JPH036479A - Azimuth measuring method and apparatus, transmission apparatus and receiving apparatus - Google Patents

Abstract

PURPOSE:To reduce the azimuth measuring error due to multipath interference and to obtain the accurate data of a pilot signal by a method wherein a transmission source transmits a radio wave subjected to angular modulation and the transmitted direct wave and the reflected wave thereof are received on a receiving side and the beat frequency signal due to both waves is converted to an electric signal which is, in turn, averaged timewise. CONSTITUTION:A transmission station 2 is composed of a transmitter 21 equipped with a pilot signal transmission antenna 23 and a receiving station 1 has direction finding antennae 12a, 12b, an averaging circuit 18 and an antenna driving part 14. The transmitted signal 3 generates a continuous wave 37 and the reflected wave 31 from the ground 5 and the others and multipath interference is generated between both waves. Since frequency is difference when the receiving station 1 receives both waves, a beat is generated and this beat is converted to an electric signal which is, in turn, averaged timewise. This signal is shown as a function of time and, when a time average is taken, the value thereof becomes 0 or becomes near to 0. As a result, the error due to the interference of the direct wave and the reflected wave and the accurate data of the azimuth of the transmission source using an amplitude comparing monopulse system is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an azimuth measuring method, an azimuth measuring system, a transmitting device, and a receiving device for determining the azimuth of a radio wave transmission source from the receiving side.

[Prior Art] Improving reception performance when communicating between a transmitting source located in a moving body such as an automobile, ship, or aircraft and a fixed or moving receiving end, or vice versa. For,
It is often required on the receiving side to point a communication directional antenna in the direction of the transmission source.

In addition, in navigation aid systems, when radio waves transmitted from a transmission source at a fixed point on land are received on a moving object such as an aircraft or ship, and the navigation position and direction are determined, the direction of the transmission source can be accurately measured. It is necessary to do so.

In these cases, since the direction of the transmission source from the reception side changes due to movement of the transmission source or the reception side, it is necessary to measure the direction of the transmission source on the reception side immediately before or during communication.

As a conventional direction measuring system, there is one shown in FIG. 5, for example.

That is, the transmitting station 2 uses the pilot signal transmitting antenna 2
3 and a radio wave transmitter 32 equipped with a transmitting antenna 24.

The direction measuring pilot signal transmitter 21 includes an oscillator 29 and an amplifier 30. The radio wave transmitter 32 includes a signal input terminal 25, an oscillator 27, and an amplifier 28.

1 On the other hand, the receiving station 1 has a direction receiving antenna 12a.

12b, a direction-finding receiver 11, an averaging circuit 18, a directional antenna driver 14, a directional antenna 15, a receiver 16, and a signal output terminal 17.

The direction finding receiving antennas 12a and 12b in FIG.
The transmitting station 2 is arranged in a plane in which the direction of the transmitting station 2 changes.

The receiving station 1 is configured to correspond to any one of the following monopulse methods: an amplitude comparison monopulse method, a monopulse method using a dual-mode spiral antenna, an amplitude phase comparison monopulse method, and a phase comparison monopulse method.

In such a system, a transmitting station 2 transmits an azimuth measurement pilot signal 3 to a receiving station l.

The receiving station 1 receives the pilot signal 3 for direction measurement with the direction finding receiver 11 via the direction finding receiving antennas 12a and 12b.

2 The receiver 11 uses an amplitude comparison monopulse method, a monopulse method using a dual-mode spiral antenna, an amplitude phase comparison monopulse method, or a phase comparison monopulse method to obtain the pilot signal 3 for direction measurement between antennas.
The direction information signal of the transmitting station 2 is generated from the amplitude ratio and phase difference. This signal is supplied to the directional antenna driver 14 through the averaging circuit 18.

The directional antenna drive section 14 directs the directional antenna 15 in the direction of the transmitting station 2 according to the direction information signal.

In this way, the directional antenna 15 receives the direct wave 47 from the transmitting antenna 24 and transmits the signal from the receiver 16 to the signal output terminal 17.

Note that since the direction-finding reception system needs to have a wide coverage area, it generally uses an antenna with a wide beam width, that is, a low gain, but in order to improve the S/N ratio,
It is necessary to narrow the passband width of the system. Furthermore, it is desirable to simplify the pilot 3 signal transmitter 21 for direction measurement.

For this reason, an unmodulated continuous wave is generally used as the pilot signal 3 for direction measurement.

[Problems to be Solved by the Invention] However, in such a conventional direction measurement system, the direction measurement pilot signal 3 There was a problem that errors were likely to occur in the direction information from the

That is, since the direct wave 37 of the direction measurement pilot signal 3 and the reflected wave 31 from the ground 5 etc. simultaneously enter the direction finding receiving antennas 12a and 12b, multipath interference occurs.

One way to reduce multipath interference is to time-average received signals over a relatively long period of time, smooth out changes in interference over time as the position of a mobile object changes, and use the average value as azimuth information. be.

However, since this method is dominated by changes in azimuth information or behavior patterns of the moving object, for example, if the moving object is stationary, the multipath interference is also fixed. Therefore, this method generates an error that does not change over time, and cannot obtain the effect of averaging.

Furthermore, in order to improve the S/N ratio by narrowing the passband width of the direction-finding receiver, it is necessary to provide an oscillator with good frequency stability on the transmitting side. Therefore, there was a problem that the manufacturing cost was high.

This has been a serious problem, especially in microwave band applications.

In addition, in conventional direction measurement systems, two lines of communication are required: a pilot signal for direction measurement and a communication radio wave.
Because different types of radio waves are required, equipment and communication costs are high.

The present invention has been made by focusing on the problems of the conventional technology, and it is possible to reduce azimuth measurement errors caused by multipath interference and obtain accurate azimuth information from a pilot signal for azimuth measurement. The object of the present invention is to provide an azimuth measuring method, an azimuth measuring system, a transmitting device, and a receiving device.

Another object of the present invention is to provide an azimuth measuring method, an azimuth measuring system, a transmitting device, and a receiving device that perform one type of communication using one type of radio wave and that require low equipment and communication costs.

[Means for Solving the Problems 1] In order to achieve the above object, the invention of Section 1 of the present application provides an azimuth measurement method in which radio waves sent from a transmission source are received by an antenna on the receiving side to determine the azimuth of the transmission source. In the method, the transmission source transmits an angle-modulated radio wave, and the receiving side receives a direct wave and a reflected wave of the transmitted radio wave, and converts a beat frequency signal due to the direct wave and the reflected wave into an electrical signal. By converting the electric signal into a signal and averaging the electric signal over time, the direction measurement error due to multipath interference is reduced.

In addition, if the direction measurement method is a direction measurement method in which the direction of the transmission source is determined by receiving with at least two antennas on the receiving side and using an amplitude comparison monopulse method, In the case of an azimuth measurement method in which the direction of the transmission source is determined by receiving with a dual mode spiral antenna and using a monopulse method, receiving is performed using at least two antennas on the receiving side and using an amplitude phase comparison monopulse method. In the case of an azimuth measurement method in which the azimuth of the transmission source is known, the azimuth measurement method in which the azimuth of the transmission source is determined by receiving with at least two antennas on the receiving side and using a phase comparison monopulse method. Either method may be used.

In these methods, the angle-modulated radio waves may be communication radio waves.

In these methods, it is preferable that the beat frequency signal has a time average value of zero power of the converted electrical signal.

These methods may include knowing the orthogonal two-dimensional orientation of the transmission source.

The invention of Section 2 of the present application provides an azimuth measurement system in which radio waves sent from a transmission source are received by an antenna on the receiving side and the direction of the transmission source is determined, comprising: a transmission source that transmits angle-modulated radio waves; an antenna on the side for receiving the direct wave and the reflected wave of the transmitted radio wave; and a signal conversion means on the receiving side for converting the beat frequency signal generated by the direct wave and the reflected wave into an electric signal. , an averaging circuit that time-averages the electric signal, and is characterized in that it reduces azimuth measurement errors due to multipath interference based on the output from the averaging circuit.

In addition, in the case of the above-mentioned direction measurement system, the direction measurement system receives data using at least two antennas on the receiving side and uses an amplitude comparison monopulse method to determine the direction of the transmission source. In the case of an azimuth measurement system that receives data from a mode spiral antenna and uses a monopulse method to determine the direction of the transmission source, on the receiving side,
In the case of an azimuth measurement system that receives data using at least two antennas and uses an amplitude phase comparison monopulse method to determine the direction of the transmission source, the system receives data using at least two antennas on the receiving side and uses a phase comparison monopulse method. The azimuth measurement system may be any of the following systems, as long as the azimuth of the transmission source is determined using the azimuth.

In these systems, the angle-modulated radio waves may be radio waves for communication.

In these systems, it is preferable that the time average value of the electrical signal into which the beat frequency signal is converted is zero.

These systems may be characterized by knowing the orthogonal two-dimensional orientation of the transmission source.

The invention of Section 3 of the present application provides a transmitting device that receives radio waves sent from a transmitting source using an antenna on the receiving side, uses a monopulse method, and is used as an azimuth measuring system for determining the azimuth of the transmitting source. It is characterized by transmitting modulated radio waves.

The invention of Section 4 of the present application provides a receiving device that receives radio waves sent from a transmission source and knows the direction of the transmission source, comprising: an antenna that receives a direct wave and a reflected wave of the transmitted radio wave; a signal converting means for converting a beat frequency signal caused by the reflected wave into an electrical signal; and an averaging circuit for time-averaging the electrical signal; It is characterized by reducing the direction measurement error caused by.

The invention of Section 4 of the present application may be characterized in that the amplitude comparison monopulse method is used as a direction finding method.

Furthermore, the antenna may be a dual-mode spiral antenna, and may be characterized in that a monopulse method is used as a direction finding method.

Further, there may be one characterized in that it is used as a direction finding method such as an amplitude phase comparison monopulse method.

Furthermore, there may be one characterized in that the phase comparison monopulse method is used as a direction finding method.

The angle-modulated radio waves used in the present invention include all frequency modulated waves or phase modulated waves, for example, linear chirp modulated signals include sinusoidal or triangular chirp modulated signals. .

Alternatively, the phase of the pilot signal may be directly temporally changed by phase modulation.

Furthermore, a plurality of receiving stations may be provided for one transmission source, or a bidirectional system having both a transmitting station and a receiving station may be used between two points.

As the electrical signal used in the present invention, for example, a voltage signal is used.

The averaging circuit used in the present invention is, for example, a low-pass filter, and the low-pass filter may be either a digital filter or an analog filter.

In the present invention, the direction finding method includes not only a method using continuous waves but also a pulse method.

[Operation] A transmission source transmits angle-modulated radio waves, and a receiving side receives direct waves and reflected waves of the transmitted radio waves using its receiving antenna.

Since direct waves and reflected waves propagate through different propagation paths, there is always a difference in propagation path length, so at the receiving point, radio waves transmitted at different times are received at the same time.

Since the transmission source performs angular modulation, the instantaneous transmission frequencies are different, and as a result, the direct wave and the reflected wave interfere, producing a beat.

On the receiving side, the beat frequency signal of the direct wave and the reflected wave is converted into an electrical signal, and the electrical signal is time-averaged.

Since the radio waves are angularly modulated, the beat frequency signal or converted electrical signal is expressed as a function of time, and when time averaged, the time average value becomes 0 or close to 0.

Therefore, errors caused by interference between the direct wave and the reflected wave are reduced.

In this way, the radio waves whose azimuth measurement error is reduced due to multipath interference are transmitted using methods such as the amplitude comparison monopulse method, monopulse method 1 using a dual-mode spiral antenna, amplitude phase comparison monopulse method, or phase comparison monopulse method. It is possible to obtain accurate direction information regarding the direction of the source.

If the antennas are arranged orthogonally, the orthogonal two-dimensional orientation of the transmission source can also be known.

3 [Embodiment 1] Various embodiments of the present invention will be described below based on the drawings. Incidentally, the same types of parts in various embodiments are given the same reference numerals and redundant explanations will be omitted.

FIG. 1 shows a first embodiment of the invention.

As shown in FIG. 1, the transmitting station 2 consists of a pilot signal transmitter 21 for azimuth measurement equipped with a pilot signal transmitting antenna 23.

The azimuth measurement pilot signal transmitter 21 includes an oscillator 29, an FM modulator 40, and an amplifier 30.

On the other hand, the receiving station 1 has a direction receiving antenna 12a.

12b, a direction finding receiver 11, an averaging circuit 18, and a directional antenna driving section 14.

The receiving station 1 is configured to correspond to the one-dimensional amplitude comparison monopulse method.

The direction finding receiving antennas 12a and 12b are antennas that use a one-dimensional amplitude comparison monopulse method as a direction finding method.

The four-directional receiving antennas 12a and 12b are arranged in a plane in which the direction of the transmitting station 2 relative to the receiving station 1 changes.

Further, the direction finding receiver 11 has a configuration compatible with a one-dimensional amplitude comparison monopulse method.

The averaging circuit 18 uses a low-pass filter.

The directional antenna drive unit 14 may be an azimuth indicator as a host system that uses azimuth information.

As the azimuth measurement pilot signal 3 transmitted from the azimuth measurement pilot signal transmitter 21 via the pilot signal transmission antenna 23, a chirp modulated wave is used as a frequency modulated wave.

Further, FIG. 6 is an explanatory diagram showing the operating principle of the amplitude monopulse method, and FIG. 7 is a graph showing the amplitude pattern.

In FIG. 6, the direction receiving antennas 12a and 12b are arranged with the main radiation direction at an angle α with respect to each other.

Directional receiving antennas 12a and 12b are connected to receiving circuits 11a and llb, respectively.

The receiver 11 includes two channel receiving circuits 11a and llb.
and an amplitude comparator 41 for comparing these outputs, and the output of the amplitude comparator 41 becomes azimuth information and is supplied to the ``first place system'' which uses this information.

The direction finding receiving antennas 12a and 12b receive pilot signals for direction measurement.

The receiving circuits 11a and llb include a direction receiving antenna 12a,
It receives the signal from 12b and performs functions such as amplitude, frequency conversion, filtering, and detection.

The amplitude comparator 41 includes two receiving circuits 11a.

11b, and generates AOA information (8 angles of arrival, angle of arrival information).
Output.

The principle of the amplitude comparison monopulse method is explained as follows.

6 As shown in Fig. 7, the pattern of the antenna 12a and the pattern of the antenna 12b are arranged at an angle α apart, so the output difference ΔE between the two receiving circuits changes depending on the arrival direction θ of the radio wave. .

This output difference ΔE(θ) is a function specific to the device, and its shape can be measured in advance, so when searching for directions, ΔE
Knowing (θ) means knowing θ, that is, the direction of arrival.

Next, the operation of this embodiment will be explained.

In FIG. 1, a transmitting station 2 transmits an azimuth measurement pilot signal 3 to a receiving station 1. The azimuth measurement pilot signal 3 is subjected to frequency modulation by the FM modulator 40, so the frequency differs from moment to moment.

The pilot signal 3 for direction measurement transmitted from the pilot signal transmission antenna 23 includes a continuous wave 37 and a reflected wave 3 generated by reflection from the ground 5 and other objects within the space propagation path.
1 is generated as a multipath component, and multipath interference occurs between the direct wave 37 and the reflected wave 31.

7. The direct wave 37 and the reflected wave 31 are received by the directional receiving antennas 12a and 12b of the receiving station l.

The direct wave 37 and the reflected wave 31 are transmitted from the pilot signal transmitting antenna 23 to the direction receiving antenna 12a.

12b, different routes are followed, resulting in a difference in propagation time. Therefore, when received by the receiving station 1, the two interfering frequency modulated waves, the direct wave 37 and the reflected wave 31, have different frequencies.

The operation of the embodiment shown in FIG. 1 will be described in the case where chirp modulation is used as the modulation format of the pilot signal 3 for azimuth measurement.

The frequency of the oscillated radio wave from the oscillator 29 is f. , time t,
When the constant is the C1 frequency modulated wave and the frequency of the chirp modulated wave is f, the formula % formula % holds true.

Further, if Δt is the propagation time difference between the direct wave 37 and the reflected wave 31, the frequency difference between the two interfering radio waves, the direct wave 37 and the reflected wave 31, is expressed as C·Δt.

FIG. 4 is an explanatory diagram of multipath interference of chirp modulated waves. The propagation time difference between the direct wave 37 and the reflected wave 31 is shown as Δt.

From the figure, it can be seen that when Δt occurs, a difference occurs between the frequencies when two waves are received.

The received electric field at the direction receiving antenna 12a is Ea, the reception electric field at the direction receiving antenna 12b is Eb, the frequency of the direct wave is fd, the frequency of the reflected wave is fr, and the amplitude of the direct wave is 1 for the direction receiving antenna 12a. Assume that the amplitude of the reflected wave is Ka, the phase is 68, the amplitude of the reflected wave with respect to the direction receiving antenna 12b is Kb, and the phase is δゎ.

E a = C, a [expj (2πfd4) + Ka
−expj(2πfr−tδa)]・・・・・・(1) E b = C, b[expj(2πfd4)+Kb−
expj(2πfr4δb)]...(2) holds true.

In these two equations, the first term represents a direct wave, and the second term represents a reflected wave. Note that C#a and Cgb indicate system constants (complex numbers), which are determined by the transmission power, the gain of each antenna, the antenna pattern, the distance between transmitting and receiving stations, etc., and are values that do not change over time. Also, in general, Ka, K
It is well known that b < 1.

On the other hand, if the propagation time difference between the direct wave and the reflected wave is Δt, then
The formula % formula % holds true.

Here, assuming that the position between the transmitting and receiving stations and the antenna orientation are fixed, the signal S representing the orientation information is expressed by the following formula.

Substituting equations (1) and (2) into equation (3) and transforming the equation yields 9... (4).

(4), assuming that there is no reflected wave, Ka=　Kb=　O, The formula holds true.

This equation (5) indicates an ideal state without reflected waves.

When there is a reflected wave, the values of Ka and Kb change,
It can be seen that as the values of Ea and Eb change, the value of S changes accordingly, causing an error.

If the frequencies of the direct wave and the reflected wave are equal, fd=
Since it is fr, it becomes .

Comparing Equation (6) with Equation (5), it can be seen that an error of 1 minute, Ka-expj6a and Kb-expjδ5 are generated in S. Furthermore, if there is no movement between the transmitting and receiving stations, this error is a fixed error and is not a function of time, so it cannot be reduced even by using an averaging circuit.

However, in this embodiment, a chirp modulated wave is used as the frequency modulated wave for the pilot signal 3 for azimuth measurement. Therefore, when received at receiving station l, the frequencies of the direct wave and the reflected wave are different, and as shown in equation (4), the beat frequency signal Ka-expj(2π(fr-fd)t
+δ8) and Kb-expj(2π(fr-fd)t
+δb) or occurs as an error. This beat frequency signal has a beat frequency fr−fd and a period 1/(f
r L) and is determined as a function of time.

The error component of equation (4), that is, the beat frequency signal Ka
-expj(2π(fr-fd)t+68) and 1
．． -expj(2π(fr-fd)t+65) is averaged over time, and the value is O.

The time averaging process is actually performed by converting the received beat frequency signal of the direct wave 2 and the reflected wave into a voltage signal and time averaging the voltage signal.

In this way, as a result of time averaging processing of the beat frequency signal using equation (5), a signal S representing azimuth information is expressed by the following equation.

This equation (7) matches equation (5). That is, it can be seen that the signal S representing the azimuth information is a signal that is not affected by reflected waves.

Therefore, it is possible to reduce azimuth measurement errors due to multipath interference and obtain accurate azimuth information from the transmitted signal.

In this embodiment, since the amplitude comparison monopulse method is used as the direction finding method, only the amplitude is used as the direction information.

Next, a case will be described in which a two-dimensional amplitude monopulse method is used as the direction search method in this embodiment.

FIG. 8 is a block diagram showing the configuration of the two-dimensional amplitude monopulse method.

Each of the four spiral antennas 44 is connected to a front end 45.

The front ends 45 are each connected to a mixer 46, and the mixer 46 is each connected to an IF amplifier & detector 47.
It is connected to the.

IF amplifier & detector 47 are each digitizer 48
It is connected to the.

Digitizer 48 is connected to interface 49.

Interface 49 is connected to digital filter 50.

This is how the device is configured.

Each component of the device has the following functions.

The four spiral antennas receive radio waves in two-dimensional directions.

The front end 45 performs amplification and frequency selection functions.

The mixer 46 performs a frequency conversion function.

The IF amplifier and detector 47 performs amplification and detection after frequency conversion.

The digitizer 48 functions to convert an analog signal into a digital signal.

The interface 49 functions to match the output signal of the digitizer 48 with the input conditions of the digital filter 50.

The digital filter 50 time-averages the beat frequency signal.

In FIG. 8, a spiral antenna 44a.

Angular information in the horizontal plane can be obtained from the output amplitude ratio of the spiral antennas 44b, and angular information in the vertical plane can be obtained from the amplitude ratio of the spiral antennas 44a and 44b. It is clear that the above-mentioned one-dimensional method can be used as is for the process of generating each of these angular information, reducing azimuth measurement errors due to multipath interference and obtaining accurate two-dimensional azimuth information from transmitted signals. Can you get it?

FIG. 2 shows a second embodiment of the present invention. Ru.

In this embodiment, the receiving station l's receiving antennas 12a, 1
A changeover switch 19 is provided between 2b and the direction finder receiver 11. This changeover switch 19 selects the direction receiving antenna 12a.

12b and measure the amplitude of each antenna.

In this way, the direction finding method of the receiving station 1 is made into a pseudo amplitude comparison monopulse method.

In the first embodiment, averaging is performed on S, but in this embodiment, the averaging operation is performed separately on Ea and Eb, and then the calculation on S is performed. .

The other points are almost the same as the configuration of the first embodiment.

As mentioned in the first example, Ea and Eb are Ea=C,
, [expj (2πf, -t)+Ka + expj(
2πfr4δa)]・・・・・・(1) Eb=C*b[eXl)j(2πfd”j)+to b−
expj(2πfr−tδb)] (2) It is expressed as follows. Furthermore, 6 Ea=Cg, l-expj(2πfd-t)[1+Ka
-eXpj(2π(fr-fd)・t+68)]
・・・・・・ (8) Eb= C*b # exp
j (2π L4) [1+Kb-expj(2π (fr
-fd)・t+δ5)] It can be transformed as (9).

Detect this output. When the detection output is Eav, E avoc l Cwa [1”Ka −expj
(2π(fr-fd) ・tδ8)]1...
... (10) E bvcc l C*b [1”K
b −eX11H2π(fr−fd)・tδb)] 1
...... (11).

The error component of equations (10) and (11), that is, the beat frequency signal Ka-expj(2π(fr −fd)
t+68) and Kb-expj(2π(fr −fd
)t+δ5), the value is
It becomes 0. Therefore, equations (10) and (11) are Eavoclc*al −・・−(12) Eb”l
c*bl --------(13).

When calculation is performed on S from equation (3) shown in the first embodiment, the following is obtained, which approximates equation (5) shown in the first embodiment.

That is, it can be seen that the signal S representing the azimuth information is a signal that is not affected by reflected waves, as in the first embodiment.

Therefore, it is possible to reduce azimuth measurement errors due to multipath interference and obtain accurate azimuth information from the transmitted signal.

FIG. 3 shows a third embodiment of the invention.

In this embodiment, a transmission wave for communication is used as it is as a pilot signal.

In this case, transmission waves for communication are frequency modulated or phase modulated.

As shown in FIG. 3, the transmitting station 2 consists of a communication transmitter 22 equipped with a transmitting antenna 24.

The transmitting station 2 includes an oscillator 27, a modulator 26, and an amplifier 28.
It consists of.

On the other hand, the receiving station l uses a direction receiving antenna 12a.

12b, a direction-finding receiver 11, an averaging circuit 18, a directional antenna driver 14, a directional antenna 15, a receiver 16, and a signal output terminal 17.

The directional antenna 15 is driven by the directional antenna driver 14 and directed in the direction of the transmitting antenna 24,
It receives the communication radio waves 4 from the transmitting antenna 24.

In this embodiment, since the configuration of the transmitting station 2 is extremely simple, it is possible to reduce the weight, making it easy to move the transmitting station 2, and when operating on batteries, battery consumption is reduced. Operation time can be increased by reducing the rate.

Next, a fourth example will be described.

This embodiment has almost the same configuration as the first embodiment, except that the receiving station 1 uses a monopulse method using a dual-mode spiral 9 antenna instead of the one-dimensional amplitude comparison monopulse method. be.

Therefore, with reference to FIG. 1, only the differences in this embodiment will be described.

That is, the receiving station 1 is configured to support the monopulse method using the dual mode spiral antenna 12.

A dual-mode spiral antenna 12 is used instead of the direction-finding receiving antennas 12a and 12b. The antenna has two outputs called Σ mode and Δ mode, and is equipped with a terminal corresponding to each mode.

Directional receiver 11 is a two-channel receiver with a channel corresponding to each mote of the antenna.

Next, the operation of this embodiment will be explained.

As in the first embodiment, a case will be described in which chirp modulation is used as the modulation format of the azimuth measurement pilot signal 3.

0 In the xyz axis coordinates, the direction receiving antenna is placed at the origin and the main radiation direction is aligned with the positive direction of the Z axis. At this time, if the angle from the Z axis on the yz plane is 0, and the angle from the X axis on the Xy plane is φ, the direction of arrival of the radio wave is
(θ, φ).

Similarly, the direction in which the direct wave is incident on the direction receiving antenna is (θ6.φ,), and the direction in which the reflected wave is incident is (θ6.φ,).
1. φr).

Let K be the amplitude of the reflected wave with respect to the direct wave incident on the direction receiving antenna, and let δ be the phase, then the ratio of the reflected wave to the incident wave can be expressed as K-exp(j δ).

Here, K generally has a relationship of Kl≦1.

Furthermore, the antenna's Σ mode pattern GΣ(θ, φ)
, Δ mode pattern is expressed as GΔ(o, φ). Also,
The frequency of the direct wave is fd, the frequency of the reflected wave is fr, the time is t, and the propagation time difference is Δt. At this time, the relationship fr; fd10·Δt holds true.

Moreover, the Σ mode terminal output EΣ is EΣ=GΣ(θ6.φd) ・expj(2πfd−t
) 10 G Σ (θ , , φ r )
・K −expj δ ・expj(2πfr−
t) −(15).

Similarly, the Δ mode terminal output EΔ is EΔ=GΔ(θ6.φd)・expj(2πfd−t)
10GΔ(θ1.φr)・K−expjδ・expj(2
πfr4) −(16).

In equations (15) and (16), the first term represents a direct wave, and the second term represents a reflected wave.

Furthermore, equations (15) and (16) are EΣ=GΣ(
θ6. φa) ・expj(2wfd-t)・GΣ
(θ6, φd) expj (2π (fr-L) 4+ δ)
Co... (17) 1 2 EΔ=GΔ (θ.

φd)・expj(2πfd−t)・(fr−f,,)−t+6) ko,
, ---(18).

The direction measurement signal S is GΔ (θd, φd) It is.

If there is no reflected wave, K=O, so Δ=0 for KΣ=, and equation (20) becomes E Σ Substituting equations (17) and (18) into equation (19), we get Become.

If the frequencies of the direct wave and the reflected wave are equal, fd=
fr, equation (20) is 1+K Σ・expj
(2π(fr-fd)t+6)(20)

However, 3 GΣ (θ6, φd) 1+K Σ・expj
δ... (22)

Comparing equation (22) with equation (21), we find that S has an error component,
It can be seen that Σ·expj δ and Δ·expj δ occur. Furthermore, if there is no movement between the transmitting and receiving stations, this error is a fixed error and is not a function of time, so it cannot be reduced even by using an averaging circuit.

4. However, in this embodiment, a chilb modulated wave is used as the frequency modulated wave for the pilot signal 3 for direction measurement. Therefore, when received by the receiving station, the direct wave and the reflected wave have different frequencies, and as shown in equation (20),
Beat frequency signal, KΣ・expj(2π(fr-fd
) to 1δ) and Δ・expN2w (fr−f,,
)t+δ) occurs as an error. This beat frequency signal has a beat frequency fr-fa and a period L/(
fr fd) and is determined as a function of time.

If we take the time average of the error component in equation (20), that is, the beat frequency signal Σ・expN2π(fr-f,,)t+δ8) and Δ・expj(2w (fr-fd)t+δb), the value becomes 0.

The time averaging process is actually performed by converting the received beat frequency signal of the direct wave and reflected wave into a voltage signal and time averaging the voltage signal.

As a result of time averaging processing of the beat frequency signal using equation (20), the signal S representing the azimuth information is expressed by the following equation.

This equation (23) matches equation (21). That is,
It can be seen that the signal S representing the azimuth information is a signal that is not affected by reflected waves.

Therefore, it is possible to reduce azimuth measurement errors due to multipath interference and obtain accurate azimuth information from the transmitted signal.

Note that in this embodiment as well, frequency-modulated or phase-modulated radio waves can be used as communication radio waves in the same manner as in the third embodiment.

FIG. 9 is a block diagram showing the configuration of a monopulse system using a four-arm spiral antenna.

4 arm spiral antenna 58 or hybrid circuit 5
Connected to 1.

The hybrid circuit 51 is a front end 526 5 It is connected to the.

Front end 52 is connected to mixer 53.

Mixer 53 is connected to IP amplifier 54.

IF amplifier 54 is connected to beam forming circuit 55.

Beam forming circuit 55 is connected to logarithmic amplifier 56 .

Logarithmic amplifier 56 is connected to adder 57.

Adder 57 is connected to averaging circuit 18 .

This is how the device is configured.

Each component of the device has the following functions.

The four-arm spiral antenna 58 receives radio waves in two-dimensional directions.

The hybrid circuit 51 separates the Σ mode and the Δ mote from the four-arm spiral antenna output.

7. The front end 52 performs amplification and frequency selection functions.

The mixer 53 performs a frequency conversion function.

The IF amplifier 54 functions to amplify the frequency-converted signal.

The beam forming circuit 55 converts the amplitude ratio and phase difference between the Σ mode and the Δ mode into amplitude information.

The logarithmic amplifier 56 functions to logarithmically compress the signal, and the adder 57 functions to generate a difference between the outputs of the logarithmic amplifier 56. A logarithmic amplifier 56 and an adder 57 perform an operation to calculate the quotient of the signals, and by performing appropriate pairwise operations, a D (Az) signal having angular information in the horizontal plane and an angular information in the vertical plane are obtained. D (Eu)
It generates a signal.

The averaging circuit 18 averages the beat frequency signal over time.

In this way, the orientation measurement error 8 due to multipath interference can be reduced, and accurate two-dimensional orientation information can be obtained from the transmitted signal.

Next, a fifth example will be described.

This embodiment has almost the same configuration as the first embodiment, except that the receiving station 1 uses a one-dimensional amplitude phase comparison monopulse method instead of the one-dimensional amplitude comparison monopulse method.

Therefore, with reference to FIG. 1, only the differences in this embodiment will be described.

The receiving station 1 is configured to support a one-dimensional amplitude phase comparison monopulse system.

The direction finding receiving antennas 12a and 12b are antennas that use a one-dimensional amplitude phase comparison monopulse method as a direction finding method.

The direction-finding receiving antennas 12a and 12b are arranged in a plane in which the direction of the transmitting station 2 changes with respect to the receiving station l.

Further, the direction finding receiver 11 has a configuration compatible with a one-dimensional amplitude phase comparison monopulse method.

FIG. 10 is a block diagram showing the configuration of the amplitude phase monopulse method.

In FIG. 1O, the direction receiving antennas 12a and 12b are arranged with the same main radiation direction.

The direction finding receiving antennas 12a and 12b are connected to a hybrid circuit 60.

The hybrid circuit 60 is connected to two receivers 11 connected by an AGC circuit 62 .

The two receivers 11 are each connected to an averaging circuit 18.

The receiver 11 on the side of the direction receiving antenna 12b is connected to a pulse analyzer 61.

This is how the device is configured.

Each component of the device has the following functions.

The direction finding receiving antennas 12a and 12b receive pilot signals for direction measurement.

The hybrid circuit 60 includes direction receiving antennas 12a, 1
2b and generates a sum signal (Σ moat) and a difference signal (Δ moat).

The 90 receiver 11 receives the Σ mode terminal output Σ and the Δ mode terminal output Δ from the hybrid circuit 6o, and performs operations such as amplification, frequency selection, frequency conversion, and detection.

The averaging circuit 18 time-averages the beat frequency signal received from the receiver 11, and is configured to time-average the beat frequency signal received from the receiver 11.
The averaging circuit 18 on the 2a side outputs AOA information (angle information).

The AGC circuit 62 functions to generate a ratio of Δ mode to Σ mode.

Next, the operation of this embodiment will be explained.

As in the first embodiment, a case will be described in which chirp modulation is used as the modulation format of the azimuth measurement pilot signal 3.

Ea is the received electric field of the direction-finding receiving antenna 12a, Eb is the receiving electric field of the direction-finding receiving antenna 12b, fd is the frequency of the direct wave, fr is the frequency of the reflected wave, and is the receiving electric field of the direction-finding receiving antenna 12a.
The amplitude of the reflected wave is Kb, the phase is 68, the amplitude of the reflected wave is Kb, and the phase is 65.
Then, as in the first embodiment, Ea=01a[expj(2πfd-t)+Ka-ex
pj(2πfr-tδa)]...(1) E b = Ctb[expj(2π fd-t
)+Kb-expj(2π fr4δb)]...
・(2) holds true.

In these two equations, the first term represents a direct wave, and the second term represents a reflected wave, as in the first embodiment.

Note that Cfiat Ctb is a system constant (complex number)
It is determined by the transmission power, the gain of each antenna, the antenna pattern, the distance between transmitting and receiving stations, etc., and is a value that does not change over time. In addition, in general, it can be considered that K, , Kb<1.

The amplitude phase comparison monopulse method used in this example is (1
This method uses a hybrid circuit to generate a sum signal and a difference signal from the outputs expressed by equations () and (2), and further measures the direction from the amplitude ratio and phase difference of these signals.

Furthermore, if Δt is the propagation time difference between the direct wave and the reflected wave, then
The formula % formula % holds true.

Here, assuming that the position between the transmitting and receiving stations and the antenna orientation are fixed, the signal S representing the orientation information is expressed by the following formula.

Eb Ea−EbEa S= ・・・・・・(24)E
a+Eb Eb 1+ Ea When a reflected wave exists, the values of K8 and Kb change,
It can be seen that as the values of Ea and Eb change, the value of S changes accordingly, causing an error.

By the way, if we substitute equations (1) and (2) into equation (24) and transform the equation, we get the following.

When a reflected wave exists, the values of K and Kb change,
It can be seen that as the values of Ea and Eb change, the value of S changes accordingly, causing an error.

In equation (25), assuming that there is no reflected wave, K8
Since = ni = 0, the formula C, b 1 + C, a holds true.

This equation (26) indicates an ideal state without reflected waves.

If the frequencies of the direct wave and the reflected wave are equal, fd=f
Since r, C, a[1+Ka-expj(2π(fr-fd)t+
68) ] (25) 3 4 C, b[1+Kb−eXpj8 b ]Cl18[1+
Ka-expJδ8ko (27)

Comparing equation (27) with equation (26), we find that S has an error component,
It can be seen that Ka-expjδ8 and Kb-expj8b are generated. Furthermore, if there is no movement between the transmitting and receiving stations, this error is not a function of time but is a fixed error, so it can only be reduced by using an averaging circuit.

However, in this embodiment, a chirp modulated wave is used as the frequency modulated wave as the pilot signal 3 for direction measurement. Therefore, when received by the receiving station, the direct wave and the reflected wave have different frequencies, and as shown in equation (25), the beat frequency signal, Ka−eXpj(2π(fr−f
,,)t+61) and Kb-expj(2π(fr-
L)t+δb) occurs as an error. This beat frequency signal has a beat frequency fr - fd and a period 1/(fr fd) and is determined as a function of time.

The error component of equation (25), that is, the beat frequency signal,
When Ka-expj (2π(fr-fd)t+δ8) and Kb-expj(2π(fr-fd)t+δb) are averaged over time, the value becomes 0.

The time averaging process is actually performed by converting the received beat frequency signal of the direct wave and reflected wave into a voltage signal and time averaging the voltage signal.

In this way, as a result of time averaging processing of the beat frequency signal using equation (25), the signal S representing the azimuth information is expressed by the following equation.

lla This equation (28) matches equation (26). That is,
It can be seen that the signal S representing the azimuth information is a signal that is not affected by reflected waves.

Therefore, it is possible to reduce azimuth measurement errors due to multipath interference and obtain accurate azimuth information from the transmitted signal.

Note that in this embodiment as well, similarly to the third embodiment, frequency-modulated or phase-modulated radio waves can be used as communication radio waves.

Next, a case will be described in which a two-dimensional amplitude phase comparison monopulse method is used as the direction search method in this embodiment.

FIG. 11 is a block diagram showing the configuration of a two-dimensional amplitude phase monopulse system.

Each of the four directional antennas 63 is connected to a hybrid circuit system 64 consisting of three monopulse comparators.

The hybrid circuit system 64 is connected to three front ends.

The three front ends 65 are connected to three mixers 66 which are connected to a local oscillator 78.

7 The three mixers 66 have three logarithmic amplifiers 67 and three
limiting amplifiers 68.

Three logarithmic amplifiers 68 are connected to two adders 69.

Three limiting amplifiers 68 are connected to two phase comparators 70.

Averaging circuit 18 is connected to adder 69 and phase comparator 70.

This is how the device is configured.

Each component of the device has the following functions.

The four directional antennas 63 receive radio waves in two-dimensional directions.

The hybrid circuit system 64 decomposes and combines the outputs of the four directional antennas, and produces one sum output (Σ) and two difference outputs (Δ
y, ΔZ).

The front end 65 performs amplification and frequency selection functions.

The local oscillator 78 and mixer 66 have a frequency of 8 It performs a conversion action.

The logarithmic amplifier 67 performs logarithmic compression of the signal.
Together with the adder 69, it performs an arithmetic operation to obtain a quotient. This is another means of obtaining the ratio of two signals.

The limiting amplifier 68 functions to maintain the signal amplitude at a constant value.

The adder 69 outputs two-dimensional azimuth information, and an output (Δy/Σ) indicating the angle in the x-y plane, x
A (Δ2/Σ) output indicating the angle in the -z plane is output.

The two phase comparators 70 each have Δy for the Σ signal.
, and outputs left and right outputs and upper and lower outputs based on the phase difference of the Δ2 signals.

The averaging circuit 18 averages the beat frequency signal over time.

In this way, it is possible to reduce azimuth measurement errors due to multipath interference and obtain accurate two-dimensional azimuth information from the transmitted signal.

Next, a sixth embodiment will be described.

9 This embodiment has almost the same configuration as the first embodiment, except that the receiving station l uses a one-dimensional phase comparison monopulse method instead of a one-dimensional amplitude comparison monopulse method.

Therefore, with reference to FIG. 1, only the differences in this embodiment will be described.

The receiving station 1 is configured to support the phase comparison monopulse method.

The direction finding receiving antennas 12a and 12b are antennas that use a phase comparison monopulse method as a direction finding method.

The direction-finding receiving antennas 12a and 12b are arranged in a plane in which the direction of the transmitting station 2 changes with respect to the receiving station l.

Further, the direction finding receiver 11 has a configuration compatible with a phase comparison monopulse method.

Next, the operation of this embodiment will be explained.

As in the first embodiment, a case will be described in which chilb modulation is used as the modulation format of the pilot signal 3 for azimuth measurement.

The received electric field at the direction-finding receiving antenna 12a is Ea, the receiving electric field at the direction-finding receiving antenna 12b is Eb, the frequency of the direct wave is fd, the frequency of the reflected wave is f, the direction-finding receiving antenna 12a.
What is the amplitude of the reflected wave for 88, the phase is 88, the amplitude of the reflected wave for the direction receiving antenna 12b is Kb, and the phase is δb
Then, as in the first embodiment, E a = C, a [expj(2πfd4
)+Ka*expj(2π fr4δa)]
・(1) E b = C, b [expj (2ff fd"j) +
nib"eXl)j(2πfr-tδb)]...
(2) holds true.

In these two equations, the first term represents a direct wave, and the second term represents a reflected wave, as in the first embodiment.

Note that Cff1a and Cl1b indicate system constants (complex numbers), which are determined by the transmission power, the gain of each antenna, the antenna pattern, the distance between transmitting and receiving stations, and are values that do not change over time. Further, in general, it may be considered that Ka and Kb<1.

The phase comparison monopulse method used in this embodiment is a method for measuring the direction from the phase difference between the outputs expressed by equations (1) and (2).

Furthermore, if the propagation time difference between the direct wave and the reflected wave is Δt, then
The formula % formula % holds true.

Here, assuming that the position between the transmitting and receiving stations and the antenna orientation are fixed, the signal S representing the orientation information is expressed by the following equation.

Ea By the way, when formulas (1) and (2) are substituted into formula (29) and the formula is transformed, S = ... (30).

(30), assuming that there is no reflected wave 1 9 And, since Ka=　Kb=　O, CIIR The formula holds true.

This equation (31) indicates an ideal state without reflected waves.

When there is a reflected wave, the value of 8 and Kb changes,
As the values of Ea and Eb change, the value of S changes accordingly, indicating whether an error occurs.

If the frequencies of the direct wave and the reflected wave are equal, L+=
Since it is fr, ...... (32).

Comparing equation (32) with equation (31), we find that S has an error component,
It can be seen that Ka''eXpJ 8 a and Kb-expj δ5 occur.Moreover, this error is not a function of time but a fixed error if there is no movement between the transmitting and receiving stations, so the average Even if a circuit is used,
It is something that can only be alleviated.

However, in this embodiment, a chilb modulated wave is used as a frequency modulated wave as the pilot signal 3 for direction measurement. Therefore, when received by the receiving station 1, the direct wave and the reflected wave have different frequencies, and as shown in equation (30), the beat frequency signal, Ka-expj(2π(fr-f
d) t+δ8) and b”eXpj(2π(fr-f
d) t+δb) occurs as an error. This beat frequency signal has a beat frequency fr −L and a period of 1
/ (fr fd) and is determined as a function of time.

The error component of equation (30), that is, the beat frequency signal,
K a-e X pJ (2π(f r -f d)
When t+δ8) and Kb-expN2π(fr-fd) are averaged over ten δb), the value becomes zero.

The time averaging process is actually performed by converting the received beat frequency signal of the direct wave and reflected wave into a voltage signal and time averaging the voltage signal.

4 Thus, as a result of time-averaging the beat frequency signal using equation (30), the signal S representing the azimuth information is expressed by the following equation.

Ila This equation (33) matches the equation (31). That is,
It can be seen that the signal S representing the azimuth information is a signal that is not affected by reflected waves.

Therefore, it is possible to reduce azimuth measurement errors due to multipath interference and obtain accurate azimuth information from the transmitted signal.

Note that in this embodiment as well, similarly to the third embodiment, frequency-modulated or phase-modulated radio waves can be used as communication radio waves.

Next, a case will be described in which a two-dimensional phase comparison monopulse method is used as the direction search method in this embodiment.

FIG. 12 is a block diagram showing the configuration of the two-dimensional phase comparison monopulse method.

5. Each of the four direction finding antennas 71 is connected to the four front ends 72.

The four front ends 72 are connected to four mixers 73 which are connected to a local oscillator 79.

The four mixers 73 are connected to four limiting amplifiers 74.

Two of the four limiting amplifiers 74 are as follows:
Connected to a 90° phase shifter.

Furthermore, the four limiting amplifiers 74 are connected to the four phase detectors 75.
It is connected to the.

The four phase detectors 75 are connected to two phase calculators 77.

The phase calculator 77 is connected to the averaging circuit 18.

This is how the device is configured.

The configuration in Figure 12 uses two sets of configurations shown in Figure 1,
The antennas are arranged in pairs orthogonal to each other. Therefore, angle information in the xy plane 6 and the xz plane can be obtained by the operation exactly the same as in the -dimensional phase comparison monopulse method.

In this way, azimuth measurement errors due to multipath interference can be reduced, and accurate two-dimensional azimuth information can be obtained from the transmitted signal.

Note that the frequency-modulated or phase-modulated radio waves used in the above-mentioned embodiments include all frequency-modulated waves or phase-modulated waves. This includes a chirp modulated signal. Alternatively, the phase of the pilot signal may be directly temporally changed by phase modulation.

Furthermore, a plurality of receiving stations may be provided for one transmission source, or a two-way system having both a transmitting station and a receiving station between two points may be used.

Further, it is preferable that the constants of the filter can be changed manually or automatically.

[Effects of the Invention] According to the direction measuring method, direction measuring system, transmitting device, and receiving device according to the present invention, the transmission source transmits angle-modulated radio waves, and the receiving side receives direct waves of the transmitted radio waves. It receives the direct wave and reflected wave, converts the beat frequency signal from the direct wave and reflected wave into an electrical signal, and averages the electrical signal over time, reducing azimuth measurement errors due to multipath interference and making it easier to use as a pilot for azimuth measurement. Accurate orientation information can be obtained from the signal.

Furthermore, in the present invention, when communication of one system is performed using one type of radio wave, equipment and communication costs are low.

[Brief explanation of drawings]

1 to 4 show various embodiments of the present invention,
FIG. 1 is an explanatory diagram of the orientation measuring device of the first embodiment, FIG. 2 is an explanatory diagram of the orientation measuring device of the second embodiment, FIG. 3 is an explanatory diagram of the orientation measuring device of the third embodiment, and FIG. The figure is an explanatory diagram of multipath interference of chirp modulated waves, Fig. 5 is an explanatory diagram of a conventional direction measuring device, Fig. 6 is an explanatory diagram showing the operating principle of the amplitude monopulse method, and Fig. 7 is an illustration of the amplitude pattern. Graph, 8 Figure 8 is a block diagram showing the configuration of a two-dimensional amplitude monopulse system, and Figure 9 is a two-dimensional amplitude monopulse system using a four-arm spiral antenna.
Figure 10 is a block diagram showing the configuration of the dimensional monopulse system, Figure 10 is a block diagram showing the configuration of the amplitude phase monopulse system, Figure 11 is a block diagram showing the configuration of the two-dimensional amplitude phase monopulse system, and Figure 12 is a two-dimensional phase comparison. FIG. 2 is a block diagram showing the configuration of a monopulse method. 1... Receiving station 2... Transmitting station 3... Pilot signal for direction measurement 11... Direction finding receiver 12... Direction finding receiving antenna 1
4... Directional antenna drive section 15... Directional antenna 16... Receiver 17...
- Signal output terminal 18...Averaging circuit 21...Pilot signal transmitter for direction measurement 22...Communication transmitter 23...Pilot signal transmission antenna 24...Transmission antenna 25...Signal input Terminal 26...Modulator
27... Oscillator 28... Amplifier 29... Oscillator 30... Amplifier 31... Reflected wave

Claims (1)

[Claims] 1. An azimuth measurement method in which radio waves sent from a transmission source are received by an antenna on the receiving side to determine the azimuth of the transmission source, wherein the transmission source transmits angle-modulated radio waves. , the receiving side receives the direct wave and the reflected wave of the transmitted radio wave, converts the beat frequency signal of the direct wave and the reflected wave into an electrical signal, and averages the electrical signal over time. A direction measurement method characterized by reducing direction measurement errors caused by multipath interference. 2. In an azimuth measurement method in which radio waves sent from a transmission source are received by at least two antennas on the receiving side and the direction of the transmission source is determined using an amplitude comparison monopulse method, the transmission source is angularly modulated. transmit radio waves,
The receiving side receives the direct wave and the reflected wave of the transmitted radio wave, converts the beat frequency signal of the direct wave and the reflected wave into an electrical signal, and averages the electrical signal over time to generate a multi-channel signal. A direction measurement method characterized by reducing direction measurement errors caused by path interference. 3. In an azimuth measurement method in which radio waves sent from a transmission source are received by a dual-mode spiral antenna on the receiving side and the direction of the transmission source is determined using a monopulse method, the transmission source uses angle-modulated radio waves. The receiving side receives the direct wave and the reflected wave of the transmitted radio wave, converts the beat frequency signal caused by the direct wave and the reflected wave into an electrical signal, and averages the electrical signal over time. An azimuth measurement method characterized by reducing azimuth measurement errors due to multipath interference. 4. An azimuth measurement method in which radio waves sent from a transmission source are received by at least two antennas on the receiving side, and the azimuth of the transmission source is determined by using an amplitude phase comparison monopulse method, wherein the azimuth of the transmission source is determined by the angle A modulated radio wave is transmitted, and the receiving side receives the direct wave and reflected wave of the transmitted radio wave, converts the beat frequency signal caused by the direct wave and the reflected wave into an electrical signal, and converts the electrical signal into an electrical signal. A direction measurement method characterized by reducing direction measurement errors caused by multipath interference by time averaging. 5. In an azimuth measurement method in which radio waves sent from a transmission source are received by at least two antennas on the receiving side and the direction of the transmission source is determined using a phase comparison monopulse method, the transmission source is angularly modulated. transmit radio waves,
The receiving side receives the direct wave and the reflected wave of the transmitted radio wave, converts the beat frequency signal of the direct wave and the reflected wave into an electrical signal, and averages the electrical signal over time to generate a multi-channel signal. A direction measurement method characterized by reducing direction measurement errors caused by path interference. 6. The direction measuring method according to claim 1, 2, 3, 4, or 5, wherein the angle-modulated radio wave is a communication radio wave. 7. Claims 1, 2, and 3, wherein the time average value of the electrical signal into which the beat frequency signal is converted is 0.
, 4, 5 or 6. 8. Claim 1, characterized in that the antennas are arranged orthogonally, and the orthogonal two-dimensional orientation of the transmission source is known.
The direction measuring method according to 2, 3, 4, 5, 6 or 7. 9. An azimuth measurement system in which radio waves sent from a transmission source are received by an antenna on the reception side to determine the direction of the transmission source, comprising: a transmission source that transmits angle-modulated radio waves; an antenna for receiving a direct wave and a reflected wave of the transmitted radio wave; a signal converting means on the receiving side for converting a beat frequency signal caused by the direct wave and the reflected wave into an electrical signal; An azimuth measurement system comprising: an averaging circuit that performs time averaging, and reducing azimuth measurement errors due to multipath interference based on the output from the averaging circuit. 10. In an azimuth measurement system in which radio waves sent from a transmission source are received by at least two antennas on the receiving side and the direction of the transmission source is determined using an amplitude comparison monopulse method, angle-modulated radio waves are used. a transmission source for transmitting; an antenna on the receiving side for receiving the direct wave and the reflected wave of the transmitted radio wave; and an antenna on the receiving side for converting the beat frequency signal of the direct wave and the reflected wave into an electrical signal. and an averaging circuit that time-averages the electrical signal, and is characterized in that it reduces azimuth measurement errors due to multipath interference based on the output from the averaging circuit. Direction measurement system. 11. Radio waves sent from a transmission source are received by a dual-mode spiral antenna on the receiving side, and angle-modulated radio waves are transmitted using a monopulse method in a direction measurement system that determines the direction of the transmission source. a transmission source; a dual-mode spiral antenna on the receiving side that receives the direct wave and the reflected wave of the transmitted radio wave; and a dual-mode spiral antenna on the receiving side that electrically converts the beat frequency signal of the direct wave and the reflected wave. It is characterized by comprising: a signal conversion means for converting into a signal; and an averaging circuit for time-averaging the electrical signal, and based on the output from the averaging circuit, azimuth measurement error due to multipath interference is reduced. Direction measurement system. 12. An azimuth measurement system in which radio waves sent from a transmission source are received by at least two antennas on the receiving side, and the direction of the transmission source is determined using an amplitude phase comparison monopulse method. a transmission source that transmits a radio wave; an antenna that is on the receiving side and receives the direct wave and the reflected wave of the transmitted radio wave; and an antenna that is on the receiving side that electrically converts the beat frequency signal of the direct wave and the reflected wave. It is characterized by comprising: a signal conversion means for converting into a signal; and an averaging circuit for time-averaging the electrical signal, and based on the output from the averaging circuit, azimuth measurement error due to multipath interference is reduced. Direction measurement system. 13. In an azimuth measurement system in which radio waves sent from a transmission source are received by at least two antennas on the receiving side and the direction of the transmission source is determined using a phase comparison monopulse method, angle-modulated radio waves are used. a transmission source for transmitting; an antenna on the receiving side for receiving the direct wave and the reflected wave of the transmitted radio wave; and an antenna on the receiving side for converting the beat frequency signal of the direct wave and the reflected wave into an electrical signal. and an averaging circuit that time-averages the electrical signal, and is characterized in that it reduces azimuth measurement errors due to multipath interference based on the output from the averaging circuit. Direction measurement system. 14. Claim 9, 10, 11, 12 or 1, wherein the angle-modulated radio wave is a communication radio wave.
The direction measurement system described in 3. 15. Claims 9 and 10, characterized in that the time average value of the electric signal into which the beat frequency signal is converted is 0.
, 11, 12, 13 or 14. 16. The antennas are disposed orthogonally, and the transmitting source
Claim 9 characterized in that orthogonal two-dimensional directions are known.
, 10, 11, 12, 13, 14 or 15. 17. In a transmitting device used in an azimuth measurement system that receives radio waves sent from a transmission source with an antenna on the receiving side and uses a monopulse method to determine the direction of the transmission source, transmits angle-modulated radio waves. A transmitting device characterized by: 18. In a receiving device that receives radio waves sent from a transmission source and knows the direction of the transmission source, an antenna that receives direct waves and reflected waves of the transmitted radio waves; A signal conversion means for converting a beat frequency signal into an electric signal; and an averaging circuit for time-averaging the electric signal, and based on the output from the averaging circuit, the direction measurement error due to multipath interference is eliminated. A receiving device characterized in that: 19. The receiving device according to claim 18, wherein the amplitude comparison monopulse method is used as the direction finding method. 20. The receiving device according to claim 19, wherein the antenna is a dual mode spiral antenna and uses a monopulse method as a direction finding method. 21. The receiving device according to claim 20, characterized in that an amplitude phase comparison monopulse method is used as the direction finding method. 22. The receiving device according to claim 21, wherein the phase comparison monopulse method is used as the direction finding method.