥＲＲ信号の位相である。 Although details will be described later, the angle error calculation means including the power calculation unit 10, the multiplication processing units 12A to 12D, the addition processing units 13A and 13B, the reciprocal calculation processing unit 14, and the multiplication processing units 15A and 15B is an ERR signal. The angle error Az _ideal of the azimuth angle AZ and the angle error El _ideal of the elevation angle EL obtained by detecting the signal with the SUM signal are expressed by the following equations (7) and (8).

Here, θ is the phase of the ERR signal when the phase of the SUM signal is used as a reference.

The angle error Az _ideal of the azimuth angle AZ and the angle error El _ideal of the elevation angle EL can be expressed by the following formula (9) from the formulas (3) to (8) only by I _s , Q _s , I _e , and Q _e. The equation (10) is obtained.

Multiplication processing unit 12A, a I _s is I signal output from the low-pass filter 9A, by multiplying the I _e is a I signal output from the low-pass filter 9C, the multiplication result (I _s I _e ) is output to the addition processing unit 13A.
The multiplication processing unit 12B multiplies Q _s that is the Q signal output from the low-pass filter 9B and Q _e that is the Q signal output from the low-pass filter 9D, and the multiplication result (Q _s Q _e ) is output to the addition processing unit 13A.

Multiplication processing unit 12C includes a I _s is I signal output from the low-pass filter 9A, multiplies the Q _e is a Q signal output from the low-pass filter 9D, the multiplication result (Q _e I _s) and outputs the addition processing section 13B.
The multiplication processing unit 12D multiplies Q _s that is a Q signal output from the low-pass filter 9B and I _e that is an I signal output from the low-pass filter 9C, and the multiplication result (I _e Q _s ) is output to the addition processing unit 13B.

The addition processing unit 13A adds the multiplication result (I _s I _e ) of the multiplication processing unit 12A and the multiplication result (Q _s Q _e ) of the multiplication processing unit 12B, and the addition result (I _s I _e + Q _s Q _e ) Is output to the multiplication processing unit 15A.
The addition processing unit 13B subtracts the multiplication result (I _e Q _s ) of the multiplication processing unit 12D from the multiplication result (Q _e I _s ) of the multiplication processing unit 12C, and the subtraction result (Q _e I _s −I _e Q _s). ) Is output to the multiplication processing unit 15B.

The power calculation unit 10 calculates the square of the signal level of the SUM signal, that is, I _s that is an I signal output from the low-pass filter 9A and Q _s that is a Q signal output from the low-pass filter 9B. The sum (I _s ² + Q _s ² ) is calculated.
When the power calculation unit 10 calculates the square sum of I _s and Q _s (I _s ² + Q _s ² ) as the signal level of the SUM signal, the reciprocal calculation processing unit 14 calculates the reciprocal of the signal level (1 / (I _s ² + Q _s ² )).

Multiplication processing section 15A may be multiplied to the inverse calculated by the inverse calculation processing section ^{_{14 (1 / (I s 2}} + Q s 2)) the addition processing unit 13A of the sum _{(I s I e + Q s} Q e) Thus, the angle error Az _ideal of the azimuth angle AZ is calculated (see equation (9)).
Multiplication processing section 15B multiplies the reciprocal is calculated by the inverse calculation processing section ^{_{14 (1 / (I s 2}} + Q s 2)) the addition processing unit 13B of the subtraction result _{(Q e I s -I e Q} s) Thus, the angle error El _ideal of the elevation angle EL is calculated (see formula (10)).

The AGC circuit 11 generates an AGC control voltage to be output to the automatic control gain amplifiers 4A and 4B based on the signal level of the SUM signal calculated by the power calculation unit 10 in order to make the signal level of the reference SUM signal constant. adjust.
However, when the C / N of the SUM signal is low, the influence of the system noise cannot be ignored, and the calculation result of the signal level of the SUM signal becomes higher than the signal level of the actual SUM signal, and the AGC circuit 11 Since the AGC control voltage output from the signal is lowered, the amount of amplification of the SUM signal and the ERR signal in the automatic control gain amplifiers 4A and 4B is suppressed, and the angle error Az _ideal of the azimuth angle AZ and the angle error El _ideal of the elevation angle EL are detected. The amount is reduced.

Therefore, in the first embodiment, the angle error amplification coefficient acquisition unit 17 acquires the angle error amplification coefficient α corresponding to the C / N of the SUM signal from the angle error amplification coefficient table 16, and the multiplication processing units 18A and 18B By multiplying the angle error amplification coefficient α by the detection amount of the angle error Az _ideal of the azimuth angle AZ and the angle error El _ideal of the elevation angle EL, a decrease in the detection amount of the angle errors Az _ideal and El _ideal is suppressed. Yes.
Specifically, it is as follows.

First, the cause of the decrease in the detection amount of the angle error Az _ideal of the azimuth angle AZ and the angle error El _ideal of the elevation angle EL is that the system noise is included in the SUM signal.
The power value C _TOTAL indicating the signal level of the SUM signal calculated by the power calculator 10 is expressed by the following equation (11).

Here, C _SUM [dBm] is the signal level of the SUM signal output from the automatic control gain amplifier 4A, T _SUM [K] is the SUM system noise temperature, and k [J / K] is the Boltzmann constant (1.38 × 10 ⁻²³ ), B [Hz] is a bandwidth of the tracking receiver (passbands of the bandpass filters 3A and 3B).
Expression (12) is an expression for converting the signal level C _SUM [dBm] of the SUM signal into a true number, and its unit is [W]. Expression (13) is an expression representing system noise.

Therefore, the AGC circuit 11 generates an AGC control voltage from the power value C _TOTAL represented by the equation (11). However, when the C / N of the SUM signal is low (particularly, the C / N is lower than 10 dB). ), The influence of the system noise is great, and it can be seen that the AGC control voltage is suppressed.
On the other hand, when the tracking receiver detects the angle error Az _ideal of the azimuth angle AZ and the angle error El _{ideal of the} elevation angle EL, the SUM signal and the ERR signal including system noise are used. The I and Q components of the SUM signal and the ERR signal each contain system noise, but each system noise is uncorrelated.

Therefore, in the detection of the angle errors Az _ideal and El _ideal , if the numerators of the equations (9) and (10) are integrated with the I component and the Q component and then averaged by filtering, the influence of the system noise is reduced. Can be ignored.
However, since the denominators of Equation (9) and Equation (10) indicate the power of the SUM signal, there is an influence of system noise.
Therefore, when the equations (9) and (10) are rewritten into equations including the influence of system noise, the following equations (14) and (15) are obtained.

Therefore, an amount corresponding angular error amplification amount of the SUM signal and ERR signal by the AGC control voltage is suppressed _{Az ideal,} will be detected amount of _{El ideal} is lowered, the angle error _Az ideal to be detected _originally, and _{El ideal} The ratio R _ERR with the actually detected angular errors Az _real , El _real is obtained by calculating (Az _real / Az _ideal ) or (El _real / El _ideal ), and is expressed by the following equation (16): become.

例えば、自動制御利得増幅器４Ａから出力されたＳＵＭ信号の信号レベルとシステム雑音が同一値のときは（Ｃ／Ｎ＝０ｄＢ）、式（１６）より、比Ｒ_ＥＲＲが１／２になるので、比Ｒ_ＥＲＲの逆数である“２”を乗算することで、本来検出すべき角度誤差を取得することができる。 In order to obtain the angular error that should be detected from the equation (16), the angular errors Az _ideal and El _ideal that are suppressed by the system noise may be multiplied by the inverse α of the ratio R _ERR .

For example, when the signal level of the SUM signal output from the automatic control gain amplifier 4A and the system noise are the same value (C / N = 0 dB), the ratio R _ERR is ½ from the equation (16). By multiplying “2” which is the reciprocal of the ratio R _ERR, the angular error that should be detected can be acquired.

Here, FIG. 3 is a characteristic diagram showing the ratio R _ERR corresponding to C / N of the SUM signal.
_Assuming that the reciprocal α of the ratio R _ERR multiplied by the angular errors Az _ideal and El _ideal suppressed by the system noise is the angular error amplification coefficient α, the angular error amplification coefficient α is expressed by Expression (17).
If the C / N of the SUM signal is known, the angle error amplification coefficient α can be calculated, and the system noise is determined by the receiving system.
Therefore, in the first embodiment, the angle error amplification coefficient α corresponding to various signal levels in the SUM signal is calculated in advance using Expression (17), so that the angle error amplification coefficient α is converted into the angle error. An angle error amplification coefficient table 16 is prepared which is stored in the amplification coefficient table 16 and stores the angle error amplification coefficient α corresponding to C / N.

  Although the angle error amplification coefficient table 16 depends on the memory capacity of the devices constituting the table, for example, a value is calculated for each 1 dB step of the signal level of the SUM signal. For example, about 50 to 100 pieces of data are stored in the table. A sufficient effect can be expected by holding the information and calculating the angle error amplification coefficient α by interpolating the table information.

Finally, a method for calculating C / N in the tracking receiver will be described.
Since the system noise can be obtained on the desk by designing the line, the system noise is stored in the device as _NSUM .
In the operation within the tracking receiver, the power value C _TOTAL indicating the signal level of the SUM signal calculated by the power calculation unit 10 is obtained by calculating the signal level C _SUM of the SUM signal and the system noise N _SUM as shown in Expression (11). It is a combination.
Therefore, by removing the system noise N _SUM stored in the device from the power value C _TOTAL calculated by the power calculation unit 10, the true signal level of the SUM signal is obtained, and C / N can be calculated. it can.

As is apparent from the above, according to the first embodiment, the signal conversion means for converting the SUM signal and ERR signal of the signal arriving from the mobile body into the baseband I signal and Q signal, and the signal conversion means Based on the I and Q signals converted from the SUM signal, the signal amplifying means for amplifying the SUM signal and the ERR signal, and the baseband I signal and Q signal converted by the signal converting means, the direction to the moving body An angle error calculating means for calculating an angle error Az _ideal of the angle AZ and an angle error El _ideal of the elevation angle EL, and the angle error amplifying means determines the angle error amplification coefficient α corresponding to C / N of the SUM signal as the angle error calculating means. since it is configured to multiply the angular error _{El ideal} angular error _{Az ideal} and elevation EL of the calculated azimuth angle AZ, the low C / N It becomes possible to suppress a decrease in the detected amount of angular error _{Az ideal} and elevation EL angular error _{El ideal} azimuthal AZ under environment, as a result, C / N is at a low environment, tracking of satellites There is an effect that can be performed.

Embodiment 2. FIG.
4 is a block diagram showing a tracking receiver according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG.
Angle error amplification factor calculating unit 19 obtains the _{C SUM} subtracts the system noise _{N SUM} from the power value _{C TOTAL} showing signal levels of the calculated SUM signal by the power calculating portion 10, from the _{C SUM} and system noise _{N SUM} Processing for calculating the angle error amplification coefficient α is performed. The angle error amplification coefficient calculation unit 19 constitutes an amplification coefficient calculation unit.

In the first embodiment, the angle error amplification coefficient table 16 that stores the angle error amplification coefficient α corresponding to C / N is created in advance, and the angle error amplification coefficient unit 17 stores the angle error amplification coefficient table C from the angle error amplification coefficient table 16. Although the angle error amplification coefficient α corresponding to / N is obtained, the angle error amplification coefficient calculation unit 19 subtracts the system noise N _SUM from the C _TOTAL calculated by the power calculation unit 10 to obtain C _SUM . The angle error amplification coefficient α may be calculated by substituting the C _SUM and the system noise N _SUM into the equation (17), and the angle error amplification coefficient α may be output to the angle error amplification coefficient unit 17.
Also in this case, the same effect as in the first embodiment can be obtained.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 antenna, 2 receiving circuit, 3A, 3B band pass filter, 4A, 4B automatic control gain amplifier (signal amplifying means), 5A, 5B analog-digital converter (signal converting means), 6 clock oscillation source (signal converting means) , 7A, 7B 90 degree phase shifter (signal conversion means), 8A to 8D detector (signal conversion means), 9A to 9D low-pass filter, 10 power calculation section (signal amplification means, angle error calculation means), DESCRIPTION OF SYMBOLS 11 AGC circuit (signal amplification means), 12A-12D Multiplication processing part (angle error calculation means), 13A, 13B Addition processing part (angle error calculation means), 14 Reciprocal number arithmetic processing part (angle error calculation means), 15A, 15B Multiplication processing unit (angle error calculation means), 16 angle error amplification coefficient table (angle error amplification means), 17 angle error amplification coefficient acquisition section (angle error amplification) Means), 18A, 18B multiplication processing unit (angle error amplification means), 19 angle error amplification coefficient calculation unit (amplification coefficient calculation means), 101 antenna, 102 receiving circuit, 103A, 103B band-pass filter, 104A, 104B automatic control Gain amplifier, 105A, 105B analog / digital converter, 106 clock oscillation source, 107A, 107B 90-degree phase shifter, 108A-108D detector, 109A-109D low-pass filter, 110 power calculator, 111 AGC circuit, 112A ˜112D multiplication processing unit, 113A, 113B addition processing unit, 114 reciprocal calculation processing unit, 115A, 115B multiplication processing unit.

Claims (2)

Signal conversion means for converting a sum signal and a difference signal of signals arriving from a mobile body into baseband I and Q signals;
Signal amplifying means for amplifying the sum signal and the difference signal based on the I and Q signals converted from the sum signal by the signal converting means;
An angle error calculation means for calculating an angle error of an azimuth angle and an angle error of an elevation angle with respect to the moving body from the baseband I signal and Q signal converted by the signal conversion means;
Angle error amplification means for multiplying the angle error amplification coefficient corresponding to the ratio of the sum signal and noise by the angle error of the azimuth and the angle error of the elevation angle calculated by the angle error calculation means ,
The angle error amplifying means is
For each ratio of the sum signal and noise, there is a table in which the reciprocal of the ratio of the signal level of the sum signal excluding the noise and the signal level of the sum signal including the noise is stored in advance as the angle error amplification coefficient. And
The signal level of the sum signal is calculated by squaring the I signal and the Q signal converted from the sum signal by the signal conversion means, and the noise determined in advance is calculated from the signal level of the sum signal. and obtaining the angular error amplification factor corresponding to the ratio of the signal level and the noise of the sum signal excluding from the table, the angle error and elevation angle of the azimuth angle calculated by the angle error calculation means the angular error amplification factor A tracking receiver characterized by multiplying the angle error of. Signal conversion means for converting a sum signal and a difference signal of signals arriving from a mobile body into baseband I and Q signals;
Signal amplifying means for amplifying the sum signal and the difference signal based on the I and Q signals converted from the sum signal by the signal converting means;
An angle error calculation means for calculating an angle error of an azimuth angle and an angle error of an elevation angle with respect to the moving body from the baseband I signal and Q signal converted by the signal conversion means;
Angle error amplification means for multiplying the angle error amplification coefficient corresponding to the ratio of the sum signal and noise by the angle error of the azimuth and the angle error of the elevation angle calculated by the angle error calculation means ,
The angle error amplifying means is
The signal level of the sum signal is calculated by summing the squares of the I signal and Q signal converted from the sum signal by the signal conversion means, and includes the signal level of the sum signal excluding the noise obtained in advance and the noise. Amplification coefficient calculation means for calculating the reciprocal of the ratio of the signal level of the sum signal as it is as the angle error amplification coefficient,
Tracking receivers, characterized in that multiplying the angular error amplification coefficient calculated by the amplification coefficient calculating section to the angle error and elevation angle error of the azimuth angle calculated by the angle error calculation means.

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