JPH0416945Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a direction finder that detects the direction of arrival of radio waves.

In conventional direction finders of this type, if there is a difference between the frequency of the received radio wave and the reception center frequency of the receiver, a phase shift occurs due to the group delay characteristic of the receiver in the intermediate frequency band, making it difficult to find the correct direction. becomes undetectable.

This invention detects the out-of-tune state of the receiver with respect to the received radio waves, and uses the detected output to stop the detection of the direction signal.

Hereinafter, embodiments of the direction finder according to this invention will be described with reference to the drawings.

In FIG. 1, an azimuth signal having a phase corresponding to the direction of the arriving radio wave is detected from the received signal by the azimuth signal detection section 11. In the figure, four rod-shaped antennas 1N, 1S, 1E, and 1W are erected at each corner of a square, with antenna 1N on the north side, 1S on the south side, 1E on the east side, and 1W on the west side with respect to the center. It is said that These antennas are switched by a switching signal from the control signal generator 12, and the receiver 1
Connect to 3. For example, by alternately receiving antennas 1N and 1S twice, as shown in FIG.
The received signal 2S from S is received twice alternately.
Next, the reception signal 2E from the antenna 1E and the reception signal 2W from the antenna 1W are alternately received twice, and then the reception signal from the antenna 1N is received again, and so on.

Received signals from these antennas are amplified by a circuit 14 in a receiver 13, further converted into intermediate frequency signals, and then sequentially received by a phase detector 15 to detect a phase change between each antenna signal. Antenna 1N as shown in Figure 2B
A signal 3N corresponding to the phase difference between the signal 2N from the antenna 1S and the signal 2S from the antenna 1S is detected, and when changing from the signal 2S to the signal 2N, the phase difference is reversed, so the signal 3S switches in a pulse-like manner. Obtained in points. Similarly, signals corresponding to the phase difference between antennas 2E and 2W are also sequentially transmitted to signals 3E and 3, respectively.
Obtained as W. The phase difference between the received signals 2N and 2S from the antennas 1N and 1S becomes larger as the arrival direction of the radio waves approaches the arrangement direction of the antennas 1N and 1S. The phase difference becomes zero, and a phase difference corresponding to the direction of arrival is obtained. For example, a quadroutier detector is used as the phase detector 15, and the detected output frequency characteristic thereof is such that the detected output level increases as the frequency increases, as shown in FIG. 6, for example. Therefore, when the input frequency of the phase detector 15 is _fl , for example, an output obtained by superimposing the waveform shown in FIG. _2B on the DC level E1 is generated as the output of the phase detector 15. That is, FIG. 2B shows only the output change due to the phase change based on the antenna switching with this DC level, for example, _E1 as a reference. The antenna switching frequency component is extracted by the wave detector 16 from the output of the wave detector 15 in which such a phase difference is detected. The output of the wave generator 16 is passed through an analog switching circuit 17 to an integrating circuit, that is, a time constant circuit 4N, 4S, 4 consisting of a capacitor and a resistor.
E and 4W are switched and the corresponding ones are stored respectively.

The signals integrated by the integrating circuits 4N, 4S, 4E, and 4W are switched by an analog switching circuit 18, and the integrating circuits
N, 4E, 4S, and 4W are repeatedly extracted in the order, and a signal train as shown in FIG. 2C, for example, is obtained. That is, in FIG. 2C, the integrating circuits 4N, 4S,
Each DC output of 4E, 4W is 5N, 5S, 5E, 5
W, the output of the switch circuit 18 is 5N, 5
E, 5S, 5W are repeated in this order. This switching speed can be arbitrarily selected, for example, one quarter of the switching speed of the switching circuit 17. This switching circuit 18
The repetition frequency component of the output is extracted by the wave generator 19 and converted into a sine wave signal as shown in FIG. 2D, and further converted into a square wave signal as shown in FIG. 2E by the waveform shaping circuit 21. The phase of this square wave signal corresponds to the direction of arrival of the radio wave with respect to the switching signal of the switching circuit 18. The principle of this azimuth signal detection section 11 is explained in, for example, Japanese Patent Application No. 127200/1982 (Japanese Unexamined Patent Publication No. 27073/1982).

For example, for the output square wave signal of the waveform shaping circuit 21 shown in FIG. 2E, the switching reference signal is as shown in FIG. 2F, and the phase difference between these two signals is detected as a numerical value (digital value). to obtain numerical data corresponding to the direction of the incoming radio wave. Control signal generator 12
uses a stable clock from the reference clock oscillator 22 to switch the antennas 1N, 1S, 1E, and 1W, control the switching circuits 17 and 18, and also generate the reference signal shown in FIG. 2F. For example, when this reference signal rises, a flip-flop 23 is set, its Q output opens a gate 20, and the clocks passing through this gate 20 are counted by a counter 24. The flip-flop 23 is reset by the rise of the output of the waveform shaping circuit 21. Therefore, the counter 24 counts the clock pulses (G in FIG. 2) from the rise of the reference signal to the rise of the square wave signal having a phase corresponding to the arrival direction of the radio wave. This count value is calculated by the central processing unit,
It is taken into so-called CPU25, and then CPU2
5 resets the counter 24.

The CPU 25 performs display operations by sequentially reading and decoding the programs stored in the ROM 26, and when the azimuth data obtained by the counter 24 is fetched a predetermined number of times, the azimuth data is averaged and the azimuth data is averaged. Numerical display 27 using the average value as an angle
to be displayed. A RAM 28 is provided for storing data required for this purpose, and an interval timer 29 is provided for controlling panel keys and the like. Furthermore, this display operation is started by detecting the arrival of a radio wave, and the output of the circuit 14 of the receiver 13 is also branched into the radio wave arrival detector 31, and the detection output of the radio wave arrival detector 31 is given to the CPU 25. When the angle is displayed, the CPU 25 starts the operation for displaying the angle. Furthermore, in this example, an analog display 32 is provided in which light emitting diodes are arranged on a circle at regular intervals and the light emitting diodes at angular positions corresponding to the angle of the incoming radio waves are lit to display the display. .

The CPU 25 performs operations as shown in FIG. 3, for example. That is, in step _S1 , it is always detected whether the radio wave arrival detection signal Sig is turned on, and if it is off, the flag F is turned off in step _S2 and the process returns to step _S1 . This flag F is stored, for example, in a flag storage area 28a in the RAM 28, as shown in FIG. When the direction of arrival of the radio wave is detected in step _S1 , the process moves to step _S3 . In step _S3 , it is checked whether data can be taken in, that is, whether the counting operation of the counter 24 has been completed, and the counting operation is completed. If not, the process returns to step _S1 , and when the counting operation is completed, data representing the count value of the counter 24 is read in step _S4 . After that, in step _S5 , it is checked whether flag F is off, and if flag F is off, it means that no radio waves have arrived until then, and in that case, in step _S6 , flag F is turned on and Let the data be average data. This average data is stored in average data area 28b within RAM28.

If the flag F is on in step _{S5 , the process moves to step S7 ,} where the count value n of the average number counter is incremented by 1 and the average number n is stored in the counter area 28c. At the same time, the operation moves to the data averaging routine _R1 . The data averaging routine _R1 is as shown in Figure 5, where the sum Ds=
It is checked in step _S8 whether ΣD is zero, and if the added value Ds is zero in step _S8 , the process immediately moves to step _S9 , and if the added value is not zero in step _S8 ,
If there is already an added value, it is detected in step _S10 whether the value obtained by subtracting the captured data D from the average data is greater than a predetermined value, for example 512. In this embodiment, this value 512 corresponds to the case where 360° corresponds to 1024, and is half of that value and corresponds to 180 degrees. If the average value calculated so far is 180 or more larger than the imported data D, proceed to step _S11 , add 1024 to the imported data D, and use the result as imported data D.
Move on to _S9 . If the difference is smaller than 512 in step _S10 , it is checked in step _S12 whether the value obtained by subtracting the captured data D from the average data is smaller than -512, that is, if the captured data D is smaller than the previous average data. Check if it is larger than 180°, and if it is larger than 180°, move to step _S13 and check if it is 360° from the captured data D.
1024 is subtracted and the result is set as the captured data D and the process moves to step _S9 . If the data captured in step _S12 differs from the average data by less than 180°, the process immediately moves to step _S9 .

In the operations in these steps _S10 to _S13 , when the measured data (azimuth) is around 0°, data values slightly larger than 0° and large data values slightly before 0° are measured, and these are used as they are. When averaged, the measured data obtained is e.g. 180°
The value will be completely different from 0°. Therefore, processing is performed to prevent such errors from occurring.

In step _S9 , the captured data D obtained as a result of step _S8 , _S11 , or _S13 is added to the total value Ds up to that point to obtain added data Ds=ΣD, which is added to the RAM 28. It is stored in the data area 28d. Also, the steps after that
In _S14 , it is checked whether the added data Ds is smaller than 0, and if it is positive, the process moves to step _S15 , and if it is negative, the added data Ds is checked in step _S16 .
A value of 1024×n, that is, n times 360° is added to Ds, and this is stored as addition data Ds in the addition data area 28d. Then move on to step S ₁₅ .
This added data Ds is divided by the n value at that time to obtain average data, which is stored in the average data storage section 28b.
to be memorized.

When the average data routine _R1 is completed in this way, it is checked in step _S16 in FIG. 3 whether the average number n matches a predetermined value N, and if not, the process returns to step _S1 . Generally, radio waves arrive continuously, and in this state, steps S ₁ , S ₃ , S ₄ , and
The processes of step S ₅ , step S ₇ , and step S ₁₆ are repeated. When n reaches the predetermined average number N in step _S16 , the average number value n and data total value Ds are set to 0 in step _S17 , and an angle calculation is performed, that is, 360÷1024×, to correspond to the average data. Obtain the numerical value DEG indicating the angle. This value is checked in step _S18 to see if it is larger than 360°, and if it is smaller, step _S19 is performed.
, and if it is larger, step S ₂₀ to set the value DEG
Subtract 360° from , use the result as DEG, move to step _S19 , and display this value as the azimuth angle on display 2
7.

In this invention, a receiver 1 for receiving radio waves is used.
The detuning state of No. 3 is detected by the detuning detection section 35. That is, for example, the output of the phase detector 15 is supplied to the low-pass wave detector 36, and the wave output thereof is supplied to the comparators 37, 3.
8 are compared with constant voltages E ₁ and E ₂ respectively. These constant voltages, for example, as shown in _FIG . highest frequency
Outputs E ₁ and E ₂ corresponding respectively to f _l and the higher lowest frequency f _h are selected. (Group delay becomes a problem mainly because the group delay characteristic of the bandpass filter 16 deteriorates at frequencies near both ends of the passband.) Therefore, the frequency of the incoming radio wave and the reception setting frequency of the receiver 13 If there is a difference between E1 and F1, the output of the phase detector 15 will be smaller than _E1 when the frequency of the converted intermediate frequency signal is lower than _f1 ,
The output of the comparator 37 becomes high level. Conversely, if the frequency of the intermediate frequency signal is higher than f _h , the detection output will be higher than E ₂ and the output of the comparator 38 will be at a high level. The outputs of these comparators 37 and 38 are further inverted and supplied to an AND circuit 43 through backflow blocking diodes 41 and 42. This AND circuit 43 outputs a low level to a terminal 44 when either of the outputs of these comparators 37, 38 becomes high level, and the azimuth calculation process of the CPU 25 is stopped by the low level.

Further, the output sides of the comparators 37 and 38 are grounded through light emitting diodes 45 and 46, and when the detuned state occurs and either of the comparators 37 and 38 reaches a high level, the corresponding one of the light emitting diodes 45 and 46 lights up. This will indicate that the unit is out of tune. The connection point between the diodes 41 and 42 is grounded through an inverter 47 and further through a light emitting diode 48. Therefore, if the outputs of the comparators 37 and 38 are both low level, that is, the receiver 13 is not out of tune with respect to the received radio waves, and the reception state is correct, the light emitting diode 48 lights up, the CPU 25 operates, and the incoming radio waves are detected. Direction detection is performed.

Further, in this example, the operation of the CPU 25 is stopped when the level of the received radio wave becomes lower than a predetermined value. That is, phase detector 1
The output of 5 is also supplied to a high-pass wave filter 49, a noise component is extracted from the output of this high-pass wave filter 49, and the noise component is detected by a wave detector 51. If there is, the inverted signal is supplied to the AND circuit 43, and the terminal 4
4 becomes low level and the operation of the CPU 25 is stopped. However, if the level of the received radio wave is higher than a predetermined value, the output of the detector 51 becomes a low level, and if the outputs of the comparators 37 and 38 are both low levels, the output of the AND circuit 43 becomes a high level. CPU2
5 becomes operational.

Note that a large number of comparators are provided on the output side of the low-pass wave generator 36, and the reference voltages thereof are appropriately varied in sequence.
Furthermore, by connecting light emitting diodes to the output sides of the comparators, the detuning state of the receiver 13 with respect to the received radio waves can be displayed on these light emitting diodes. When the radio wave disappears from the radio wave reception state, or when the state becomes significantly detuned, the CPU 25 stops the direction detection operation using the new direction signal, but it instructs the direction based on the data measured so far. In that case, the lighting state of the light emitting diodes 45 and 46 indicates the direction of the radio waves obtained up to that point, indicating that the reception state is not correct or that the radio waves have been cut off. You can know.

The direction finder of this invention is not limited to the type shown in FIG. 1, but can also be applied to so-called Doppler direction finders, goniometer type direction finders, and the like. The detection direction can be indicated not only by numerical display, but also by arranging light emitting elements on the same circle at equal intervals on the display 32 as shown in FIG. This invention can also be applied to a direction finder with a light on or a pointer display.

In the conventional technology, if the receiver 13 was significantly out of tune, the error in the measured direction value would increase, and there was a risk that it would lead to an unexpected accident due to trusting the measured value without knowing this, but with this invention, in such a case, Since the direction detection is interrupted and measurement values with large errors are not displayed, there is no such fear.
Safety is improved accordingly.

According to this invention, the CPU 25 also controls the receiver 1.
3 is out of tune by a predetermined value or more, the direction detection operation is interrupted and unnecessary operations are not performed, thereby saving energy.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of the direction finder according to this invention, Fig. 2 is a waveform diagram to explain its operation, Fig. 3 is a flowchart showing an example of its processing operation, and Fig. 4 is a RAM A diagram showing the storage area in
FIG. 5 is a flowchart showing a processing example of the averaging routine, and FIG. 6 is a diagram showing an example of the detection characteristics of the phase detector 15. 1N, 1S, 1E, 1W...Antenna, 4N,
4S, 4E, 4W...Integrator circuit, 11...Direction signal detection unit, 13...Receiver, 15...Phase detection circuit, 17, 18...Switching circuit, 21...Waveform shaping circuit, 35...Separation Adjustment state detection section, 37, 38...
Comparator, 44...Signal output terminal for controlling operation/inoperation of the CPU 35, 45, 46...Light emitting diode for detuning indication.

Claims (1)

[Claims for Utility Model Registration] A direction finder that receives radio waves with a receiver, processes the received signals in a central processing unit to calculate direction, and displays the arrival direction of the radio waves, in the intermediate frequency band of the receiver. The group delay is
detuning detection means for detecting a state in which the receiver is detuned with respect to received radio waves to the extent that the azimuth component included in the received signal affects detection of the direction of arrival of the radio waves; and detection of the detuning means. A direction finder comprising: means for canceling the azimuth calculation process in the central processing unit by outputting an output.