JPH0129428B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for detecting signals generated by the switching connection in a received signal obtained by receiving radio waves while sequentially switching and connecting antennas arranged at intervals on the circumference. The present invention relates to a direction finder having a circuit configuration capable of detecting a phase change as a signal for measuring the arrival direction of the radio waves.

[Conventional technology]

This type of direction finder is a so-called stationary type that measures the direction of arrival of radio waves by arranging receiving antennas with the same characteristics at equal intervals on the circumference and sequentially switching and connecting them to extract the phase change of the received signal. There is a Doppler direction finder, for example, as described in Japanese Patent Publication No. 56-35828, the direction of the incoming radio wave can be determined by sequentially switching antennas to receive signals and then comparing the obtained direction information with the antenna standard. I can do it. In order to realize such a direction finder, it is necessary to switch the antenna at high speed, and for this purpose, a diode (or transistor), etc. is inserted into the circuit, and the current flowing through it greatly reduces its operating resistance. It is common to switch the antenna output signal by taking advantage of the change in the antenna output signal.

[Problem to be solved by the invention]

When the direction finding radio waves are in the LF or HF band, the lower limit of the reception frequency and the frequency of the antenna switching signal are not far apart, so if the antenna is switched in a rectangular manner, higher harmonics of the switching current flowing through the diode will be generated. It may be mixed into the received signal, causing a beat disturbance or a drop in S/N, making it impossible to detect the direction.

Furthermore, if a large switching rectangular wave is applied to each antenna, harmonic components may be radiated from there and cause interference. In order to remove reception interference caused by harmonics, it is sufficient to insert a filter that removes the components, but since the high-order harmonics of a square wave signal are extremely high-order, it is actually a problem to remove them with a filter, etc. It's almost impossible.

Needless to say, measurement becomes impossible if the noise component matches the frequency of the received radio wave.
Even if it were possible to remove some of the harmonics by inserting an extremely narrow filter, there would be problems such as azimuth measurement being impossible at frequencies before and after the filter due to the influence of the phase characteristics of the filter.

In the case of a rotating Doppler direction finder that rotates one antenna at high speed and obtains a phase change due to the Doppler effect in the received signal, this problem does not occur because the Doppler phase change only changes in the form of a SIN wave. .

However, if the radio waves are in the LF or HF band, the radius of rotation of the antenna must be extremely large, which is impossible, so a stationary Doppler must be used.

Therefore, there is a problem in that it is desired to develop a stationary type device that solves the above-mentioned disadvantages.

[Means to solve the problem]

The present invention provides a switching signal that is applied to a switching circuit for making a switching connection provided corresponding to each antenna.
switching signal means for forming a signal comprising a half-wave portion of a wave; and an overlapping connection in which each antenna is provided with an overlapping portion in which the switching connection to the preceding antenna and the switching connection to the subsequent antenna of two adjacent antennas overlap. means and the switching connection of this overlapping part,
By providing a switching circuit that connects the half-wave portion of the SIN wave to decrease the output from the preceding antenna and increase the output from the subsequent antenna, the above-mentioned It is designed to solve the following problems.

〔Example〕

Examples will be described below with reference to figures.

FIG. 1 shows an overall system diagram of the present invention, and FIG.
FIG. 4 shows one embodiment of the present invention in FIG. 3, and FIG. 5 shows its waveform diagram. Each number in the waveform diagram is shown in Figures 2 and 4.
Corresponds to the numbers shown in the figure.

Next, a detailed explanation will be given with reference to the drawings.

1 in FIG. 1 is a group of omnidirectional antennas arranged at equal intervals on the circumference. 2 is a switching circuit for switching each of the antenna groups, which controls the output of each antenna by controlling the current flowing through the diode.
Operates to turn on and off. 3 is a switching signal generator that generates switching signals for switching each antenna, 4 is a receiver, and 5 is a direction indicator for receiver 4.
The IF output is amplified and detected and compared with the reference pulse to count the direction and indicate the direction on the CRT or numerical display, as well as the synchronization pulse and other reference pulses for synchronizing with the reference pulse for antenna switching. Occur. Figure 2 shows the details of the dotted line part in Figure 1.
The case of switching this antenna will be explained.

_A1 to _A4 are omnidirectional antennas, _C1 to _C5 are DC blocking capacitors, CH1 to CH5 are high frequency blocking coils, Da and Db are rectifier diodes,
R is a current limiting resistor and T is a transformer. 6 is a switching signal generation circuit with a period t as shown in FIG.
Generates a SIN wave voltage and passes it through the transformer T to the rectifier Da,
Db is added to generate half-wave rectified waveforms as shown in FIGS. 4 and 5. 7 is a 90° phase shifter which generates rectangular waves like 2 and 3 with a 90° phase difference from 1 in FIG. 8
and 9 are shift registers that drive the shift register 9 at the rising edge of the waveform of 2, respectively.
Make selection pulses like 8 and 7,9. In other words, these selection pulses form a plurality of rectangular wave signals in which 1/2 of the rectangular waves overlap. _S1 ～ _S4
is a semiconductor switch that operates so that the input and output terminals are conductive when the control terminal C is "H" (HIGH VOLTAGE), and by applying selection pulses as shown in Figure 3, 6, 7, 8, and 9, the diode D is switched on. Turn on each circuit of ₁ to D ₄ in sequence to generate the half-wave rectified waveforms 4 and 5.
are applied respectively. 10 is a diode D ₁ to _{D 4}
It is connected to the negative power supply -V through a constant current circuit into which all the current flows. As is clear from the waveforms in Figure 3, 6 to 9, the switching diode circuits are switched two by two in duplicate, and near the maximum value of each half-wave rectified voltage, the current in the adjacent circuit becomes almost zero and flows into the constant current circuit. All currents are from one circuit only. In other words, in Figure 3
At time _t12 , both circuits _D1 and _D2 are ON, but both half-wave rectified voltages are 0.

Therefore, 1/2 of the constant current I flows through _D1 and _D2 . After this point, the voltage at 4 becomes zero and the voltage at 5 increases. Therefore, the current in D ₂ increases, but the current in D ₁ does not immediately become zero, and the current I increases so that the product of the difference between the currents of D ₁ and D ₂ and the resistance R becomes equal to the voltage difference of 4.5. Allocated to D ₁ and D ₂ . That is, if R is zero, switching occurs instantaneously at _t12 , but if IR=E, the current in the adjacent circuit, ie, _D1, continues until the half-wave rectified voltage reaches E. (However, the diode is assumed to have ideal characteristics). Therefore, each diode is switched continuously and smoothly, and the overlapping time can be freely set by adjusting I and R.

As described in Japanese Patent Publication No. 56-35828, if vertical antennas placed at equal intervals on the circumference are sequentially switched in a rectangular manner, the phase of the received signal will be as shown in Figure 3-10, and when this is detected by a detector, The signal shown in FIG. 3, which changes impulsively at the moment of switching, is obtained. By integrating this, the signal shown in Fig. 3-10 with the original phase is obtained, and by comparing it with the reference signal, the arrival direction of the radio wave can be determined. When switching occurs, the switching is not instantaneous, but is performed gradually, with the two antenna outputs overlapping each other according to the half-wave rectified waveform, as described above. In other words, only one antenna is turned on at the peak point of the half-wave rectified wave,
Once the peak point is exceeded, the next antenna output gradually overlaps and the switching progresses, so when this receiver output is detected, it does not become an impulse like the one shown in Figure 3, 11 above, but a half-wave rectified wave for switching. Since the phase changes very slowly from one peak point to the next peak point, a signal with gradual changes as shown in FIG. 312 is obtained. By integrating this, a waveform with the original phase as shown in FIG. 3 is obtained, and by comparing the phase with the reference signal, the direction of the arriving radio wave can be determined.

As described above, the detected signal obtained by antenna switching according to the present invention is a signal that changes gradually compared to the detected signal obtained by rectangular switching, but rather by rotating one antenna along the circumference. This is close to the detected signal obtained at the time of the test.

FIG. 4 shows another embodiment. In the figure, 11 is an X'tal or self-excited oscillator, and 12 is a frequency divider which divides the output of the oscillator and applies the resulting multi-bit binary digital signal to a function generator 13.

Also, the rectangular wave shown in FIG. 5b is sent to the semiconductor switch 14,
Rectangular waves e and f having a period of t and having a phase difference of 90° from the rectangular wave b are applied to shift registers 8 and 9. 13 is a function generator, for example SIN ROM
(READ ONLY MEMORY) and DAC
(DIGITAL TO ANALOG CONVERTER), etc., and is addressed by the binary output signal of the frequency divider and reads the SIN wave from the SIN ROM.
The DAC converts it into an analog signal, generating the double-wave rectified waveform shown in Figure 5a. Note that if the number of bits of the binary output signal is increased, the SIN wave after conversion will be the ideal one.
It becomes close to a SIN wave. 14 is a semiconductor switch which is turned on and off by a rectangular wave b synchronized with the double-wave rectified wave a sent from the frequency divider 12 to obtain half-wave rectified waveforms such as c and d.

The output of the semiconductor switch 14 is sent to amplifiers 15 and 16.
The output of the amplifier 15 is applied to the switches S ₁ and S ₃ , and the output of the amplifier 16 is applied to the switches S ₂ and S ₄ . On the other hand, the outputs e and f of the frequency divider 12
is added to shift registers 8 and 9, and g~
Selection pulses overlapped by half cycles such as k are obtained. These are added to S ₁ to _{S 4} respectively, and the operation described in FIG. 2 is performed.

〔Effect of the invention〕

As described above, each diode switching is performed continuously and smoothly, and there is no need to adjust each diode circuit individually, and high-order harmonic noise and circuit adjustment are easily eliminated due to instantaneous switching, and the measurement sensitivity is extremely high. It is possible to realize a direction finder with high performance.

Further, according to the present invention, the switching connection to the preceding antenna and the switching connection to the subsequent antenna of two adjacent antennas of each of the antennas A ₁ to _{A 4} which are sequentially switched and connected overlap. The switching connection of the overlapping portion is such that the output from the preceding antenna is decreased and the output from the subsequent antenna is increased by the half-wave portion of the SIN wave. Depending on the circuit, switching connections are made.

In this way, by connecting the antennas in such a way that the output from the antenna in the first order is decreased and the output by the antenna in the second order is increased, the synthesis from the two antennas obtained by the switching connection is achieved. The output, that is, the received signal, is as if
The phase of the signal received by the first antenna gradually changes to the phase of the signal received by the second antenna, which alleviates the sudden phase change that occurs in conventional switching connections. It has the advantage of being able to provide a desired direction finder that solves the problems of .

[Brief explanation of drawings]

Figure 1 is an overall system diagram of the present invention, Figures 2 and 4.
The figure shows an embodiment of the present invention, and FIGS. 3 and 5 show operational waveform diagrams. 1... Omnidirectional antenna group, 2... Switching circuit,
3... Switching signal generator, 4... Receiver, 5... Direction indicator, 6... Switching signal generation circuit, 7... 90° phase shifter, 8, 9... Shift register, 10... Fixed Current circuit, 11...X'tal or self-excited oscillator, 12
... Frequency divider, 13 ... Function generator, 14 ... Semiconductor switch, 15, 16 ... Amplifier, A ₁ - A _o ...
...Omnidirectional antenna, C ₁ to C ₅ ... DC blocking capacitor, CH1 to CH5... High frequency blocking coil, D ₁ to _{D 4} ... Switching diode, Da,
Db... Rectifier diode, E... SIN wave voltage amplitude, S ₁ to S ₄ ... semiconductor switch, T... transformer,
R...Current limiting resistance, I...Constant current circuit current.

Claims (1)

[Claims] 1. Receiving radio waves while sequentially switching and connecting antennas arranged at intervals on the circumference, and measuring the phase change caused by the switching and connection in the received signal, and measuring the direction of arrival of the radio waves. In a direction finder having a circuit configuration capable of detecting a signal (hereinafter referred to as a directional component signal), a. switching signal
a switching signal means for forming a signal comprising a half-wave part of a SIN wave; b an overlapping portion where the switching connection to the preceding antenna and the switching connection to the subsequent antenna of each of the two adjacent antennas of each said antenna overlap; and (c) a switching connection of the overlapping portion, whereby the output from the preceding antenna is decreased and the output from the subsequent antenna is increased by the half-wave portion. A direction finder, comprising: the switching circuit connected to the switching circuit. 2. Claims The direction finder according to claim 1, further comprising: a) the switching circuit configured by controlling the current of a diode; b) converting the half-wave portion of the SIN wave into a SIN wave voltage. c) the overlapping portion is constituted by an overlapping portion of a plurality of rectangular wave signals in which 1/2 of the rectangular waves are overlapped; A direction finder comprising: