JP2502938Y2 - Direction finder - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direction finder for detecting the arrival direction of radio waves.

[0002]

2. Description of the Related Art In a conventional direction finder of this type,
For example, the clock corresponding to the phase difference between the phase detection signal and the reference signal is counted and the direction of the incoming radio wave is digitally obtained.

[0003]

In a conventional direction finder of this type, if there is a deviation between the frequency of the received radio wave and the reception center frequency of the receiver, the group delay characteristics in the intermediate frequency band of the receiver cause However, there is a problem that a correct azimuth cannot be detected due to a phase shift and the error of the azimuth measurement value increases.

[0004]

This invention detects the detuning state of a receiver with respect to a received radio wave, and stops the azimuth calculation processing in the central processing unit by the detection output.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, an azimuth signal having a phase corresponding to the direction of an incoming radio wave is detected by a azimuth signal detector 11 from a received signal. In the figure, four rod-shaped antennas 1N, 1
S, 1E, 1W are placed at each corner of the square, and the antenna 1N is on the north side, 1S is on the south side, 1E is on the east side, and 1W is on the west side with respect to the center thereof. These antennas are switched by the switching signal from the control signal generator 12 and connected to the receiver 13. For example, antenna 1N, 1S
2 is alternately received, and the reception signal 2N from the antenna 1N and the reception signal 2S from the antenna 1S are alternately received twice as shown in FIG. 2A. Next antenna 1
Received signal 2E from E, received signal 2 from antenna 1W
W is alternately received twice, and then the same thing is repeatedly received, such as reception of the antenna 1N.

Received signals from these antennas are received by the receiver 1.
3, the signal is amplified by the circuit 14 and further converted into an intermediate frequency signal, which is subsequently received by the phase detector 15 to detect a phase change between the antenna signals.
As shown in FIG. 2B, the signal 3N corresponding to the phase difference between the signal 2N from the antenna 1N and the signal 2S from the antenna 1S.
Is detected and the phase difference is reversed when the signal 2S changes to the signal 2N, the signal 3S is obtained in pulse form at the switching point. Similarly, the signals corresponding to the phase difference between the antennas 2E and 2W are sequentially obtained as the signals 3E and 3W, respectively. Received signals 2N from antennas 1N and 1S,
The phase difference between 2S depends on the direction of arrival of the radio wave from the antennas 1N and 1N.
The phase difference increases as it approaches the array direction of S, and when it comes from the direction perpendicular to the array direction, the phase difference becomes zero,
A phase difference corresponding to the direction of arrival can be obtained. The switching frequency component of the antenna is extracted by the filter 16 from the output of the detector 15 in which such a phase difference is detected. The output of the filter 16 is an integration circuit in the analog switching circuit 17, that is, a time constant circuit 4 including a capacitor and a resistor.
It is switched to N, 4S, 4E, 4W and the corresponding ones are stored respectively.

The integrated signals of the integrating circuits 4N, 4S, 4E and 4W are switched by the analog switching circuit 18, and the integrating circuits 4N and 4N corresponding to north, south, east and west of the antenna.
It is repeatedly taken out in the order of E, 4S, and 4W.
A signal train as shown in C is obtained. That is, in FIG. 2C, the DC outputs of the integrating circuits 4N, 4S, 4E, and 4W are 5N,
Assuming 5S, 5E, and 5W, the output of the analog switching circuit 18 is repeated in the order of 5N, 5E, 5S, and 5W. This switching speed can be arbitrarily selected and is, for example, one fourth of the switching speed of the analog switching circuit 17. The output of the analog switching circuit 18 has its repetitive frequency component taken out by the filter 19, and is converted into a sinusoidal signal as shown in FIG. 2D. Further, the waveform shaping circuit 21 is converted into a square wave signal as shown in FIG. 2E. . The phase of this square wave signal corresponds to the arrival direction of the radio wave with respect to the switching signal of the analog switching circuit 18. The principle of the azimuth signal detecting section 11 is described in, for example, Japanese Patent Application Laid-Open No. 58-27073.

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). Obtain numerical data corresponding to the direction of incoming radio waves. The control signal generator 12 is a reference clock oscillator 2
Antenna 1N, 1S, with stable clock from 2
Switching for 1E, 1W, analog switching circuits 17 and 1
8 is performed, and the reference signal of FIG. 2F is also created.
The flip-flop 23 is set by the rise of this reference signal, for example, and the Q output opens the gate 20, and the clock passed through the gate 20 is counted by the counter 24.
The flip-flop 23 is reset by the rise of the output of the waveform shaping circuit 21 counted by. Therefore, the clock from the rising edge of the reference signal to the rising edge of the square wave signal having the phase corresponding to the arrival direction of the radio wave (Fig. 2G).
Are counted by the counter 24. This count value is taken in by the central processing unit, so-called CPU 25, and then the CPU 2
5 resets the counter 24.

The CPU 25 performs a display operation by sequentially reading and decoding the program recorded in the ROM 26. When the azimuth data obtained by the counter 24 is fetched a predetermined number of times, the azimuth data is averaged, The average value is displayed as an angle on the numerical display 27. A RAM 28 is provided for storing data necessary for that purpose, and an interval timer 29 is provided for controlling panel keys and the like. Further, this display operation is started upon detection of arrival of a radio wave, and the output of the circuit 14 of the receiver 13 is also branched and input to the radio wave arrival detector 31, and the detection output of the radio wave arrival detector 31 is sent to the CPU 25.
CPU 25 starts the operation for displaying the angle. Further, in this example, an analog display 32
Also, there is provided a display 32 in which the light emitting diodes are arranged at equal intervals on one circle and the light emitting diodes at an angular position corresponding to the angle of the incoming radio wave are lit and displayed.

The CPU 25 operates as shown in FIG. 3, for example. That is, in step S1, it is always detected whether or not the radio wave arrival detection signal Sig is turned on. If it is off, the flag F is turned off in step S2 and the process returns to step S1. The flag F is stored in the flag storage area 28a in the RAM 28 as shown in FIG. 4, for example. When the arrival direction of the radio wave is detected in step S1, the process proceeds to step S3, and it is checked in step S3 whether data can be taken in, that is, whether the counting operation of the counter 24 is finished. If the counting operation is not finished, Returning to step S1, when the counting operation is completed, the count value of the counter 24 is fetched in step S4. After that, in step S5, it is checked whether or not the flag F is off. If the flag is off, there is no arrival of radio waves. At that time, the flag F is turned on in step S6, and the data acquired at that time is averaged. Let data d. The average data d is stored in the average data area 28b in the RAM 28.

When the flag F is turned on in step S5, the process proceeds to step S7, the count value n of the average number counter is incremented by 1 in step S7, and the average number n is stored in the counter area 28c. At the same time, the operation is moved to the data averaging routine R1. Data averaging routine R1
Is the added value Ds as shown in FIG.

It is checked in step S8 whether [Equation 1] is zero. If the added value Ds is zero in step S8, the process immediately moves to step S9. If the added value is not zero in step S8 and there is a value already added, Average data d in step S10
The value obtained by subtracting the acquired data D from is a predetermined value, for example, 51
Detects if it is greater than 2. This value 512 is the case where 360 ° is associated with 1024 in this embodiment,
It is half the value, which corresponds to 180 degrees. The average value d calculated up to that time is 180 more than the captured data D.
If it is larger than 0 °, the process moves to step S11, and 1024 is added to the fetched data D, and the result is fetched data D and the process shifts to step 9. When the difference is smaller than 512 in step S10, the value obtained by subtracting the fetched data D from the average data d in step S12 is −51.
It is checked whether it is smaller than 2, that is, whether the captured data D is 180 ° or more larger than the average data d up to then, and if it is 180 ° or more, step S13.
It is 360 degrees from the data D that was taken to 1
024 is subtracted, and the result thereof is taken in as data D to move to step S9. If the difference between the data taken in step S12 and the average data d is smaller than 180 °, the process immediately goes to step S9.

In the steps S10 to S13, when the measured data (azimuth) is near 0 °, a data value slightly larger than 0 ° and a large data value just before 0 ° are measured. If they are averaged as they are, the measured data obtained will be, for example, around 180 °, which is a value completely different from 0 °. Therefore, it is a process for preventing such an error.

In step S9, the fetched data D obtained as a result of step S8 or S11 or S13 is added to the total value Ds obtained so far to obtain added data Ds = ΣD, which is added to the RAM 28. Record in area 28d. Further, after that, in step S14, it is checked whether or not the addition data Ds is smaller than 0. If the addition data Ds is positive, the process proceeds to step S15, and if the addition data Ds is negative, the addition data Ds is multiplied by 1024 × n, that is, n times 360 °. Add the value of and add it to the data D
This is stored in the addition data area 28d as s. After that, the process proceeds to step S15, and the addition data Ds is divided by the n value at that time to obtain the average data d, which is stored in the average data storage unit 28b.

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 they do not match, the process returns to step S1. In general, radio waves arrive continuously, and in this state, step S1, step S3, step S4, step S5, step S
7. The process of step S16 will be repeated. When n reaches the predetermined average number N in step S16, the average number n and the data total value Ds are calculated in step S17.
Is 0, and the angle calculation is performed by calculating 360 ÷ 1024 × d, and a numerical value D indicating the angle corresponding to the average data d is obtained.
Get EG. The value is set to 3 in step S18.
If it is smaller than 60 °, the process proceeds to step S19. If it is greater than 60 °, 360 ° is subtracted from the value DEG in step S20, and the result is regarded as DEG. The numerical value of is displayed on the display 27.

In this invention, the detuning state of the receiver 13 with respect to the modulated reception signal is detected by the detuning detector 35.
That is, for example, the output of the phase detector 15 is the low-pass filter 36.
And their filtered outputs are compared with constant voltages E1 and E2 in comparators 37 and 38, respectively. These constant voltages are, for example, as shown in FIG. 6, the highest frequency on the low side where the group delay described above becomes a problem with respect to the center frequency f0 of the straight line portion in the detection frequency characteristic of the phase detector 15. The outputs E1 and E2 corresponding to f1 and the higher minimum frequency fh are selected. The group delay becomes a problem mainly because the group delay characteristic of the bandpass filter 16 deteriorates at frequencies near both ends of the pass band.

Therefore, if there is a deviation between the frequency of the incoming radio wave and the reception setting frequency of the receiver 13, the output of the phase detector 15 is smaller than E1 when the converted intermediate frequency is lower than f1. Then, the output of the comparator 37 becomes high level. On the contrary, when the frequency of the intermediate frequency signal is higher than fh, the detection output becomes larger than E2 and the output of the comparator 38 becomes high level. These comparators 37, 38
The output of is passed through the backflow blocking diodes 41 and 42 and is further inverted and supplied to the AND circuit 43. The AND circuit 43 outputs a low level to the terminal 44 when any one of the outputs of the comparators 37 and 38 becomes high level, and the bearing calculation processing of the CPU 25 is stopped by the low level.

Further, the respective output sides of the comparators 37 and 38 are grounded through the light emitting diodes 45 and 46, and when any one of the comparators 37 and 38 becomes high level due to the detuned state, the light emitting diodes 45 and 46 correspond to each other. The object lights up and it is displayed that it is in the detuning state. The ground points of the diodes 41 and 42 are grounded through an inverter 47 and a light emitting diode 48. Therefore, when the outputs of the comparators 37 and 38 are both low level, that is, the receiver 13 is not detuned with respect to the received radio wave, or in the correct reception state, the light emitting diode 48 is turned on and the CPU 25 is operated to detect the incoming radio wave direction. Is detected.

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, the output of the phase detector 15 is also supplied to the high-pass filter 49, a noise component is extracted from the output of the high-pass filter 49, and the noise component is detected by the detector 51. When the level is equal to or higher than the predetermined level, the inverted signal is supplied to the AND circuit 43, the terminal 44 becomes low level, and the operation of the CPU 25 is stopped. However, when the level of the received radio wave is equal to or higher than the predetermined value, the output of the detector 51 becomes low level, and the comparator 3
If both outputs of 7 and 38 are low level, AND circuit 4
The output of 3 becomes high level, and the CPU 25 becomes operable.

The low-pass filter 36 is provided with a large number of comparators on the output side, the reference voltages of the comparators are sequentially changed appropriately, and light-emitting diodes are connected to the output sides of the comparators to receive radio waves. The detuning status of the receiver 13 with respect to can also be displayed on these light emitting diodes.
When the radio wave disappears from the reception state of the radio wave or when it becomes a large detuning state, the CPU 25 stops the azimuth detection operation by the new azimuth signal, but instructs the azimuth based on the data measured up to that time. In that case, the direction indication for the radio waves obtained from the lighting state of the light emitting diodes 45, 46 to that time,
At present, it can be known that the reception is not correct or the radio wave is blocked.

The direction finder of the present invention is not limited to the type shown in FIG. 1, but can be applied to so-called Doppler direction finder and goniometer type direction finder. The indication of the detection direction is not limited to the case of numerical display, and for example, as shown in FIG. 1, in the display 32, the light emitting elements are arranged at equal intervals on the same circle, and one light emitting element corresponding to the radio wave arrival direction is turned on. Alternatively, the present invention can be applied to a direction finder that displays a pointer.

[0021]

According to the prior art, if the receiver 13 is largely detuned, the error in the direction measurement value increases, and the measurement value may be trusted without knowing it, which may lead to an unexpected accident. In this invention, the direction detection in that case is interrupted,
Since we do not display measurement values with large errors,
There is no such fear and safety is improved accordingly. Further, according to the present invention, when the receiver 13 is detuned by a predetermined value or more, the CPU 25 interrupts the azimuth detection operation to prevent unnecessary operation, thereby saving energy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a direction finder according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation.

FIG. 3 is a flowchart showing an example of the processing operation.

FIG. 4 is a diagram showing a storage area in a RAM.

FIG. 5 is a flowchart showing a processing example of an averaging routine.

FIG. 6 is a diagram showing an example of detection characteristics of a phase detector 15.

[Explanation of symbols]

1N, 1S, 1E, 1W Antenna 4N, 4S, 4E, 4W Integrator circuit, 11 Direction signal detection unit 13 Receiver 15 Phase detection circuit 17, 18 Analog switching circuit 21 Waveform shaping circuit 35 Detuning state detection unit 37, 38 Comparison Device 44 Signal output terminals for controlling the operation / non-operation of the CPU 35 45, 46 Light emitting diode for detuning display

Claims (2)

(57) [Scope of utility model registration request] 1. A signal (hereinafter referred to as a detection signal) obtained through a bandpass filter from a signal (hereinafter referred to as a modulated reception signal) in which a received signal is phase-modulated in accordance with the arrival direction of a radio wave.
A direction finder obtained as a signal (hereinafter, referred to as a direction display signal) for displaying the arrival direction based on the following: a. Detuning detection means for detecting that the center frequency of the modulated reception signal is at a frequency deviating from the center frequency of the bandwidth of the bandpass filter, and obtaining a detuning detection signal, b. A direction finder, comprising means for stopping the azimuth display using the direction display signal obtained based on the detection signal by the detuning detection signal. 2. The direction finder according to claim 1 of the utility model registration claim, comprising: a. Means for low-pass filtering the modulated received signal to obtain a low-pass filtered signal; b. Means for high-pass filtering the modulated received signal to obtain a high-pass filtered signal; c. The detuning detection signal by comparison detection signal means for comparing and detecting the level of the low-pass filtered signal with a predetermined level to obtain a comparison detection signal, or detection signal means for detecting the high-pass filtered signal to obtain a detection signal Direction finder which constitutes the detuning detection means for obtaining.