JP7261933B2 - Radio wave direction finding system and radio wave direction finding method - Google Patents

Description

The present invention relates to a direction finding system for detecting the direction of arrival of radio waves.

One technique for detecting the direction of arrival of radio waves is the interferometer method. FIG. 4 is a schematic diagram showing the principle of the interferometer direction finding technique. Here, it is assumed that one incoming radio wave 30 is received by two antennas 101a and 101b. At this time, assuming a wavefront 200 that is a line perpendicular to the direction of arrival of the radio wave 30, the signal phase difference is the same at points along the wavefront 200. FIG. In FIG. 4, the antenna 101a is on the wavefront 200, and the distance between the wavefront 200 and the antenna 101b when a line 201 perpendicular to the wavefront 200 is drawn from the antenna 101b is the path difference. The phase difference between the signals received by the two antennas 101a and 101b can be calculated from this path difference and the wavelength ratio of the radio wave 30, and the direction of arrival of the radio wave 30 can be estimated from this phase difference.

FIG. 5 shows a configuration example of a conventional radio wave direction finding apparatus. In the conventional example of FIG. 5, an incoming radio wave 30 is received by five azimuth measurement antennas 101a, 101b, 101c, 101d, and 101e. The radio waves 30 received by each antenna are input to the radio wave direction finding device 100 via coaxial cables 102a, 102b, 102c, 102d, and 102e, respectively. Received signals input to the direction finding apparatus 100 are subjected to processing such as signal amplification, modulation to an intermediate frequency, and filtering in receiving sections 104a, 104b, 104c, 104d, and 104e. A received signal processed by each receiving unit, which is a receiving system provided for each antenna, is converted into a digital signal by an A/D conversion unit 109, and then sent to a DSP (Digital Signal Processor) and an FPGA (Field Programmable Gate Array). ) is passed to the signal processing unit 110 configured by a logic device such as.

The signal processing unit 110 detects the phase difference between the antennas in the received signal of the radio wave 30 from each antenna, and calculates the direction of arrival of the radio wave 30 based on the information of the phase difference and the known distance between the antennas. conduct. In order to accurately calculate the direction of arrival of radio waves, it is necessary to know the distance between antennas in advance. Further, since the distance between the antennas is proportional to the wavelength of the radio wave whose arrival direction is to be detected, the distance between the antennas increases as the radio wave having a longer wavelength is to be detected.

A local signal oscillator 108 generates a local frequency used for mixing, filtering, and modulation processing in each receiving section 104a, 104b, 104c, 104d, and 104e. However, it is difficult to match phase characteristics in all receiving systems. Therefore, by supplying a common local frequency generated from one local signal oscillator 108 to all receiving systems using a distributor 107, the phase characteristics of each receiving system are approximated.

In order to eliminate phase characteristic errors, switch circuits 103a, 103b, 103c, 103d, and 103e are provided between each antenna and each receiving system, and a test signal oscillator 106 for generating a test signal for calibration is provided. Connected. A common test signal generated from test signal oscillator 106 is supplied to all receiving sections using distributor 105 .

In such a conventional radio wave direction finding apparatus 100, first, the switch circuits 103a, 103b, 103c, 103d, and 103e are switched so as to be connected to the test signal generator 106, and the test signal is transmitted to the respective receiving sections 104a and 104b. , 104c, 104d, and 104e to calibrate the receiving system. At this time, the signal processing section 110 detects the phase difference of the test signal that has passed through each receiving system and stores it in the memory. After that, the switching circuits 103a, 103b, 103c, 103d, and 103e are switched to the antenna side to receive the incoming radio waves 30. FIG. At this time, the signal processing unit 110 detects the phase difference between the antennas in the reception signal of the radio wave 30 from each antenna, corrects it using the phase difference calculated by calibration and stored in the memory, and detects the arrival of the radio wave 30. Calculate direction.

Various inventions have been proposed so far with respect to techniques for detecting the direction of arrival of radio waves. For example, in Patent Document 1, each of a plurality of terminals estimates the direction of arrival of an interference wave and transmits it to a base station, and the base station calculates the most probable direction of arrival based on the estimation result of each terminal. It is disclosed to Further, Patent Literature 2 discloses estimating the direction of arrival of radio waves and displaying the direction of arrival of radio waves and the position of an antenna that received the radio waves superimposed on map information.

JP 2009-296247 A JP 2012-47473 A

The distance between antennas for azimuth measurement increases in proportion to the wavelength of the radio wave whose direction of arrival is to be estimated. In order to estimate the direction of arrival of a radio wave with a wavelength of 10 m with an error of 1° or less, it is necessary to secure a distance of about 40 to 50 m between the antennas. However, a mobile station such as a ship or an aircraft cannot secure such a long distance on the mobile station. For this reason, an antenna for estimating the direction of arrival of radio waves with long wavelengths could not be installed as a ground fixed station.

SUMMARY OF THE INVENTION The present invention has been made in view of the conventional circumstances as described above. for the purpose.

In order to achieve the above object, in the present invention, a radio wave direction finding system is configured as follows.
That is, in a radio wave direction finding system for estimating the direction of arrival of radio waves, each has an antenna for receiving radio waves, and measurement of the position of the antenna and transmission of the received signal of the radio waves and the local frequency synchronized between the mobile stations. A radio wave direction finding device having a function of estimating the direction of arrival of radio waves based on a plurality of mobile stations that detect phase differences, and the antenna positions and phase differences of received signals obtained from each of the plurality of mobile stations. and

Here, at least one of the plurality of mobile stations may be configured to include a radio wave direction finding device. Also, the radio wave direction finding device may be provided in two or more mobile stations.

Also, any one of a plurality of mobile stations transmits a synchronization signal for synchronizing local frequencies among mobile stations, and other mobile stations that have received the synchronization signal transmit their own local frequencies to the synchronization signal. may be configured to synchronize with the transmission source of the
In this case, the other mobile station may calculate the correlation between the received synchronization signal and the pre-stored signal pattern, and align the phase of the local frequency of its own station at the timing when the correlation is maximized.

According to the present invention, it is possible to estimate the direction of arrival of radio waves even in a mobile station in which it is difficult to secure a distance between antennas for azimuth measurement.

1 is a block diagram showing a configuration example of a radio wave direction finding system according to an embodiment of the present invention; FIG. Block diagram showing a configuration example of a signal processing unit in the radio wave direction finding system of FIG. FIG. 2 is a flow chart for explaining the flow of direction finding of radio waves by the direction finding system of FIG. 1; 1 is a schematic diagram showing the principle of interferometer direction finding technique; FIG. 1 is a block diagram showing a configuration example of a conventional radio wave direction finding system; FIG.

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of a radio wave direction finding system according to one embodiment of the present invention. The radio wave direction finding system of this example includes a plurality of mobile stations 10 . Although two mobile stations 10a and 10b are shown in FIG. 1, three or more may be provided.

The mobile station 10a includes an azimuth measuring antenna 11a for receiving incoming radio waves 30, a radio wave direction finding device 13a for detecting the arrival direction of the radio waves 30, and a coaxial cable 12a for connecting the antenna 11a and the radio wave direction finding device 13a. is equipped with. Similarly, the mobile station 10b is connected to an azimuth measuring antenna 11b for receiving incoming radio waves 30, a radio wave direction finding device 13b for detecting the arrival direction of the radio waves 30, and the antenna 11b and the radio wave direction finding device 13b. A coaxial cable 12b is mounted. Other connection cables may be used instead of the coaxial cables 12a and 12b. Although the mobile station 10a will be described below as an example, the mobile station 10b has the same configuration.

In the mobile station 10a, radio waves 30 received by the antenna 11a are input to the radio wave direction finding device 13a via the coaxial cable 12a. The received signal input to the direction finding device 13a is subjected to processing such as signal amplification, modulation to an intermediate frequency, and filtering in a receiving section 16a, which is a receiving system. The received signal processed by the receiving section 16a is converted into a digital signal by the A/D converting section 19a, and then transferred to the signal processing section 20a configured by a logic device such as a DSP or FPGA.

A local frequency used for mixing, filtering, and modulation processing in the receiving section 16a, which is a receiving system, is generated from a local signal oscillator 18a. The radio wave direction finding device 13a further includes a transmission unit 15a as a transmission system. The radio wave direction finding device 13a also includes a switch circuit 14a so that the connection of the antenna 11a can be switched between the transmission section 15a (transmission system) and the reception section 16a (reception system). The switch circuit 14a is switched to connect the antenna 11a to the transmitter 15a when the mobile station 10a performs a transmission operation, and connects the antenna 11a to the receiver 16a when the mobile station 10a performs a reception operation. can be switched to

The A/D conversion unit 19a includes an analog-to-digital (AD) conversion circuit that converts the analog signal input from the reception unit 16a into a digital signal, and a digital-analog conversion circuit that converts the digital signal input from the signal processing unit 20a into an analog signal. (DA) It has a conversion circuit.

The signal processing unit 20a processes the digital signal input from the A/D conversion unit 19a, measures the current position of the antenna 11a, detects the phase difference between the received signal of the radio wave 30 and the local frequency, and determines the direction of arrival of the radio wave 30. , etc. FIG. 2 shows a configuration example of the signal processing section. The signal processing unit 20a shown in FIG. , the direction-of-arrival calculator 23a for calculating the direction of arrival of the radio wave 30, the current antenna position positioning unit 24a for measuring the current position of the antenna 11a, and the position of the antenna of another moving body (for example, the antenna 11b of the moving body 10b). and a storage unit 26a for storing the position information of each antenna.

A radio wave direction finding system according to the present invention will be described with reference to the flowchart of FIG.
First, in the mobile station 10a, the transmission unit 15a of the direction finding device 13a synchronizes the local frequency of the receiving unit 16a of the direction finding device 13a with the local frequency of the receiving unit 16b of the direction finding device 13b. A synchronization signal generated from the signal generator 17a is transmitted to the mobile station 10b (step S1).
In the mobile station 10b, the receiver 16b performs reception processing for the synchronization signal transmitted from the mobile station 10a (step S21). After that, the synchronization signal detector 21b correlates the received synchronization signal with a known signal pattern (the signal pattern of the synchronization signal stored in advance), and detects the local frequency of the receiver 16b at the timing when the correlation becomes maximum. are aligned (step S22).

Next, in the mobile station 10a, the antenna current position positioning unit 24a of the radio wave direction finding device 13a acquires the current position of the antenna 11a using satellite positioning such as GPS (Global Positioning System) (step S2). In the mobile station 10a, the acquired current position information of the antenna 11a is stored in the storage unit 26a (step S3).
Also in the mobile station 10b, the antenna current position positioning unit 24b of the radio wave direction finding device 13b acquires the current position of the antenna 11b using satellite positioning such as GPS (step S23). The mobile station 10b transmits the acquired current position information of the antenna 11b to the mobile station 10a (step S24).

In the mobile station 10a, the receiving unit 16a performs a process of receiving the current location information of the antenna 11b transmitted from the mobile station 10b (step S4). The other antenna position acquisition unit 25a stores the received current position information of the antenna 11b in the storage unit 26a (step S5). As a result, the current location information of the antenna 11a and the current location information of the antenna 11b are stored in the storage unit 26a of the mobile station 10a.

After performing the above processing, the direction of arrival of the radio wave 30 is detected jointly by the direction finding device 13a of the mobile station 10a and the direction finding device 13b of the mobile station 10b.
That is, in the mobile station 10a, the radio wave reception phase difference detection unit 22a of the radio wave direction finding device 13a detects the phase difference between the received signal of the radio wave 30 and the local frequency when the radio wave 30 is received by the antenna 11a (step S6 , S7). Similarly, in the mobile station 10b, the radio wave receiving phase difference detection unit 22b of the radio wave direction finding device 13b detects the phase difference between the received signal of the radio wave 30 and the local frequency when the radio wave 30 is received by the antenna 11b (step S25, S26). Hereinafter, the phase difference between the received signal of the radio wave 30 and the local frequency is referred to as "phase difference at reception".

The mobile station 10b transmits the detected reception phase difference to the mobile station 10a (step S27). The mobile station 10a performs reception processing of the phase difference at reception transmitted from the mobile station 10b (step S8). After that, in the mobile station 10a, the direction-of-arrival calculation unit 23a of the radio wave direction detection device 13a stores the reception phase difference detected by the mobile station 10a and the reception phase difference detected by the mobile station 10b in the storage unit 26a. Based on the current positional information of the antenna 11a and the current positional information of the antenna 11b, the direction of arrival of the radio wave 30 is calculated by a predetermined arithmetic processing (interferometer method in this example) (step S9).

As described above, in the radio wave direction finding system of this example, the mobile station 10a measures the current position of its own antenna 11a and calculates the phase difference between the received signal of the radio wave 30 and the local frequency synchronized between the mobile stations. Detect and perform. Similarly, the mobile station 10b measures the current position of its own antenna 11b and detects the phase difference between the received signal of the radio wave 30 and the local frequency synchronized between the mobile stations. After that, the radio wave direction finding device 13a mounted on the mobile station 10a estimates the direction of arrival of the radio wave 30 based on the current position of each antenna and the phase difference at the time of reception obtained by each of the mobile stations 10a and 10b. do.

According to such a configuration, the positional relationship between the azimuth measurement antennas 11a and 11b can be changed simply by moving at least one of the mobile stations 10a and 10b, so that a sufficient distance can be secured between these antennas. can do. In addition, since the mobile stations 10a and 10b have their local frequencies synchronized with each other, it is possible to detect the phase difference at the time of reception while matching the phase characteristics of the respective receiving systems. Therefore, it is possible to estimate the direction of arrival of radio waves even in a mobile station such as a ship or an aircraft, where it is difficult to secure a distance between antennas for azimuth measurement.

Here, in the above description, the direction of arrival of radio waves is estimated by the direction-of-arrival detection device 13a mounted on the mobile station 10a. I do not care. Alternatively, direction finding may be performed using three or more mobile stations. That is, for example, the mobile station 10a obtains the current position of the antenna and the reception phase difference from other mobile stations 10c, 10d, and 10e (not shown) in addition to the mobile station 10b, and obtains the current position and phase difference of each antenna. The direction of arrival of radio waves may be estimated based on the phase difference at the time of reception. Also, a ground fixed station communicably connected to each mobile station may be provided with a radio wave direction finding device for estimating the direction of arrival of radio waves.

Further, in the above description, the mobile station 10a transmits a synchronization signal for synchronizing the local frequencies among the mobile stations, and the mobile station 10b synchronizes its own local frequency with the mobile station 10a. It may be reversed. That is, the mobile station 10b may transmit a synchronization signal for synchronizing the local frequencies among the mobile stations, and the mobile station 10a may synchronize its own local frequency with the mobile station 10b.

Further, in the above description, after the mobile station 10b (1) measures the position of the antenna 11b and transmits the current position information to the mobile station 10a, (2) the phase difference between the received signal of the radio wave 30 and the local frequency is detected and the phase difference at reception is transmitted to the mobile station 10a, the order of (1) and (2) may be reversed. Considering that the mobile station 10b moves, it is desirable that the antenna position measurement timing and the reception phase difference detection timing are as close as possible.

In the above description, the mobile stations 10a and 10b share one antenna 11a and 11b for transmission and reception, respectively, but separate antennas for transmission and reception may be provided.

Further, in the above description, the interferometer method is used to calculate the direction of arrival of the radio wave 30, but other methods such as the MUSIC (MULTIPLE SIGNAL CLASSIFICATION) method may be used.

Although the present invention has been described based on one embodiment, it goes without saying that the present invention is not limited to the radio wave direction finding system described herein, and can be widely applied to other radio wave direction finding systems. stomach.
In addition, the present invention provides, for example, a method including technical procedures related to the above processing, a program for causing a processor to execute the above processing, and a storage medium storing such a program in a computer-readable manner. is also possible.

It should be noted that the scope of the invention is not limited to the illustrated and described exemplary embodiments, but includes all embodiments that achieve equivalent effects for which the invention is intended. Moreover, the scope of the invention may be defined by any desired combination of the specific features of each and every disclosed feature.

INDUSTRIAL APPLICABILITY The present invention can be used in a radio wave direction finding system that detects the direction of arrival of radio waves.

10a, 10b: mobile station 11a, 11b: antenna for direction measurement 12a, 12b: coaxial cable 13a, 13b: radio wave direction finding device 14a, 14b: switch circuit 15a, 15b: transmitter 16a, 16b : receiver 17a, 17b: sync signal oscillator 18a, 18b: local signal generator 19a, 19b: A/D converter 20a, 20b: signal processor 21a, 21b: sync signal detector 22a, 22b: Phase detection unit during radio wave reception 23a, 23b: Direction of arrival calculation unit 24a, 24b: Current antenna position positioning unit 25a, 25b: Other antenna position acquisition unit 26a, 26b: Storage unit 30: Arrival radio wave 101a, 101b, 101c, 101d, 101e: antennas for azimuth measurement, 102a, 102b, 102c, 102d, 102e: coaxial cables, 103a, 103b, 103c, 103d, 103e: switch circuits, 104a, 104b, 104c, 104d, 104e: receiver, 105: distributor, 106: test signal generator, 107: distributor, 108: local signal generator, 109: A/D converter, 110: signal processor

Claims (5)

In a radio wave direction finding system that estimates the direction of arrival of radio waves,
A plurality of mobile stations movable independently of each other, each having an antenna for receiving the radio wave, and measuring the position of the antenna and local synchronization between the received signal of the radio wave and the mobile station a plurality of mobile stations that detect a phase difference with a frequency;
and a radio wave direction finding device having a function of estimating the direction of arrival of the radio wave based on the position of the antenna and the phase difference of the received signal obtained by each of the plurality of mobile stations. Radio direction finding system. In the radio wave direction finding system according to claim 1,
A radio wave direction finding system, wherein at least one of the plurality of mobile stations includes the radio wave direction finding device. In the radio wave direction finding system according to claim 1,
any one of the plurality of mobile stations transmits a synchronization signal for synchronizing a local frequency between mobile stations;
A radio wave direction finding system, wherein another mobile station that has received the synchronization signal synchronizes its own local frequency with the transmission source of the synchronization signal. In the radio wave direction finding system according to claim 3,
The radio wave direction finding system, wherein the other mobile station calculates the correlation between the received synchronization signal and a pre-stored signal pattern, and aligns the phase of the local frequency of the own station at the timing when the correlation is maximized. . In a radio wave direction finding method for estimating the direction of arrival of radio waves,
A plurality of mobile stations that can move independently of each other, and each of the plurality of mobile stations having an antenna for receiving the radio wave measures the position of its own antenna, and between the received signal of the radio wave and the mobile station. detecting the phase difference with the local frequency synchronized with
A radio wave direction finding method, wherein a radio wave direction finding device estimates the direction of arrival of the radio wave based on the position of the antenna and the phase difference of the received signal obtained by each of the plurality of mobile stations.

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