JPH10170621A - Radio wave direction finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the arrival direction with high accuracy even on a measuring radio wave of a high frequency by arranging a calibration antenna to output a calibration radio wave, and removing an error factor up to reaching respective receiving parts in a process of impressing a calibration signal on the respective receiving parts. SOLUTION: A calibration radio wave 20 is outputted at ordinary times through a calibration antenna 17 from a calibration signal generator 18 when a device is put in an operating condition. Receiving parts 2a to 2c receive only the calibration radio wave 20 received by receiving antennas 1a to 1c or a synthetic wave of the calibration radio wave 20 and a measuring radio wave 3, and send them to a direction measuring processing part 19 as received signals e1 to e3. The processing part 19 holds a difference between the newest phase difference of the calibration radio wave 20 and a known reference phase difference corresponding to the direction of the predetermined antenna 17 as the newest calibration phase difference. When the measuring radio wave 3 exceeding a specified electric field by a prescribed value or more is inputted, the arrival direction of the measuring radio wave 3 is calculated by a phase difference from a known reference phase, and is also corrected by the holding newest calibration phase difference, and the accurate arrival direction is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave direction detecting device for detecting a direction of arrival of a radio wave, and more particularly to a radio wave direction detecting device that uses a radio wave having a certain electric field level or higher as a measured radio wave.

[0002]

2. Description of the Related Art For example, when controlling illegal radio waves,
It is necessary to specify the source of the illegal radio wave. In such a case, a measuring vehicle equipped with a radio wave direction detecting device is arranged at a plurality of positions, and each direction of arrival of the illegal radio wave is measured by the radio wave direction detecting device mounted on each measuring vehicle. Then, an extension line of each arrival direction of the same illegal radio wave is drawn from the position of each measurement vehicle, and an intersection point of these extension lines is estimated as a transmission position of the illegal radio wave.

In each radio wave direction detecting device, as shown in FIG. 8, for example, five receiving antennas 1a, 1b, 1c, 1d, 1e are arranged at different positions on the circumference. Each receiving antenna 1a, 1b, 1c, 1d, 1
e, each of the receiving units 2a, 2b, 2c, 2d, 2e
Receives the same measurement wave 3 via the antennas 1 a to 1 e, the received signals _{a 1, a 2, a 3} , a 4, a interferometric (or interferometer) as ₅ method processing unit 4 Send to

[0004] The interferometric method processing unit 4 obtains each phase difference phi ₁ to [phi] ₅ from the received signals _{a 1, a 2, a 3} , a 4, a 5 , for example, reference signal input, this The arrival direction α of the measurement radio wave 3 is calculated from each of the phase differences φ _{1 to} φ ₅ and displayed on the display unit 5 as, for example, a graphic.

FIG. 10 is a diagram showing the principle of measurement using the interferometer system. For the sake of simplicity, it is assumed that three receiving antennas 1a, 1b, 1c are arranged at a plurality of positions on the circumference of a radius R. Measurements Telecommunications 3 each receiving antenna 1a, 1b, so can be regarded as incident parallel to 1c, each reception antenna 1a, 1b, the received signal a ₁ of the radio wave received by 1c, in a _2, a ₃ Causes phase differences φ ₁ , φ ₂ , φ ₃ with respect to the reference signal corresponding to the arrival time differences. Therefore, from the phase differences φ ₁ , φ ₂ , φ ₃ , using the radius R, the circumferential position of each of the receiving antennas 1 a, 1 b, 1 c and the wavelength λ, the arrival direction of the measurement radio wave 3 with respect to the reference direction. α is found.

[0009] As shown in FIG. 9, by employing the MUSIC method operation processing unit 7 instead of the interfero method operation processing unit 4, the arrival directions of a plurality of radio waves 3 and 6 arriving from a plurality of directions simultaneously can be controlled. Can be identified.

However, in order to accurately measure the arrival direction α of the measurement radio wave 3, it is necessary to accurately determine the phase differences φ _{1 to} φ ₅ . Generally, each of the receiving units 2a to 2e has a unique phase deviation component. Therefore, each receiving unit 2a
It is necessary to cancel the phase deviation component in the process of calculating the arrival direction α by previously examining the inherent phase deviation component of .about.2e.

In particular, when the measurement radio wave 3 has a high frequency, FIG.
As shown in FIG. 1, the receivers 2a, 2b, and 2c that receive the measurement radio wave 3 via the receiving antennas 1a, 1b, and 1c employ a superheterodyne system. After the frequency of each received signal of the measurement radio wave 3 is reduced to the intermediate frequency, the signal is input to the azimuth measurement processing unit 8 employing the interfero system or the MUSIC system.

However, in the local oscillator, the signal combiner 9 and the BPF 10 for generating the intermediate frequency signal in the superheterodyne system, all the receiving sections 2a,
It is difficult to match the phase characteristics over 2b and 2c.

Therefore, as shown in FIG. 11, one local oscillator 11 common to each of the receiving units 2a, 2b, 2c is provided, and each of the receiving units 2a, 2b, 2c is provided from the local oscillator 11 via a distributor 12. The local oscillating signal g is supplied to the signal synthesizer 9 of FIG.

By supplying the common local oscillation signal g to each of the receiving units 2a, 2b, and 2c, the phase characteristics of each of the receiving units 2a, 2b, and 2c can be largely approximated.

However, when the measurement radio wave 3 has a high frequency, a slight difference in the phase characteristics still remaining in the reception units 2a, 2b, 2c may greatly affect the measurement value. In order to eliminate such inconvenience, as shown in FIG. 11, each of the receiving antennas 1a, 1b, 1c and each of the receiving units 2a, 2b, 2
and a switching circuit 13a, 13b, 13c, respectively, and a common calibration signal c supplied from a calibration signal generator 15 via a distributor 14 to one of the switching terminals of the switching circuits 13a, 13b, 13c. doing.

In the radio wave direction detecting device having such a configuration, each of the switching circuits 13a, 13b, and 13c is connected to the calibration signal generator 15 before the measurement of the measured radio wave 3 is actually started.
And the same calibration signal c from the calibration signal generator 15 is received by each of the superheterodyne receiving units 2a, 2b,
2c. The direction measurement processing unit 8 converts the phase differences θ ₁ , b ₁ , b ₂ , b ₃ of the received signals b ₁ , b ₂ , b ₃ with respect to the reference signal into the intermediate frequency output from the receiving units 2 a, 2 b, 2 c when the calibration signal is input. θ ₂ and θ ₃ are detected and stored as a calibration phase difference. Therefore, assuming that there is no error, the calibration phase differences θ ₁ , θ ₂ , and θ ₃ all have the same value.

Next, each switching circuit 13a, 13b, 13c
Is switched to the antenna side. Then, each of the receiving units 2a, 2
b and 2c receive the measurement radio wave 3 via each of the receiving antennas 1a, 1b and 1c and send out the reception signals a ₁ , a ₂ and a ₃ converted to the intermediate frequency to the direction measurement processing unit 8. .
The direction measurement processing unit 8 detects the phase differences φ ₁ , φ ₂ , φ ₃ of the received signals a ₁ , a ₂ , a ₃ with respect to the reference signal. Then, the detected phase differences φ ₁ , φ ₂ , φ ₃ are corrected by the calibration phase differences θ ₁ , θ ₂ , θ ₃ . The direction of arrival α of the received signal 3 is calculated based on the above-described method using the corrected phase differences φ ₁ , φ ₂ , and φ ₃ .

[0015]

However, FIG.
The calibration signal c shown in FIG.
The radio wave direction detecting device applied to each of the receiving units 2a, 2b, and 2c via the communication device has the following problem to be solved.

That is, the frequency of the measurement radio wave 3 is UH
If the frequency becomes higher sequentially, such as F, quasi-microwave, microwave, etc., it is very difficult to supply the calibration signal c to each of the receivers 2a, 2b, 2c in the same phase via each of the switching circuits 13a, 13b, 13c. become.

For example, when the frequency of the measurement radio wave 3 is 5 GHz, the wavelength λ is about 60 mm, and when measuring the phase difference with an accuracy of 1%, the distributor 14 of the calibration signal c sends the signals from the respective switching circuits 13 a, 13 a. It is necessary to set the lengths of the signal lines composed of coaxial cables up to 13b and 13c equally with an accuracy of 0.6 mm. Similarly, each of the switching circuits 13a, 13b, 13
It is necessary to produce the mechanical dimensional accuracy of c with an accuracy of 0.6 mm.

To reduce the length error of the signal line to 0.6 mm or less, or to reduce the dimensional error of each of the switching circuits 13a, 13b and 13c to 0.6 mm or less requires a very advanced manufacturing technique, and Not a target.

Even if the device can be manufactured with the above-described dimensional accuracy, the use environment of this radio wave direction detecting device is outdoors, and if it is irradiated with direct sunlight from one side, only a specific signal line and a specific switching circuit will be used. Is thermally expanded, and the above-mentioned allowable dimensional error range is easily broken. Thus, there is a concern that a large measurement error may occur depending on the use environment.

In addition, when used for a long period of time after production, aging occurs, and it becomes difficult to maintain the allowable dimensional error range. Further, the positional relationship between the antennas receiving the measurement radio waves and the length of each signal line from each antenna to each switching circuit are also affected by the use environment and aging, so that the phase differences φ ₁ , φ ₂ , the calculation accuracy in calculating the arrival direction α of the received radio wave ₃ from φ ₃ is reduced.

The present invention has been made in view of such circumstances, and a calibration signal is output by providing a calibration antenna for outputting a calibration radio wave in addition to a plurality of receiving antennas for receiving a measurement radio wave. In the process of applying to the receiving unit, it is possible to remove the error factor until reaching each receiving unit,
Provide a radio direction detection device that can simultaneously compensate for the mounting accuracy of each receiving antenna, deterioration due to use environment and aging, and detect the direction of arrival of the measurement radio wave with high accuracy even if the measurement radio wave has a high frequency. The purpose is to do.

[0022]

According to a first aspect of the present invention, there is provided a radio wave direction detecting apparatus comprising: a plurality of receiving antennas disposed at different positions from each other; A plurality of receiving units for receiving the same radio wave and outputting the same as a received signal, a calibration signal generator for outputting a calibration signal, and a calibration signal disposed in a predetermined reference direction for each receiving antenna. Calibration antenna that outputs the calibration signal output from the generator as a calibration electric wave of the specified electric field level, and phase difference detection that detects the phase difference between the received signals output from each receiver in a fixed cycle. Means, a direction-of-arrival calculation unit for calculating the direction of arrival of the radio wave arriving from the phase difference detected by the phase difference detection means, and a signal level for detecting the signal level of the reception signal output from each reception unit. And a signal detected by the phase difference detecting means when the signal level detected by the signal level detecting means is a specified signal level corresponding to the electric field level of the calibration radio wave. Phase difference storage means for storing and holding the latest phase difference among the phase differences as a calibration phase difference; and when the signal level detected by the signal level detection means exceeds a prescribed signal level by a predetermined level or more, the received radio wave is regarded as a measured radio wave. Correction operation means for performing a correction operation using the phase difference and the calibration phase difference stored in the phase difference storage means for the arrival direction of the measured radio wave calculated from the phase difference sequentially detected by the phase difference detection means. And

According to a second aspect of the present invention, there is provided a radio wave direction detecting device according to the first aspect, wherein the direction of arrival calculating means determines the received radio wave from the phase difference between the measured radio waves detected by the phase difference detecting means. An error phase difference removing means for removing an error phase difference caused by including the calibration radio wave is added.

According to a third aspect of the present invention, a plurality of receiving antennas are provided at different positions from each other, and the same radio wave is received via each of the receiving antennas and output as a received signal. A plurality of receiving units,
A calibration signal generator that outputs a calibration signal, and is disposed in a predetermined reference direction with respect to each receiving antenna, and outputs a calibration signal output from the calibration signal generator as a calibration electric wave having a specified electric field level. A calibration antenna, phase difference detecting means for sequentially detecting a phase difference between received signals output from each receiving unit at a constant period, and a signal for detecting a signal level of the received signal output from each receiving unit When the signal level detected by the level detection means and the signal level detected by the signal level detection means is a specified signal level corresponding to the electric field level of the calibration radio wave, the received radio wave is regarded as the calibration radio wave, and each phase difference sequentially detected by the phase difference detection means is detected. Phase difference storage means for storing and holding the latest phase difference as a calibration phase difference, and radio waves received when the signal level detected by the signal level detection means exceeds a specified signal level A calibration radio wave cutoff unit that cuts off the output of the calibration radio wave from the calibration antenna, assuming that it is a measurement radio wave, and a phase difference sequentially detected by the phase difference detection unit after the calibration radio wave interruption, as a phase difference between the measurement radio waves. Radio wave arrival direction calculation means for calculating the arrival direction of the measured radio wave based on the phase difference and the calibration phase difference stored in the phase difference storage means.

(Operation) In the radio wave direction detecting device configured as described above, a calibration antenna for outputting a calibration electric wave of a specified electric field level is provided in addition to a plurality of receiving antennas. The calibration antenna is disposed in a predetermined reference direction with respect to each reception antenna.

It is assumed that the radio waves received by each receiving antenna of the radio wave direction detecting device are two types of radio waves: a calibration radio wave having the specified electric field level and a measurement radio wave exceeding the specified electric field level by a predetermined level or more. .

In a state where no measurement radio wave exceeding the specified electric field level exceeds a predetermined level, a calibration radio wave is always received, and the latest phase difference of this calibration radio wave and the direction of a predetermined calibration antenna are set. The difference from the corresponding known reference phase is stored and held as the latest calibration phase difference.

Then, when a measurement radio wave exceeding the specified electric field level by a predetermined level or more is input, a phase difference between the measurement radio wave and a known reference phase corresponding to the reference direction is calculated,
The arrival direction of the measured radio wave is calculated from the phase difference. Then, the calculated direction of arrival is corrected by the latest calibration phase difference stored and held, and the accurate direction of arrival of the measured radio wave is finally obtained.

In this case, each calibration phase difference measured by the calibration radio wave includes all the mounting accuracy of each receiving antenna, the length from each receiving antenna to each receiving unit, and the phase deviation in each receiving unit. Value.

Therefore, it is possible to increase the accuracy of the arrival direction of the measurement radio wave obtained by each of the calibration phase differences and each phase difference obtained by the measurement radio waves. Furthermore, since the calibration radio wave is always output and the latest calibration phase difference is always stored and held, even if the measurement environment such as temperature changes, the calibration phase difference immediately before the input of the measurement radio wave is used. A more accurate arrival direction can be calculated.

In another invention, an error phase difference caused by the fact that the received radio wave includes the calibration radio wave is removed from the phase difference between the detected measurement radio waves. Therefore, an even more accurate direction of arrival can be calculated.

Next, when measuring the phase difference with respect to the measurement radio wave while the calibration radio wave is constantly being output from the calibration antenna, the received signal (calibration signal) of the calibration radio wave is changed to the reception signal of the measurement radio wave (the target signal). Signal) will be described.

For the sake of simplicity, the calibration signal c (t) of the calibration other radio wave received via one of the plurality of reception antennas and the target signal d (t) of the measurement radio wave will be described. ). It is also assumed that the frequency of the calibration signal c (t) is equal to the frequency of the target signal d (t). Then, the target signal d (t) and the calibration signal c (t) are expressed by the following (1) (2)
It is shown by the formula.

[0034] d (t) = A COS ( ω c t + φ) ... (1) c (t) = B COS (ω c t + θ) ... (2) However, omega _c is the frequency of the calibration radio and measuring radio waves, φ
Is a phase difference between the target signal d and an arbitrarily set reference signal, and θ is a phase difference between the calibration signal and the same reference signal in the receiving unit. A is an amplitude corresponding to the signal level of the measurement radio wave, and B is an amplitude corresponding to the signal level of the calibration radio wave.

When the measured radio wave is received, the received signal s (t) includes the target signal d (t) and the calibration signal c (t), so that equation (3) is obtained. s (t) = d (t) + c (t) (3) The frequency ω _c of the received signal s (t) is shifted to the intermediate frequency using the local oscillation frequency of the receiving unit, and the high frequency component is further reduced. After removal by LPF, the in-phase component x _l
And the orthogonal component _xq are given by equations (4) and (5).

[0036] _{x l = A COSφ + B COSθ} ... (4) x q = A sinφ + B sinθ ... (5) Accordingly, by constantly output a calibration wave from the calibration antenna, the received signal s generated by incident constantly receiving antenna The phase error ε _P of (t) from the target signal d (t) is given by the following equation (6).

Ε _P = tan ⁻¹ (x _q / x _l ) −φ = tan ⁻¹ [(A sin φ + B sin θ) / (A COS φ + B COS θ)] − φ (6) It can also be understood from equation (6). Thus, the condition that the phase error ε _P has the maximum value is that the difference h = (θ−φ) between the phase difference θ of the calibration signal c (t) and the phase difference φ of the target signal d (t) is 90 °. It is time to become.

FIG. 5 shows the difference h = (θ) between the phase differences θ and φ.
-Φ) and the phase error ε _P are shown. Note that the solid line characteristic in the figure is the phase error ε _P characteristic when the difference between the signal level of the measurement radio wave and the signal level of the calibration radio wave is set to 20 dB, and the dotted line characteristic in the diagram is the signal level of the measurement radio wave and the calibration radio wave. It is a phase error ε _P characteristic when the difference from the signal level is set to 40 dB.

When the level difference is 20 dB, the maximum phase error ε _P is 5.7173 ° (degree), but when the level difference is 40 dB, the maximum phase error ε _P is only 0.5729 ° (degree).
In this way, by using the calibration radio wave having a signal level sufficiently lower than the measurement radio wave, even if the calibration radio wave is always output, the phase error caused by the calibration radio wave included in the measurement of the phase difference of the measurement radio wave is reduced. It is very small, and the arrival direction α of the calibration radio wave can be measured with sufficient accuracy.

Next, a specific method for removing an error phase difference caused by the inclusion of the calibration signal from the phase difference measurement of the received signal s (t) will be described. This description relates to claim 2.

(4) The in-phase component x of the base band represented by the equation (5)
[B COS θ] and [B sin θ] on the right side of _l and the orthogonal component x _q are terms caused by the calibration radio wave. This section
As shown by the equation (7), this becomes a factor of the phase error ε _P , and eventually causes a decrease in accuracy of the arrival direction α of the calibration radio wave.

Here, the calibration signal c (t) based on the calibration radio wave
In the state where the measurement radio wave is not received, the amplitude B of the calibration signal c (t) and the phase difference θ between the calibration signal and the local oscillation signal in the receiving unit are high because the signal is always received when the measurement radio wave is not received. It is possible to measure with accuracy.

Therefore, from equations (4) and (5), [B COSθ]
And [B sin θ], the in-phase component x in the baseband even if the calibration radio wave is continuously output.
can remove the term due to the calibration signal c (t) from _l and quadrature component x _q, errors due to calibration wave from the arrival direction of the finally measured radio α it can be removed.

Therefore, if a method for removing the error phase is provided, the level of the calibration signal is 10 to 10 times lower than the measurement level.
Even if it is only as low as 20 dB, it can be measured sufficiently. In another invention, the output of the calibration radio wave is cut off when the signal level of the received signal exceeds a specified signal level. Then, in a state where the calibration radio wave is not received, the arrival direction of the measurement radio wave is calculated from each phase difference of the received measurement radio wave and the calibration phase difference.

In this case, the input / output operation for the calibration radio wave is performed. However, since the reception signal of the calibration radio wave does not overlap the reception signal of the measurement radio wave from the beginning, the phase error ε _P is calculated in the process of calculating the arrival direction of the measurement radio wave. There is no need to perform the removal process.

[0046]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a schematic configuration of a radio wave direction detecting apparatus according to a first embodiment of the present invention. FIG.
The same parts as those of the conventional radio wave direction detecting device shown in FIG. Therefore, the detailed description of the overlapping part is omitted.

As shown in FIG. 2, the three receiving antennas 1a, 1b, and 1c are distributed and arranged on the circumference of a radius R. A distance L from the center of a circle in a predetermined reference direction with respect to the three receiving antennas 1a, 1b, 1c.
The calibration antenna 17 is provided at a position separated by only a distance. Specifically, three receiving antennas 1a, 1b, 1
c and one calibration antenna 17 are fixed to the same frame. If the distance L is about 30 cm, for example, if the frequency ω _c of the measurement radio wave 3 is about 5 GHz, sufficient performance can be obtained.

[0048] The radio direction-finding apparatus for measuring the direction of arrival of a particular radio wave having a pre-specified frequency omega _c and a predetermined electric field level. A calibration signal generator 18 is connected to the calibration antenna 17. This calibration signal generator 18
Is the radio wave output calibration wave 20 having a frequency omega _c having the same frequency omega _c measurement wave 3 that is to be measured in the arrival direction in this radio direction finding apparatus via the calibration antenna 17. The electric field level of the output calibration radio wave 20 is the measurement radio wave 3
The output level of the calibration signal generator 18 is adjusted so as to be a predetermined reference level lower than the electric field level by, for example, 40 dB.

The calibration signal generator 18 constantly outputs the calibration radio wave 20 while the apparatus is in operation.
Each of the superheterodyne receivers 2a, 2b, and 2c including the amplifier 16, the signal combiner 9, and the BPF 10 has a common local oscillator 11 and a local oscillator with respect to each signal combiner 9 via the distributor 12 from the local oscillator 11. A signal g is provided.

Each of the receiving sections 2a, 2b, 2c receives only the calibration radio wave 17 received via the corresponding one of the receiving antennas 1a, 1b, 1c or a radio wave in which the calibration radio wave 17 and the measurement radio wave 3 are combined. Then, the received signals e ₁ , e ₂ , and e ₃ whose reception frequency ω _c has been lowered to the intermediate frequency are sent to the next direction measurement processing unit 19.

The direction measurement processing section 19 is configured, for example, as shown in FIG. The received signals e ₁ , e ₂ , and e ₃ input from the receiving units 2a, 2b, and 2c are A /
After being converted into digital values by the D converters 21a, 21b, and 21c, the digital values are input to an arithmetic processing unit 22 configured by an information processing device such as a microcomputer.

The signal level detector 23 detects the signal level of each of the received signals e ₁ , e ₂ , and e ₃ , and determines the average signal level as the specified signal level corresponding to the specified electric field level of the calibration radio wave 20. It is determined whether the signal level is a target signal level corresponding to the measured radio wave 3 which exceeds a predetermined signal level, for example, 40 dB, from the specified signal level, and the determination result and each signal obtained from the signal level are determined. Are sent to the arithmetic processing unit 22.

The arithmetic processing unit 22 includes a phase difference detecting unit 2.
4, timer 25, phase difference memory 26, measured value memory 2
7, amplitude value memory 28, arrival direction calculation unit 29, display unit 3
0 is provided.

The phase difference detector 24 calculates the phase difference between the input digital received signals e ₁ , e ₂ and e ₃ . Specifically, the phase differences β ₁ , β ₂ , and β ₃ with respect to the arbitrarily set reference signal are sequentially detected at a constant period T _S based on the signal from the timer 25.

Then, when the determination result from the signal level detecting section 23 is the specified signal level, the phase difference detecting section 24
The phase differences β ₁ , β ₂ , β ₃ sequentially detected are stored in a phase difference memory 2.
6 is written as each calibration phase difference θ ₁ , θ ₂ , θ ₃ of the calibration radio wave. On the other hand, when the determination result from the signal level detector 23 is the measurement signal level, the phase differences β ₁ , β _1
2 and β ₃ are transferred to the measured value buffer 27.
_1, φ _2, written as φ _3.

The phase difference memory 26 updates the previously stored calibration phase differences β ₁ , β ₂ , β ₃ with the new calibration phase differences β ₁ , β ₂ , β ₃ inputted. That is, the latest calibration phase differences β ₁ , β ₂ , and β ₃ are always stored and held.

The measured value buffer 27 stores and holds the phase differences φ ₁ , φ ₂ , and φ ₃ of the sequentially input target signal in a predetermined time series. The amplitude memory 28 stores and holds the amplitude B of the calibration signal input from the signal level detection unit 23 and the amplitude A of the received signal including the calibration signal and the target signal.

The direction-of-arrival calculator 29 calculates the phase differences φ ₁ , φ ₂ , φ ₃ of the target signal and the calibration phase differences θ ₁ , θ _{2 of} the calibration signal.
The arrival direction α of the measurement radio wave 3 is calculated by using the values ₂ and θ ₃ and the amplitudes A and B, and is output to the display unit 30 for display.

FIG. 4 is a flowchart showing the overall operation of the direction measurement processing section 19 shown in FIG. When the measurement process is started and the short time ΔT has elapsed (S1), the signal level detection unit 23
Detect the signal levels of the received signals e ₁ , e ₂ and e ₃ (S2). If the signal level is the specified signal level (S3), it is determined that the received signal is a calibration signal, and the short time ΔT is added to the elapsed time T in S4 (T = T + ΔT). If the elapsed time T after the addition has not reached the specified period T _S such as one second (S5), the process returns to S1 and waits for the elapse of the minute time ΔT.

A prescribed period T _{S in which} the elapsed time T after the addition is 1 second
, The calibration signal is read (S6), the calibration phase differences θ ₁ , θ ₂ , and θ ₃ are calculated by the phase difference detection part 24 (S7), and written to the phase difference memory 26 (S8). Then, the elapsed time T is cleared to 0 (S8), the flow returns to S1, and the elapse of the short time ΔT is waited.

In S3, if the signal level of the received signals e ₁ , e ₂ , e ₃ detected by the signal level detecting section 23 is the target signal level corresponding to the measured radio wave 3 exceeding the prescribed signal level by a predetermined signal level, It is determined that the received signal is the target signal, and the received signal is measured for the specified time T _M (S
10), then was confirmed that the frequency matches the frequency of the calibration signal (S11), the phase difference phi ₁ of the target signal in the phase difference detection part 24, phi _2, and calculates the phi ₃ (S12).

Next, the calculated phase differences φ ₁ , φ
_2, due to the calibration signals included in the phi ₃ is present,
The above-described phase errors are converted into the calibration signal amplitude B and the calibration phase differences θ ₁ , θ ₂ , θ ₃ stored in the phase difference memory 26.
Is calculated using Then, each phase difference φ ₁ , φ ₂ , φ ₃
, And removes each phase error (S13).

Thereafter, each phase difference φ of the corrected target signal φ
₁ , φ ₂ , φ ₃ and each calibration phase difference θ ₁ , θ ₂ ,
In the theta _3, it calculates the arrival direction α of the measurement electric wave 3 using Intafero method or MUSIC method described above (S1
4). Then, a display is output on the display unit 30 (S15).
Thereafter, the elapsed time T is cleared to 0 (S16), and S1
And waits for the elapse of the minute time ΔT.

In the radio wave direction exploring apparatus thus constructed, in addition to the receiving antennas 1a, 1b and 1c for receiving the measurement radio wave 3, the calibration radio wave 2 having a specified electric field level is used.
A calibration antenna 17 for outputting 0 as a radio wave is provided. The calibration antenna 17 is connected to each of the receiving antennas 1a. 1b. 1c is disposed in a predetermined reference direction.

The arrival direction of the calibration radio wave 20 is a known reference direction. When the radio wave arrives from the reference direction, each phase difference of each received signal is determined by a known reference direction corresponding to a predetermined direction of the calibration antenna 17. The difference from the phase is stored as the latest calibration phase difference θ ₁ , θ ₂ , θ ₃ .

When a measured radio wave exceeding the specified electric field level by a predetermined level or more is input, the arrival direction of the measured radio wave is calculated from the phase differences φ ₁ , φ ₂ , φ ₃ measured at this time. Then, the calculated arrival direction a is corrected by the latest calibration phase differences θ ₁ , θ ₂ , θ ₃ stored and held, and finally the accurate arrival direction a of the measured radio wave is obtained.

In this case, each of the calibration phase differences θ ₁ , θ ₂ , and θ ₃ measured by the calibration radio wave 20 includes the mounting accuracy of each of the receiving antennas 1a, 1b, and 1c, and the receiving antennas 1a, 1c.
These values include the lengths from 1b, 1c to the receiving units 2a, 2b, 2c and the phase deviations in the receiving units 2a, 2b, 2c.

Therefore, the accuracy of the arrival direction of the measurement radio wave 3 obtained by each of the calibration phase differences and each phase difference obtained by the measurement radio wave 3 can be increased. In addition, calibration radio wave 2
0 is always output, and the latest calibration phase difference θ ₁ ,
Since θ ₂ and θ ₃ are stored and held in the phase difference memory 26, even if the measurement environment such as temperature changes, the more accurate arrival direction is calculated because the calibration phase difference immediately before the input of the measurement radio wave is used. it can.

Each phase difference φ of the detected measurement radio wave is
_The error phase difference ε _p resulting from the fact that the received radio wave includes the calibration radio wave 20 is removed from ₁ , φ ₂ , and φ ₃ . Therefore, the more accurate arrival direction α can be calculated.

(Second Embodiment) FIG. 6 is a block diagram showing a schematic configuration of a radio wave direction detecting apparatus according to a second embodiment of the present invention. The same parts as those of the radio wave direction detecting device of the first embodiment shown in FIG. Therefore,
The detailed description of the overlapping part is omitted.

In the second embodiment, a switch 31 is provided between the calibration signal generator 18 and the calibration antenna 17. This switch 31 is connected to the direction measurement processing unit 19a.
The opening and closing are controlled by. The rest is almost the same as the radio wave direction detecting device of the first embodiment shown in FIG.

Then, the direction measurement processing unit 19a executes a process of calculating the arrival direction α for the measured radio wave 3 according to the flowchart shown in FIG. In the flowchart of FIG. 7, the same steps as those in the flowchart of FIG. 4 are denoted by the same reference numerals. Therefore, the description of the overlapping part will be omitted.

In the second embodiment, in S3, the received signals e ₁ ,
If the signal levels of e ₂ and e ₃ are the target signal levels corresponding to the measured radio wave 3 exceeding the specified signal level by a predetermined signal level, the received signal is determined to be the target signal, and the received signal is determined for the specified time T _M. Is measured (S10), and after confirming that the frequency matches the frequency of the calibration signal (S1).
1), the switch 31 is opened to cut off the calibration radio wave 20 (S11a). After shutting off, each phase difference φ of the target signal
₁ , φ ₂ and φ ₃ are calculated (S12).

Then, the process immediately proceeds to S14, where the phase differences φ ₁ , φ ₂ , φ _{3 of} the target signal and the calibration phase differences θ ₁ , θ ₂ , θ _{3 of the} calibration signal are used as the interferometric method or the MUSIC method described above. Is used to calculate the arrival direction α of the measured radio wave 3 (S14). Then, a display is output on the display unit 30 (S15). Thereafter, the elapsed time T is cleared to 0 (S
16) Return to S1 and wait for the elapse of the minute time ΔT.

In the radio wave direction searching device thus configured, the switch 30 is turned on / off with respect to the calibration radio wave 20.
Although the cutoff operation is performed, the calibration signal 2
Since the received signal of 0 is not superimposed from the beginning, it is not necessary to perform the process of removing the phase error ε _P in the process of calculating the arrival direction α of the measurement radio wave 3. Therefore, the operation program can be simplified and the operation processing speed can be improved.

The present invention is not limited to the above embodiments. In each embodiment, the number of receiving antennas is three, but the number is not particularly limited to three, and may be five or seven.

[0077]

As described above, in the radio wave direction detecting apparatus of the present invention, a calibration antenna for outputting a calibration radio wave is provided in addition to a plurality of reception antennas for receiving the measurement radio wave.

Therefore, in the process of applying the calibration signal to each of the receiving sections, it is possible to eliminate the error factors until the calibration signal reaches each of the receiving sections, and to simultaneously deteriorate the mounting accuracy of each receiving antenna due to the use environment and aging. Compensation can be performed, and even if the measurement radio wave has a high frequency, the arrival direction of the measurement radio wave can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a radio wave direction detecting device according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a relative position between a receiving antenna and a calibration antenna of the radio wave direction finding apparatus.

FIG. 3 is a detailed block diagram of a direction measurement processing unit of the radio wave direction detecting device.

FIG. 4 is a flowchart showing the operation of the radio wave direction detecting device.

FIG. 5 is a diagram illustrating a relationship between a phase difference and a phase error.

FIG. 6 is a block diagram showing a schematic configuration of a radio wave direction detecting device according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the radio wave direction detecting device.

FIG. 8 is a schematic configuration diagram of a general radio wave direction detecting device that employs an interferometer system.

FIG. 9 is a schematic configuration diagram of a general radio wave direction detecting device employing the MUSIC method.

FIG. 10 is a diagram showing the principle of measuring the direction of arrival of a radio wave using a phase difference.

FIG. 11 is a block diagram showing a schematic configuration of a conventional radio wave direction detecting device.

[Explanation of symbols]

 1a, 1b, 1c receiving antenna 2a, 2b, 2c receiving unit 3 measurement radio wave 9 signal combiner 10 BPF 17 calibration antenna 18 calibration signal generator 19, 19a direction measurement processing unit 20 Calibration radio wave 22 arithmetic processing unit 23 signal level detection unit 24 phase difference detection unit 26 phase difference memory 29 arrival direction calculation unit

Claims (3)

[Claims] 1. A plurality of receiving antennas (1a, 1b, 1c) arranged at different positions from each other, and a plurality of receiving antennas receiving the same radio wave via each of the receiving antennas and outputting the same as a received signal. Part (2a, 2b, 2c)
A calibration signal generator (18) that outputs a calibration signal, and is disposed in a predetermined reference direction with respect to each of the receiving antennas, and outputs a calibration signal output from the calibration signal generator to a specified electric field level. A calibration antenna (17) for outputting a radio wave as a calibration radio wave; and a phase difference detecting means (24) for sequentially detecting a phase difference between the received signals output from the respective receiving units at a constant cycle. An arrival direction calculation unit (29) for calculating an arrival direction of an incoming radio wave from the phase difference detected by the phase difference detection unit; and a signal level detection unit (23) for detecting a signal level of a reception signal output from each of the reception units. ), When the signal level detected by the signal level detection means is a specified signal level corresponding to the electric field level of the calibration radio wave, the received radio wave is regarded as a calibration radio wave, and is sequentially detected by the phase difference detection means. Of each phase difference A phase difference storage means (26) for storing and holding the latest phase difference as a calibration phase difference; and measuring the received radio wave when the signal level detected by the signal level detection means exceeds the specified signal level by a predetermined level or more. Assuming that the radio wave is a radio wave, the direction of arrival of the measured radio wave calculated from the phase difference sequentially detected by the phase difference detection means is corrected using this phase difference and the calibration phase difference stored in the phase difference storage means. A radio wave direction detecting device comprising: 2. The arrival direction calculating unit removes an error phase difference caused by the received radio wave including a calibration radio wave from a phase difference between the measured radio waves detected by the phase difference detecting unit. 2. The radio wave direction detecting apparatus according to claim 1, further comprising an error phase difference removing unit that performs the operation. 3. A plurality of receiving antennas (1a, 1b, 1c) disposed at different positions from each other, and a plurality of receiving antennas for receiving the same radio wave via each of the receiving antennas and outputting the same as a received signal. Part (2a, 2b, 2c)
A calibration signal generator (18) that outputs a calibration signal, and is disposed in a predetermined reference direction with respect to each of the receiving antennas, and outputs a calibration signal output from the calibration signal generator to a specified electric field level. A calibration antenna (17) for outputting a radio wave as a calibration radio wave, and a phase difference detecting means (24) for sequentially detecting a phase difference between reception signals output from each of the receiving units at a fixed cycle, Signal level detecting means (23) for detecting the signal level of the received signal output from the receiving unit; and when the signal level detected by the signal level detecting means is a specified signal level corresponding to the electric field level of the calibration radio wave, The received radio waves are regarded as calibration radio waves, and the phase difference storage means (26) for storing and holding the latest phase difference among the phase differences sequentially detected by the phase difference detection means as a calibration phase difference, and the signal level detection means Inspection When the signal level exceeds the specified signal level, the received radio wave is regarded as a measurement radio wave, and a calibration radio wave cutoff unit (31) for cutting off the output of the calibration radio wave from the calibration antenna, The phase difference sequentially detected by the phase difference detecting means is used as the phase difference between the measured radio waves, and the direction of arrival of the measured radio wave is calculated from the phase difference and the calibration phase difference stored in the phase difference storing means. A radio wave direction detecting device comprising a radio wave arrival direction calculation means (29).