JP2005207837A - Direction finding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direction finding apparatus which decides the arrival direction/distance of radio waves with high precision using a simple configuration. <P>SOLUTION: Directional patterns 4a to 4l of directional antennas 3a to 3l, respectively, are set so that adjacent directional patterns (for example, 4a and 4b) partly overlap each another (at least nearly half thereof). On the basis of the difference Rs(=Ra-Rb) in the receiving level received by the directional antennas 3a to 3l, the deviation amount in the direction from the direction of the directional antenna 3a (direction having maximum sensitivity) is determined, thereby deciding the arrival direction of radio waves with high precision. The distance is estimated by considering the amount of decrease in receiving level according to the amount of deviation of direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a direction detector that detects an arrival direction and a distance to a transmission source by receiving radio waves transmitted from the transmission source with a directional antenna.

Radar and mobile communication base stations are required to accurately estimate the direction of incoming radio waves (see Patent Document 1). The technology of Patent Document 1 is that a plurality of directional antennas (for example, eight are arranged at equal intervals on the circumference), a smaller number of receivers (for example, four) than the antennas, and a connection relationship between the antennas and the receivers. First, every other antenna is connected to each receiver, and in this state, the direction of arrival of radio waves is roughly estimated, and then four antennas whose directions are close to the estimated direction of arrival Are connected to each receiver to estimate the direction of arrival of radio waves in detail. For estimating the direction of arrival of radio waves, a MUSIC (MUltiple SIgnal Classification) algorithm or an ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) algorithm can be used.
JP 2002-107439 A

  However, these algorithms perform detection using a phase difference. Therefore, in order to accurately detect the direction, it is necessary to increase the number of directional antennas and simultaneously increase the number of receivers that can detect signals. . In addition, since it is necessary to detect the phase difference with high accuracy, it is necessary to operate each receiver precisely in synchronization. It takes time to perform the determination process.

  Accordingly, an object of the present invention is to provide a direction detector that can accurately determine the arrival direction and distance of radio waves with a simple configuration.

  In order to solve the above problems, a direction finder according to the present invention includes an antenna that can switch directivity, a detection unit that detects a reception level of a signal received by the antenna, and a plurality of antennas that switch the directivity of the antenna. In a direction finder that includes a direction / distance estimator that estimates the direction / distance of a radio wave source based on the reception level detected under directivity conditions, the antenna is used for radio waves from a specific direction, A directivity pattern that is partially overlapped so that reception is possible under at least two directivity conditions is set, and the direction / distance estimation unit determines the source of the radio wave based on the relationship between the reception level and the directivity pattern. It is characterized by estimating the direction / distance of.

  According to the present invention, radio waves arriving from a certain direction are received under a plurality of directional conditions of two or more types having a directional pattern having sensitivity thereto. Here, the reception level under each directivity condition varies depending on the relationship between the direction of arrival of radio waves and the directivity pattern of the received antenna and the reception environment (output of the transmission source, distance from the transmission source, atmospheric conditions, etc.). Since the reception environment is the same under any directivity condition, the difference in reception level under each directivity condition depends on the difference in the relationship between the direction of arrival of radio waves and the directivity pattern. Therefore, the arrival direction of the radio wave is determined using the difference in reception level and the difference in directivity pattern.

  According to the present invention, since the radio wave arrival direction is determined from the reception level based on the relationship between the directivity pattern and the radio wave arrival direction, it is not necessary to perform radio wave reception under a plurality of directivity conditions at the same time. The measurement can be performed by shifting to Therefore, it is not necessary to provide a plurality of receivers, and the antenna can be measured by switching a plurality of directional antennas, and a single antenna with variable directivity can be used. Therefore, the configuration can be simplified. Then, by performing direction determination based on the directivity pattern, it is possible to accurately perform direction determination with a small number of antenna elements.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

  FIG. 1 is a block diagram of a direction finder according to the present invention. This detector 1 has twelve directional antennas 3 a to 3 l, and any one of the antennas 3 a to 3 l is connected to a receiving unit 5 that extracts radio waves from a transmission source by a switch 12. The reception unit 5 is connected to a reception level detection unit 6 that detects the level of the reception signal, and the output of the reception level detection unit 6 is input to the direction / distance estimation unit 7. The direction / distance estimator 7 obtains an estimated direction correction table 8 storing data necessary for estimating the estimated direction from the received level difference, and a received level when the antenna is directed to the original radio wave arrival direction. It is connected to a reception level correction table 9 that stores data necessary for this, and is configured to be able to read data. The estimated direction correction table 8 and the reception level correction table 9 are stored in ROM, RAM, or various storage media. The direction / distance estimation unit 7 controls the operation of the antenna switching unit 10 that controls the operation of the switch 12 and outputs to the display unit 11 that displays the detection result.

  2 and 3 show the arrangement of the directivity patterns of the antennas 3a to 3l. Here, the direction of the antenna a (the direction having the maximum sensitivity) is set to 0 degree, and an angle taken clockwise from this direction is referred to as an azimuth angle. The antennas 3b to 3l are arranged at an azimuth angle of 30 degrees, that is, to face an azimuth angle (30 × n) degrees (n is an integer of 1 to 11). Each of the antennas 3a to 3l has symmetrical directivity patterns 4a to 4l having sensitivity in a direction of ± 30 degrees from the direction. That is, the directivity patterns 4a to 4l are arranged so as to be shifted by 30 degrees, and the directivity patterns 4 are arranged so as to overlap with each other by approximately half the azimuth angle between the adjacent antennas 3. Accordingly, when the azimuth angle θ is (n−1) × 30 degrees <θ <n × 30 degrees (n is an integer of 1 to 11), two antennas (for example, 3a at 0 to 30 degrees) And 3b) have sensitivity, and when θ is n × 30 degrees (in this case, n is an integer of 0 to 11), only one antenna (only 3a at 0 °) has sensitivity. Will have.

  Next, the operation of the detector 1, that is, a method for estimating the arrival direction / distance of the radio wave using the detector 1 will be described. Here, as shown in FIG. 4, an example will be described in which a radio wave from the transmitter 2 is received by the detector 1 and its arrival direction is estimated. FIG. 5 is a flowchart of the direction estimation operation. This process is executed by the direction / distance estimating unit 7 unless otherwise specified.

  First, by sequentially switching the switch 12 by the antenna switching unit 10, the reception antenna 3 connected to the reception unit 5 is sequentially switched from the antenna 3a to the antenna 3l, and the signal level (reception received) by each of the antennas 3a to 3l. The reception level detector 6 obtains the level and unit of dB) (step S1).

  Next, in order of increasing reception level, the central directivity angles of the antenna 3 are set to φ1, φ2,..., And the reception levels at that time are set to R1, R2,.

  After the setting, the reception level R1 is compared with the threshold value Rth (step S3). In the case of R1 <Rth, it is determined that the reception level is insufficient for accurately performing the direction / distance estimation, and the process is terminated without performing the direction / distance estimation. If R1 ≧ Rth, R2 and Rth are further compared (step S4).

  If it is determined in step S4 that R2 ≧ Rth, the process proceeds to step S5, and a reception level difference Rs between R1 and R2 is obtained. Then, an estimated direction correction amount Δφe is obtained from the estimated direction correction table 8 based on the reception level difference Rs (step S6). FIG. 6 is a graph of an example of the data in the estimated direction correction table 8. Since the directivity patterns of the antennas 3a to 3l are arranged as shown in FIG. 3, it is ideal according to Δφe (= φr−φ1) that is an angle formed between the actual radio wave arrival directions φr and φ1. Specifically, Rs changes as shown in FIG. That is, Δφe can be obtained according to the magnitude relationship between Rs and φ1 and φ2. If R1 ≧ Rth in step S4, the estimated direction correction amount Δφe is set to 0 (step S7). In step S8, φ1 + Δφe is set as the direction estimated value φe. Thereby, φr can be estimated with high accuracy.

  Next, an estimated value Re of the reception level when the direction of the antenna 3 matches the arrival direction of the radio wave is obtained. First, the reception level correction amount ΔRe is obtained from the reception level correction table 9 based on the estimated direction correction amount Δφe (step S9). FIG. 7 is a graph showing an example of data in the reception level correction table 9. From the directivity patterns of the antennas 3a to 3l, ΔRe, which is the difference between Re and R1, changes as shown in FIG. 7 according to Δφe. That is, ΔRe can be obtained from Δφe. Then, Re is obtained as the sum of the obtained ΔRe and R1 (step S10). Thereby, the estimated reception level Re when the direction of the antenna 3 and the arrival direction of the radio wave are matched can be obtained with high accuracy.

  Next, a distance Lt from the obtained estimated reception level Re to the transmitter 2 is calculated (step S11), the obtained direction estimated value φe and the estimated distance Lt are output to the display unit 11 (step S12), and the process is terminated. .

  For example, as shown in FIG. 3, when φr = about 12 °, the antenna 3a oriented in the 0 ° direction and the antenna 3b oriented in the 30 ° direction have sensitivity, and the respective reception levels are Ra, Rb. As a result, φ1 = 0 ° and φ2 = 30 °, and R1 = Ra and R2 = Rb are set. Here, the difference between Ra and Rb corresponds to the gain level difference of the directivity pattern, and the difference corresponds to the amount of azimuth shift, so that the estimated direction correction amount Δφe is 12 as described above with reference to FIG. And can be estimated as φe = 12 °.

  According to the present invention, since the distance can be estimated with a resolution smaller than the number of directivity patterns, the estimation accuracy can be easily improved. In addition, since it is not necessary to perform reception by each antenna at the same time, the reception unit 5 and the reception level detection unit 6 can be used in common, and the apparatus configuration is simple. Furthermore, considering the directivity pattern, the reception level is corrected to the reception level in the direction of maximum sensitivity, and the distance is obtained. Therefore, an error in calculating the distance due to the deviation of the actual radio wave arrival direction and antenna direction is effective. Therefore, accurate distance calculation can be performed.

  Here, the case where there are 12 directivity patterns has been described as an example, but the number of patterns is not limited to this. However, it is preferable that adjacent patterns overlap at least approximately half. Further, the directivity pattern may be arranged so that three or more patterns overlap, and the direction / distance of the radio wave transmission source may be estimated by walking along the system between the three or more reception levels and the directivity pattern. .

  In addition, switching a plurality of directivity patterns in this way may be realized by changing the actual orientation of an antenna having a directivity pattern, in addition to switching antennas having different directivity patterns by a switch. In addition, a directivity pattern to be used may be selected from a plurality of directivity patterns using an antenna whose electronic directivity can be switched, such as a phased array antenna.

It is a block block diagram of the direction finder based on this invention. It is a figure explaining arrangement | positioning of the directivity pattern of the antenna of FIG. It is another figure explaining arrangement | positioning of the directivity pattern of the antenna of FIG. It is a figure which shows the positional relationship of a transmitter and a detector. It is a flowchart of the direction estimation operation | movement by the apparatus of FIG. It is a graph explaining an estimated direction correction table. It is a graph explaining a reception level correction table.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Detector, 2 ... Transmitter, 3a-3l ... Antenna, 4 ... Directivity pattern, 5 ... Reception part, 6 ... Reception level detection part, 6 ... Reception level detection part, 7 ... Direction and distance estimation part, 8 ... Estimated direction correction table, 9 ... Reception level correction table, 10 ... Antenna switching section, 11 ... Display section, 12 ... Switch.

Claims (1)

An antenna that can switch directivity, a detection unit that detects a reception level of a signal received by the antenna, and a radio wave signal based on reception levels detected under a plurality of directivity conditions by switching the directivity of the antenna. In a direction finder equipped with a direction / distance estimator for estimating the direction / distance of the transmission source,
Each directivity pattern at the time of antenna directivity switching is set so that adjacent directivity patterns overlap at least approximately half of the azimuth angle, and the direction / distance estimation unit determines the relationship between the reception level and the directivity pattern. A direction finder that estimates the direction and distance of a radio wave source based on the above.

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