JPS604876A - Ppi display apparatus - Google Patents

Abstract

PURPOSE:To attain to enhance the accuracy and stability of PPI display by enhancing operation accuracy, by generating an antenna angle signal, a set azimuth signal and a sine/cosine signal corresponding to both signals by digital treatment. CONSTITUTION:The antenna angle signal from a transmitter 10 is converted by an A/D converter 11 and the converted signal is applied to a change-over device 17 while receives the addition of an angle correcting signal by an adder 12. On he other hand, binary azimuth angle data set to a transmitter 13 is imparted to the change-over device 17 and a BCD converter 14 corresponding to the setting operation by a manipulator and the converted output is supplied to a LED numerical value display device 16. A control circuit 29 supplies a timing signal to the change-over device 17 and the other predetermined circuit. In this case, the selective output of the change-over device 17 is supplied to sine and cosine signal generators 18, 19 and signals of a sine value and a cosine value respectively corresponding to the angle data and an electron azimuth angle are selected through latches 20a-20d by a selector 21 to be respectively held through switches 23a-23d by circuits 24a-24d after converted by a D/A converter 22 while sweep signals are generated on the basis of each hold value by generators 26a, 26b to be supplied to orthogonal deflection coils 28a, 28b.

Description

[Detailed Description of the Invention] a. Industrial Field of Application The present invention is a method for displaying information from radar, sonar, etc. on a round OR screen using an electron beam (suspended) using a polar coordinate deflection method <PPl method. This invention relates to a PPI display device.

b. Prior art Conventionally, used for information display of radar, sonar, etc. 1]P
As a single display device, there is one shown in FIG. 1, for example.

In Fig. 1, 1 is an antenna angle transmitter, which usually uses a resolver etc. to generate a sine (
s i nθ1) and cosine (CaSO3) signals are generated. 2 is an electronic azimuth transmitter that transmits a setting azimuth signal for the azimuth line displayed on the CRT screen.
inθ2) and cosine (CaSO3), usually
A resolver or a sine/cosine generation potentiometer is used. The outputs of the antenna angle transmitter 1 and electronic direction transmitter 2 are input to signal switchers 3Δ and 3B, respectively, and the signal switchers 3Δ and 3B are supplied from the outside. It is switched in accordance with the switching control signal, and selects the sine and cosine signals of either the antenna angle transmitter 1 or the electronic azimuth transmitter 2, respectively, and supplies them to the sweep A3 light generators 4Δ and 4B.

The 4m signal generators 4△ and 4B integrate the sine and cosine signals as DC voltage signals supplied from the signal switchers 3△ and 3B and convert them into a sweep signal that changes in a sawtooth pattern to generate a sweep current. The deflection currents supplied to the amplifiers 5Δ and 5B and amplified by the sweep current amplifiers 5A and 5B are passed through the orthogonal deflection coils 5a and 6t of the CRT, respectively, and the polar coordinate deflection of the electron beam produces an image of radar, sonar, etc. or a set direction. Lines are displayed in PPI.

On the other hand, the sweep signal generators 4a and 4B receive an off-center control signal in the X-axis direction (left/right direction) and a Y-axis control signal from the outside, respectively.
It is provided with an off-center control signal in the axial direction and vertical direction, and has an off-center function that allows each sweep starting point of the antenna angle deflection signal or azimuth line sweep signal to be independently moved to any position on the CRT screen. . That is, by time-divisionally supplying the off-center control signal corresponding to the A-center of the antenna angle deflection signal and the azimuth line deflection signal in synchronization with the switching control signals supplied from the outside of the signal switching devices 3Δ and 313, The antenna information and the 1ω starting point of the azimuth line can be arbitrarily determined as Xγ.

However, in this conventional PPI display device, generation of sine and cosine signals corresponding to the antenna angle θ1 and generation of sine and cosine signals corresponding to the set azimuth angle θ2 of the azimuth line are performed in an analog manner. The accuracy of each sine and cosine signal is determined by the mechanical and electrical accuracy of a transmitter such as a resolver. It has been difficult to increase the resolution of targets detected by radar, sonar, etc. beyond a certain level.

In addition, there are various display methods for radar PPI display necks, such as r l-I E A D U P j
When displaying an image with the bow of the ship called directly above the PP1 screen, and when displaying an image with the north direction on the map called r NORT 1-1 kJ l”J set directly above the PP1 screen. case and further r COtJ R
The set course of the ship, called S EUPJ, is 1-'
There are cases where an image is displayed directly above both sides of the PI.

Therefore, in the case of r N OR T l - I U P J, the deviation angle between the own ship's heading and the north direction is detected and the radar antenna angle, which changes from moment to moment, is constantly corrected by the deviation angle. The display must be covered, as well as the RC
In the case of OR8E UPJ, it is necessary to detect the deviation angle between the own ship's bow direction and the set course, and to constantly correct and display the deviation angle on the radar antenna angle.

However, it is difficult to correct these deviation angles in the antenna angle signal, which is a conventional analog signal, and to obtain sine and cosine signals corresponding to the corrected angles.
There were also problems in terms of accuracy and cost (-).

Furthermore, since all signal processing is analog, it is easily affected by temperature, and of course electrical humidity compensation is provided, but when used in relatively harsh environments such as ships, temperature Even with compensation, it was not possible to completely eliminate the influence of temperature, and there was a problem that stability was compromised.

C1 Purpose of the Invention A PPI display device that displays information by sweeping an m beam on a round CRT screen using a polar coordinate deflection method.
rNOR1'l-I LJPJ and rcOUR3E U
It is possible to easily realize correction equations for deviation angles in order to obtain various display methods such as The present invention aims to provide a PPI display device that is capable of displaying PF-'I with improved temperature accuracy and has excellent stability and is almost unaffected by electrical noise. purpose.

d1 Summary of the Invention In order to achieve this object, the present invention provides methods for generating an antenna angle, generating a set azimuth angle signal for setting an azimuth line, and correcting the antenna angle by adding a deviation angle to the antenna angle. generation, and further these antenna angles or setting forces 4<1
The entire generation of sine and cosine signals corresponding to each angle signal is performed by digital signal processing.

e. Embodiment FIG. 2 is a block diagram showing an embodiment of the present invention.

First, to explain the configuration, 10 is an antenna angle transmitter, for example, a synchro transmitter or a shaft encoder (
A transmitter such as an angle encoder) is used. Reference numeral 11 denotes a digital converter that converts the angle signal 01 digitally output from the antenna angle transmitter 10 according to the antenna angle into a binary digital angle signal. As this digital converter 11, a synchro digital converter is used when the antenna angle transmitter 10 is a synchro transmitter, and a pulse counter is used when the antenna angle transmitter 10 is an incremental one-way shaft encoder. used.

Here, if the number of bits is set to 12 bits as a binary digital angle signal converted by the digital converter 11, it will have a correspondence relationship between binary angle bits and weight angles as shown in Table 1 below. .

Table 1 As is clear from Table 1, the most significant bit MSBa 1 of the digital angle signal represents 180', and the following 2
The weight of bit a2 is reduced by half to 90', and the last 12th bit is the most significant bit, S13a12 is 0, 0.
It corresponds to 87890625°.

The antenna angle θ1 converted into a digital angle signal consisting of binary bits in Table 1 is, for example, T I
741-883Δ, 7418283, etc., in a required number (3 in this example)).

Further, in this example, the antenna correction angle signal Δθ, which is similarly composed of binary 12 bits 1 to 1, is supplied to the other input of the digital adder 12.

This antenna correction angle supplement i1E signal Δθ is, for example, if you want to display the radar display with the north direction, called rNORTl-IUl)J, directly above the PPI. It is the angle of deviation between the gyro compass and the gyro compass.

In addition, if the screen is displayed with the set ship's course, called l' COURS E U IC, 1, directly above the PPI, the change between the own ship's bow force and the set course is displayed. This is the difference angle, and it is calculated by measuring the ship's heading from the north using the gyro compass, which serves as a reference, and the set course heading from the north, and calculating the difference between them to obtain 1q.

Of course, the usual r l-I E A D U I-' j
When displaying the screen with the ship's heading directly above 1DPI, there is no need for correction, so change the correction angle to △θ.
=0.

Furthermore, in the case of displaying only r HE A D U I) J, the digital adder 12 may be omitted and the output of the digital converter 11 may be directly supplied to the digital signal switch 17.

In this manner, the digital adder 12 obtains the sum of the two input angles (θ1+Δθ), and this signal is supplied to one of the digital signal switchers 17. The output θ2 from the electronic azimuth angle digital transmitter 13 is also applied to the other input of the digital signal switch 17, to which the output (θ1+Δθ) from the digital adder 12 is applied to one input.

Here, the electronic azimuth angle digital transmitter 13 digitally generates the set azimuth of the azimuth line to be displayed on the CR double screen, and can be configured with, for example, a binary addition/subtraction counter, based on the azimuth setting operation. By adding or subtracting one pulse according to the addition or subtraction operation signal, a digital azimuth representing the desired azimuth θ2 is generated as the count value of the addition/subtraction counter.

The digital data of the azimuth angle θ2 generated by the electronic azimuth angle digital transmitter 13 is also transmitted to the digital converter 11 which outputs the digital angle signal of the antenna angle.
Similarly to digital data, for example, 1 not shown in Table 1 above.
It becomes binary digital data of 2 bits 1~.

The output of the electronic azimuth angle digital transmitter 13 is simultaneously supplied to the other input of the digital signal switch 17.
It is also supplied to a binary/BCD converter 1/I provided for numerically displaying the azimuth angle θ2 set in the electronic azimuth angle digital transmitter 13. Binary/BCD converter 14 [
J, for example, can be composed of P R0M memory, P
Digital data representing the set azimuth angle θ2 from the electronic azimuth angle digital transmitter 13 is used as the address signal of the ROM memory, and the BCD code representing the azimuth angle stored in advance at the address corresponding to the J digital data is used as the electronic azimuth. The configuration is such that Jζ is read from the address data θ2 from the angle digital oscillator 13. Binary/BCD converter 1/IJ: The read B C1,') code representing the set azimuth angle θ2 is latched at fixed time intervals by the data latch circuit 15, and the LED numerical display 16 displays, for example, 0.
．． 1 unit angle, zunachi l'ooo, oj to I'35
The set azimuth angle θ2 is displayed numerically by driving the display segment 1 using LEDs.

In this way, the set azimuth angle θ2 of the azimuth line is numerically displayed in real time on the IED numerical display 16 based on the binary data from the electronic azimuth angle 1a digital transmitter 13. It is possible to set an arbitrary azimuth angle θ2 while looking at the display on the device 16.

On the other hand, the digital data representing the antenna angle (θ1+80) supplied to the digital signal switch 17 and the digital data representing the azimuth angle θ2 of the azimuth line are converted into digital signals t, 7J by externally supplied switching control signals. When the converter 17 operates, one of the incoming data is read out and supplied to the sine generator 18 and the cosine generator 19. The sine generator 18 and the cosine generator 19 can be configured with a PROM memory, for example, like the binary/BCD converter 14, and can be configured with digital data of the antenna angle (θ1+Δθ) or the azimuth supplied from the digital signal switch 17. Set the digital value of angle θ2 as address data,
The sine and cosine values stored in advance in the PROM corresponding to the address data are read out by address designation using each digital data, and sine digital data and cosine digital data are output, respectively.

Data latch circuits 20a, 20b, 20c, and 20d latch sine and cosine value data (including sign and numerical data) from the sine generator 18 and cosine generator 19, respectively.

That is, the sine digital data read out from the sine generator 18 is sent to the data latch circuit 20a.

Alternatively, it is latched to 20b and the value is held.

Similarly, cosine digital data read out from one cosine generator is latched by the data latch circuit 20C or 20b, and its numerical value is held. Data latch circuit 20
The outputs of a, 20b, 20c and 20d are respectively applied to a digital signal selector 21, and this digital signal selector 21 selects one of these four latch inputs and outputs it to the next stage. is supplied to the D/A converter 22 of. In this embodiment, the D/A converter 22 converts the digital data to the 12 pins 1 into an analog DC voltage with positive and negative polarities such as ±1V or ±5V.
/ Output J of A converter 22 is analog switch circuit 2
3a, 23b, 23c and 23d, respectively. The analog switch circuits 23a to 23d are elements that can take on two states, a conductive (ON) state or a non-conductive (OFF) state, depending on a control signal supplied from the outside, and when in a conductive state, the input positive, Negative DC voltage is output as is, while when non-conducting, no input voltage is output. In this way, the respective output voltage signals from the analog switch circuits 23a to 2ζ3d are connected to the corresponding one S/1 and the smoothing circuit 24a.

24, b, 21 and 24-d.

Here, the S/l-1 circuit is an abbreviation for sample-and-hold circuit, which samples the input voltage value supplied when the analog switch in the previous stage is conducting, takes in -C, and holds that value when the analog switch is not conducting ( Hold.

In this embodiment, as will be explained later, the human input signal is sampled during -1/4 of the cycle, and the remaining 3/4
I am trying to hold the period of . In addition, the smoothing circuit smoothes out the steep signal voltage changes that would occur on the output side when there is no smoothing circuit when there is a voltage difference ΔE = EN+1-EaJ between the previous input value EN and the current input value EH+1. The S/H and smoothing circuit 24 is a circuit for extracting a smoothly changing output signal, and each of these two circuits (a sample bold circuit and a smoothing circuit) is built in series.

S/1'' and the outputs of the smoothing circuits 24a and 24b are respectively supplied to an analog switch 25a, and similarly S/1-1
The outputs of smoothing circuits 24.0 and 24d are respectively supplied to analog switch 25b. Analog switch 25a
and 25b select one of the two input signals and output it to the output side. The outputs from the analog switches 25a and 25b are applied to sweep signal generators 26a and 26b, respectively, and are processed in a sawtooth manner by integrating signal voltages proportional to the sine and cosine that have already been converted from digital data to analog data and smoothed. It generates a sweep signal that changes to
and 271), the deflection current is supplied to each of the orthogonal deflection coils 28a and 28b of the CRT, and
Information based on the antenna angle (θ1 + Δθ) or set azimuth angle θ2 after 1 m of deflection of the electron beam with respect to the RT screen
The direction line to be marked is displayed.

Furthermore, an off-center control signal in the X-axis direction (left/right direction) and an off-center control signal in the Y-axis direction (up/down lj direction) are simultaneously supplied to the sweep signal generators 26a and 26b from the outside, respectively, for the antenna angles d5 and 7. The starting points of the sweep signal and the azimuth line sweep signal can be independently moved to arbitrary positions.

Next, the present invention in FIG. 2 will be described in detail with reference to the signal waveform diagram in FIG. 3.

First, an analog antenna angle signal from an antenna angle transmitter 10, for example a synchro transmitter, is sent to a digital converter 1.
1, e.g. in a sink [1 digital converter, 12
It is constantly converted into a binary angle signal θ'1 of pin 1-, which is applied to one input of the digital adder 12. Also,
Similarly, the other input of the digital adder 12 has a binary 1
Since 0 is supplied to the antenna correction angle signal consisting of two hits, the sum of these two signals (θ1+80) is always outputted to the output side of the digital adder 12.

On the other hand, in response to the setting operation by the operator to set the azimuth line in an arbitrary direction, the count value of the addition/subtraction counter changes by the increase/decrease operation signal to the electronic azimuth/angle digital generator 13. The binary digital data of the azimuth angle θ2 set in the azimuth angle digital transmitter 13 is binary /B
It is given as address data to the CD converter 14, and the BCD code corresponding to the address data is read out, latched by the data latch circuit 15 at fixed time intervals, and displayed numerically on the IEO numerical display 16. 16
Set an arbitrary azimuth angle by looking at the numerical display.

The set azimuth angle θ2 of the azimuth line set in the electronic azimuth angle digital transmitter 13 in this way is supplied to the binary digital digital signal switch 17 and the 11j control supplied from the timing control circuit 29. Signal e2 or C
/l, either the digital angle signal (θ1+Δθ) from the digital adder 12 or the digital azimuth signal θ2 from the electronic azimuth angle digital transmitter 13J is selected and output from the digital signal switch 17.

Now, in QFJ such as radar or sonar, the third-
A periodic trigger signal e1 as shown in FIG. 1 is generated, and radio waves and ultrasonic waves are periodically transmitted based on this.

When this trigger signal e1 is supplied to the timing control circuit 29, the timing control circuit 29 sequentially generates the above timing signals.

First, an amber angle selection signal e2 as shown in FIG. 3(2) is generated and supplied to the digital signal switch 17.

The digital signal switch 17 directly connects the digital adder 1
Select the input signal (θ1+Δθ) from 2 and output it.

Next, the timing control circuit 29 generates a latch signal e3 of the antenna angle sine/cosine as shown in FIG. 3(3), and supplies this to the data latch circuits 20a and 20C.

Then, the antenna angle signal @(θ1+Δθ) from the digital signal switch 17 is transmitted to the sine generator 18 and the cosine generator 1.
9 as address signals, and as a result, the sine generator 18 and cosine generator 19 read out the sine and cosine values corresponding to the address data (i.e. angle data), and these values are sent to the data latch circuit. 20a and 2
0c, respectively.

Next, the timing control circuit 29 generates an electronic azimuth angle selection signal e4 as shown in FIG. 3(4), and supplies this to the digital signal switch 17. Since the digital signal switch 17 immediately selects and outputs the input signal θ2 from the electronic azimuth angle digital transmitter 13, this signal θ2 is similarly given to the sine generator 18 and cosine generator 19 as address data, and the sine A sine value and a cosine value corresponding to the electronic azimuth angle θ2 are read from the generator 18 and the cosine generator 19.

Next, the timing control circuit 29 generates an electronic azimuth sine/cosine latch signal e5 as shown in FIG. 3(5), and supplies it to the data latch circuits 20+1 and 20d. Therefore, data latch circuits 20b and 20d respectively latch the sine and cosine values corresponding to the electronic azimuth θ2.

Two latch signals e from this timing control circuit 29
3 and e5, the two latch output signals latched by the data latch circuits 20a, 20C, 20b, and 20d change as shown in FIG. 3 (6) and (7). This shows that data 1 to 211 are latched after a certain period of time from trigger signal e1.

Subsequently, the timing control circuit 29 generates the antenna angle sine selection signal @e6 (FIG. 3(8)) and supplies it to the digital signal selector 21 and the analog [1] switch circuit 23a. As a result, digital data indicating the sine value of the antenna angle (01+Δθ) from the data latch circuit 20a is selected by the digital No. 15 selector 21, and this is
The voltage is converted into a no-analog voltage by the /A converter 22, and is then held as a non-pull voltage by S/11 and the smoothing circuit 24a via the analog switch circuit 23a, which has become conductive.

Next, the timing control circuit 29 generates an antenna cosine selection signal e7 as shown in FIG. , finally the antenna angle (θ1+
The ablog voltage indicating the cosine value of 80) is sampled and held.

Next, the timing control circuit 29 generates an electronic azimuth angle sine selection signal 8e8 as shown in FIG. The analog voltage is sampled and held in the smoothing circuit 24b without showing the sine value of the electron position angle θ2.

Next, the timing control circuit 29 generates an electronic azimuth angle cosine selection signal e9 as shown in FIG. An analog voltage representing the cosine value of the electronic azimuth 02 is sampled and held in the circuit 24d.

In this way, one bird periodically receives the antenna angle (θ1
+Δθ) and the respective sine and cosine values of the electronic azimuth θ2 are S/I-1 and the smoothing circuit 24a.

24C, 24b and 24. d is held, and this operation is repeated every time a signal is generated, and the changes in each cycle are smoothed out, so that the two sets of angles (θ1+△θ) and θ2 correspond to The analog sine and cosine values are always output to the S/H and smoothing circuits 24a to 24d.
It is output from

Next, the timing control circuit 29 is operated as shown in FIG. 3 (12) and (13).
An antenna angle a photographing selection signal et10 or an electronic azimuth angle sweep selection signal e10 is generated and supplied to analog switches 25a and 251j. Analog switch 25
When the antenna angle one-pulse selection signal e10 is supplied to a and 25b, S/l-1 and smoothing circuit 2
The sine and cosine values corresponding to the antenna angles (θ1 to 80) from 4a and 24c are selected and supplied to sweep signal generators 26a and 26b, and analog switches 25a and 25bk: electronic azimuth angle sweep. Selection signal e1
If 0 is supplied, the S/H and smoothing circuit 24
push/pull generators 268 and 2 from b and 24d, respectively;
6b.

Therefore, the sweep signal generators 26a and 26b generate sweep signals that vary in a sawtooth pattern by integrating the sine and cosine voltage signals, and provide the sweep signals to the sweep current amplifiers 27a and 27b. At this time, if external J:X and Y@off-center control signals are supplied to the sweep signal generators 26a and 26b, the sweep starting point is moved from the origin, which is the center of the CR7 screen, to an arbitrary position on the CRT. can be done.

The sweep current amplifiers 278 and 271) current amplify the input sweep signal and apply it to orthogonal deflection signals 28a and 2.
81), a sweep operation can be performed on CR'I-. Also, by stopping the antenna angle sweep signal once every N times (for example, 32 times) and replacing it with an electronic azimuth angle signal, the sweep of the electronic azimuth line is displayed simultaneously with the sweep of the antenna angle on the PP1 screen. be able to. Of course, normally, a video signal, a distance mark signal, etc. can be simultaneously displayed on P P 1.1- in synchronization with the antenna angle sweep signal.

10 Effects of the Invention Next, the present invention will be described in detail.In a PPI display device that displays information by sweeping an electron beam across a circular CRT screen using a polar coordinate deflection method, the generation of an antenna angle,
Generation of the setting azimuth signal for setting the azimuth line, r N
ORT 11 UPJ and rcOUR8E UPJ
Add the deviation angle to the antenna angle to obtain the display −(
Since the generation of the corrected antenna angle and the generation of sine and cosine signals corresponding to each signal of these antenna angles or set azimuth angles are all performed by digital signal processing, the signals used for digital calculation processing are By increasing the number of pins, for example 12 pins 1~, extremely high calculation precision can be obtained, and highly accurate radar images and PPI display of azimuth lines can be realized. .

Further, since the circuit elements used for digital signal processing can be commercially available ICs, the reliability is high and the cost can be reduced.

Furthermore, since it is a digital signal processing method, the effects of temperature and electrical noise that were problems with conventional analog signal processing methods are significantly reduced, and it is sufficiently stable even in harsh operating environments such as ships. Operation can be guaranteed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional device, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a timing chart showing operating signal waveforms of the embodiment of Fig. 2. It is. 10: Antenna angle oscillator 11: f digital converter 12: Digital adder 13: N-element azimuth angle digital oscillator 14: Binary/BCD converter 15.20a to 20d: Data ludge circuit 16:
LED numerical display 17: Digital signal switch 18: Sine generator 19: Cosine generator 21: Digital signal selector 22: D/Δ converter 23a to 23d: Analog switch circuit 2MIa to 2
4d: :S/l-1 and smoothing circuit 25a, 25b near I] switcher 26a, 26b: sweep signal generator 27a, 27b: 4m ffNQ amplifier 28a, 28b
: orthogonal deflection] -1'/L. 29: Timing control circuit patent applicant Tokyo Keiki Co., Ltd. Patent attorney Attorney in charge 1) Properly written spontaneously) August 12, 1981 Kazuo Wakasugi, Commissioner of the Japan Patent Office (Pa'・'1./, -゛1. Indication of the case Patent Application No. 1134.91 of 1982 2. Name of the invention PPr display device 3. Person making the amendment Relationship to the case Patent applicant address 2-chome, Minamikan IJ, University H, Tokyo 16-4b Name (338) Co., Ltd. 1 Tokyo Keiki 4, Substitute! Person Address 15-8 Nishi-Shimbashi 3-J, Minato-ku, Tokyo 4th floor, Nishi-Shimbashi Chuo Building 1-゛＼ , :41.-9 , mouth. 6. Contents of correction (1) Specification, page 8, line 18, “Sweep signal generator 4aJ
is corrected with [n bright signal generator 4AJ. (2) r20bJ on page 20, line 16 of the specification
Correct with dJ. (3) In the drawings, correct Figure 3 by adding it to a separate sheet. that's all

Claims (3)

[Claims] (1) In a PPI display device that displays information by sweeping an electron beam across a round CRT display screen using a polar coordinate deflection method, the set azimuth of the azimuth line to be displayed on the CR7 screen can be set in response to an arbitrary azimuth setting operation. A digital azimuth transmitter that generates a digital azimuth; an azimuth display means that converts the digital azimuth signal generated by the digital azimuth transmitter into a display code signal and displays the numerical value on the CRT screen or its vicinity; and an antenna. an antenna angle transmitter that generates an angle signal; a digital angle converter that converts the antenna angle signal from the antenna angle transmitter into a digital angle signal; an output of the digital azimuth transmitter and an output of the digital angle converter; a sine/cosine generator that generates sine and cosine output signals corresponding to the digital angle signal or digital azimuth signal selected by the signal switch; a data holder that outputs and holds sine and cosine values corresponding to angles and digital azimuths from the sine/cosine generator; and a data holder that sequentially selects the output of the data holder according to set timing. an analog/digital converter that converts the output of the signal selector into an analog signal; and an analog/digital converter that converts the output of the signal selector into an analog signal; a sample hold circuit; a smoothing circuit that smooths the output signal of the → non-pull bold circuit; and an analog signal switch that selects the output signal of the smoothing circuit according to a set timing. a sweep signal generator that generates an antenna angle sweep signal or an azimuth sweep signal proportional to the output signal of the analog signal switch; and a current amplification proportional to the output signal of the sweep signal generator to the orthogonal deflection coil of the CRT. A PPI display device comprising: a current amplifier that supplies a deflection current. (2) The sweep signal generator is characterized in that it is provided with an off-center means for varying the origin position of the antenna angle sweep signal and the azimuth line (suspension signal) by an external signal [Claim 1] PPI display device as described. (3) In a PPI display device that displays information by sweeping an electron beam across a round CRl-display screen using a polar coordinate deflection method, the setting azimuth of the azimuth line to be displayed on the CR king screen in response to an arbitrary azimuth setting operation. A digital azimuth transmitter that digitally generates the angle; and an azimuth display that converts the digital azimuth signal generated by the digital azimuth transmitter into a display code signal and numerically displays it on or near the CRT screen. means, an antenna angle transmitter for generating an antenna angle signal, a digital angle wave converter for converting the antenna angle signal from the antenna angle transmitter into a digital angle signal, and an output of the antenna angle converter. a digital adder that adjusts and outputs the signal and a required antenna correction angle; and a signal switch that selects the output of the digital azimuth transmitter and the output of the digital adder according to a set timing. a sine/cosine generator that generates sine and cosine output signal tones corresponding to the corrected digital antenna angle signal or digital azimuth signal selected by the signal switch; a data holder that outputs and holds sine and cosine values corresponding to each azimuth from the sine/cosine generator; and a signal selector that sequentially selects the output of the data holder according to a set timing. , an analog-to-digital converter that converts the output of the signal selector into an analog signal, and a ripple hold that samples and holds the output signal of the analog-to-digital converter through an analog switch that is sequentially selected according to a set timing. a smoothing circuit for smoothing the output signal of the one number hold circuit; an analog signal switch for selecting the output signal of the smoothing circuit according to a set timing; and a smoothing circuit for smoothing the output signal of the one number hold circuit; A sweep signal generator that generates an antenna angle sweep signal or an azimuth line sweep signal; and a current amplifier that supplies a deflection current to the orthogonal deflection coil of the CRT by current amplification proportional to the output signal of the sweep signal generator. A PPI display device characterized by: 4) The sweep signal generator according to claim 3, characterized in that the sweep signal generator is provided with an off-center means for varying one hemostasis position of the antenna angle sweep signal and the azimuth line sweep signal by an external signal. l) I)! Display device.