JPS61233385A - Echo detector - Google Patents

Abstract

PURPOSE:To detect even a detection signal of low level by discriminating signal pulses and a noise from each other according as the pulse width of the detection signal is longer than a prescribed value or not. CONSTITUTION:A discriminating means 34 discriminates whether the pulse width of each pulse in a received signal is longer than the prescribed value or not, and the signal is supplied to a gate 35 if it is discriminated that this pulse width is longer than the prescribed value. The output of an A/D converter 14 is delayed in a delay circuit 36 by a time corresponding to the delay required for discrimination of the means 34 and is supplied to the gate 35. Only the part, where it is discriminated by the means 34 that the pulse width is longer than the prescribed value, of the output signal of the converter 14 passes gate 35, but the other parts where the pulse width is not longer than the prescribed value are eliminated as a noise. The output of the gate 35 is supplied to a buffer memory 15 to take out a signal. Thus, even a buried signal whose level is lower than the noise level can be detected, and the noise is eliminated surely.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is applicable to radar, sonar, fish detection, etc.3;
Emit wave pulses such as radio wave pulses and ultrasonic pulses,
That reflected wave! It receives a digital signal C; converts it and stores it in a memory, reads out the memory in synchronization with the scanning of a scanning display, and displays the read signal as an image on a scanning display. related.

``Prior art'' For example, in a radar, as shown in FIG.
A pulsed radio wave is radiated from the antenna 12 in the directional direction by the transmission pulse input from the antenna 1, and the reflected wave is received by the antenna 12 and further amplified and detected by the receiver 13.

The output of the receiver 13 is sampled by the AD converter 141- at a certain period, and more specifically, it is sampled at a sampling period corresponding to the detection range (each sample value is converted into a digital signal of one bit or a plurality of fixed bits). The converted digital signal is stored in a buffer memory 15.
are stored sequentially. The stored detection signal, i.e. the received signal, is read out in the blanking section ζ: of the scanning display 16 and stored in the buffer memory 15 (-) and is stored in the main memory 17.
will be forwarded to. The main memory 17 can store pixels corresponding to each position on the display surface (2) of the scanning display 16, and synchronizes with the scanning of the scanning display 16.
7 is read out, and the read output is, for example, converted into a color signal by the color converter 18 and supplied as a display signal that displays a color according to the value of the digital signal of the color display 16C.

The scanning of the display surface of the scanning display 161 is mainly carried out by concentric circular scanning (-scanning) and horizontal/vertical scanning, and the scanning method C;
Therefore, writing to and reading from the main memory 17C differs. Spiral scanning (for example, patent application 1987)
-224464 "Soda Detector" (The main memory 17 is scanned for writing, reading, and displaying.
Method ζ as described in No. 5361 "Coordinate transformation display device":
Therefore, it is done. In either case (in the case of radar), the pointing direction of the antenna 12 is rotated by the motor 19g, and an angular pulse is generated from the ζ-angle pulse generator 21 at every fixed angle, and this is transmitted to the write address generator 2.
2, and the write address in data transfer 1: from the buffer memory 15 to the main memory 17 is transferred from the write address generator 22 through the selector 23Y to the main memory 17 (
Two are given. A read address generator 24 is also provided, and the read address generator 24 generates a scanning signal to perform spiral scanning or horizontal/vertical scanning on the scanning display 16I, and also generates a read address. The address from the device 24 is supplied to the main memory 17 through the selector 23, and the main memory 17 is connected to the scanning display 1.
It is read out in synchronization with the scanning of No. 6.

[Problems to be Solved by the Invention] Conventional techniques (in the second case, the fifth
As shown in Figure AC 3; level L1 or higher in the received signal is a signal pulse, r=1J2 is lower than noise, and the level Lt
jd is taken out and stored in the main memory 17 (-). Therefore, even noise that exceeds the I level L1Y is taken out as a signal pulse, as shown by 31 in FIG. 5A.
Furthermore, signal pulses 32 below the level LIJ2 are removed as noise.

Therefore, reflected signals from far away have low levels, are removed as noise, and are not displayed.

The noise 31 is a narrow pulse, and when directly displayed, it appears as a minute dot on the display screen and is barely noticeable. However, note the received signal +J
(If ≦2, then the narrow fiber 31 is equivalent to one pixel of the display screen, as shown in FIG. 5Bc.) This noise component becomes conspicuous.Particularly, if a display device 16 with a limited number of scanning lines is used, the narrow noise 41', j' will be enlarged. Therefore, if there are many noise components, a large amount of noise will appear on the ammonium screen, and a small signal pulse such as one pixel will be easily overlooked.

For example, if the special electric detection range is long, the length is 5.
Reflective objects at 0 m are also displayed as one pixel, and short noises are also displayed as one pixel, making it difficult to distinguish between noise and signals. The reflected signal from the object has a lower level, and therefore the threshold level L1'fJ
r: You want to set it low, but if you set it low, the noise will be noticeable, and the presence of signal pulses will generally be transcribed as small on a wide screen, making it difficult to see. Even if there are signals with a relatively large level difference (for example, when two signals are displayed with different colors, ≦2), even a signal with a large reflection level may be difficult to read when displayed on the order of one pixel.

SUMMARY OF THE INVENTION An object of the present invention is to provide an echo detector that can detect even low-level signals, remove noise, and provide an easy-to-read display.

``Means for Solving Problems'' This invention uses a determining means (2) to determine whether the length of each pulse in a received signal is equal to or greater than a predetermined value, and only those determined to be equal to or greater than the predetermined value are extracted as signals. Therefore, the signal is extracted as a signal pulse by means (2), and those below a predetermined value are removed as noise, and only the signal extracted by this signal extraction means is stored as a digital signal in the memory (= after being stored, the signal is displayed on the scanning display). Supplied as.

"Example" Figure 1 shows an example of an echo detection device according to the present invention (2).
Components corresponding to those in FIG. 4 are given the same reference numerals, and only essential parts of the invention are shown. In this invention, a determining means 34 is provided. The output of the receiver 13 is branched and supplied to the determining means 34 (:), and it is determined in the determining means 346 whether or not the pulse width of each pulse in the received signal is greater than or equal to a predetermined value. , for example, a high level is output and this is supplied to the gate 35 +-.DA converter 14
The output of the necessary (in response to the delay circuit 36'Y is supplied to the gate 35). The gate 35 is therefore connected to the AD converter 1.
Only the portions determined by the determining means 34 during the output of No. 4 to have pulse widths equal to or greater than a predetermined value are passed through, and pulse widths equal to or less than the predetermined value are removed as noise. The output of gate 35 is supplied to buffer memory 15.

In other words, the gate 35 constitutes a signal extraction means.

In this determination means 34, for example, as shown in FIG. , as shown in FIG. 2B (2). It is formed into a pulse waveform. It is determined whether the width of each pulse is equal to or greater than a predetermined value, and only the signal pulse corresponding to the portion determined to be equal to or greater than the predetermined value is outputted. Therefore, in FIG. 2, not only the high-level signal 37 but also the low-level signal 32 is extracted as shown in FIG. Therefore, the noise 31 whose level is higher than Ll is also removed as shown in FIG. 2C (:) without being treated as a signal pulse.

In Fig. 1 (-, the delay of the delay circuit 36!) is correctly and easily performed (-), the output of the AD converter 14, that is, the digital signal (-) is followed by the converted signal ζ, and the output is supplied to the gate 35. In the case where digital signal traces are
Of the converted signals, as shown in Figure 2 CC, a digital signal corresponding to a signal pulse 37°32 with a pulse width greater than a predetermined value is supplied to the buffer memory 15, and the blank portion is removed and stored as 0 in the buffer memory. 15.

In addition, like this (- when using a digital delay circuit (-
However, analog delay circuits should be used.
A delay circuit and an analog gate circuit are inserted in the front stage of the D converter 14, and the analog gate circuit passes signals determined to have a pulse width greater than or equal to a predetermined pulse width, and only the signals that have passed are sent to the AD converter 14+. = Therefore, it is also possible to convert it into a digital signal.

A specific example of the determining means 34 is shown in FIG. Further, FIG. 3 ζ 2 shows a case where the AD converter 14 is constructed using a part of this determining means 34 . That is, the output of the receiver 13 is supplied to the comparator 38 in the determining means 34, and the threshold value L
0, the level portion thicker than Lo is set to high level, and the portion smaller than this is set to low level; that is, the binary digital signal (-converted) as shown in Figure 2B (2) is compared. The output of the shift register 39 is supplied to the data terminal 1) (- and is also supplied to the clear terminal C) (U) through the C inverter 41. The clock terminal ckl2 of the shift register 39 is supplied with a clock. , this clock has a period considerably smaller than the pulse width to be discriminated, for example, 40 nanoseconds, and the minimum pulse width to be detected as a signal pulse is 32
0 nanosecond, and the 8th bit for shift register 39! will be output.

Therefore, the pulse shown in FIG.
When 1-1 is input, a high level is shifted in the shift register 39 from the rising edge of the clock pulse.
If the pulse width is shorter than 320 nanoseconds, the inverter 4
1 output (Y), that is, the shift register 39 is cleared at the falling edge of that pulse. However, in this example (
- In the case where the input pulse to the shift register 391 is longer than 320 nanoseconds, an output is obtained from the shift register 39, and this output is added with 280 nanoseconds in the additional circuit 43.
(-Therefore, the signal length is added by the shortened length, and the output of the gate circuit 43 is supplied to the gate circuit 35a and 35b as the output of the determination means 34, and also supplied to the encoder 44-2 at the same time. Ru.

On the other hand, the output of the receiver 13 is also supplied to comparators 45, 46, and the comparators 45, 46 are connected to each other as shown in FIG.
-Reference level L1. L2 and the signal are compared. These reference levels L1. When the signal level is higher than L2, a high level is outputted from the comparators 45 and 46, and when it is lower, a low level is outputted. The outputs of the comparators 45 and 46 are sent to the delay circuit 36a.

36bY is supplied to gates 35 at 35bc. The delay circuits 36a and 36b provide a delay corresponding to the delay in the determining means 34.

The outputs of the gates 35a and 35b are supplied to the encoder 44. In the encoder 441-, for example, the determination means 3
If the output of gate 4 is high level and the output of gate 35 a + 35b is low level, set "0.1" to gate 35.
If the output of only gate a is high level, set it to 1.0j, and if both gates 35a and 35b are at high level, set it to 1.1.
” are output respectively.

For example, on the display 16+-, the code "0.1" is green;
@1,0" is displayed in yellow, and "1.1" is displayed in red. The output of this encoder 44 is supplied to the buffer memory 15.

□ This invention is applicable not only to radar, but also to sonar, fish finder, and special equipment (displaying the 21 detection signal as one display line and arranging the display line in parallel in the order of the oldest detection signal). , each time a new detection signal is obtained, the display line is sequentially shifted toward the older one in the array direction, and the display is similar to recording on recording paper. This is not limited to the case where one that stores information for one screen of the display 16 is used.
No. 9-155221 "Echo detector"C; a device ζ- as shown is also applicable. In other words, the output of the receiver 13 is converted into a digital signal by the AD converter 14 and sent to the buffer memory 15 (-
The buffer memory 15 is read out under the control of the control unit 61, and the sweep signal generator is activated by a signal synchronized with the reading by the control unit 61, a signal from the angular pulse generator 21 indicating the pointing direction of the antenna 12, etc. 62 is driven, and this sweep signal generator 62 (:Therefore, the scanning display 16 is swept in the angular direction (two directions) corresponding to the directional direction of the antenna 12, and the output read from the memory 15 at this time is sent to the DAf converter 63. (2) An analog signal (- is converted and supplied as a display signal to the scanning display 16 (-).

In this way, the scanning display 1 will be displayed regardless of the detection range.
6, and the configuration for this purpose becomes simple. Unlike the main memory shown in FIG. 4C, this memory 15 can store one detection signal as a relatively large number of pixels without being affected by the number of scanning lines on the display screen. Even in this case, there is a risk that narrow noise that would not normally be one bit may be magnified and displayed as one bit, and there is also a risk that a small signal of one bit may be overlooked.
:Thus, these problems can be solved.

Also, in the above, a color display was used, but when using a black and white display! : This invention can also be applied.

"Effect of electric protection" As described above, according to the present invention, whether the pulse width in the detection signal is greater than or equal to a predetermined value (; therefore, signal pulses and noise are discriminated and only signal pulses are extracted; It can also detect hidden signals that are considered to be below the noise level, and since it uses memory, the noise will be enlarged and displayed unless the noise is removed reliably. Special C: It is difficult to see when a lot of noise is displayed. However, this can be reliably removed.Especially when the detection distance is long (secondarily, the level of the signal from a reflected object from a distance is low, and it is conventionally difficult to distinguish this from noise). However, according to this invention, this distinction can be made reliably.
Noise is removed even from small signals on the display screen, resulting in a sufficiently legible display. Note that the pulse width for detection as a signal pulse can be changed according to GIN, if necessary. For example, in the example of Fig. 3 (-, shift register 3
By changing the shift stage at which the output of 9 is obtained, the criterion for the pulse width for determining signal pulses and noise can be changed. It is also desirable to change the reference level L0 for the comparator 38ζ2 so that it can be set to suit various situations. It is also possible to change or increase the number of conversion bits per sample of the AD converter so that more levels are determined and differentiated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of the essential parts of the echo detection device according to the present invention, Fig. 2 is a time chart for explaining its operation, and Fig. 3 is the determining means which is the essential part of the invention. 34 is a block diagram showing an example of an AD converter using the same, FIG. 4 is a block diagram showing the general configuration of a radar, and FIG. 5 is a diagram showing the conventional distinction between signal pulses and noise. A time chart for explanation and FIG. 6 is a block diagram showing a schematic configuration of a conventional pond type radar. 11: transmitter, 12: antenna, 13: receiver, 14:
AD converter, 15: buffer memory, 16: scanning display, 17: king memory, 18: color converter, 34: determination means, 35: gate as signal extraction means, 36: delay circuit. Patent Applicant Koden Manufacturing Co., Ltd. Agent Taku Kusano Procedural Amendment (
(Spontaneous) December 27, 1985 1, Display of the case Tokuken Showa 60-748852, Title of the invention Echo detector 3, Person making the amendment Relationship to the case Patent applicant Koden Seisakusho 4, Agent Tokyo 4-2-21 Shinjuku, Shinjuku-ku
Sumo Building 5, subject of amendment Detailed Description of the Invention and Drawing 6, Contents of Amendment (1) On page 3, line 6 of the specification, "color display 16" is corrected to "scanning display 16". (3) In the same book, page 12, line 1, ``When the output is at a high level,'' is corrected to ``When the output is at a high level.'' (4) In the same book, page 12, line 4, ``Only two gates 35a and 35b'' is corrected to ``Both gates 35a and 35b''. (5) Add the numeral ``34'' to Figure 3 as shown in red on the attached copy. that's all

Claims (1)

[Claims] (1) Emit a wave pulse, receive the reflected wave, convert the received signal to a digital signal with an AD converter, store the digital signal in memory, and synchronize the memory with the scanning of the scanning display. In the echo detection device, the readout signal is supplied as a display signal to the scanning type display device to display it as an image, and it is determined whether the length of each pulse in the received signal is equal to or greater than a predetermined value. What is claimed is: 1. An echo detection device comprising: a determination means for outputting pulses determined by the determination means to be equal to or greater than a predetermined value as signal pulses, and a signal extraction means for removing pulses equal to or less than the predetermined value as noise.