JPH0512666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention relates to a direction display device used in ships and the like.

``Prior art'' For example, as shown in ``Japanese Unexamined Patent Publication No. 131574/1980,'' sine wave data and cosine wave data are read out from a fixed memory, and reception is performed using the sine wave data and cosine wave data. Balanced modulation of the signal, so that the amplitude of each
A direction finder configured to obtain two balanced modulated signals with a phase difference of 90° is considered.

In other words, in a direction finder with this structure, the video carrier signal is amplitude-modulated by the received signal, and the amplitude-modulated video carrier wave is applied to two balanced modulators, and the two balanced modulators are also input from the memory. A sine wave signal and a cosine wave signal obtained by reading and DA conversion are applied to perform balanced modulation, and the balanced modulation output is applied to the X-Y axis of the cathode ray tube to display the arrival direction of the radio wave.

``Problems to be Solved by the Invention'' In conventional direction finding devices, a video carrier wave is amplitude-modulated by a received signal. If the polarity of this amplitude modulation is such that the level of the video carrier wave is zero when there is no received signal, then the balanced modulation signals given to the cathode ray tube display will be mutually zero when there is no received signal. Therefore, a cathode ray tube display displays a dot. As a result, there is an inconvenience that the phosphor screen is burnt.

For this reason, when there is no received signal,
Set the modulation polarity of the modulator to output the video carrier wave with maximum amplitude. By setting the modulation polarity of the modulators in this way, when there is no reception signal, the two balanced modulators are given the maximum amplitude video carrier wave, and their outputs are the maximum amplitude two-phase balanced modulation signal. is output. As a result, when there is no reception signal, a circle with a diameter determined by the amplitude of the video carrier wave is displayed on the cathode ray tube. This circular display prevents burn-in on the fluorescent screen of the cathode ray tube and improves reliability.

However, in a direction finder with this structure, in order to change the diameter of the circle displayed when no received signal is received, the amplitude of the video carrier wave applied from the video carrier generator to the modulator must be adjusted. However, when adjusting the amplitude of the video carrier wave, if the input-output characteristics of the balanced modulator do not match, the amplitude of the balanced modulation signal output from the balanced modulator will change and the shape of the circle will be deformed. There are drawbacks. For this reason, balance adjustment is required to match the input-output characteristics of the two balanced modulators, which requires a troublesome adjustment work.

An object of the present invention is to provide a direction display device having a structure that does not require adjustment work in this respect.

"Means for Solving the Problems" The present invention provides an orientation display device that has a structure that can generate a balanced modulation signal without using a balanced modulator, and that can simplify the structure and eliminate the trouble of adjustment. .

In this invention, the amplitude data of sine waves and cosine waves are stored in a memory device, and this memory device is used to control the rotation of the antenna.
In other words, it is configured to read out in synchronization with the rotation of the goniometer to obtain a two-phase balanced modulation signal having an amplitude phase of a sine wave and a cosine wave.

Here, in particular, the amplitude data stored in the memory is amplitude modulated pulse data separated by data representing zero voltage, this amplitude modulated pulse data is read out and DA converted, and the DA converted output is given to the DC blocking means. Accordingly, a balanced modulation signal can be obtained from this DC blocking means. As a result, according to the present invention, no balanced modulator is required at all, so there is no need to make adjustments to match the input-output characteristics of the two balanced modulators. Further, since neither a video carrier generator nor a modulator is required, there is an advantage that the structure can be simplified.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a pair of antennas having directivity, 2 is a goniometer that extracts the azimuth component from the antenna 1, and 3 is a motor that rotates the moving coil of the goniometer 2. 4 indicates a rotary encoder. This rotary encoder 4 rotates together with the goniometer 2, and outputs one pulse CK ₁ and 0.2° per rotation.
Assume that one pulse CK ₂ is output for each pulse.
5 is a sense determining antenna, 6A and 6B are sense switches, 7 is a receiver, and 8 is a detector. Detection by the detector 8 is, for example, negative polarity detection, and the negative polarity detection output is supplied to the direction display device 9.

The direction display device 9 according to the present invention includes a pair of memory devices 11A and 11B, an address counter 12 that provides an address signal to the memory devices 11A and 11B,
DA converters 13A, 13 that perform DA conversion on digital data read from the storage devices 11A, 11B
B, and amplifiers 14A and 14B that amplify the DA conversion outputs of the DA converters 13A and 13B to a predetermined level.
, DC blocking means 10A, 10B, resonators 15A, 15B excited by the output signals of the DC blocking means 10A, 10B, and resonators 15A, 15B.
A cathode ray tube display 16 whose output signal is given to an X-axis input terminal and a Y-axis input terminal, and a cathode ray tube display 1
and a sense determining circuit 17 which applies a brightness modulation signal to the brightness modulation terminal G of No. 6 to determine the direction of arrival of radio waves.

In this invention, a pair of memory devices 11A and 11
It is characterized in that amplitude-modulated pulse data having sine wave-like amplitude data and cosine-wave-like amplitude data is stored in B.

The signal waveforms read from this pair of memories 11A and 11B and subjected to DA conversion are shown in FIGS. 2A and 2B.
The amplitude modulation pulses Pa and Pb shown in FIGS. 2A and 2B have peak value envelopes shaped like sine waves and cosine waves, and data for one cycle as a whole is written in the memories 11A and 11B. amplitude modulated pulse
Pa and Pb each have their phases reversed in the first half cycle and the second half cycle in one cycle. These amplitude modulated pulses Pa and Pb are applied to the DC blocking means 10A and 10B, and by removing the DC component contained in the amplitude modulated pulses Pa and Pb, the carrier wave is generated every half period as shown in C and D in FIG. So-called two-phase balanced modulation signals Sa and Sb whose phases are reversed are obtained.

As the memories 11A and 11B, semiconductor memories such as ROM can be used, for example. As for the resolution of the write data, for example, amplitude data changed by 0.2 degrees is written alternately with zero data for each address. Also, the resolution in the amplitude direction is, for example, 255
Quantize into steps.

Memory units 11A and 11B are address counters 12
A count output signal is given from , and the addresses from the first address to the last address are repeatedly read out. This readout period is 0.2° obtained from the rotary encoder 4 so as to match the rotation period of the goniometer 2.
A pulse CK ₂ outputted with a resolution of
The address counter 12 is reset by CK ₁ , and the rotation of the goniometer 2 and the memory devices 11A and 11 are reset.
The relationship between the reading cycles of B is always made to match. Reference numeral 18 denotes a synchronization circuit, and the synchronization circuit 18 is used to match the timing of resetting the address counter 12 with the timing of the goniometer 2 passing the reference point.

Here, rotary encoder 4 and synchronous circuit 18
A phase adjustment means 21 is provided between the two. This phase adjustment means 21 is, for example, a preset counter 21.
A and a phase setter 21B that provides a set value to the preset counter 21A. The phase setter 21B can be configured by, for example, a digital switch.

The preset counter 21A can be either an up counter or a down counter.
For example, a case where a down counter is used will be explained. Set a value corresponding to the delay angle in the phase setter 21B, and apply the set value to the synchronization pulse CK ₁ .
It is sufficient to preset the preset counter 21A with the pulse CK2, and then count down the preset value with the pulse _CK2 . For example, to delay synchronization pulse CK ₁ by 1°, 1/0.2 = 5, that is, phase setter 2
1B is set to a digital value equivalent to "5" in decimal notation, and this set value is preset to the preset counter 21A at the timing of synchronization pulse _CK1 .
When 5 pulses CK ₂ are input by counting down the preset value with pulse CK ₂ ,
Decrement signal from preset counter 21A
CK ₁ ′ is obtained.

Therefore, this carry down signal CK ₁ ' is sent to the synchronization circuit 18.
through the reset terminal R of the address counter 12.
By giving , the phase of the readout start point of the memories 11A and 11B is set by 1° relative to the rotational phase of the antenna 1.
It can be delayed by a minute. Therefore, by setting an arbitrary value to the phase setter 21B, it is possible to adjust the phase of the azimuth component and the phase of the two-phase balanced modulation signal generated from the memory devices 11A and 11B into an arbitrary relationship. As a result, even if the azimuth component obtained from the antenna 1 is delayed by the receiver 7, the detector 8, etc., the structure allows electronic adjustment of the reference point of the azimuth component and the phase of the two-phase balanced modulation signal. ing.

Amplitude modulated pulse data having sine amplitude data and amplitude modulated pulse data having cosine amplitude data read from the memories 11A and 11B are applied to DA converters 13A and 13B for DA conversion. this
Amplitude modulated pulses Pa and Pb shown in FIG. 2A and B are obtained by DA conversion.

These amplitude modulated pulses Pa, Pb are amplified to a predetermined level by amplifiers 14A, 14B as required, and supplied to DC blocking means 10A, 10B. The direct current blocking means 10A, 10B can be constituted by a capacitor. DC blocking means 10A, 1
By applying amplitude modulation pulses Pa and Pb to 0B, balanced modulation signals Sa and Sb shown in FIG. 2C and D are obtained. These balanced modulation signals Sa and Sb are sent to the resonator 15.
A and 15B, and the waveform of the carrier component of the balanced modulation signals Sa and Sb is shaped into a sine wave and is applied to each of the X-axis and Y-axis input terminals of the cathode ray tube display 16.

On the other hand, a constant DC bias voltage -E _B is applied from the operational amplifier 19 to the reference voltage terminals REF of the DA converters 13A and 13B, and the detection output signal of the wave detector 8 is applied to the other input terminal of the operational amplifier 19 to provide DC bias. A detection output signal is superimposed on the voltage -E _B , and this superimposed signal is applied to the reference voltage terminal REF of the DA converters 13A and 13B.

Reference numeral 17 indicates a sense determination circuit. By turning on the sense determining switches 6A and 6B, the sense determining circuit 17 controls the gate 17B to open and becomes operational. That is, the signal received by the sense antenna 5 is added to the azimuth component extracted by the goniometer 2, and the gate 17B is controlled to open, and a brightness modulation signal is applied to the brightness modulation terminal G of the cathode ray tube display 16 through this gate 17B. As this brightness modulation signal, for example, the least significant bit signal of the address signal for reading out the memories 11A and 11B can be used. The lowest bit signal of the address signal matches the frequency of the carrier component of the balanced modulation signals Sa and Sb, and this brightness modulation signal is transmitted to the amplifier 17C, the DC blocking means 17D and the resonator 17E.
By supplying the signal to the brightness modulation terminal G of the cathode ray tube display 16 through the antenna 1, one polarity component of the signal components received by the antenna 1 is erased, and only the image projected by the one polarity component is displayed. . At this time, the image changes from a propeller shape to a cardioid shape, and the direction of arrival of the radio waves is determined by the direction of the cardioid. 17F is a polarity setting circuit that sets the polarity of the brightness modulation signal for sense determination.
The polarity of the brightness modulation signal is selected by the signal applied to the input terminal 17A of the polarity setting circuit 17F. This selection of polarity is determined in advance by the arrangement of the receiving antenna 1 and the sense antenna 5, and once determined at the time of installation, it is not changed thereafter.

"Operation" According to the configuration of the present invention described above, the memory 11A
Since the amplitude data of the sine wave and cosine wave amplitude modulated pulses are read out alternately from the DA converters 13A and 11B together with the zero amplitude data, the amplitude data of the sine wave and cosine wave amplitude modulation pulses are read out from the DA converters 13A and 13B in a sinusoidal manner as shown in FIGS. 2A and 2B. A modulated amplitude modulated pulse Pa and an amplitude modulated pulse Pb whose amplitude is modulated in a cosine wave shape can be obtained.

In the absence of a received signal, the operational amplifier 19
From each reference voltage terminal of DA converter 13A, 13B
Since a constant bias voltage -E _B is applied to REF, the amplitude modulation pulses Pa and Pb output from the DA converters 13A and 13B have sine wave and cosine wave amplitudes synchronized with the rotation of the goniometer. (See time points T ₀ to _{T 1} in FIG. 3 D and F) These amplitude modulated pulses Pa and Pb are passed through the DC blocking means 10A and 1
0B, the balanced modulation signal Sa (third
Figure E) and a balanced modulation signal Sb (Figure 3G) can be obtained. Therefore, the balanced modulation signals Sa and Sb are transmitted to the cathode ray tube display 1 through the resonators 15A and 15B.
6, a circle with a radius determined by the bias voltage _-EB is drawn on the tube surface of the cathode ray tube display 16, as shown in FIG. That is, in a state where there is no received signal, the signals at times _T0 to _T1 shown in FIGS. 3E and G are given as display signals, and a display image as shown in FIG. 4 is obtained. If the resonators 15A and 15B are not provided, the carrier signals of the balanced modulation signals Sa and Sb will be rectangular waveforms and will be given to the X and Y axes.
Because the speed at which the electron beam is deflected from one side to the other is fast, a circle is drawn with no brightness inside. When such a display method is adopted, the resonators 15A and 15B are not required.

On the other hand, for example, if a radio wave arrives from a direction deviated by 90 degrees from the direction of the ship's course, the detected output signal of the detector 8 will have a waveform as shown at times T ₁ to _{T 2} in FIG. 3B. This detection output signal is sent to the operational amplifier 19.
As a result, a signal obtained by superimposing the detection output signal on the bias voltage -E _B is obtained at the output of the operational amplifier 19 as shown at time T ₁ to _{T 2} in FIG. 3C. This superimposed signal is transferred to DA converters 13A and 13B.
By applying the reference voltage to the reference voltage terminal REF, the DA converters 13A and 13B output the voltage at time T ₁ shown in FIG. 3 D and F.
Amplitude modulated pulses Pa′ and Pb′ modulated to amplitudes as shown in ~T ₂ are obtained. This amplitude modulated pulse
By supplying Pa' and Pb' to the resonators 15A and 15B, the resonators 15A and 15B are
Balanced modulation signals Sa′ and Sb′ shown in are obtained. These balanced modulation signals Sa' and Sb' are
By applying this to the axis and Y axis, a propeller-shaped image as shown in FIG. 5 appears. In other words, when radio waves arrive and there is a received signal, E and G in Figure 3
The signals at times T ₁ to _{T 2} are applied as display signals to the cathode ray tube display 16, and a display image as shown in FIG. 5 is obtained. As usual, a sense signal is added to this propeller-shaped image to determine the direction of arrival of the radio waves.

"Effects of the Invention" As explained above, according to the present invention, by changing the bias voltage applied to the operational amplifier 19, the reference voltage of the DA converters 13A and 13B is changed, and the circle displayed when there is no signal is The diameter can be adjusted.

Here, in particular, the DA converter is manufactured so that the relationship between the change in the reference voltage and the amplitude of the analog output signal precisely matches without any instrumental error due to its purpose of use.

As a result, according to the structure of the present invention, even if the diameter of the circle displayed when there is no signal is changed, there will be no inconvenience such as the shape of the circle deforming into an ellipse, and a normal state can be obtained without adjustment. I can do it. This provides the advantage that the direction-finding device can be manufactured easily.

Further, according to the present invention, a circular image is displayed in a no-signal state, and a no-display state occurs in the event of a failure, so that it is possible to determine whether there is a failure or a no-signal state.

"Modified Embodiment" In the above description, the case where unipolar amplitude modulated pulse data is stored in the memory devices 11A and 11B is explained.
As shown in FIG.
It can also be stored in A and 11B. In this case, a balanced modulation signal can be obtained directly from the DA converters 13A, 13B, and the DC blocking means 10A,
Does not require 10B. However, DA converter 13
A, 13B requires a bipolar DA converter that can DA convert positive and negative digital signals.

As another example, as shown in FIG. 7, it may be configured to store amplitude modulated pulse data having, for example, a positive polarity DC component E _DC . This seventh
In the case of the figure, the DA converters 13A and 13B may have the function of DA converting a unipolar digital signal. In this case, the balanced modulation signals Sa and Sb shown in FIG. 2C and D can be obtained by taking out the DA conversion output via the DC blocking means 10A and 10B.

[Brief explanation of the drawing]

FIG. 1 is a system diagram for explaining one embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the main parts of the present invention, and FIG. 3 is the operation of the entire direction display device according to the present invention. Waveform diagram for explaining, 4th
5 and 5 are front views, and FIGS. 6 and 7 are front views for explaining examples of display results in the direction display device.
The figure is a waveform diagram for explaining a modified embodiment of the present invention. 1: Receiving antenna, 2: Goniometer, 3: Motor, 4: Drive circuit, 5: Sense antenna, 6
A, 6B: Sense switch, 7: Receiver, 8: Detector, 9: Direction display device, 11A, 11B: Memory device, 12: Address counter, 13A, 13B:
DA converter, 14A, 14B: amplifier, 15A,
15B: Resonator, 16: Cathode ray tube display, 17:
Sense determining circuit, 18: synchronous circuit, 19: operational amplifier, 21: phase adjustment means, 21A: preset counter, 21B: phase setter, Pa: amplitude modulation pulse with sine wave amplitude, Pb: cosine wave amplitude Amplitude modulated pulse with, Sb: two-phase balanced modulated signal.

Claims (1)

[Scope of Claims] 1A A pulse generator that generates a reference pulse synchronized with the rotation of a moving coil of a goniometer connected to a direction finding antenna and a clock pulse for each minute rotation angle of the moving coil, The sine wave and cosine wave data are read from the memory by the clock pulses output by the generator, and this read output is converted into analog by a pair of DA converters to create a two-phase balanced modulation signal, and this two-phase balanced modulation signal and the azimuth are converted into analog signals by a pair of DA converters. In an azimuth display device that displays the arrival direction of radio waves by combining with information, B. Adjacent pulses from the DA converter are separated by zero voltage, and the envelope of the peak value of the pulse is shaped like a sine wave or a cosine wave. An amplitude modulated pulse is output, and this amplitude modulated pulse is applied to a DC blocking means, which removes the DC component of the amplitude modulated pulse, so that a rectangular wave having the period of the amplitude modulated pulse has positive and negative symmetry. A two-phase balanced modulation signal that is amplitude-modulated is generated, this two-phase balanced modulation signal is given to a tuning circuit, the rectangular wave signal that makes up the balanced modulation signal is converted to a sine wave, and the rectangular wave signal that is made up of this sine wave is C is configured to provide a two-phase balanced modulation signal to the display, and also provides a reception signal and an analog subtraction signal of a constant bias voltage to the reference voltage terminals of the pair of DA converters, and when there is no signal, the pair of DA converters The amplitude of the analog signal output from the converter is set to the maximum value determined by the value of the constant bias voltage, and the analog signal with the maximum amplitude is used to display a circular image representing a no-signal state on the display. A direction display device characterized by comprising: