JPS634152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an azimuth measurement device that measures the direction of arrival of radio waves, and more particularly to a direction measurement device that instantly and accurately detects the direction of arrival of radio waves over a wide frequency band.

FIG. 1 shows an example of this type of direction measuring device that has been used conventionally.

The detailed operation will be explained below.

As shown in FIG. 1, radio waves arriving from the direction H○ have the same characteristics and are received by antennas 101 and 102 installed at a distance D between them.
Compared to the signal received by the antenna 101, the signal received at 02 has propagated a longer distance by DsinH○, so a phase delay θ shown in the following equation occurs.

θ=2πDsinH/○/λ...(1) Here, λ indicates one wavelength in the space of the arriving radio wave, the amplitudes of the signals received by the antennas 101 and 102 are both equal at E, and there is a phase difference between them. Therefore, there is θ. These two signals are sent to the phase detector 103 through transmission paths having exactly the same length, and the phase difference θ is detected. As a result, the phase detector 103
The output of voltage is output.

The above two signals from the phase detector 103 are sent to a phase angle calculation circuit 104. Since there is a relationship shown in the following equations (3) and (4) between the two signals shown in equation (2), the phase difference θ between the two signals received by the antennas 101 and 102 is independent of the signal amplitude E. is required.

θ=tan ⁻¹ A (4) Here, A indicates the ratio of the two output voltages of the phase detector 103. There is a relationship between θ and the radio wave arrival azimuth H○ as shown in equation (1), which can be expressed in the form of equation (5).

H○=sin ^-1 (θ/2π) (λ/D) ...(5) In the azimuth calculation circuit 105, the θ sent from the previous stage
From the value, the radio wave arrival azimuth H○ is calculated based on equation (5) and outputted to the output terminal 106.

However, in this conventional device, the wavelength λ of the arriving radio wave must be known in advance in order to calculate the radio wave arrival angle H○ from the actually measured value of θ, as is clear from equation (5).

Normally, there is a relationship fλ=C between the wavelength and the frequency f (C: speed of light), so if the frequency f is used instead of the wavelength λ, the frequency of the incoming radio wave is After measuring the frequency of the incoming radio wave by other means,
The direction of arrival must be calculated. Therefore,
The drawback was that it was not possible to measure the direction of arrival of radio waves whose frequency changed moment by moment.

Furthermore, if the frequency of the actually received radio waves is different from the frequency predicted in advance, there is a drawback that an error occurs in the radio wave arrival azimuth H○ calculated based on equation (5).

The present invention divides the output of each antenna into two, and
The present invention provides an azimuth measuring device that solves the above-mentioned drawbacks by delaying one of the distributed outputs for a predetermined time and using a combination of four signals: the delayed signal and the undelayed signal.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows the configuration of an embodiment based on the present invention. 201 and 202 are antennas having the same characteristics, and the distance between them is D.

The signals received by antennas 201 and 202 are
The signals are sent to two independent power dividers 203 and 204 through transmission lines of equal length. One of the signals divided into two by the power splitter 203 is sent to the phase detector 208 through the delay line 205, and the other is sent to the phase detector 207 as is. Similarly, one of the signals divided into two by the power splitter 204 is passed through the delay line 206 to the phase detector 207.
and the other is directly sent to phase detector 208 . Phase detectors 207 and 208 detect the phase difference between the two input signals, and send it to the next phase angle calculation circuits 209 and 210, and further to the azimuth calculation circuit 2.
11, the radio wave arrival azimuth angle is determined from the two types of phase difference angle signals obtained by the phase angle calculation circuits 209 and 210, and is sent to the output terminal 212.

Next, the operation will be explained in detail based on FIG.

Radio waves arriving from the H○′ direction are antennas 201 and 2
Received at 02. Between the two signals received by the antennas 201 and 202, as in FIG. 1, a phase difference θ shown in equation (1) is generated. As a result, the antenna 201,2
The amplitudes of the signals received at 02 are all equal to E, and there is a phase difference θ between them. A signal received by the antenna 201 is divided into two by a power divider 203, and one is sent directly to a phase detector 207 (this signal is called signal A). The other is the delay time Td
is sent to the phase detector 208 through the delay line 205 (this signal is called signal C).

Signal C has a phase delay of θd compared to signal A. The following relationship exists between θd, the delay time Td of the delay line, and the frequency f of the arriving radio wave.

θd=2πfTd...(6) Similarly, the signal received by the antenna 202 has a power of 2
The divider 204 divides the signal into two parts, one of which is connected to the delay line 205.
The signal is sent to the phase detector 207 through a delay line 206 with a delay time Td having exactly the same characteristics (this signal is referred to as signal B). The other signal is sent directly to phase detector 208 (this signal is referred to as signal D).
As a result, signal B has a phase delay of θ+θd with respect to signal A. Similarly, signal D has a phase delay of θ with respect to signal A. Note that θ and θd are as described in (1) above.
and (6).

The phase detectors 207, 208 and the phase angle calculation circuits 209, 210 are similar to the phase detector 103 in FIG.
It has the same characteristics as the phase angle calculation circuit 104 and detects and calculates the phase difference between two input signals of each phase detector and sends it to the next azimuth calculation circuit 211.

The phase detector 207 receives the signals A and B and sends a signal expressed by the following equation to the phase angle calculation circuit 209.

Esin (θ+θd) Ecos (θ+θd) ...(7) Furthermore, the phase angle calculation circuit 209 performs the same processing as the calculations shown in equations (3) and (4), and the signals A and B
The phase difference θ+θd is sent to the next azimuth calculation circuit 211. Let this phase difference θ+θd be θa.

On the other hand, the phase detector 208 and the phase angle calculation circuit 2
Phase difference θ−θd between signals C and D sent to 10
is detected, calculated, and sent to the azimuth calculation circuit 211. Let this phase difference θ−θd be θb. θa and θb
is the value actually measured by the arrival of radio waves.

From equations (1) and (6) and the relationship fλ=C, θa=θ+θd=2πf・D/CsinH○′+2πfTd……(8) θb=θ−θd=2πf・D/CsinH○′−2πfTd……(9) It is expressed as

From equations (8) and (9), H○′=sin ^-1 (θa+θb/θa−θb)C/D・Td……(
10) is required.

The azimuth calculation circuit 211 calculates the radio wave arrival direction H○ based on equation (10) from θa and θb sent from the previous stage.
is calculated. In equation (10), D and Td are preset values, and C is the speed of light in space, both of which are known values. H○ can be determined without being affected by the frequency f of the incoming radio waves.

The frequency and azimuth range that can be addressed by the present invention is
Measurement is possible within a range that satisfies −π<θa<π −π<θb<π (11) in equations (8) and (9).

As is clear from the above explanation, the direction finding device according to the present invention can instantaneously measure the direction of arrival of radio waves regardless of the frequency within the frequency range targeted by the device. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional direction measuring device, and FIG. 2 is a block diagram of a direction measuring device according to the present invention. 101, 102, 201, 202... antenna,
103, 207, 208...phase detector, 104
... Arithmetic circuit, 105, 211... Azimuth calculation circuit, 203, 204... Two power dividers, 205,
206...Delay line, 209, 210...Phase angle calculation circuit.

Claims (1)

[Claims] 1. Two antennas installed at predetermined intervals, first and second power dividers that are installed corresponding to these antennas and divide the output of each antenna into two, and the first and second power dividers. first and second delay means provided for one output of the output and for delaying this output by a predetermined time; and the other output of the first power divider and the output of the second delay means. and a second phase detector that detects a phase difference between the other output of the second power divider and the output of the first delay means;
An azimuth measuring device comprising: an azimuth calculator that calculates a radio wave arrival angle from the outputs of the first phase detector and the second phase detector.