JPS6339877B2 - - Google Patents

Description

[Detailed description of the invention]

When installing a direction finder on a ship or the like, it is unavoidable that there are many objects near the antenna that disturb radio waves, such as masts or stays.
In particular, vertical antennas used to determine sense are highly influenced by masts, stays, etc. because the high-frequency grounding point becomes unstable, and the amplitude and phase of the output fluctuate significantly depending on the direction of arrival of radio waves, making the sense unclear. It often happens. The present invention eliminates such drawbacks and
It is an attempt to accurately measure the direction of arrival of radio waves by always performing a clear sense. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, in which the outputs of a pair of frame-shaped antennas 1 and 2 arranged so that their directivities are orthogonal to each other are applied to balanced modulators 3 and 4. For example, it is modulated with signals a and b having a phase difference of 90 degrees, which are sent out from a low frequency oscillator 5 of 135 Hg, and in addition to polarity controllers 6 and 7, a signal generator 8
The polarity of the radio frequency is controlled by the output. In addition, an omnidirectional vertical antenna 9 and its output can be added 90
A first sense circuit consisting of a degree phase shifter 10 is provided and its output is applied to a switch circuit 11, and the output of this switch circuit and the outputs of the modulators 3, 4 and polarity controllers 6, 7 are applied to a synthesis circuit 12. There is. The output of the combining circuit 12 is sent to the radio receiving circuit 13.
In addition, the 135 Hg low frequency signal is demodulated by amplification and detection, and is applied to the level detector 15 and phase detection circuit 16 via the narrow band filter 14 of the above frequency. When the output of the filter 14 exceeds a predetermined level, the level detector 15 detects, for example, 0.5
Since the signal is sent out with a minute delay of about seconds, this signal opens the switch circuit 11 and activates the signal generator 8. Further, a low frequency signal of a suitable constant phase is applied from the oscillator 5 to the phase detection circuit 16 as a phase reference. The output signal is applied to a display 17 such as a cathode ray tube or a digital phase meter to indicate the arrival direction of the radio wave, and the output signal is also applied to a signal generator 8. In this device, when the level detector 15 is not sending out a signal, the switch circuit 11 is closed, and the signal generator 8 sends a signal to the controllers 6 and 7 to cut off the output of the frame antennas 1 and 2. 0" is added. When the device is started, the outputs of the frame antennas 1 and 2 are modulated by the signals a and b having a phase difference of 90 degrees in the balanced modulators 3 and 4, respectively, and the outputs of the first sense circuit of the vertical antenna 9, etc. The output is applied to a synthesis circuit 12 via a switch circuit 11. The synthesized signal is applied to the receiving circuit 13, and the output low frequency component of the oscillator 5 is demodulated, and the noise component is completely removed by the narrow band filter 14. Therefore, by detecting the phase of the output signal of the filter 14 with the phase detection circuit 16, the direction of arrival of the radio wave can be displayed on the phase indicator 17 (Japanese Patent Application Laid-Open No. 1983-1999).
No. 124079). Assuming that enough radio waves are incident on the antennas 1, 2, and 9 for the above-mentioned operation to be completed, a sufficiently large output signal will be sent out from the filter 14, so that the level detector 15 will detect a very small signal as described above. A signal is sent out with a time delay of , and this signal opens the switch circuit 11 and cuts off the output of the first sense circuit. Further, when the output of the detector 15 is applied to the signal generator 8, the output signal of the phase detection circuit 16,
Therefore, depending on the arrival direction of the radio wave, signals as shown in the following table are added from the generator 8 to the polarity controllers 6 and 7, and the controller outputs the signal "1".

[Table] When ``-1'' is added, the output polarity of the frame antenna is sent out without being inverted, and when ``-1'' is added, the polarity is inverted and sent out. Frame type antennas 1, 2 and polarity controllers 6, 7, etc. are the second
Forms a sense circuit. The antenna 1 is the second
As shown in the figure, the antenna 2 is placed in the direction of an angle of 90-270° indicating the direction of arrival of radio waves, and the antenna 2 is placed in the direction of 0-180°.
Assuming that both the antennas 1 and 2 send out outputs of positive polarity when the arrival direction of the radio waves is in the range of 0 to 90 degrees as shown by arrow w, in this state, the polarity controllers 6 and 7 Since the signal "1" is applied to both of them, the outputs of the above antennas are transmitted without reversing the polarity. Furthermore, if the direction of arrival of radio waves falls within the range of 90 to 180 degrees, the polarity of the output of the antenna 2 will be reversed. However, at the same time, the signal applied to the controller 7 becomes "-1" and an output having the opposite polarity to the input is obtained. Furthermore, when the direction of arrival of the radio wave is in the range of 180 to 270 degrees, the polarities of the outputs of the antennas 1 and 2 will both be in opposite phase, but the signals applied to the controllers 6 and 7 will also be "-".
1", and when the angle is between 270 and 360 degrees, the antenna becomes 1.
Only the output of the controller 6 has an opposite phase, but at the same time only the signal applied to the controller 6 becomes "-1" and its polarity is reversed. Therefore, the controllers 6 and 7 always send outputs with the same polarity as when the radio waves arrive in the range of 0 to 90 degrees, regardless of the direction in which the radio waves arrive. Furthermore, from the direction shown by arrow w in Fig. 2, line segment 0
- Assuming that a radio wave with an intensity given by p is incident, antennas 1 and 2 have 0-s and 0-r, respectively.
The output shown is generated. Since these outputs are combined in the same phase in the combining circuit 12 as described above, they are applied to the receiving circuit 13 as an input with the intensity shown by the line segment 0-v. Also, change the direction of arrow w to 0
When the angle changes within the range of ~90 degrees, point v moves with a trajectory given by arc A passing through point 0, centering on point q in the direction of 45 degrees from point 0. 90 more
Similarly, when the incident angle is 180°, 180~270°, or 270~360°, the locus of arc B, C, D, etc. is taken, and the phase is the same as when the incident angle is 0~90°. It is. That is, when the level detector 15 sends a signal and the output of the first sense circuit is cut off as described above, the output of the second sense circuit consisting of the frame antennas 1, 2, controllers 6, 7, etc. becomes balanced. It is applied to the receiving circuit 13 along with the outputs of the modulators 3 and 4, and
The output of the sense circuit has approximately constant intensity as shown by the four arcs A, B, C, and D in FIG. 2, and also always has a constant phase regardless of the direction of incidence of the radio waves. Therefore, by detecting the phase of the output signal demodulated by the receiving circuit 13 by the detecting circuit 16 and displaying it on the display 17, it is possible to know the direction of arrival of the radio wave. Moreover, in this case, since the sense input is obtained by the frame antennas 1 and 2, it is ensured that the outputs of the modulators 3 and 4 have a constant phase and amplitude. That is, unlike the output of a vertical antenna, fluctuations in phase and amplitude do not occur regardless of the output of a frame-shaped antenna due to the influence of nearby disturbing objects, so extremely accurate azimuth can be stably measured. Note that when starting the measurement, as described above, the output of the first sense circuit is first used to switch the polarity by the controllers 6 and 7, so in this case, erroneous observation of the direction may occur as described above. The erroneous observation is 0 to 90°, 90 to 180°,
Of course, if it is within the range of ..., no problem will occur. In addition, if the true incident direction of the radio wave is arrow x in the range of 0 to 90 degrees as shown in Figure 2, if we assume that this is erroneously observed in the range of 90 to 180 degrees as shown in arrow y. , when the point where the arrow x intersects with the arc A is t, and the point where the arc A is extended by approximately the same distance in the opposite direction to the point t is u, the output of the second sense circuit is a value indicated by 0-u. Become. But arrows x and y
Since the angle between them, that is, the measurement error, is generally a relatively small value, there is no risk that the outputs 0-u will become so small that they will become impossible to observe by the second sense circuit. Furthermore, once accurate observation is started by the second sense circuit as described above, the output of this sense circuit becomes the normal value 0-t, so that the second sense circuit operates in a normal state thereafter. As described above with respect to the embodiments, the present invention can obtain an output for sense determination using a directional frame-shaped antenna. Therefore, unlike the sense decision output from a vertical antenna, there is no instability in the effective grounding point or significant fluctuations in the output due to nearby disturbing objects, and the directional output can be reliably kept at a constant phase and a nearly constant rate of sealing. A sense output having a certain width can be obtained, and therefore, an effect that accurate measurement can be stably performed can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of an embodiment of the present invention, Figure 2 is a diagram showing the configuration of an embodiment of the present invention.
The figure is a diagram explaining the principle of the present invention. In the figure, 1 and 2 are frame antennas, 3 and 4 are balanced modulators, 5 is a low frequency oscillator, 6 and 7 are polarity controllers,
8 is a signal generator, 9 is a vertical antenna, 10 is a 90 degree phase shifter, 11 is a switch circuit, 12 is a synthesis circuit, 1
3 is a receiving circuit, 14 is a filter, 15 is a level detector, 16 is a phase detection circuit, and 17 is a display.

Claims (1)

[Claims] 1 A pair of frame-shaped antennas arranged so that the directivity is orthogonal to each other, a first sense circuit that shifts the output of the vertical antenna by 90 degrees, and 2 having a phase difference of 90 degrees.
an oscillator that sends out two low frequency signals; a pair of modulators that modulate the outputs of each of the pair of frame antennas with each of the two low frequency signals; a receiving circuit that receives the combined output of the modulator and demodulates a signal having the same frequency as the output of the oscillator; a phase detection circuit that detects the phase of the demodulated output of the receiving circuit; and an output signal of the phase detection circuit. It consists of an indicator that indicates the direction in which the radio waves arrive, and furthermore, the outputs of the pair of frame-shaped antennas are combined with appropriate polarity according to the output signal of the phase detection circuit, so that the polarity remains constant regardless of the direction in which the radio waves arrive. a second sense circuit that obtains a signal having a phase and a substantially constant amplitude, and a circuit that switches the input applied from the first sense circuit to the receiving circuit to the output of the second sense circuit as necessary. A direction finder characterized by: