JPH0513585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a radio direction finder that detects the arrival direction of radio waves using received signals obtained by switching antennas arranged at intervals.

[Prior art] This type of direction finder has two
A detection signal is obtained by detecting the phase difference that occurs when the reception signals of the two antennas are alternately switched, and the above detection signal is obtained when the arrival direction of the radio wave is changed with respect to the line passing through each antenna. In a wireless direction finder capable of detecting the arrival direction of a radio wave based on the amplitude change of the detection signal, a meter detects a change in the detection signal sound that makes the amplitude change of the detection signal audible, or a meter detects the amplitude change of the detection signal. The configuration in which instructions are given by changing the needle position is disclosed in Utility Model Application No. 61-50930, Utility Model Application No. 61-50931 (Utility Model Application No. 1983-162679, Utility Model Application No. 62-173080) or Japanese Patent Application Laid-Open No. 61-1982 by the applicant of the present application. -139770 etc.

And the above-mentioned Utility Application No. 61-50930 (Utility Application No. 62-50930)
162679), the 6th
It has the configuration as shown in the figure, and each part is operated by signals as shown in FIG.

In the figure, spaced antennas 101A,
Each output of antenna 101B is alternately and continuously switched by switching signal a and b from switching circuit 103 in switching scanning circuit 102 to create a switching reception signal c in which the outputs of antennas 101A and 101B are alternately arranged, and the signal is sent to the attenuation circuit. In the case of a stronger radio wave than 116, the switching reception signal c is appropriately attenuated and fed to the selection amplification circuit 104, which selects and amplifies the reception signal of the target radio wave to generate a selection signal c1.

A direction detection circuit 105 generates a phase detection wave for detecting a phase difference occurring at each switching point in the selected amplified signal c1 to generate a detection signal d.

The detected value of the detection signal d is maximum when the arrival direction of the radio wave is on the extension of the line connecting antennas 101A and 101B, and minimum when it is perpendicular to this, and it depends on whether the arrival direction is forward or backward. Therefore, the polarity of the signal changes, so in the case of this phase detection,
Similar to the well-known phase detection, the amplitude will be output with a positive polarity or the amplitude will have a negative polarity, as shown in the signal d in FIG.

By applying the detection signal d to a bandpass filter circuit (BPF) 106 whose center frequency is, for example, 2 kHz, the frequency corresponding to the switching period of the switching signals a and b is converted into an alternating current component consisting of the fundamental wave component of the detection signal d. Then, a delay circuit 107 generates a delay signal f in which the zero cross point y of the direction signal e coincides with the starting edge of the switching signals a and b.

The synchronous wave rectifier circuit 108 takes out one of the specified signal sections of the switching signals a and b with the same polarity and inverts the polarity of the other signal section, and performs the switching and scanning of the antennas 101A and 101B. Create a wave signal g.

Therefore, the rectified wave signal g becomes a pulsating waveform signal with a polarity that has a certain agreement with the arrival direction of the radio wave.

A DC signal h obtained by smoothing the rectified signal g by a smoothing circuit 109 is converted to a voltage frequency conversion (V/F conversion) circuit 1
10, an azimuth sound signal k is generated which is converted into an audible frequency signal whose frequency changes in accordance with the value of the DC signal h.

The direction sound signal k passes through a sound switching circuit 111 and a sound output circuit 112 for mixing with an audio sound signal m, which will be described later, and is output as a detection signal sound for aurally determining the arrival direction of the radio wave through an earphone 113. .

On the other hand, the audio detection circuit 114 selects the amplified signal c1.
After detecting the communication content in the radio waves, a notch filter circuit 115 removes the switching frequency Fc of the switching signals a and b to remove the scanning noise signal caused by the switching signals a and b, thereby creating an audio signal m.

A sound switching circuit 111 outputs the azimuth sound signal k and the audio sound signal m, either singly or as a mixture.

Further, the direct current signal n is applied to the voltage of the meter 121 so that the direction of arrival of the radio waves can be visually determined from the maximum or minimum point.

With these conventional technologies, the antenna spacing can be reduced to make the entire device compact, and when the antenna itself is rotated with respect to the direction of arrival of radio waves, the magnitude of the audio signal changes, and this change The direction of arrival can be detected by instructions.

[Problems to be Solved by the Invention] The above-mentioned conventional technology relies on a detection signal that detects the phase difference that occurs when two antennas are switched, so the signal contained within one period of the detection signal is , only one positive and negative pulse-like signal can be obtained, so if the radio waves to be detected are weak and the S/N ratio is poor, the fluctuation of this one pulse signal will directly become the fluctuation of the direction of arrival indication. This has the disadvantage of making it impossible to obtain stable instructions.

In addition, if the frequency at which the received signal of each antenna is switched is an audible frequency, the detection signal that detects the phase difference at the time of switching becomes an audible frequency, and this audible frequency should be used as the detection signal sound. In reality, since the click frequency caused by switching is mixed in, if this is directly used as a detection signal sound, there will be a problem that changes in the detection signal sound cannot be heard due to the click noise.

For this reason, a circuit configuration is provided in which the detection signal is smoothed and converted into a DC signal, and then this DC signal is V/F converted to an audible frequency signal to obtain the detection signal sound. In addition to complicating the configuration, the rise of the detection signal sound is delayed due to the transient characteristics of the smoothing circuit, etc.
There are some inconveniences, such as the inability to respond to very short radio waves.

[Means for solving the problem] This invention obtains a detection signal by detecting the phase difference that occurs when the reception signals of the antennas arranged at intervals as described above are switched in a predetermined order, and also detects the phase difference between each antenna. In a radio direction finder that can detect the direction of arrival of radio waves based on the amplitude change of the detection signal obtained when the direction of arrival of the radio waves is changed with respect to the line passing through, the three antennas described above are used. Switching for switching each of the above-mentioned received signals by means of a plurality of antenna means arranged at intervals on a straight line, sequential switching in which each antenna is sequentially switched in the order in which the antennas are arranged, and reciprocating switching in which the sequential switching is made back and forth. By providing means and, the above-mentioned problem of not being able to obtain a stable detection signal when the radio waves are weak and the S/N ratio is poor can be solved, and the switching frequency can be used to sequentially switch the antennas in the order in which they are arranged. switching means for switching each of the above-mentioned received signals by sequential switching, and reciprocating switching that reciprocates the sequential switching at an audible frequency lower than the above-mentioned sequential switching frequency; a filtering means having a low-pass filtering configuration that passes frequencies lower than the above-mentioned sequential switching frequency; and a signal obtained based on the above-mentioned detection signal is filtered by the above-mentioned filtering means. A complex configuration is required to smooth the detection signal by providing a detection signal sound means for obtaining the above-mentioned detection signal sound from the obtained audible frequency signal, and further to perform V/F conversion to make the detection signal sound an audible frequency. This system is designed to solve the above-mentioned inconveniences.

[Example] Examples will be described below with reference to the drawings.

In FIG. 1, antennas 10A, 10B, 10
C, 10D, 10E are 1/ of the wavelength λ of the radio wave to be detected
antennas spaced in a straight line at intervals of not more than 2;
For example, an omnidirectional vertical antenna.

The switching circuit 12 receives the received signals 10a of each antenna,
After switching 10b, 10c, 10d, and 10e sequentially from 10a to 10e, repeating the operation of sequentially switching from 10e to 10a.
That is, from the antenna at one end to the other end, and then from the antenna at the other end to the original antenna at one end,
Then, the switching is performed so that this process is repeated again.

In other words, the switching detection signal 12a is output by performing sequential switching in the order in which each antenna is arranged, and reciprocating switching in which the sequential switching is made back and forth.

The switching wave circuit 13 generates a switching signal 13a for causing the switching circuit 12 to perform a switching operation, for example, a rectangular wave signal having a frequency around an audible frequency.

The selective amplification circuit 14 selects the frequency and band of radio waves for direction detection, amplifies the switching detection signal 12a to a required output, and outputs a received signal 14a.

The FM detection circuit 15 detects the FM signal (communication signal such as audio modulation) in the received signal 14a to obtain a communication sound signal 151a, and also detects the received signals 10a, 1 of each antenna at the time of switching of the switching circuit 12.
The detection signal 15 is obtained by detecting the phase difference between 0b,...10e.
1b and output them as a detected signal 15a.

The filter circuit 16 blocks the portion of the detection signal 15a higher than the audio frequency and outputs the portion of the lower frequency range as a low frequency signal 16a.

The speaker 17 converts the low frequency signal 16a into audible sound and outputs it.

When the radio waves to be detected are AM modulated, the AM detection circuit 18 performs AM detection on the received signal 14b before carrying out the amplitude limiting operation for FM detection of the amplified signal in the selective amplification circuit 14, and outputs a low frequency signal 18a. do.

In Figure 2, when the distance l between each antenna is less than 1/2 of the wavelength of the radio wave, changing the angle θ of the direction β in which the radio wave arrives with respect to the direction α of the line passing through each antenna, between each received signal of the antenna (for example, 10a, 10b, 10b, 10c,
...) changes as shown in FIG. 2b.

In other words, when a radio wave arrives from either direction (θ = 0° or 180°) on a line passing through each antenna, the absolute value of the phase difference φ between the received signals of adjacent antennas becomes maximum, and , orthogonal direction (θ=90°
or 270°), the directivity has a change in which the absolute value of the phase difference φ becomes the minimum.

Therefore, even when the direction of the antenna pair is rotated with respect to the arrival direction of the radio waves, the phase difference φ changes in the same way.

In FIG. 3, the upper detection signal 15a is a signal sequence when there is no communication sound signal 151a and only the detection signal 151b, and the lower detection signal 15a is a signal example when the communication sound signal 151a and detection signal 151b are mixed. It is. The detection signal 151b is an output obtained by a radio wave arriving from the β direction of angle θ and a phase difference φ ₀ corresponding to that direction, and the detection signal at each switching time sequentially switches the received signal of each antenna. It appears at a frequency _F1 with a period t, and becomes a signal whose polarity is inverted every 1/2 of the switching period T.

Therefore, the detected signals 15a, 151 in FIG.
The size of the phase difference φ ₀ shown in b changes with the directivity shown in FIG. 2b as θ changes.

Here, when the number of antennas is 5 and the frequency of sequential switching, that is, the sequential switching frequency F ₁ is 3.5 kHz, the frequency of the round-trip switching period T, that is, the round-trip switching frequency F ₂ is 0.7 kHz.

Therefore, if the filter circuit 16 is configured with a simple reduction filter circuit 16 that passes frequencies of about 3 kHz or less, that is, it passes frequencies higher than the round-trip switching frequency and sequentially lower than the switching frequency. If a reduction filter configuration is provided to allow the filter to pass through, the clicking sound with many harmonic components at a frequency of 3.5 KHzHz or higher due to sequential switching will be controlled, and the frequency of reciprocating switching will be reduced.
Since only the fundamental wave component of F ₂ will appear in the audible sound signal, the detection signal sound will be output as a signal sound that is easy to hear.

The number of antenna arrays and the sequential switching frequency _F1 increase or decrease the frequency bandwidth of the switching deep signal 12a, so the selection characteristics of the selection amplifier circuit 14,
In other words, it is necessary to set it in consideration of the relationship with the amplification bandwidth. Considering these conditions, it is desirable to have four or more antennas, but logically, three antennas can achieve the purpose.

[Modification example] This invention can be implemented in the following modifications.

(1) A similar effect can be obtained by arranging the antennas at irregular intervals.

(2) As shown in FIG. 4, the antennas are arranged at unequal intervals similar to a sine value, so that the envelope 15b of the detected output 15a is shaped like a sine wave as shown in FIG. Since the fundamental wave component of the detection output 15a in this case is the same as the envelope 15b, the filtering circuit 16 can be made simpler, and in some cases, even if the filtering circuit 16 is omitted, Clicking noise caused by switching can be reduced to an unnoticeable level.

[Effect] According to the present invention, since three or more antennas are arranged, the number of pulsed signals obtained within one cycle of the detection signal that detects the phase difference at the switching point is equal to the number of antennas arranged. Since the amount of signal energy within one cycle of the detection signal increases, a stable detection signal can be obtained even when the radio waves are weak and the S/N ratio is poor.

In addition, the sequential switching frequency for switching each received signal is necessarily higher than the round-trip switching frequency corresponding to the frequency of the detection signal sound by the number of antennas, and there is a large frequency difference between the sequential switching frequency and the round-trip switching frequency. Therefore, the clicking noise caused by sequential switching can be filtered out using a simple low-pass filtering configuration.

Further, by arranging the antennas at sinusoidal intervals, the detection signal sound can be made clearer, and in some cases, a filter circuit can be made unnecessary.

It should be noted that, in light of well-known conventional technology, it is obvious that determining whether the radio waves are in the opposite direction when they arrive from the opposite direction by 180 degrees needs to be addressed as a separate issue from the configuration that achieves the above features. It is.

[Brief explanation of the drawing]

The drawings show an embodiment, and FIG. 1 is a block configuration diagram, FIGS. 2a and 2b are diagrams explaining the principle, FIGS. FIG. 6 is a block diagram of the prior art, and FIG. 7 is a signal waveform diagram of each part of the prior art.

Claims (1)

[Claims] 1. A detection signal is obtained by detecting the phase difference that occurs when the reception signals of the antennas arranged at intervals are switched in a predetermined order, and the arrival direction of the radio wave is determined with respect to the line passing through each of the antennas. A radio direction finder (hereinafter referred to as a device) capable of detecting the direction of arrival based on a change in the amplitude of the detection signal obtained when changing the antenna, the antenna being three or more. antenna means disposed at intervals on a straight line; and switching means for switching each of the received signals by sequential switching for sequentially switching the antennas in the order in which they are arranged, and reciprocating switching for reciprocating the sequential switching. A device characterized by: 2. The device according to claim 1, characterized in that the device includes the antenna means in which the antennas are arranged at irregular intervals. 3. The device according to claim 1, characterized in that the device includes the antenna means in which the antennas are arranged at unequal intervals in a sinusoidal manner. 4. Obtain a detection signal that detects the phase difference that occurs when the received signals of the antennas arranged at intervals are switched in a predetermined order, and when the direction of arrival of the radio waves is changed with respect to the line passing through each of the antennas. A radio direction finder (hereinafter referred to as a device) capable of detecting the direction of arrival based on a detection signal sound in which the amplitude change of the obtained detection signal is made into an audible sound, wherein the antenna is connected to three or more antennas. a plurality of antenna means disposed at intervals on a straight line; a switching means for switching each of the received signals by sequential switching for sequentially switching in the order in which the antennas are arranged; and reciprocating switching for reciprocating the sequential switching; . An apparatus comprising: the antenna means in which each of the antennas is arranged at unequal intervals in a sinusoidal manner. 5. Obtain a detection signal that detects the phase difference that occurs when the received signals of the antennas arranged at intervals are switched in a predetermined order, and when the direction of arrival of the radio waves is changed with respect to the line passing through each of the antennas. A radio direction finder (hereinafter referred to as a device) capable of detecting the direction of arrival based on a detection signal sound in which the amplitude change of the obtained detection signal is made into an audible sound, wherein the antenna is connected to three or more antennas. a plurality of antenna means disposed at intervals on a straight line; sequential switching in which the antennas are sequentially switched in the order in which the antennas are arranged using a sequential switching frequency; and reciprocating switching in which the sequential switching is performed back and forth using an audible frequency lower than the sequential switching frequency. Therefore, a switching means for switching each of the received signals; a filtering means having a low-pass filter configuration that passes frequencies higher than the round-trip switching frequency and lower than the sequential switching frequency; and the detection. Detection signal sound means for obtaining the detection signal sound using the audible frequency signal obtained by filtering the signal obtained based on the signal by the filtering means. 6. The device according to claim 5, characterized in that the device includes the antenna means in which the antennas are arranged at unequal intervals. 7. The device according to claim 5, characterized in that the device includes the antenna means in which the antennas are arranged at unequal intervals in a sinusoidal manner.