JP2008193311A - Automatic tracking device for multi-horn antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of automatic tracking of a horn antenna in microwave communication which uses an analog wave or digital wave. <P>SOLUTION: The tracking device is provided with: an LNA and a frequency converter 106 for amplifying and performing frequency conversion to an output signal selected by an antenna input switch 105 out of a plurality of signals outputted by the multi-horn antenna; an IF demodulator 107 for demodulating an IF signal from the output signal; and a control voltage creation part 108 for outputting an azimuth angle control voltage and an angle of elevation control voltage of the multi-horn antenna on the basis of the output signal of the IF demodulator 107 and a signal from the timing generator 109. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a configuration of an automatic tracking device that, when receiving a microwave transmitted from a helicopter or the like, tracks an arrival direction of the microwave at a base station.

  As a technique for tracking a helicopter or a mobile relay vehicle, the present applicant has already proposed an invention relating to a tracking multihorn antenna as described in Patent Document 1. In Patent Document 1, a primary radiator is disposed near the focal point at the center of the front of a parabolic reflector, a pair of azimuth angle detection horns are tilted upward and downward, respectively, in a vertical plane, and a pair of elevation angle detection horns. A tracking multi-horn antenna is disclosed that is tilted left and right in the horizontal plane. Since the tracking multihorn antenna has a wide pulling angle and a higher pulling sensitivity, it is useful in the current tracking system. Since a multi-horn is used for these communications, the radio wave used for tracking uses the same type of radio wave as the main horn.

The conventional analog wave tracking device obtains the input electric field strength from the radio wave obtained from each horn antenna, obtains the control voltage of the drive unit that drives the antenna from the electric field strength, and controls them to be equal to each other on the left and right and up and down is doing. For example, when the electric field strength obtained from the two left and right horn antennas is larger on the left side than on the right side, the left and right electric field strengths are controlled to be equal by rotating the antenna.
Therefore, if the electric field strength is extremely deteriorated, the electric field strength cannot be obtained, the tracking limit value is reached, and the tracking cannot be performed.

  In recent years, digitalization has also progressed in the field of microwave communication, and communication using digital modulation such as QAM (Quadrature Amplitude Modulation) and OFDM (Orthogonal Frequency Division Multiplexing), which is different from conventional analog FM (Frequency Modulation) waves, is popular. It is.

  In the case of a digital communication device, unlike an analog communication device, it has a correction function that corrects errors during transmission, so the input electric field strength may be much lower than that of an analog communication device, and even if the noise level is higher than the signal level, it is received. Is possible. In such a state, the horn antenna cannot be tracked even if the multi-horn antenna automatic tracking device in the conventional analog communication device is used.

  Therefore, the present applicant has already proposed the invention described in Patent Document 2 regarding these digital communication devices. Patent Document 2 discloses a circuit capable of estimating the input electric field strength even when the signal component is smaller than the noise component. According to this, a correlation value of the same data included in the signal component is calculated, and the maximum correlation value is calculated. The input electric field strength can be calculated from the value, and as a result, it is possible to detect the input electric field strength wider than the conventional one.

Japanese Patent Publication No. 5-45081 JP 2006-13591 A

  In the case of communication using digital waves, an error during transmission can be corrected. Therefore, according to the invention disclosed in Patent Document 2, the input electric field strength is much lower than that of communication using conventional analog waves. Even if the noise level is higher than the signal level, reception is possible.

  However, in the case of digital wave communication, it is possible to demodulate with the main horn antenna even if there is some degradation, but if the conventional analog wave tracking circuit is used, the electric field strength becomes the limit value. In such a case, only the tracking device reaches the tracking limit value, which causes a problem that the tracking function itself does not operate. As a result, the evaluation of the entire system becomes low.

  An object of the present invention is to provide an automatic tracking device for a multi-horn antenna that can be used in both analog wave and digital wave communication devices.

The present invention has been made to solve the above problems,
The invention according to claim 1 is an automatic tracking device for a multihorn antenna that tracks the direction of arrival of radio waves by a multihorn antenna, and switches and outputs a plurality of signals output from the multihorn antenna by an antenna switching signal. Antenna output switching means, frequency conversion means for amplifying and frequency converting the output signal of the antenna output switching means to obtain an IF signal, IF signal demodulating means for demodulating the IF signal, and output signal of the IF signal demodulating means An electric field strength calculating means for calculating a received electric field strength based on the received electric field strength, a first control voltage calculating means for calculating a control voltage for controlling the driving means of the multi-horn antenna from the received electric field strength, and an IF demodulating means. Quadrature demodulating means for quadrature demodulating the output signal, and calculating a correlation for a predetermined period with the output signal of the orthogonal demodulating means Correlation calculating means, maximum value detecting means for detecting the maximum value of the output signal of the correlation calculating means, and second control voltage calculating means for calculating the control voltage based on the output signal of the maximum value detecting means, An adder for adding the output signals of the first and second control voltage calculating means, and an azimuth control voltage and an elevation angle control voltage of the multihorn antenna by a predetermined calculation based on the output signal of the adder. A control voltage generating means for outputting is provided.

  According to a second aspect of the present invention, in the automatic tracking device for a multihorn antenna according to the first aspect, the correlation calculation means has a QAM / OFDM selector switch, and the predetermined period includes the QAM / OFDM. When the changeover switch is on the QAM side, it is the period of the synchronous part of the output signal of the orthogonal demodulation means, and when the QAM / OFDM changeover switch is on the OFDM side, it is the guard interval period of the output signal of the orthogonal demodulation means. It is characterized by being.

  Still further, the invention according to claim 3 is the automatic tracking device for a multi-horn antenna according to claim 1, wherein the predetermined calculation is performed by sampling and holding the output signal of the adder by a signal synchronized with the antenna switching signal. Then, the sampled and held output signal is calculated.

  According to a fourth aspect of the present invention, in the automatic tracking device for a multi-horn antenna according to the first aspect, the correlation calculation is a digital calculation.

  Furthermore, the invention according to claim 5 is the automatic tracking device for a multihorn antenna according to claim 1, characterized in that the multihorn antenna is composed of four horn antennas on the left, right, and top and bottom.

According to the first aspect of the present invention, the control voltage is created from the addition result of the first control voltage by the circuit used in the conventional tracking by the analog wave and the second control voltage by the maximum value of the correlation calculation. As a result, in addition to the tracking by the conventional analog wave, the digital wave can be tracked, and the reliability of the entire system is improved.
Further, in the case of only the conventional analog wave, the correlation calculation unit does not operate, but since the addition is performed, the conventional analog wave system can be supported.

  According to the second aspect of the present invention, since the predetermined period is the same part included in the digital wave, an actual arithmetic circuit can be realized by a delay element such as a shift register, and the circuit scale is increased. Therefore, it becomes suitable.

  Furthermore, according to the invention described in claim 3, since the sample-and-hold is performed by the signal synchronized with the antenna switching signal, the signal that has been selected and processed can be sample-and-held, and real-time processing becomes possible. This is suitable as a tracking device.

  According to the invention described in claim 4, the correlation calculation can be digitally calculated. As a result, it can be configured by one chip, and the circuit scale is not increased, which is preferable.

  And according to invention of Claim 5, the said multihorn antenna can use four horn antennas of right and left, and up and down, and it is easy to perform azimuth angle control and elevation angle control, As a result, as a tracking device This is preferable.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing the best mode for carrying out the present invention. As shown in the figure, the automatic tracking device for a multi-horn antenna according to the present embodiment includes a horn antenna input terminal 101 (RIGHT), 102 (LEFT), 103 (UPPER), and 104 (LOWER), and an antenna input. It comprises a changeover switch 105, an LNA / frequency converter 106, an IF (Intermediate Frequency) demodulator 107, a control voltage generator 108, a timing generator 109 for generating an antenna switching signal, and output terminals 110 and 111. ing.

  The antenna input changeover switch 105 switches the output of the multihorn antenna input from the horn antenna input terminals 101, 102, 103, and 104 based on the switching signal SEL (SELECT) generated from the timing generator 109. The output of the antenna input changeover switch 105 is amplified by low noise by an LNA (Low Noise Amp.) And a frequency converter 106.

  The output of the horn antenna is the same frequency as the radio wave received by the main horn. That is, it is a signal in the SHF (Super High Frequency) band, and this SHF wave is converted into a UHF (Ultra High Frequency) wave and further frequency-converted (down-converted) into a VHF (Very High Frequency) wave.

  The signal converted to the VHF band is converted to an intermediate frequency by the IF demodulator 107, and the signal demodulated to the IF band signal controls a motor (not shown) of the antenna driving unit by the control voltage generator 108. A voltage is generated, and an azimuth control voltage is output from the output terminal 110, and a control voltage of the elevation angle is output from the output terminal 111. The timing generator 109 generates timing signals based on FIG. 3 described later.

FIG. 2 is a block diagram showing a detailed configuration of the control voltage generator 108.
As shown in the figure, the control voltage generator 108 includes an input terminal 201, an AGC amplifier 202, a demodulator 203, a field strength calculator 204, a control voltage calculator A205, an orthogonal demodulator 206, a synchronization detector 207, a QAM / OFDM. From the changeover switch 208, the correlation calculation unit 209, the peak value detection unit 210, the control voltage calculation unit B 211, the adder 212, the sample hold circuits 213, 214, 215 and 216, the calculation units 217 and 218, and the output terminals 110 and 111 It is configured.
QAM is an abbreviation for orthogonal amplitude modulation, and OFDM is an abbreviation for orthogonal frequency division multiplexing.

  Next, the operation will be described. The IF signal input from the input terminal 201 is amplified by the AGC amplifier 202 so that a constant output can be obtained. The output of the AGC amplifier 202 is detected by the demodulator 203, and a gain control signal is generated so that the output of the AGC amplifier becomes constant. Based on this gain control signal, the received field strength calculation unit 204 calculates the received field strength, and the control voltage calculation unit A205 calculates the antenna drive voltage from the received field strength.

  The output of the AGC amplifier 202 is input to the quadrature demodulator 206 and quadrature demodulated to become an IQ signal. Note that the processing after the quadrature demodulator 206 is all performed digitally.

The IQ signal is input to the synchronization detection unit 207 and the QAM / OFDM switch 208. When the QAM / OFDM selector switch 208 is on the QAM side, the synchronization detection unit 207 detects the synchronization portion of the QAM signal, selects the output thereof, and the correlation calculation unit 209 performs autocorrelation calculation on the synchronization portion.
When the QAM / OFDM selector switch 208 is on the OFDM side, the correlation calculation unit 209 performs autocorrelation calculation on the guard interval portion. Note that the QAM / OFDM switch 208 can be set before reception because the type of digital wave can be known in advance.

  The peak value detection unit 210 detects a peak value for each predetermined period with respect to the output of the correlation calculation unit 209, and the control voltage calculation unit B211 calculates a control voltage based on the peak value. The outputs of the control voltage calculation unit A205 and the control voltage calculation unit B211 are added by the adder 212. The added control voltage is supplied to the sample hold circuits 213 to 216, and the timing generator 109 shown in FIG. Only one sample and hold circuit is sampled by the sampling signal S / H from. The other sample and hold circuits are in the hold state as they are.

  In this way, the control voltage for each horn antenna is obtained, and based on this control voltage, it is calculated by the calculators 217 and 218 so as to be one control signal left and right and up and down, and the AZ signal and elevation of the azimuth control voltage signal are calculated. An angle control voltage signal is output from the output terminal as an EL signal.

  Next, the control voltage of each horn will be described. The detection level of each horn antenna is as shown in FIG. 4 with respect to the lead-in angle, and the output level of the paired horn antenna is constant when it becomes an intersection. That is, the control is performed so that the left and right or upper and lower horn antenna levels are equal, not the peak value of the horn antenna output.

  If the relationship between the pull-in angle and the control voltage of the drive portion shown in FIG. 4 is obtained in advance, the control voltage can be obtained from the detection level. The azimuth angle is the left and right horn antennas, and the elevation angle is the upper and lower horn antennas.

  For example, when data such as a control voltage of 2 V is obtained from the detection level of the right horn antenna and a control voltage of 5 V is obtained from the detection level of the left horn antenna, the control voltage is calculated so that the detection level value is the same. Go and perform angle control. In this case, the difference between the control voltages is taken as 3V, and a sign indicating the direction is attached to the difference and supplied to the drive portion, thereby controlling the left and right detection levels to be the same.

  As shown in FIG. 4, when there are two angles at the detection level, control is performed using a small angle, and when the left and right are not at the same level, control is performed using a large angle. Note that the same applies to the upper and lower sides.

  Next, the operation of the timing generator 109 that creates the timing used by the antenna selector switch 105 and the control voltage generator 108 will be described with reference to FIG.

  The CLOCK signal is a pulse train in which one cycle is 0.22 msec. QA, QB, QC and QD are output signals when the CLOCK signal is counted by the counter. QA is a countdown of the CLOCK signal, QB is a countdown of QA, QC is a countdown of QB, and QD is a countdown of QC. Based on these four count signals, antenna switching signals SEL (RI), SEL (LE), SEL (UP) and SEL (LO) are created, and the switching time per horn is changed to 0.88 msec.

  SEL (RI) is an AND (logical product) of QC and QD and inverted. SEL (LE) is an AND (logical product) of the inverted QC and QC. SEL (UP) is an AND (logical product) of the inverted QC and QD, and SEL (LO) is an AND (logical product) of the inverted QC and the inverted QD. ) And reversed. The antenna selection signal is active low.

The same applies to the error voltage sampling signal. That is, S / H (RI) is obtained by inverting QA, inverting QB, and ANDing QC and QD (logical product), and S / H (LE) is inverted QA. And QB inversion, QC inversion, and QD and AND (logical product).
S / H (UP) is an AND (logical product) of the inverted QA, the inverted QB, the inverted QC and QD, and the S / H (LO) is An AND (logical product) of an inverted version of QA, an inverted version of QB, an inverted version of QC, and an inverted version of QD.
In any case, the last one clock is the sample period.
In this way, the antenna selection signal and the error voltage sampling signal are generated and supplied to the antenna changeover switch 105 and the control voltage generation unit 108.

The embodiment of the present invention is not limited to the above embodiment. For example, when the received field strength reaches the limit value in the field strength calculation unit 204, the control voltage may be set to 0 and added to the result of the correlation calculation.
In the description of FIG. 2, the A / D converter, the D / A converter, and the like are omitted, but they are necessary for digital processing and need to be inserted at an appropriate location. Furthermore, although QAM and OFDM are used as digital wave communication, other digital communication such as BPSK and QPSK are useful if they include a synchronization portion.

  The present invention relates to an automatic tracking device for a multi-horn antenna, and is particularly suitable for communication by a mobile object. In practice, it is communication between the helicopter and the base station or communication between the mobile relay vehicle and the base station that requires tracking. Furthermore, the present invention is configured to control based on the result of mixing the conventional analog wave and the latest digital wave calculation, and by a simple modification to deactivate the digital wave part, It can also be applied to a tracking system using only analog waves.

It is the block diagram which showed the best form regarding implementation of this invention. It is a detailed block diagram of the control voltage preparation part of the best form regarding implementation of this invention. It is the figure which showed the timing chart of the timing generator of the best form regarding implementation of this invention. It is a graph which shows the relationship between an antenna angle, the azimuth, and the output level of each horn for elevation angle detection.

Explanation of symbols

101 Horn antenna input terminal (RIGHT)
102 Horn antenna input terminal (LEFT)
103 Horn antenna input terminal (UPPER)
104 Horn antenna input terminal (LOWER)
DESCRIPTION OF SYMBOLS 105 Antenna input switch 106 LNA and frequency converter 107 IF demodulator 108 Control voltage preparation part 109 Timing generator 110, 111 Output terminal 201 Input terminal 202 AGC amplifier 203 Demodulator 204 Electric field strength calculation part 205 Control voltage calculation part A
206 Quadrature Demodulation Unit 207 Synchronization Detection Unit 208 QAM / OFDM Switch 209 Correlation Calculation Unit 210 Peak Value Detection Unit 211 Control Voltage Calculation Unit B
212 Adder 213, 214, 215, 216 Sample hold circuit 217, 218

Claims (5)

In an automatic tracking device for a multihorn antenna that tracks the direction of arrival of radio waves by a multihorn antenna,
An antenna output switching means for switching and outputting a plurality of signals output from the multihorn antenna by an antenna switching signal;
Frequency conversion means for amplifying and frequency converting the output signal of the antenna output switching means to obtain an IF signal;
IF signal demodulating means for demodulating the IF signal;
Electric field strength calculating means for calculating the received electric field strength based on the output signal of the IF signal demodulating means;
First control voltage calculating means for calculating a control voltage for controlling the driving means of the multi-horn antenna from the received electric field strength;
Orthogonal demodulation means for orthogonally demodulating the output signal of the IF demodulation means;
Correlation calculating means for calculating a correlation for a predetermined period with respect to the output signal of the orthogonal demodulating means;
Maximum value detecting means for detecting the maximum value of the output signal of the correlation calculating means;
Second control voltage calculating means for calculating the control voltage based on an output signal of the maximum value detecting means;
An adder for adding the output signals of the first and second control voltage calculation means;
An automatic tracking device for a multihorn antenna, comprising control voltage generating means for outputting an azimuth angle control voltage and an elevation angle control voltage of the multihorn antenna by a predetermined calculation based on an output signal of the adder. The correlation calculation means has a QAM / OFDM selector switch,
The predetermined period is a period of a synchronization portion of the output signal of the orthogonal demodulation means when the QAM / OFDM switch is on the QAM side, and the orthogonal demodulation is performed when the QAM / OFDM switch is on the OFDM side. 2. The automatic tracking device for a multi-horn antenna according to claim 1, wherein the interval is a guard interval period of the output signal of the means.   2. The multi-horn antenna according to claim 1, wherein the predetermined calculation is an operation of sampling and holding the output signal of the adder by a signal synchronized with the antenna switching signal, and calculating the sampled and held output signal. Automatic tracking device.   2. The automatic tracking device for a multi-horn antenna according to claim 1, wherein the correlation calculation is a digital calculation.   2. The automatic tracking device for a multi-horn antenna according to claim 1, wherein the multi-horn antenna includes four horn antennas on the left, right, and upper and lower sides.

Images