JPH0425665Y2 - - Google Patents

Description

[Detailed explanation of the invention] "Industrial application field" This invention extracts the output of each antenna in a time-sharing manner when the pointing direction of the figure-8 directional antenna is directed in four directions shifted by 90 degrees from each other. Combine each output with the omnidirectional antenna, detect the combined output,
The present invention relates to a time-division direction finder that calculates the detection output and detects the direction of arrival of radio waves.

``Prior Art'' Figure 1 shows a conventional time-division direction finder. Two loop antennas 11 and 12 are arranged orthogonally, and the orientation direction of the loop antenna 11 is north-south direction.
It is assumed that the orientation direction of the loop antenna 12 is oriented in the east-west direction. The loop antennas 11 and 12 are connected to antenna switching devices 13 and 14 that constitute directional antenna output extraction means. The antenna switching units 13 and 14 are, for example, diode switch circuits, and these antenna switching units 13 and 14 are connected to the timing signals outputted from the timing signal generator 15 in FIGS.
For example, switching is controlled by a timing signal with a frequency of 40Hz as shown in the diagram, and the loop antenna 1
Signals N-S and E-W induced by signals 1 and 12, and signals S-N and W-E whose polarities have been switched, are extracted in a time-division manner. In other words, when the direction of the figure-8 directional antenna is oriented in four directions that differ by 90 degrees,
This means that two antenna outputs are taken out in a time-division manner. On the other hand, the phase of the signal C induced in the omnidirectional sense antenna 16 is shifted by 90 degrees in a phase shift circuit 17, and the signal C is made to have the same phase as the output signals of the loop antennas 11 and 12, and is extracted in a time-division manner in a combining circuit 18. It is combined with the signals of the loop antennas 11 and 12.
From the synthesis circuit 18, V _N =C+(N-S), V _E =C+
(E-W), V _S =C+(S-N), V _W =C+(W-
Four types of voltages V _N , V _E , V _S , and V _W corresponding to E) are obtained. Output voltage signals V _N , V _E , of the combining circuit 18
V _S and V _W are supplied to a high frequency circuit 21 in the receiver 19, the output of the high frequency circuit 21 is detected by a detection circuit 22, and the detected output is supplied to a speaker 24 via a low frequency amplifier 23 as necessary. , the received signal can be heard as sound.

The above time-division signal V _N obtained from the detection circuit 22,
V _E , V _S , V _W are peak hold circuits 1N, 1E, 1S,
Each peak value is held at 1W, and a stable peak hold voltage is obtained from the peak hold circuits 1N, 1E, 1S, and 1W. The peak hold voltage is selectively extracted by the multiplexer 25, and the AD exchanger 26 converts the time-division signals V _N , V _E , V _S , V _W into digital signals at the period of the clock CP ₁ (FIG. 2A). The digital signal is converted into a signal, and the digital signal is taken into the arithmetic unit 27.

In this example, the computing unit 27 is constituted by a microcomputer. As is well known, a microcomputer is composed of a central processing unit 28, a read-only memory 29, a writable/readable memory 31, an input port 32, and an output port 33, and each of these elements is connected to a bus line 34. A predetermined operation is performed by the central processing unit 28 sequentially reading, decoding, and executing programs stored in the read-only memory 29.

The timing generator 15 receives the clock signal CP2 from the output port 33 of the arithmetic unit 27, and generates the timing signals P _a to P _d (B to E in FIG. ₂ ) and the clock signal CP2.
I am making CP ₁ (Figure 2 A). Therefore, arithmetic unit 2
The operation of 7 and the digital signal input from the AD converter 26 are synchronized, and the arithmetic unit 27 can discriminate and capture the time-division signals V _N , V _W , V _S , and _VE respectively. .

Time division signal taken in via input port 32
V _N , V _W , V _S , and _VE are stored in respective areas provided in the memory 31 that can be written and read. A cardioid characteristic 43 is obtained by combining the figure-8 directivity characteristic 41 of the loop antenna (FIG. 3A) and the omnidirectional characteristic 42 of the sense antenna. As shown in FIG. 3B, the output voltages V _N , V _E , V _S , and V _W of the combining circuit 18 correspond to the output voltages when the cardioid characteristics are directed north, east, south, and west, respectively. The example shown in FIG. 2F is a time-division signal when radio waves arrive from the north as indicated by arrow 44. Because of this relationship, the quadrant of the radio wave arrival direction is determined as follows.

When V _N −V _S >0, V _E −V _W >0, the first quadrant V _N −V _S >0, V _E −V _W <0, the second quadrant V _N −V _S <0, V _E -V _W <0, the third quadrant V _N -V _S <0, V _E -V _W >0, the fourth quadrant Also, vector operation of (V _E -V _W )/(V _N -V _S ) Execute. The numerical value D obtained by this vector calculation is tan θ (θ represents the correspondence with the direction of arrival of the radio wave, and the angle θ is calculated from the value of D by referring to the conversion table stored in the memory 35. The radio wave arrival direction is determined from the obtained quadrant.In other words, when it is determined that it is in the first quadrant, θ° is set as the arrival direction, and the second
When it is determined that it is in the quadrant, the angle value (360-θ)° is used as is, and when it is determined that it is in the third quadrant, it is used as is (180
+θ)° is set as the direction of arrival, and when it is determined that it is in the fourth quadrant, the direction of arrival is set as (180−θ)°. The obtained radio wave arrival direction is displayed on the display 36 through the output port 33. The central processing unit 28 executes the above Θ processing.

"Problem to be solved by the invention" When obtaining the time-division signals V _N , V _E , V _S , V _W in this way and calculating the direction using them, the loop antenna in the combining circuit 18 Output V _l
When the ratio _{of the} sense antenna output V _C to The large level output of the small side lobe generated in the opposite direction is almost the same, but since these cannot be distinguished, the calculation result may be in the wrong direction. Therefore, in this type of time-division type direction finder, it is necessary to satisfy K≧1. In order to meet this condition, in conventional time-division direction finders, each level (amplitude) of the loop antenna output and sense antenna output on the input side of the combining circuit 18 is measured, and while checking the measurement results, K≧1 is determined. In other words, in the past, the ratio K was not automatically determined, but the loop antenna output and the sense antenna output were each measured separately using a level measuring device. Alternatively, each level of the time-division signals V _N , V _E , V _S , and V _W can be displayed simultaneously, with V _N at the maximum at the azimuth of arrival of 0°, and 2 of V _N at V _E = V _W.
It was adjusted so that V _S =0. This is difficult to adjust during implementation.

"Means for Solving Problems" According to this invention, in a time-division direction finder, when the directional direction of the figure-8 directional antenna is directed to each of the first to fourth directions, the detection output V _N , _VE ,
Means is provided for calculating a ratio K from V _S , V _W and the calculated radio wave arrival direction θ.

When the radio wave arrival direction is now in the θ direction relative to the north,
The amplitude of the voltage obtained from the loop antenna 11 is V _Y =V _l cosθ as shown in Fig. 4A, and the amplitude of the voltage obtained from the loop antenna 12 is as shown in Fig. 4B.
As shown in , V _X =V _l sinθ. The amplitude of the voltage obtained from the sense antenna 16 is V _C , the phase difference between the loop antenna output and the sense antenna output in the combining circuit 18 is φ, and the angular frequency of the arriving radio wave is ω.
Then, the output of the loop antenna 11 is expressed by equation (1).

V _l cosωt・cosθ (1) The output of the sense antenna is V _C cos (ωt + φ) (2). Adding equations (1) and (2) gives equation (3).

(V _l cosθ＋V _C cosφ) cosωt−V _C sinφ・sinωt (3) The amplitude value of equation (3) is V _N = |V _Y +V _C | =V _l √ ² +2・+ ² K=V _C /V _l (4) becomes. Similarly, the signals V _E , V _S , and V _W are each expressed by the following equations.

^V _{E = | V} ^​ _{​ ​ ​ ​} ^{​ ​} _{​ ​} −V _C | =V _l √ ² −2・+ ² (7) Equation (8) is calculated from equations (4) to (7) to find the direction of arrival θ.

V _E −V _W /V _N −V _S = tanθ (8) V ² / _E + V ² / _W / V ² / _N + V ² / _S = 2V ² / _l (K ² + sin ² θ) / 2V ² / _l (K ² +cos ² θ)=
Calculate A and further By calculating the ratio K, the ratio K can be obtained.

Embodiment The time-division direction finder according to this invention can use the same device as shown in FIG. 1, for example, and the calculation processing in the calculation unit 27 may be changed. An example of the processing operation in the arithmetic unit 27 is shown in FIG. In this example, V ² _N , V ² _E , V ² _S , and V ² _W are calculated in order to calculate the radio wave arrival direction θ. In this way, the orientation can be accurately determined without being affected by the phase shift φ. Routine quadrant determination
R ₁ is determined in the first to fourth quadrants as described in the "prior art" section, that is, by using V _N , V _E , V _S , and V _W . However _, this quadrant ^judgment can _be made _{by using} ^{the relationship shown} in _FIG .
It may also be done by S ₇ . Any of the quadrants determined in steps _S4 to _S7 is stored in the read/write memory 31.

On the other hand, in the angle calculation routine R ₂ |V ² / _E −V ² / _W /V ²
/ _N −V ² / _S |=D′ is calculated. (Step S ₈ ). Next, referring to the conversion table, the calculation result of step _S8 is read out from the memory 35 using D' as the address.
Find the angle θ of tan ^-1 D′ (step S ₉ ). Note that the conversion table 35 stores in advance the relationship between the value of tan θ and θ of 0° to 90°.

Next, according to the result of the quadrant judgment routine _R1 obtained earlier, if it is the first quadrant, set θ°, if it is the second quadrant, set it to (360-θ)°, and if it is the third quadrant, set it to (180+θ). °
When in the fourth quadrant, (180-θ)° is calculated to obtain the azimuth (step S ₁₀ ). Direction measurement is carried out at regular intervals, and the direction measurement results for a plurality of times, for example, 20 or 40 times, are stored in a readable/writable memory 31, and each time a new direction measurement result is obtained, the oldest direction measurement result is stored. Then, calculate the average value of the latest 20 or 40 azimuth measurement results that have always been obtained (step S ₁₁ ), and further calculate the fixed error caused by antenna placement etc. with respect to the average azimuth measurement result. (step)
_S12 ), the corrected radio wave arrival direction is displayed on the display 36.
(Step _S13 ).

For example, as shown in FIG. 7, the display 36 displays the radio wave arrival direction as a digital value on the azimuth display section 51, and also displays the frequency of the received radio wave on the frequency display section 52 as necessary. Furthermore, the channel of the radio wave is displayed on the channel display section 53. In addition, the analog display section 54 shows the arrival direction θ of the radio wave.
is performed by the linear display 55. In this linear display, for example, 36 linear electrodes are formed radially in a liquid crystal display, and one of the linear electrodes is selected to display the image in units of 10 degrees. In FIG. 1, the average number of times in step _S11 in FIG. 5 can be specified as 20 or 40 using the keyboard 37.

In this invention, the K measurement routine is shown in Figure 5.
R ₃ is provided. This routine first performs the following calculation (step _S14 ).

V ² / _E + V ² / _W / V ² / _N + V ² / _S = 2V ² / _l (K ² + sin ² θ) / 2V ² / _l (K ² + cos ² θ) =
A(10) Next, K is obtained from equation (10) using the following equation (step S ₁₅ ).

(11) Prepare the memory 38 in the arithmetic unit 27 in FIG.
The value of cos θ is stored in advance in this memory 38 within the range of 0° to 90°, and the value of cos θ is obtained by referring to this memory 38 using θ obtained in step _S9 . ) K can be found by calculating the equation. The result of this calculation may be displayed, and depending on whether the result is greater than or equal to 1, the result may be adjusted so that it becomes greater than or equal to 1. If K becomes too large, it becomes nearly omnidirectional, making it difficult to detect the direction. Therefore, K must not be made larger than the range in which direction detection using unidirectionality is possible. Also, the amplitude of the output of the loop antenna V _l
When V C is constant and the amplitude V _C of the output of the sense antenna _is increased, the ratio of the DC component of the time series of V _N , V _E , V _S , V _W to the variation width becomes the minimum at V l = V _C , and this As V _C becomes larger, the variation width is constant and the DC component becomes larger, that is, V _N , V _E ,
The absolute values of V _S and V _W increase, and the width of change is the same, and the direction detection is based on the changes in V _N , V _E , V _S , and V _W , so the AD converter 26 From the point of view of reducing the number of bits and detecting the direction with as high precision as possible, the closer K is to 1, the better.

This K is displayed, for example, at the eighth point on the display 36.
It is displayed on the channel display section 53 as shown in the figure (step _S16 ). Also, at that time, the frequency display section 52
The detection output level of each time-division signal value V _N , V _E , V _S , V _W may be displayed.

Further, depending on the case, with or without displaying such a display, it is determined whether the value of K calculated by the calculator 27 is 1 or more, and if it is smaller than 1, it is determined. The level adjuster 55 inserted between the sense antenna 16 and the combining circuit 18 is controlled by one step through the output port 33, that is, the sense antenna output V _C that increases the sense antenna output V _C by a certain amount is a loop antenna. K until it becomes equal to or larger than the output V _l
By automatically performing the calculation of K and controlling and adjusting the level adjuster 55 for each step.
can also be set to 1 or more.

When the phases of the outputs of the loop antenna and the sense antenna in the combining circuit 18 are the same,
As shown in FIG. 9A, the voltage of the antenna is V _l ,
When V _C is equal, the maximum combined output is twice V _l , the minimum is zero, and it changes between zero and 2V _l . On the other hand, if there is a phase shift between the loop antenna output and the sense antenna output in the synthesis circuit 18, these outputs become a vector sum as shown in FIG. 9B, so the maximum amplitude V _n is smaller than 2V _l . Become. When a phase shift occurs between the outputs of both antennas in the combining circuit 18, the range of amplitude change obtained depending on the direction becomes narrower, and therefore, for example, the AD converter 26
Since the number of conversion bits is limited, the accuracy of azimuth calculation deteriorates, and the resolution of azimuth measurement decreases. From this point of view, it would be convenient to check whether there is a phase shift between the loop antenna output and the sense antenna output in the combining circuit 18. The operation of the computing unit 27 is provided with a phase shift measurement routine _R4 as shown in FIG. For example, equation (12) is calculated (step _S17 ).

V ² / _N + V ² / _S + V ² / _E + V ² / _W / V ² / _N − V ² / _S = 2K ² + 1/2Kcosθcosφ=B (12) This B and the ratio K and angle θ obtained earlier Then, calculate the following equation (13) to find the phase shift φ (step S ₁₈ ).

φ=cos ⁻¹ (2K ² +1/2BKcosθ)) (13) This calculated phase shift φ is displayed on the display 36 (step S ₁₉ ). This display digitally displays the calculated phase angle φ on the azimuth angle display section 51 as shown in FIG.
The phase angle φ is similarly displayed in analog form.

This phase shift φ may be calculated as follows. That is, V _N +V _S /V ² / _N -V _S =K ² +cos ² θ/2Kcosθcosφ=C (14) By calculating the following equation using this C, the angle θ obtained earlier, and the ratio K, φ can be found. .

φ=cos ^-1 (K ² + cos ² θ/2KCcosθ) = cos ^-1 (2K ² +1+2cos ² θ/4KCcosθ) (15) The phase shift φ calculated in this way is displayed on the display 36. From the results, 90° phase shift circuit 1
The amount of phase shift in step 7 may be adjusted so that the phase difference φ is from zero to a predetermined value or less. This can also be done automatically. In other words, the arithmetic unit 27 determines whether the phase shift φ is greater than or equal to a predetermined value, and if it is greater than or equal to the predetermined value, the output port 33 is
The phase shift circuit 17 is controlled so that the phase difference φ is reduced by a predetermined value, further calculation is performed to obtain φ, and the phase shift amount of the phase shift circuit 17 is adjusted by the predetermined value again. Make sure that φ is equal to or less than a predetermined value. When automatic adjustment is performed in this way, it is not necessary to display the phase shift φ.

The calculation of this phase difference φ is 5° or 5° within the range of ±90°.
Rough measurements in 10° increments are sufficient. Therefore, the phase difference φ may be calculated by simply rounding it off and displaying it on the analog display unit 54 in units of 10°. This analog display section 54
It is sufficient to use a linear pattern provided in units of 10°, that is, 36 linear patterns arranged at equal angular intervals. On the other hand, the value of tan θ is stored in the memory 35 at intervals of 0.2° within the range of 0 to 90°, and the azimuth θ is digitally displayed on the azimuth display unit 51 in units of 1° by rounding calculation. The analog display section 54 displays the angle in units of 10 degrees. Also, cosθ is stored in the memory 38 in the range of 0 to 90°.
It is sufficient to memorize the ratio at intervals of 0.2°, and the calculation of the ratio K may be rounded off and digitally displayed in the range of 0.0 to 9.9. This ratio K phase difference φ can be calculated during maintenance and inspection, and its display can be used as a guide for the adjustment level during sense adjustment or sense inspection, or it can be automatically adjusted as described above. You can also do this. Direction measurement, ratio K measurement, phase shift φ
It is determined by the input from the keyboard 37 whether the measurement is performed or not.

In Fig. 1, peak hold circuits 1 _N , 1 _E ,
The respective outputs of 1 _S and 1 _W are supplied to squaring circuits 2 _N , 2 _E , 2 _S , and 2 _W as shown by dotted lines to perform squaring operations, and the squared outputs are sequentially switched from the multiplexer 25. You may take it out. By doing so, the square calculation in the calculator 27 can be omitted.

In the above description, a figure 8 directional loop antenna is used, but an adkotok antenna may also be used. Alternatively, instead of using two sets of loop antennas or adkotoku antennas, you can use only one of them to rotate the antenna itself, or use two sets of fixed antennas and equivalently rotate the pointing direction using a goniometer. The output may be combined with the sense antenna output, and the combined output may be taken out at points corresponding to four angular positions whose directivity directions are 90° apart. Of course, the four antenna pointing directions are not limited to the four directions of north, south, east, and west; for example, when the antenna is mounted on a moving object, four directions that are perpendicular to each other with respect to the nose direction of the aircraft can be used. .

"Effects of the invention" As described above, according to this invention, the ratio K is calculated using the calculator 27 for calculating the azimuth θ, and the level measuring device measures each level of the loop antenna output and the sense antenna output. There is no need to provide a , and there is no need to calculate the ratio K from the results of each level measurement.

[Brief explanation of drawings]

Figure 1 is a block diagram showing a conventional time-division direction finder that can be applied to this invention;
The figure shows the relationship between the antenna switching signal in Figure 1 and the time-division signal obtained from the antenna synthesis circuit, and Figure 3 shows the figure-of-eight directivity characteristics, the composite characteristics of the directional antenna, and their switching rotation. A diagram showing the characteristics,
Fig. 4 is a diagram showing an example of the characteristics of the loop antenna 11, the radio wave arrival direction, and the voltage amplitude induced in each loop antenna, Fig. 5 is a flowchart showing an example of the calculation process of the ratio K in this invention, and Fig. 6 is a diagram showing the relationship between the square output and the quadrant, FIG. 7 is a diagram showing an example of the direction measurement display on the display, FIG. 8 is a diagram showing an example of the indication of the ratio K and phase shift φ, and FIG. 9 is a diagram of the loop antenna. FIG. 6 is a diagram for explaining an amplitude change based on a phase shift in a combining circuit of an output and a sense antenna output.

Claims (1)

[Claim for Utility Model Registration] The output of the figure-8-shaped directional antenna when the direction of the figure-8-shaped directional antenna is directed in the first to fourth directions shifted by 90 degrees from each other on the radio wave arrival direction detection plane. A directional antenna output extraction means for extracting the directional antenna output in parts, a combining circuit for combining the output of the directional antenna output extraction means and the output of the sense antenna in substantially the same phase, and a detection circuit for detecting the combined output of the combining circuit. and the detection outputs V _N , V _E , of the detection circuit corresponding to when the pointing direction is directed to the first to fourth directions.
Means for obtaining V ² _N , V ² _{E ,} V ² _S , V ² _W by squaring V S and V _W , and (V ² _N −V ² _S )/(V ² _E −V ^2W ₎
=D; a display for determining θ that satisfies D=tan ^-1 θ from the calculation result and displaying the θ as the radio wave arrival direction; the radio wave arrival direction θ; and the detection output V _N , V _E ,
A time-division direction finder comprising means for calculating a ratio K between the output of the sense antenna and the output of the figure-eight directional antenna from V _S and V _W.