JP4948485B2 - Direction finding device - Google Patents

Description

  The present invention relates to an apparatus for receiving radio wave signals such as communication waves and radar waves, and more particularly to an azimuth detecting apparatus for detecting the location of a radio wave source.

  As a method of detecting the location direction of a radio wave transmission source, a series of pulse signals transmitted from the radio wave transmission source are received by two or more reception systems, and the pulse arrival direction is obtained from the time difference of the pulse arrival times obtained in each reception system. It is common. For example, in the conventional technique described in Patent Document 1, in each receiving system, a pulse arrival time is obtained for each pulse from a received pulse received by each antenna, and then a signal processing unit , Statistical processing is performed for each reception system for a plurality of pulse arrival times related to a series of pulse signals obtained in each reception system, and the time difference between the pulse arrival times between the reception systems is obtained. The pulse arrival direction is obtained based on the distance between the antennas of each receiving system and the propagation speed of the pulse signal. This makes it possible to detect the pulse arrival direction with high accuracy.

JP 2003-215225 A

  In the conventional azimuth detection technique, it is necessary to provide a plurality of reception systems including an antenna and a pulse detector, and it is necessary to increase the antenna interval in order to improve accuracy. Therefore, there has been a problem that the apparatus becomes large-scale.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an azimuth detecting device that can detect the azimuth of a radio wave source using a single receiving system.

  An azimuth detection apparatus according to the present invention is an azimuth detection apparatus that is mounted on a moving platform and detects an arrival direction of a radio wave while moving, and provides a pulse arrival time to each pulse detected from a reception radio wave and outputs it. A reception system, and a frame extraction unit for detecting a pulse signal repeated with periodicity based on the pulse arrival time of the pulse detected by the reception system, and extracting a frame period of a pulse train having the repetition pattern as one frame; A virtual pulse train generation unit that generates a virtual pulse train when it is assumed that the pulse train detected at a certain measurement point and the frame period of the pulse train are continuously received at the same measurement point; and a certain measurement point The distance between the next measurement points is calculated, and based on this calculated distance, the difference in arrival time of radio waves when both measurement points are assumed to be fixed is calculated. A pulse time difference calculation unit that outputs the arrival time difference as a pulse time difference between a virtual pulse train at a certain measurement point generated by the virtual pulse train generation unit and a pulse train actually received at the next measurement point obtained by the reception system; A time difference error compensation unit that averages the calculated pulse time difference for each frame, and an azimuth calculation unit that calculates the location direction of the corresponding radio wave source based on the averaged pulse time difference.

  According to the present invention, the azimuth finding device based on a single receiving system is moved to a single receiving system azimuth finding device mounted on a mobile platform, so that a plurality of receiving systems can be used in a pseudo manner to locate the radio wave source. Is calculated. Therefore, compared with the prior art, it is possible to reduce the number of components and reduce the scale of the apparatus, and there is an effect of improving the degree of freedom in installation.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a functional configuration of an azimuth detection apparatus according to Embodiment 1 of the present invention.
The azimuth detection device is mounted on a mobile platform such as an aircraft, a ship, or a vehicle and performs azimuth measurement. A single antenna 1, a pulse detection unit 2, a frame extraction unit 3, a virtual pulse train generation unit 4, and a pulse time difference calculation. The unit 6 includes a time difference error compensation unit 7 and an azimuth calculation unit 8. The azimuth detecting device according to the first embodiment is characterized in that a pulse signal is detected from an incoming radio wave only by a single receiving system including the antenna 1 and the pulse detector 2.

Next, the operation of the direction finding device will be described.
Now, this azimuth detection device is mounted on a moving platform and is capable of receiving multiple / multiple types of pulse signals transmitted by a radio wave source such as a general radar device according to a certain periodicity while moving linearly at a constant speed. It is assumed that direction detection is performed by receiving.
When the antenna 1 receives an incoming radio wave, it outputs the received signal to the pulse detector 2. When the received signal of the antenna 1 includes a series of pulse signals transmitted from a radio wave transmission source, the pulse detector 2 sequentially detects the pulse signals and extracts basic information of the pulse such as frequency and pulse width. Then, a pulse arrival time (TOA; Time Of Arrival) is sequentially given to each pulse and output to the subsequent frame extraction unit 3 and the pulse time difference calculation unit 6. The pulse signal detected by the pulse detector 2 is expressed as shown in FIG. In FIG. 2, the horizontal axis is the frame period, the vertical axis is the number of frames, and the pulse train is folded and displayed for each frame period according to the TOA. Actually, there are cases where a plurality of types of pulse trains are received, but here, one type of pulse train is shown as an example for explanation.

  The frame extraction unit 3 detects a pulse signal repeated with periodicity based on the pulse arrival time of the pulse detected by the pulse detection unit 2, and extracts the frame period of the pulse train with the pattern as one frame. Therefore, first, the frame period is changed with respect to the state of the pulse train shown in FIG. 2, and each pulse is set to be aggregated in the minimum time range for each type as shown in FIG. In this case, temporary pulse data is stored in a storage memory or the like, and the horizontal axis is set so that a time zone in which the density is maximum is formed in the vertical axis direction. Next, the frame period set in this way is extracted as the frame period of the received pulse train. The extracted frame period corresponding to the detected pulse train is given to the virtual pulse train generator 4.

  In the virtual pulse train generation unit 4, based on the pulse train detected at a certain measurement point and the frame period of the pulse train extracted by the frame extraction unit 3, the pulse train is assumed to be continuously received at the same measurement point. Generate and output as a virtual pulse train. Here, since the direction finding device is moving, it no longer exists at the measurement point that actually received the pulse train, but the reception system remains at this original measurement point, and the next measurement of the destination A virtual state in which radio waves are measured at two points is created with a receiving system that actually receives signals at a point.

  As shown in FIG. 6, in the azimuth detecting device, the distance from the radio wave source 11 changes with the movement of the platform, but it is assumed that a receiving system is installed at each of the measurement points 12 and 13 and 2 When it is assumed that two receiving systems receive radio waves of pulse trains transmitted simultaneously from the radio wave transmission source 11, a time difference occurs between the two received pulse trains. On the other hand, as shown in FIG. 4, a time difference (this is a pulse time difference) ΔT (1) occurs between the virtual pulse train predicted at the point A and the pulse train actually received at the point B. Further, when the actual pulse train detected at the point B and the virtual pulse train generated at the point A are folded and displayed continuously for each frame period according to the TOA, as shown in FIG. 5, the actual pulse train 9 and the virtual pulse train are shown. A pulse time difference ΔT occurs between 10. In other words, the pulse time difference between the virtual pulse train predicted at the point A and the pulse train actually received at the point B is simultaneously transmitted from the radio wave source 11 at a plurality of measurement points 12 and 13 that are fixed in FIG. It can be regarded as a difference in arrival time of radio waves when received.

Based on the above idea, in the pulse time difference calculation unit 6, the pulse between the virtual pulse train at a certain measurement point generated by the virtual pulse train generation unit 4 and the pulse train actually received at the next measurement point obtained by the pulse detection unit 2. Calculate the time difference. Specifically:
In FIG. 6, it is assumed that the platform is moving horizontally, and there are two fixed measurement points 12 and 13 for radio waves transmitted simultaneously from the radio wave source 11. When the arrival time difference of radio waves occurs, the distance between two measurement points is L, the arrival time difference of radio waves is ΔT, the speed of light (or radio wave velocity) is c, the line perpendicular to the moving line of the platform and the arrival direction of radio waves are Assuming that the formed angle is θ, the relationship of equation (1) is established as is well known.
c · ΔT = L · sinθ
ΔT = (L / c) · sin θ (1)

Here, since the direction finding device is actually mounted on the platform and moving, the distance L between the two measurement points 12 and 13 is the movement distance of the platform, so the time required for movement between the two measurement points. Assuming that Δt is the measurement time and v is the moving speed of the platform, the distance L between the two measurement points is expressed by equation (2).
L = v · Δt (2)
Further, if the measurement times at the two measurement points 12 and 13 are T1 and T2, the measurement time Δt is expressed by equation (3).
Δt = T2-T1 (3)
Accordingly, the arrival time difference ΔT of the radio waves at the two fixed measurement points 12 and 13 can be calculated from the equations (1) to (3). Here, at the measurement point 12, assuming that a virtual pulse train is received instead of the actual pulse train, the arrival time difference ΔT of the radio wave is the difference between the actual received pulse train at the measurement point 13 and the virtual pulse train at the measurement point 12. The difference in pulse time.

The time difference error compensation unit 7 averages the pulse time difference calculated by the pulse time difference calculation unit 6 for each frame to compensate for an error between the time differences.
Next, the azimuth calculation unit 8 calculates the arrival direction of the radio wave, that is, the location direction of the radio wave transmission source by a known process based on the pulse time difference averaged by the time difference error compensation unit 7.
The direction finding device can detect a time difference of ~ μsec. If it is mounted on an aircraft with a speed of about 300kt, the measurement time is several seconds to several tens of seconds. If it is ten seconds or more, it becomes possible to perform a required measurement.

  As described above, according to the first embodiment, a single reception system including the antenna 1 and the pulse detector 2 sequentially detects pulses from the received radio wave, and gives a pulse arrival time to each detected pulse. The frame extraction unit 3 detects a pulse signal that is repeated with periodicity based on the pulse arrival time of the pulse detected in the reception system, and extracts the frame period of the pulse train with the pattern as one frame. The virtual pulse train generation unit 4 is assumed to be continuously received at the same measurement point based on the pulse train detected at a certain measurement point and the frame period of the pulse train extracted by the frame extraction unit 3. A pulse train is generated, and the pulse time difference calculation unit 6 uses the measurement time T1 when the pulse is actually received at a certain measurement point and the measurement time T when the pulse is actually received at the next measurement point. And the distance between the two measurement points is calculated from the moving speed v of the platform, and based on the calculated distance, the difference between the arrival times of the radio waves when the two measurement points are assumed to be fixed is calculated, and the virtual pulse train generator 4 is generated as a pulse time difference between a virtual pulse train at a certain measurement point generated at 4 and a pulse train actually received at the next measurement point obtained by the reception system, and is calculated by the pulse time difference calculation unit 6 by the time difference error compensation unit 7. The calculated pulse time difference is averaged for each frame, and the direction calculation unit 8 calculates the location direction of the radio wave transmission source based on the average value of the pulse time difference calculated by the time difference error compensation unit 7. Therefore, it is possible to calculate the azimuth of the radio wave generation source by using a plurality of reception systems in a pseudo manner by mounting an azimuth detection device with a single reception system on the mobile platform. The number of devices can be reduced to reduce the size of the device, and the effect of improving the degree of freedom in installation can be obtained. In addition, the cost can be reduced.

Embodiment 2. FIG.
FIG. 7 is a block diagram showing a functional configuration of an azimuth detection apparatus according to Embodiment 2 of the present invention. In the figure, parts corresponding to those in FIG. The configuration of the second embodiment newly includes a GPS (Global Positioning System) receiver 51 that acquires position information of a platform (or direction finding device) used instead of the moving speed of the platform. Moreover, it replaces with the pulse time difference calculation part 6 of Embodiment 1, and the pulse time difference calculation part 61 which performs a process using position information is provided.
In FIG. 7, the GPS receiver 51 receives the GPS signal, acquires the position information of the platform every moment, and gives it to the pulse time difference calculation unit 6. The pulse time difference calculation unit 6 extracts the platform position corresponding to the measurement time at which a pulse is actually received at a certain measurement point and the next measurement point from the input position information, and calculates the distance between the two measurement points. . Next, based on the calculated distance between the two measurement points, the arrival time difference of the radio wave when it is assumed that both measurement points are fixed is calculated, and this arrival time difference is generated by the virtual pulse train generation unit 4. In addition, the pulse time difference between the virtual pulse train at a certain measurement point and the pulse train actually received at the next measurement point obtained by the reception system is output to the time difference error compensation unit 7.

  As described above, according to the second embodiment, the distance between the measurement points is obtained from the position information of the platform obtained from the GPS signal, and the pulse time difference is calculated. Therefore, the same effect as in the first embodiment is obtained. available. Further, even when a change occurs in the platform speed or flight direction during the measurement, an accurate distance can be calculated from the position information, so that ambiguity in azimuth measurement can be improved.

Embodiment 3 FIG.
Here, in the first embodiment, the measurement is continuously performed a plurality of times in a state where the platform is in a constant velocity linear motion. In this case, the pulse time difference ΔT generated between the actual pulse train 9 and the virtual pulse train 10 in the frame shown in FIG. 5 is considered to be a linear function of time. Therefore, in the time difference error compensation unit 7 in the third embodiment, an approximate function is obtained by processing the pulse time difference sequentially calculated by the pulse time difference calculation unit 6 by a plurality of measurements using the least square method. Correct the time difference group. This approximate function is as shown in FIG. In FIG. 8, 14 represents a pulse time difference at each time, and 15 represents an approximate line of the pulse time difference. Next, the azimuth calculation unit 8 calculates the signal arrival azimuth, that is, the azimuth of the radio wave transmission source, based on the approximate function obtained above.
Therefore, according to the third embodiment, since the azimuth of the transmission source is obtained using the approximate function of the pulse time difference, it is possible to obtain a higher azimuth than in the case of the first embodiment. Further, even if the third embodiment is applied to the second embodiment, the same effect can be obtained.

It is a block diagram which shows the function structure of the direction finding apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the output pulse signal of the pulse detection part which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the pulse signal by the process of the frame extraction part which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement of the pulse time difference calculation part which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the virtual pulse which concerns on Embodiment 1 of this invention, and the pulse of a real signal. It is explanatory drawing which shows the relationship between the signal arrival time difference in the measurement condition which concerns on Embodiment 1 of this invention, and an azimuth | direction. It is a block diagram which shows the function structure of the direction finding apparatus by Embodiment 2 of this invention. It is explanatory drawing which shows the approximate function of the pulse arrival time difference calculated by the time difference error compensation part which concerns on Embodiment 3 of this invention.

Explanation of symbols

  1 antenna, 2 pulse detection unit, 3 frame extraction unit, 4 virtual pulse train generation unit, 6, 61 pulse time difference calculation unit, 7 time difference error compensation unit, 8 bearing calculation unit, 51 GPS receiver.

Claims (4)

In a direction finding device that is mounted on a moving platform and detects the direction of arrival of radio waves while moving,
A single receiving system consisting of an antenna and a pulse detector that outputs a pulse arrival time to each pulse detected from the received radio wave,
A frame extraction unit for detecting a pulse signal repeated with periodicity based on a pulse arrival time of a pulse detected in the reception system, and extracting a frame period of a pulse train having the repetition pattern as one frame;
A virtual pulse train generation unit that generates a virtual pulse train when it is assumed that the pulse train detected at a certain measurement point and the frame period of the pulse train are continuously received at the same measurement point;
Calculate the distance between one measurement point and the next measurement point, and based on this calculated distance, calculate the arrival time difference of radio waves assuming that both measurement points are fixed. A pulse time difference calculation unit that outputs a pulse time difference between the virtual pulse train at the certain measurement point generated by the virtual pulse train generation unit and the pulse train actually received at the next measurement point obtained by the reception system;
A time difference error compensation unit that averages the calculated pulse time difference for each frame;
An azimuth detecting device comprising an azimuth calculating unit that calculates a location azimuth of a corresponding radio wave transmission source based on the averaged pulse time difference.   The pulse time difference calculation unit calculates the difference between the measurement times when a pulse is actually received at one measurement point and the next measurement point, and calculates the distance between the two measurement points based on this time difference and the moving speed of the platform. The azimuth detecting device according to claim 1. A GPS receiver for receiving GPS signals and acquiring platform position information;
The pulse time difference calculation unit extracts the position of the platform corresponding to the measurement time when the pulse is actually received at a certain measurement point and the next measurement point from the position information acquired by the GPS receiver, and between the two measurement points. The azimuth detecting apparatus according to claim 1, wherein the distance is calculated. In continuous measurement and direction detection,
The time difference error compensation unit obtains an approximate function using the least square method based on the pulse time difference instead of averaging the pulse time difference for each frame,
4. The azimuth according to claim 1, wherein the azimuth calculation unit calculates a location azimuth of a corresponding radio wave source based on the obtained approximate function of the pulse time difference. Detecting device.

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