JPH0315991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a direction finder using a circular array antenna, and more particularly to a direction finder with improved direction display performance.

[Technical background of the invention]

A direction finder using a circular array antenna is shown in FIG. In FIG. 1, the outputs of a plurality of antennas 1 to 8 (the number of antennas is arbitrary, but eight antennas are shown as an example) arranged at equal intervals on the circumference are guided by a feeder. and is supplied to the scanner 9. The scanner 9 is
Always select two antennas in a predetermined relative positional relationship, for example two antennas adjacent to each other,
Scanning is performed by sequentially switching all antennas at a fixed time. In this way, two high frequency outputs are obtained from the scanner 9: the B channel output 10 selected with respect to the scanning direction and the A channel output 11 delayed with respect to the scanning direction. The output of the scanner 9 is supplied to first and second receivers 13 and 14. The reception frequencies of the first and second receivers 13 and 14 are controlled in conjunction with each other, and only signals of desired frequency components are extracted from the output of the scanner 9. The first and second limiters 15 and 16 are connected to the first and second receivers 13 and 1.
The intermediate frequency signal from 4 is introduced, the amplitude modulation component is removed, and the signal is supplied to the phase detector 17. The phase detector 17 detects a phase difference between the B channel output and the A channel output of the scanner 9 as a reference. Figure 2 shows
FIG. 3 is a diagram showing the relationship between circular array antennas and radio wave arrival directions. Assuming that the radio wave arrives from the θ direction, and assuming that the average value of the azimuth angles at the positions where the two antennas selected by the scanner 9 are installed is φ, the output V _D of the phase detector 17 is as follows. It becomes like this.

V _D = -C・2πD/λ・sin(−θ) ...(1) where λ: Radio wave wavelength D: Antenna spacing C: Proportionality constant The output of this phase detector 17 is determined by the first and second multiplication. It is supplied to containers 21 and 22. Signal generator 18
is supplied with the azimuth signal 12 obtained from the scanner 9, generates a sine signal 19 and a cosine signal 20 having phases different from each other by 90 degrees, and supplies them to first and second multipliers 21 and 22, respectively. First multiplier 21
supplies the result of multiplication of the phase detection output and the sine signal 19 to the first low-pass filter 23 . Further, the second multiplier 22 supplies the result of multiplying the phase detection output and the cosine signal 20 to the second low-pass filter 24 . The first and second low-pass filters 23 and 24 remove the rotational frequency component of the scanner from the multiplication output and output the Y-axis signal Vy and the X-axis signal Vx, respectively. Assuming that the sine signal Vs is Vs=-sin()...(2) and the cosine signal Vc is Vc=cos()...(3), the low-pass filter outputs VxVy are as follows.

This low-pass filter output is transmitted to the third and fourth multipliers 2
5 and 26, and is multiplied by the output of the display low frequency oscillator 27. third and fourth multipliers 25,
The output of 26 is supplied to the display 28, and the output of the display 2
Drive 8. The output waveform of the display low frequency oscillator 27 can be a triangular wave, a sawtooth wave, a sine wave, etc. with each DC voltage superimposed, and this display low frequency oscillator output causes the display 28 to have a starting point of 0 volts. As a result, the bright spot can be changed between a constant value on the + side or one side. Therefore, the display 28 displays the arrival direction of the radio waves.
This can be done by using a direction indicating line extending straight from the center.

[Problems with background technology]

In the direction finder shown in FIG.
The length of the upper direction display line is the Y-axis signal shown in equation (4).
It is proportional to the root mean square value of Vy and the X-axis signal Vx. Therefore, the length of the direction indicator line is the antenna spacing D
is uniquely determined from the wavelength λ of the radio wave. When detecting the direction of incoming radio waves, information regarding not only the direction of arrival but also the signal strength of the desired signal may be required. However, only direction information was obtained from the direction indicator line in the direction finder, and no information regarding signal strength was obtained.

[Object of the Invention] The present invention has been made in consideration of the above-mentioned circumstances, and it is possible to obtain not only information on the arrival direction of radio waves but also signal strength information by adding information regarding the input signal strength to the direction display line. The purpose is to provide a direction finder that can.

[Summary of the invention]

The present invention multiplies the filter output from which the rotational frequency component of the scanner has been removed by a low frequency signal for display, and also provides a means for changing the amplitude of the input signal of the display in accordance with the received signal strength. The length of the display line is changed in accordance with the received signal strength.

[Embodiments of the invention]

Hereinafter, a third embodiment of the direction finder according to the present invention will be described.
This will be explained with reference to the figures and FIG. Figure 3 shows
FIG. 1 is a circuit configuration diagram illustrating an embodiment of a direction finder according to the present invention. In FIG. 3, the same components as in FIG. 1 are given the same numbers as in FIG. 1, and the explanation thereof will be omitted, and the differences will be mainly explained.

That is, in FIG. 3, the first receiver 13
is equipped with an automatic gain control circuit (AGC), which includes a display low frequency oscillator 27 and third and fourth multipliers 2.
A fifth multiplier 29 is further provided between the multipliers 5 and 26. The AGC control signal 30 is a signal corresponding to the received signal strength, and this AGC control signal 3
0 is supplied to the fifth multiplier 29. The fifth multiplier 29 outputs the low frequency output for display and the AGC control signal 3.
0 and sends the multiplication output to the third and fourth multipliers 2
5,26. As a result, it is possible to obtain a low frequency signal for display (1 KHz is required) whose amplitude corresponds to the received signal strength, and furthermore, the low pass filters 23 and 24 from which the rotational frequency component (about 100 Hz) of the scanner 9 has been removed can be obtained. By multiplying the output of , by this low frequency signal, the third,
The amplitude of the output signals of the fourth multipliers 25 and 26 can be made to correspond reliably to the received signal strength.

Therefore, the direction indicated by the direction display line on the display 28 is stabilized, and the direction display line is lengthened when the received signal strength is high, and shortened when the received signal strength is low. The length of the direction display line can be changed in accordance with the received signal strength.

In this case, for a signal with an extremely low received signal strength, the orientation display line becomes shorter and the orientation reading accuracy decreases. However, when the received signal strength is extremely low, the signal-to-noise ratio of the output of the phase detector 17 is low, so the direction indicated by the direction display line fluctuates due to noise components. That is, the indicated direction on the screen is not displayed as a straight line, but varies in a fan-like manner.
This fan-shaped variation in the indicated direction becomes larger as the direction display line becomes longer, and the screen becomes difficult to see due to flickering. Therefore, if the received signal strength is extremely low, even if the direction display line is long, the indicated direction will fluctuate, making it impossible to improve the direction reading accuracy. In other words, in this case, it is only necessary to know that the indicated direction is changing, and a short direction display line is sufficient.Moreover, since the change in the indicated direction is smaller, the screen becomes easier to see.

FIG. 4 is a circuit diagram illustrating another embodiment of the direction finder according to the present invention.

In the case of FIG. 4, compared to the case of FIG. 3, instead of providing the fifth multiplier 29 in FIG.
The difference is that a sixth multiplier 31 is provided between it and 22.

In other words, in this case, the phase detection output and the AGC
The control signal 30 is multiplied by a sixth multiplier 31, and the multiplication result is supplied to the first and second multipliers 21 and 22.

That is, by controlling the amplitude of the phase detection output in accordance with the received signal strength, the length of the direction display line on the display 28 is changed in accordance with the received signal strength.

In this case, the frequency component corresponding to the AGC control signal 30 is transmitted to the first and second low-pass filters 23 and 24.
There is a possibility that the effect of the AGC control signal 30 will not appear on the display 28 as it is because it is blocked by the AGC control signal 30. However, the present invention does not strictly measure the signal strength based on the length of the orientation display line, but rather makes it possible to determine the strength of the signal based on the length of the orientation display line. Therefore,
Even with the configuration shown in FIG. 4, it is possible to obtain information regarding signal strength, and almost the same effect as in the configuration shown in FIG. 3 can be obtained.

Various embodiments of the present invention are possible in addition to the embodiments shown in FIGS. 3 and 4.

That is, instead of providing the sixth multiplier 31 on the output side of the phase detector 17 as shown in FIG. An eighth multiplier is provided, and the seventh and eighth multipliers multiply the AGC control signal 30 by the output of the signal generator 18, and the multiplier output is transmitted to the first and second multipliers 21, respectively. , 22.

Further, a ninth multiplier is provided between the first multiplier 21 and the first low-pass filter 23, and the result of multiplication of the AGC control signal 30 and the output of the first multiplier 21 is transmitted to the first low-pass filter 23. A tenth multiplier is provided between the second multiplier 22 and the second low-pass filter 24, and a multiplication result of the AGC control signal 30 and the output of the second multiplier 22 is supplied to the low-pass filter 23. The second low-pass filter 2
4 may be supplied.

Further, an eleventh multiplier is provided between the first low-pass filter 23 and the third multiplier 25, and the multiplication result of the AGC control signal 30 and the output of the first low-pass filter 23 is multiplied by the third multiplier. A twelfth multiplier is provided between the second low-pass filter 24 and the fourth multiplier 26 to multiply the AGC control signal 30 by the output of the second low-pass filter 24. The result is passed to the fourth multiplier 6
It may also be supplied to

Further, a 13th multiplier is provided between the third multiplier 25 and the display 28, and the AGC control signal 30 and the third
A fourteenth multiplier is provided between the fourth multiplier 26 and the display 28, and a fourteenth multiplier is provided between the fourth multiplier 26 and the display 28.
The result of multiplication by the output of the multiplier 26 may be supplied to the display 28.

Furthermore, in the embodiments shown in FIGS. 3 and 4, the AGC circuit is added to the first receiver 13,
The second receiver 1 receives the control signal 30 of this AGC circuit.
4 are linked and controlled, but the second receiver 14
An AGC circuit may be added to the first receiver 13 and the first receiver 14 to control the first receiver in conjunction with each other, or an AGC circuit may be added to each of the first and second receivers 13 and 14,
Each receiver may be controlled independently. Furthermore, it is not necessarily necessary to use an AGC circuit as a control circuit that outputs a signal corresponding to the received signal strength.
A means for detecting the signal strength independently of AGC may be provided, and this means may derive a dedicated control signal to control the length of the direction display line.

〔Effect of the invention〕

As explained above, according to the direction finder according to the present invention, it is possible to obtain a stable and highly accurate indicated direction on the display, and also to control the length of the direction display line in accordance with the received signal strength. By this,
Information regarding not only the arrival direction of radio waves but also the received signal strength can be obtained. Furthermore, for signals with extremely low received signal strength, it is possible to make the azimuth variation due to noise inconspicuous and make the screen easier to see, thereby improving the azimuth display performance.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram explaining a direction finder using a circular array antenna, Figure 2 is a diagram explaining the relationship between the circular array antenna and the radio wave arrival direction, and Figure 3 is a diagram explaining the relationship between the circular array antenna and the radio wave arrival direction.
FIG. 4 is a circuit diagram illustrating one embodiment of the direction finder according to the present invention, and FIG. 4 is a circuit diagram illustrating another embodiment of the direction finder according to the present invention. 1-8...Antenna, 9...Scanner, 13,1
4... Receiver, 15, 16... Limiter, 17...
...Phase detector, 18...Signal generator, 21,2
2, 25, 26, 29, 31...multiplier, 23,
24... Filter, 27... Low frequency signal generator,
28...Indicator.

Claims (1)

[Claims] 1. A plurality of antennas disposed on the circumference at predetermined intervals to capture incoming radio waves, and antennas having a predetermined relative positional relationship among the plurality of antennas are selected and arranged in the same direction. a scanner that sequentially switches to scan the antenna; a first and second receiver that is supplied with the output of the scanner corresponding to the antenna selected by the scanner and selectively extracts a desired signal; 2
first and second limiters for removing amplitude modulation components contained in the output signal of the receiver;
a phase detector for detecting the phase difference between the output signals of the limiter; a signal generator to which the azimuth signal obtained from the scanner is supplied and generates a sine signal and a cosine signal; a first multiplier that multiplies the output signal of the phase detector; a second multiplier that multiplies the cosine signal from the signal generator by the output signal of the phase detector; first and second filters for removing the rotational frequency component of the scanner from the output signal of the multiplier;
a low frequency signal generator that generates a display low frequency signal, and third and fourth filters that multiply the signal from the low frequency signal generator by the output signals of the first and second filters. a multiplier, a display to which the output signals of the third and fourth multipliers are supplied and displays the direction of arrival of the incoming radio waves, and an amplitude of the signal supplied to the display to indicate the intensity of the incoming radio waves. A direction finder comprising variable means for changing the direction in accordance with the direction. 2. The variable means includes a control circuit that detects the signal strength extracted by the receiver and outputs a signal whose amplitude corresponds to the signal strength, the low frequency signal generator, and the third and fourth multipliers. and a fifth multiplier interposed between the control circuit and the third and fourth multipliers to supply a multiplication output of the low frequency signal and the output signal of the control circuit to the third and fourth multipliers. A direction finder according to claim 1. 3. The variable means includes a control circuit that detects the signal strength extracted by the receiver and outputs a signal whose amplitude corresponds to this signal strength, the phase detector, and the first and second multipliers. A sixth multiplier interposed therebetween supplies a multiplication output of the phase detection output signal and the output signal of the control circuit to the first and second multipliers. The direction finder according to item 1. 4. The variable means includes a control circuit that detects the signal strength extracted by the receiver and outputs a signal whose amplitude corresponds to the signal strength, the signal generator, and the first and second multipliers. seventh and eighth multipliers which are interposed between the signal generator output signal and the control circuit output signal and supply the multiplier output to the first and second multipliers;
A direction finder according to claim 1, characterized in that it is constituted by a multiplier. 5. The variable means includes a control circuit that detects the signal strength extracted by the receiver and outputs a signal whose amplitude corresponds to the signal strength, the first and second multipliers, and the first and second multipliers. Ninth and tenth multipliers are interposed between the first and second filters and supply a multiplication output of the first and second multiplier output signals and the output signal of the control circuit to the first and second filters. A direction finder according to claim 1, characterized in that it is comprised of: 6. The variable means includes a control circuit that detects the signal strength extracted by the receiver and outputs a signal whose amplitude corresponds to this signal strength, the first and second filters, and the third and fourth filters. 11th and 12th multipliers that are interposed between the multiplier and supply the multiplication output of the first and second filter output signals and the output signal of the control circuit to the third and fourth multipliers; A direction finder according to claim 1, characterized in that it is comprised of: 7. The variable means is arranged between a control circuit that detects the signal strength extracted by the receiver and outputs a signal whose amplitude corresponds to the signal strength, the third and fourth multipliers, and the display. 13th and 14th multipliers are inserted into the control circuit and supply the multiplication output of the third and fourth multiplier output signals and the output signal of the control circuit to the display device. A direction finder according to claim 1. 8. The control circuit according to any one of claims 2 to 7, wherein the control circuit is an automatic gain control circuit provided in at least one of the first and second receivers. direction finder.