JPS61281986A - Echo detector - Google Patents

Abstract

PURPOSE:To make the display of a target easy to see by shaping a signal, which is detected with a level lower than that of a target signal buried in noise, to a pulse signal of square wave and extending the pulse width taken out from a sampling means thereafter to write it in a memory. CONSTITUTION:A waveform shaping circuit 31 shapes a reception signal Sc from a receiver 13 to output a pulse wave Sd. A sampling means 32 is provided with a D type flip flop 32A, an inverter 32B, and a gate 32C, and the pulse wave Sd and a clock pulse Sa of a clock terminal CK are given to the means 32 to output a pulse signal Se. A pulse width extending means 33 receives the signal Se from the means 32 and outputs a signal Be whose pulse width is extended. A buffer memory 15 receives the signal Pe, and one-bit components of the signal due to the target in the signal received by the memory 15 are added to data. Thus, the display of the target is distinguished easily because the target image is diplayed more large than the noise image.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is applicable to radio waves, such as radar, sonar, and fish finders.
Emit wave pulses such as sound waves and receive the reflected waves,
The present invention relates to an echo detection device that converts the received signal into a digital signal, supplies the digital signal to a scanning display as a display signal, and displays the position of a target on the display.

``Prior Art'' For example, in a radar, as shown in FIG. The output of the receiver 13 (hereinafter referred to as the received signal) is amplified and detected by the receiver 13.
The converter 14 samples at a constant period, more specifically, at a sampling period according to the detection range, and each sample value is converted into a plurality of digital signals with a certain number of bits, and the converted digital signal is stored in the buffer memory 15. Stored sequentially. buffer memo l71
The detection signal stored in 5, that is, the received signal, is scanned.
The data is read out during, for example, a blanking interval of the '-shaped display 16 and transferred to the main memory 17. The main memory 17 can store pixels corresponding to each position on the display surface of the scanning display 16, and the main memory 17 is read out in synchronization with the scanning of the scanning display 16, and the readout output is is converted into a color signal by a color converter 18 in the display 16, and displayed on the color display 16 as a color corresponding to the value of the digital signal.

For example, a digital signal is 2 bits, and these digital values are (0, O), (0, 1), (1, O), (
1, 1) are displayed as blue, green, yellow, and red, respectively.

Scanning of the display surface of the scanning display 16 is as follows:
A so-called spiral scanning method that scans concentrically and a horizontal/vertical scanning method are mainly used, and writing to the main memory 17 and successive output differ depending on the scanning method. In spiral scanning, for example, Japanese Patent Application No. 57-2
Writing, reading, and display scanning of the main memo IJ17 are performed as shown in No. 24464 "Radar Detection Device",
In addition, for horizontal and vertical scanning, for example, Utility Model Application No. 59-1353
This is done by a method as shown in No. 61 "Coordinate Transformation Display Device". In any case, in the case of radar, the pointing direction of the antenna 12 is rotated by the morph 19, and an angular pulse is generated from the angular pulse generator 21 at every fixed angle, and this is supplied to the write address generator 22.
A write address for data transfer from buffer memory 15 to main memory 1717 is given from write address generator 22 to main memory +J17 through selector 23.

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 16, and at the same time, the address from the read address generator 24 is generated. The signal is supplied to the main memory 1717 through the selector 23, and the main memory 17 is read out in synchronization with the scanning of the scanning display 16.

Additionally, the sampling period of the AD converter 14 and the clock period of the buffer memo IJ 15 are range-switched to a length proportional to the length or shortness of the display range of the detection distance, that is, the size of the distance range displayed on the display 16. By switching by the device 25, the number of memory bits of the buffer memory 15 and the main memory +717, that is, the number of memory addresses, remains the same.
It is configured so that the size of the distance range can be displayed accordingly.

"Problem to be Solved by the Invention" After sampling the received signal of the reflected signal obtained by the above-mentioned transmitted pulse and importing it into memory, the readout output is given to a display to indicate the position of the target. In the display echo detection device, the signal acquired by each sampling is associated with at least the minimum storage length of the memo IJ 17, that is, one address, and this is displayed as one pixel on the display 16. Therefore, even if the received signal is a narrow pulse-like noise signal (noise) such as white noise (Gaussian noise) or clock noise, if the signal is above a certain level, the noise will be Even though the pulse width is originally extremely small for one pixel, there is a problem in that when it is written to one address in the memory 17, it is displayed as a target having an area of one pixel.

As one method for solving this problem, as shown in FIG.
A possible method is to take out only II+Soi+Sea and input these signals into the main memory 17.

According to this method, it is certainly possible to remove noise No. 13 with a low level, that is, a lot of noise. However, as shown in FIG. 6 with the symbol SO4+sos, the signal having the same level as the low-level noise may include a reflected signal from a target object to be detected.

Therefore, in the method using this level difference, all signals below the set level are regarded as noise and removed, so there is an inconvenience that targets with low radio wave reflectance cannot be captured.

For this reason, it is possible to set the setting level L0 to a low value, but if the setting level L0 is set low, the noise removal rate will naturally decrease. As described above, the noise removal method using the level difference has a problem in that contradictory conditions exist between the noise removal rate and the target extraction rate.

The present invention provides an echo detection device having a noise removal means that solves this problem.

"Means for Solving the Problem" In this invention, the received signal is detected at a level lower than the target signal buried in the noise as described above, and is shaped into a rectangular pulse waveform. By providing a sampling means for sampling a signal with a function similar to a pulse width filter, and a pulse widening means for widening the pulse width of the signal extracted by the sampling means, and by providing a configuration for writing the widened signal to the memory. , which can solve the above problem.

[For production]

According to the configuration of the present invention, at the stage of waveform shaping, the signal of the target object is also captured, but the probability of capturing noise signals increases. However, since the noise signal is a narrow pulse, it is removed by a pulse width filter function at the sampling stage, leaving mainly the target signal, and this signal is widened, so the part removed by sampling is restored or emphasized. Emphasize the display of targets so that they are easy to see.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In this invention, a waveform shaping circuit 31 is provided on the output side of the receiver 13, and the waveform shaping circuit 31 shapes the received signal Sc shown in FIG. 2 outputted from the receiver 13 into the pulse wave Sd shown in the same figure. The waveform shaping circuit 31 can be constituted by a voltage comparator, for example, a digital comparator 31B, which compares the set voltage ER generated in the potentiometer 31A and the received signal Sc.

The voltage ER set to the potentiometer 31A in the waveform shaping circuit 31 is the conventional setting voltage L for noise removal.
Set to a voltage lower than 0. As a result, the waveform shaping circuit 31
The signals outputted from the target signal S, SZ, which are below the noise signal level, are the pulse waves Sd in Fig. 2.
S3 is also included, but Nl+Nz due to the noise signal,
N: +, "-" are also mixed and output.

The pulse wave Sd output from the waveform shaping circuit 31 is given to the sampling means 32. The sampling means 32 includes, for example, a D-type flip-flop 32A and an inverter 32.
B and a gate 32C.

In other words, the pulse wave S shown in FIG. 2 is output from the waveform shaping circuit 31 to the data input terminal of the D-type flip-flop 32A.
A negative logic pulse wave shown in d is given.

(In the figure, it is shown inverted to positive logic.) Separately, the pulse wave Sd is applied to the AND gate 32C through the inverter 32B. This signal from the output terminal of the D-type flip-flop 32A is applied to the other input terminal of the AND gate 32C. A clock pulse Sa having a period Tk shown in FIG. 2 is applied to the clock terminal Ck of the D-type flip-flop 32A, and the logic state of the pulse I'd is read every time it rises. The period Tk of this clock pulse Sa is set to a time width that is wider than the width of the target noise signal and narrower than the width of the transmission pulse St transmitted from the antenna 12.

In other words, by setting this time width, an output is not obtained with a narrow pulse input that is less than the set-up time width required for the operation of the D-type flip-flop 32A, and the noise signals N,, N,, etc. are removed. It has a pulse width filter function that restricts only the noise signal Nx having a pulse width longer than the set amplifier time that coincidentally coincides with the rise of this set up to appear on the output side.

Examples of each time value in the case of radar are as follows.

・Transmission pulse width T L −−−−−−−−−−−−
---500na・Period Tk of clock pulse Sa
・・・・・−−−−−1−−−−・−・−60ns・D
Cent-up time Ts of type Flipflossop 32A -・・−・−・−2003・
Output delay time Tdl of D-type flip-flop 32A -・-・・・・・・20
Output delay time Td2 of ns/inverter 32B...-----1----
- 5 ns Therefore, a signal like the pulse signal Se shown in FIG. 2 is obtained from the AND gate 32C. In the above specific example, if we look at the time relationship of each signal in detail, we can see that there is a case where the signal N× due to noise coincidentally coincides with the cent amplifier time Ts of the D-type flip-flop 32A, and a case where the signal N
When n does not match that, the time relationship of each signal is as shown in Figure 4, so the pulse width of the noise signal N appearing in the output signal Se of the AND gate 32C becomes small, and the pulse width due to the target object becomes smaller. The portion of the signal Sx whose starting edge is before the starting point of the clock pulse Sa is cut off, and when the trailing edge ends in the middle of the clock pulse Sa, it is extended to the end point of the relevant cycle of the clock pulse Sa at the stage of the signal Sd. However, at the stage of signal Se, it is shortened to the same point as the original signal Sd.

This pulse signal Se is a rising signal Sd output from the waveform shaping circuit 31 in synchronization with the rising edge of the clock signal Sa applied to the clock terminal Ck of the D-type flip-flop 32A.
It becomes a pulse waveform that falls in synchronization with the rise of .

Here, the period Tk of the clock pulse Sa, that is, the sampling period is always constant, which is different from the sampling method of the conventional AD converter 14.

On the other hand, the period Tr of the clock pulse Sr of the buffer register 15 is changed in proportion to the length or shortness of the range set by the range switch 25, as in the conventional case. The period Tr in the shortest range is made to match the period Tk.

Therefore, the ranges of the range selector 25 are now 0.5 miles, 1 mile, 2 miles, 4 miles, 8 miles, and 16 miles.
If there are 6 stages of miles, up to a range of 2 miles, even if the signal Se is input as is to the buffer memory 15, the signals S,, S,, - due to the target object will be the minimum 2 bits of the buffer memory 15. There is a signal width that extends over the above range, and it can be confirmed as an image of the target object on the image screen of the display 16, but
At a range of 4 miles or more, this width becomes only 1 bit, and on the other hand, the signal Nx due to noise also becomes 1 bit, making it difficult to distinguish between the target and the noise on the video screen. A configuration is provided in which only the target signal is widened.

The output pulse signal Se of the sampling means 32 is given to the pulse widening means 33. This pulse widening means 33 can be composed of a shift register 33A and an OR gate 33B. A clock Pa having a period Tb four times as wide as the sampling period Tk of the sampling means 32 is applied to the clock terminal Ck of the shift register 33A as shown in FIG. The shift register 33A reads the pulse wave Se applied to the data input terminal every time this clock Pa rises, and outputs from the output terminal Ql the logic state of the read data Pc delayed by one clock.
The output terminal Q2 reads this at the next rising edge of the clock and outputs Pd which is the logical state of the human input signal delayed by two clocks.

Therefore, pulses Pc and Pa as shown in FIG. 3 are output from the output terminals Q and Q2 of the shift register 33A.

This shift register 33A includes a D-type flip-flop 3
Since it is constructed by connecting multiple circuit elements similar to 2A in series, the signal Nx due to noise has a width of less than seven nodes up time, so a shift operation cannot be performed, and the terminal Q + ,
A signal corresponding to this noise signal Nx does not appear in Qt.

Output pulses Pc and Pd of output terminals Q1 and 02 of shift register 33A and input pulse S of shift register 33A
By applying e to the OR gate 33B and calculating the logical sum of these, a signal Pe. whose pulse width has been expanded as shown in FIG. 3 can be obtained. Each pulse width of this pulse Pe is such that the width of the back noise signal Nx of the pulse Se output from the waveform shaping circuit 31 remains unchanged, and only the pulse width of the part of is at least two periods of clock pulse Pa, exactly 8X
This means that the Trl time is added. In order to operate the pulse widening means 33 and the sampling means 32 when the range is set to 4 miles or more, a control signal output in conjunction with the range switch 25 is applied to the clear terminal CL. Then, in the range in which this widening means is operating, for example, the 4 mile range, the period T' of the clock pulse S' of the buffer memory 15 is set to 8XTk, so the data Db taken into the bumper memory IJ15 is As shown in Figure 3, the signal Nx due to noise does not become data of more than 1 bit (1 clock), and only the signal SI+ Sz, ``-...'' due to the target object becomes 1.
The data will be an additional bit, and the data will never be less than 2 bits. In the above explanation, the D-type flip-flop 32A of the sampling means 32 is assumed to be one stage, but by connecting it in two stages as shown in FIG. 7, the signals sr and Se can be changed to the signals Sf2 and Se2 in FIG. It is also possible to remove the signal Nx due to noise at this stage. Furthermore, the third point is that similar results can be obtained without using the output Pc of the shift register 33A.
It will be easier to understand from the diagram.

Furthermore, when the AD converter 14 has multiple levels (multiple bit levels) and a color-converted image is displayed, the lowest level among the multiple levels is selected by the sampling means 32. The same operation can be performed by configuring the device to take in data through the pulse widening means 33, and to take in data at higher levels in the same manner as in the prior art.

"Operations and Effects of the Invention" According to the present invention, the above-described pulse width filter function in the sampling means makes it possible to detect target signals below the noise level and remove narrow noise signals. By using the pulse widening means, even if there is a signal that has passed through the sampling means, only the target signal is added by one focus at the stage when the data is taken into the buffer memory, so that the target image appears in the displayed image. It is possible to provide an echo detection device in which the S/N ratio is always larger than the noise image, and even an amateur can easily distinguish the S/N ratio.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining one embodiment of the present invention, FIGS. 2 to 4 are waveform diagrams for explaining the invention in detail, and FIG. 5 is a block diagram for explaining the conventional technology. A block diagram, FIG. 6 is a waveform diagram for explaining the operation of FIG. 5,
FIG. 7 is a connection diagram for explaining a modified embodiment of the main part of the present invention. 13: Receiver, 15: Buffer memory, 16: Display,
17: Main memory, 31: Waveform shaping circuit, 32: Sampling means, 33: Pulse widening means. Patent applicant: Kohden Seisakusho Co., Ltd. Director Taku Kusano Off-drawing procedure amendment (voluntary) August 16, 1985 1. Case indication Patent application 1986-123867 2. Name of the invention Echo detection device 3. Amendment Relationship with the case of the person who made the patent application: Kohden Seisakusho Co., Ltd. 4, agent: 4-2-21 Shinjuku, Shinjuku-ku, Tokyo Column 6: Detailed explanation of the invention of the Sumo Building, Contents of the amendment

Claims (1)

[Claims] (1) A. Emit a wave pulse and receive the reflected wave,
In an echo detection device that captures the received signal into a memory, reads out the received signal from the memory and provides it to a display, and displays the position of the target on the display, B. samples the received signal and has a pulse width shorter than the sampling period; C. A pulse widening means for widening the pulse width of the signal taken out from the sampling means and writing the pulse with the widened pulse width into the memory as a received signal. An echo detection device characterized by: