JPS60205382A - Signal processing system - Google Patents

Abstract

PURPOSE:To obtain a signal processing system with a superior signal to clutter ratio by averaging the main signal of the signal processing system on specific condition. CONSTITUTION:An input IF signal (a) is supplied to a digital memory 15 through a logarithmic amplifier 11 and driven with clock pulses which has a period 1/N as large as pulse width. Then, an averaging circuit 16 receives and averages signals of the 1st and the (N')th (N'<N) step memories of the memory 15 or >=3 out of the 1st - the (N')th step memories. Consequently, the probability of wrong warning is decreased and the dispersion of a signal itself including a clutter is reduced in addition, thereby improving the detection probability of a desired signal.

Description

[Detailed Description of the Invention] [Field of orthopedics of the invention] The present invention suppresses clutter that spreads far and near, left and right, or up and down in devices that transmit and receive pulses, such as marine radar and ultrasonic equipment, and transmits necessary signals. Regarding the signal processing method obtained.

(Technical disadvantages of the invention and its problems) Conventional received signal processing systems of this type are shown in FIGS. 1 and 3, for example.
There are some things not shown in the figure.

Figure 1 shows the STC circuit (5 intensity tim
econtro+C1rcuit), linear amplifier, and FTC circuit (fast time constant
This shows a signal processing method consisting of a circuit.

In FIG. 1, 1 is a linear amplifier that amplifies the IF signal a, and 2 is an envelope detector that detects the output signal from the linear amplifier 1. Reference numeral 3 denotes an FTC circuit which differentiates the video signal d, which is the output of the detector 2, and produces an output e. This output e is then displayed via a video amplifier (not shown). 4 is an STC circuit, and the STC bias voltage C
occurs. SW is a switch for bypassing the FTC70 circuit 3.

FIG. 2 is a diagram showing signal waveforms at various parts in FIG. 1, where the vertical axis represents the signal amplitude or voltage, and the horizontal axis represents 1. a is the input signal to the linear amplifier 1, bl is the output signal of the linear amplifier 1 when the STC output Shingetsu signal is used, C is the output signal of the STC circuit 4, and b2 is the output of the linear amplifier 1 according to the above STC output signal. The signal d is the output signal of the detector 2 from which b2 is detected and is sent to the F-C circuit 3. e is the output signal of the F-C circuit 3. Furthermore, when the switch SW is closed,
This FTC70 circuit 3 output signal e becomes the same as the detection signal d. The left signal 8A of the input received signal waveform a represents sea surface reflection, the right signal 8 represents clutter due to raindrop reflection, and T
I, T2. and T3 represents a signal caused by a target object.

The disadvantage of this signal processing method is that it attenuates the amplitude of the signal (), but does not stabilize the variance of clutter amplitude fluctuations, and averages out the vibrational fluctuations of the received signal itself, including clutter. There is also no function to make it smaller.

Next, the method shown in FIG. 3 will be explained. Figure 3 is a constant false alarm rate device using a logarithmic amplifier! E and below CF A R (
constant false alarm rate
) device] is a block diagram showing the configuration of a Loo-CF AR reception system. In the same figure, 5
is a logarithmic amplifier including a wave detector, which amplifies the received signal a from the flF or IF and outputs the signal a. 6 is a digital memory using, for example, a digital shift register, which is driven by a clock pulse having a period corresponding to the time of the transmission pulse width, stores signals @b sequentially, and stores one memory content 5- from the middle. At the same time, the contents of each of the N4 memories are also output separately. 7 is an adder, which stores M from the digital memory 6.
Add the contents of each memory in Il. 8 is a divider,
The output of the adder 7 is multiplied by 1/M and the average value is output. 9 is a subtraction device which subtracts the output of the divider 8 from the output of the digital memory 6 and outputs the difference. 10 is an inverse logarithmic amplifier, which has a signal-to-clutter ratio (hereinafter referred to as S/C) before inputting this device.
(referred to as ratio). The output of the amplifier 10 is displayed on a display via a video amplifier (not shown).

FIG. 4 is a diagram showing signal waveforms at various parts in FIG. 3, where the vertical axis represents amplitude and the horizontal axis represents time. a is the input signal waveform, b is the output signal waveform of the logarithmic amplifier 5, and C is the output signal waveform of the paralysis device 9. The operation of this LOQ-CFAR reception system will be explained using FIGS. 3 and 4. When a signal such as a sea surface reflection signal, that is, a received signal @a containing clutter whose probability density distribution (hereinafter referred to as Ddf) of its amplitude has a Rayleigh distribution, passes through the logarithmic amplifier 5, the magnitude of the average amplitude of the clutter is 6 - the average value. The variance from the average amplitude value is kept constant and output as a signal waveform as shown in FIG. 4. When this signal is input to the digital memory 6 which is driven by a zero clock signal with a period equal to the transmission pulse width,
The memory contents for one cycle are taken out from the middle. On the other hand, the magnitude of the signal, that is, the amplitude value, of each memory content of M1 before and after the memory content taken out above is calculated by the adder 7.
Then, a divider 8 performs division by 1/M to obtain an average value. Then, the difference between the signal of the memory content taken out from the previous intermediate and the average value from the divider 8 is obtained by the numbing device 9, so that the dispersion of clutter becomes constant. In this way, better characteristics of fixed translation alarm rate can be obtained.

Further, by passing through an anti-logarithmic amplifier 10, a waveform before inputting this device is obtained. In this way, the clutter having a Rayleigh distribution can be made to have a constant amplitude, so it is possible to determine a threshold value, keep the false alarm rate of clutter constant, and detect a target object.

The drawback of this signal processing method is that the output after the LOQ-CFAR processing still contains variance of amplitude fluctuations determined by the constant of the logarithmic amplifier. There are also losses due to the finite number of digital memory steps used to average the signal.

Note that the larger the number of steps in the memory, the better from the standpoint of averaging, but on the other hand, if a small target is near a large target, there is a problem in that the small echo signal may be masked by the large echo signal.

Next, the integration receiver HN will be explained. This device is a device that receives the detection signal d output from the detector 2 in FIG. 1 and processes the signal. That is, the detected signal d is stored in a digital memory as one cycle of the radar pulse signal, and its output is delayed by one cycle, then sent to an adder via a divider, and added to the input detected signal d. is output. In radar, in an environment where there is a target over several cycles and there is clutter, noise, interference, etc. that are uncorrelated in each cycle, s,' c
The ratio is improved by a maximum of n times when the division ratio is 1.

In marine radar, clutter such as sea surface reflection has a high sweep-to-sweep correlation (close to 1), which has the drawback that it is hardly possible to improve S,7'(,tE).

[Purpose of the invention]

The present invention was made based on these circumstances, and its purpose is to average-process the main signal (the signal itself), which has been overlooked by conventional signal processing methods, under specific conditions. The object of the present invention is to solve and overcome the above-mentioned conventional problems and drawbacks, and to provide a signal processing method that is cheaper and has a better S/C ratio.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by the following configuration.

First, a reflected wave from a target object based on a transmission pulse train of a constant period is received in the form of its envelope, and the target object is irradiated by the first reception signal received by the reflected wave and the transmission pulse, and is simultaneously received. The present invention is characterized in that at least one other received signal having a gap smaller than the signal collection range is extracted, and the first received signal and the other received signal are subjected to average processing.

Second, the reflected wave from the target object based on the transmission pulse train of a constant period is received in the form of its envelope, and the target object is irradiated by the first reception signal received by the reflected wave and the transmission pulse, and the target object is simultaneously obtained. At least one other received signal having a smaller gap than the collection range of the received signals to be received is extracted, the average value of the first received signal and the other received signal is obtained, and this average value is used as the transmitting pulse m. The present invention is characterized in that sample-and-hold processing is performed from the time point * based on a criterion that is smaller than the collection range of the simultaneously obtained received signals.

Thirdly, the reflected wave from the target object due to the emitted beam of the transmitted pulse train of a constant period is received in the form of its envelope, and the target object is irradiated by the first received signal received by the reflected wave and the transmitted pulse. At least one other received signal having a smaller gap than the collection range of simultaneously obtained received signals is extracted, the average value of the first received signal and the other received signal is obtained by 10-, and this average value is used for the transmission. Angle IQ separated from the reference direction of the pulse emitting beam by an angular distance smaller than the collection range of the simultaneously received signals! It is characterized in that the signal lla is processed based on .

Fourth, the reflected wave from the target based on the transmission pulse train of a constant period is received in the form of its envelope through a linear amplifier with STC, and the first reception signal received by the reflected wave and the transmission pulse are At least one other received signal having a smaller gap than the collection range of the received signals obtained simultaneously when the target is irradiated by is extracted, and the first received signal is calculated from the average value of the first received signal and the other received signal. The method is characterized in that the average value of a plurality of amplitudes of the received signal or other received signals is subtracted.

Note that the "collection range of simultaneously received signals" in the present invention refers to the following range. That is, the transmission pulse width of the antenna is τ, the electromagnetic wave propagation speed is C1, the distance from the antenna to the target is r, and the horizontal and vertical beam widths of the antenna are θh, θe.
Then, the volume Ve in which the target object is irradiated by the transmitted wave is Ve=(πcr27θhθe)/8, where θh and θe are expressed in radians. The volume Ve defined by this formula is the spread in the far and near directions for the pulse emission, and the spread in the left and right directions and directions perpendicular to the beam. This refers to the collective range of received signals obtained at the same time.

(Embodiment of the invention) FIG. 5 is a block diagram showing the configuration of an embodiment of the invention. In the figure, 11 is a logarithmic amplifier including an envelope detector,
Amplify the input IF signal.

12 is a digital memory driven by a clock pulse having the same period as the pulse width; 131. is an adder that adds M signals from the digital memory 12, and 14 is a divider that converts the output of the adder 13 into 17'M. On the other hand, 15 is a digital memory driven by a clock pulse with a cycle of 1/N of the pulse width, and 16 is a digital memory 15 with 11 and N'
Receive the signal of the th step memory and set the average value to 1
η is an averaging circuit, and 17 is a sample and
This is a hold (S, -'l-1) circuit. 18 is a subtracter that subtracts the output of the divider 14 from the output of the S2,/H circuit 17. FIG. 6 shows signal a in FIG.

The timing relationship between b and c is shown.

FIG. 7 and subsequent figures are diagrams showing other embodiments of the present invention.

FIG. 7 is a diagram showing an example in which the present invention is applied to a receiving system in which video output signal processing is performed using a linear amplifier with STC, and FIG. 8 shows signals a, b, c,
It is a figure which shows the waveform diagram of d.

The display trigger is delayed by (N"/N) τ19.

Also, the S/H circuit 20 cuts off the ^ range and adjusts the timing.

FIG. 9 is a diagram showing an example in which the logarithmic amplifier 11 is used to process a video output signal.

FIG. 10 shows an example 13- in which only the main signal averaging circuit is extracted, and the delay circuit 19 may be of a digital type or an analog type.

FIG. 11 is a diagram showing an example in which the circuit portions subsequent to the logarithmic amplifier 11 of FIG. 9 are connected in two stages in series.

Figure 12 shows the main signal that has been averaged and is LOO-CFAR.
FIG. 3 is a diagram illustrating an example of the configuration.

FIG. 13 is a diagram showing an example in which the intermediate memory contents of the digital memory 12 are added to the averaging circuit 16 of FIG.

FIG. 14 is a diagram showing an example in which the digital memory 15 in FIG. 5 is omitted. This embodiment works as follows.

The amplified and detected video signal is sent to digital memory 12. Digital memory 12 is the first half, M/2
The part corresponding to (even number) or (M+1)/2 (odd number) steps is driven by a timing pulse with an interval of (N-/N>1 time, and then half, M/2<even) or (M+1)7 It is driven by timing pulses with a time interval of /2 (odd number) steps and a pulse width of 14. The first half starts from the first memory and every Nth memory, and the second half adds 1 for each memory! -I M signals are sent to the adder 13, the added signals are transferred to the divider 14, and the average value is sent to the subtracter 18. In addition, the signals of the island first and N'th memories among the N11l memories in the first half are taken out, sent to the averaging circuit 16 to become an average value, and sent to the sample-and-hold circuit 17. , formatted and subtractor 1
8 and the sample and hold circuit 17
The average value from the divider 14 is reduced, and the output is a constant S
/C ratio signal is obtained.

FIG. 15 is a diagram showing still another embodiment.

One of the video signals is amplified and detected by the logarithmic amplifier 11.
One is by the analog delay circuit 19 (N = , /N)T
The signal enters the averaging circuit 16 with a delay of time and is averaged with the signal directly entering the averaging circuit 16, then the delay circuit 19-
The output is output from the subtracter 18 in accordance with the delay of the low-pass filter 21.
sent to. On the other hand, the output of the logarithmic amplifier 11 passes through a low-pass filter 21 and is sent to a subtracter 18. Thus, the subtracter 18 subtracts the output of the low-pass filter 21 from the output of the delay circuit 19-.

FIG. 16 shows yet another embodiment of the invention.

The difference between this embodiment and the embodiment of FIG. 5 is that the number of outputs sent from digital memory 12 to adder 13 is one less, M
-1, and the divisor at the divider is M-1. The operation is the same as the embodiment shown in FIG.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the variance of the signal itself in which clutter, which is a mutually independent random event, is mixed, and as a result, it is possible to improve the detection probability of a desired signal, and to average the random events. Therefore, the detection probability can be increased regardless of the shape of the probability density distribution of clutter included in the signal, such as Weibull, Rayleigh, or lognormal distribution.

[Brief explanation of drawings]

Figures 1 to 4 show a conventional example. Figure 1 is a block diagram showing the configuration of a signal processing system consisting of a 310 circuit, a linear amplifier, and an FTC circuit. Figure 2 is the same as Figure 1. 1. Figure 3 is a block diagram showing the configuration of the LOO-CFAR reception system of a constant false alarm rate device using a logarithmic amplifier. Figure 4 is a diagram showing the signal waveforms of each part in Figure 3. FIG. 5 and FIG. 6 are diagrams showing one embodiment of the present invention, FIG. 5 is a block diagram showing the configuration, and FIG. 6 is a diagram showing the timing relationship of signals of each part in FIG. 5. , Figure 7~
FIG. 16 is a diagram showing another embodiment of the present invention. 11... Logarithmic amplifier, 12.15... Digital memory, 13... Adder, 14... Divider, 16...
・Averaging circuit, 17.20...Sample and hold (S/H) circuit, 18...Subtractor, 19.19
-...Delay circuit, 21...Low pass filter. Applicant's representative Patent attorney Takehiko Suzue 17- Procedural amendment Showa et al. 6.^8 Japan Patent Office Commissioner Manabu Shiga 1, Indication of case Patent application 1982-6277 February 2, Name of invention Signal processing method 3 , Relationship with the case of the person making the amendment Patent applicant (338) Tokyo Co., Ltd. 1tl Device 4, Agent 5, Voluntary amendment 8, Contents of amendment (1) The scope of the patent claims is amended as shown in the attached sheet. (2) In the second line of page 4 of the specification, ``1 is an IF multiplied signal'' is corrected to ``1 is an intermediate frequency (hereinafter abbreviated as 1.F) signal''. (3) From page 4, line 19 of the same book to page 5, line 1 [The switches SW are the same. J [In addition, switch SW
is switched from the FTC circuit side terminal p1 to the bypass side terminal p2, the output signal e becomes the same as the detection signal d. ” he corrected. (4) In the same page, page 5, line 15, change "logarithmic amplifier, RF or" to "logarithmic amplifier, radio frequency (hereinafter abbreviated as RF)"
or,” corrected. (5) ``Probability density distribution'' on page 6, line 18 of the same page is corrected to ``probability density function.'' (6) In the third line of page 7 of the same book, "this signal" is corrected to "this signal". (7) [Input the memory for one cycle from the middle when inputting] in lines 5 and 6 of page 7 of the same book. Then, from the middle tap of this memory 6 to the memory 2-- is corrected. (8) Same as page 7, line 13 [The variance becomes constant. (Thus, a better J is obtained. A signal with constant variance and the mean value removed is obtained. In this way, correct J. to "
Insert the phrase "therefore." (10) “Maximum 0 times” on page 8, line 19 of the same book was changed to “maximum E
I am corrected. (11) Insert the phrase "substantially" after "cheaper," in line 8, page 9 of the same book. (12) Insert the phrase "(with respect to the time with respect to the transmitted pulse)" next to "small distance" in the 6th line of page 10 of the same page. (13) Same - page 10, line 18, next to “small gap” is “(regarding vertical and horizontal spread of the antenna beam)”
Insert the lexical phrase. (14) Correct the [Reference direction] in the second line of page 11 to "!1 semi-direction". (15) Same - page 11, line 5 “!!It’s closed.” 3
- Insert the following sentence after . Fourth, the reflected wave from the target based on the transmitted pulse train of a constant period is received in the form of its envelope via a logarithmic amplifier, and the first received signal received by the reflected wave and the transmitted pulse are used to generate the object. At least one other received signal having a smaller gap than the collective range of received signals obtained simultaneously when the target is irradiated is extracted, and the first received signal is calculated from the average value of the first received signal and the other received signal. The method is characterized in that the average value of multiple amplitudes of the signal or other received signals is subtracted. (16) Same - page 11, line 6, change “fourthly” to “fifthly”
I am corrected. (17) On page 11, line 17, insert the phrase "generally" after [is]. (18) Same-page 11, line 19, "goal" is corrected to "object". (19) In the first line of page 12 of the same book, "the volume on which the target is irradiated" is corrected to "the volume of the target that is thus irradiated and generates reflections that are simultaneously received at the receiving point." . (20) In the same book, page 12, line 6, [and the extent perpendicular to these directions] is corrected to [and the extent perpendicular to these directions]. (21) Insert the following sentence next to "Range" on page 12, line 9 of the same book. However, for things like sea surface reflections in marine radar, it is possible that only the pulse width and horizontal (left and right) beam width are involved, and the vertical (up and down) beam width is not involved. do. (22) Same - page 13, 1st line to 2nd line [N-th step memory signal] to rN'(N-<N)-th step memory signal, or 1st to N' Correct the signal of step memory 311 and above among the 311 and above. (23) Insert the following sentence next to "It's a subtractor." on page 13, line 7. In this embodiment, the signals of the first and Nth step memories of the digital memory 15 or the signals of the first to Nth step memories are
Signals from three or more step memories up to the first one are received and averaged. By doing so, it becomes possible to lower the false alarm probability and also reduce the dispersion of the signal at the signal extraction tap. As a result, detection performance at a predetermined false alarm probability can be improved. Note that, from the viewpoint of efficiency, it is desirable that the number of common parts of clutter included in the signals to be averaged is small. Therefore, it is better to have armor as close to N as possible. (24) Same-page 13, line 15 [Display trigger is (N-
/N) Delay at τ19. Correct J to "The display trigger is delayed by (N=/N)τ in the delay circuit 19."<25) On page 14, line 10 of the same book, after "This is a diagram showing an example.", it says, "The added delay circuit is for delaying the input signal by (N-/N)τ." Insert a sentence. (26) Same page 14, line 16, ffi la M Line 20, “M/2 (even number) ~ time interval” is FM/2 (if M is an even number) or (M+1)/2 (M is (In the case of an odd number) The portion corresponding to the step is driven by a timing pulse at a time interval of τ/N, and the remaining portion is driven at a time interval of τ. (21) In the same book, page 15, line 11, "by the average value" is corrected to "by the average value." (28) Correct "T time" on page 15, line 16 to "1 hour". (29) ``Figure 15'' on page 16, line 8 is corrected to ``Figure 5''. (30) Insert the following after "Same as Example" on page 16, line 9 of the same book. Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, only the case where the separation in the collective range of simultaneously received signals is in the radial direction, that is, the distance (or distance), is shown.
This may be a case of separation in terms of circumferential direction) or solid angle. Furthermore, in the above embodiment, the average value to be subtracted from the output of the logarithmic amplifier is calculated from signals at multiple points before and after the point in time (point); Bye. (31) "Probability density distribution" on page 16, lines 15 and 16 of the same page is corrected to rpd fJ. (32) Correct the drawings in Figures 1, 2, 4, 5, 7, 8, 9, 12, 14, and 16 as shown in the attached sheet. =8-2. Claims (1) A reflected wave from a target object based on a transmission pulse train of a constant period is received in the form of its envelope, and a first reception signal received by the reflected wave and the transmission The target object is irradiated with a pulse, and at least one other received signal having a smaller gap than the collective range of simultaneously received signals is extracted, and the first received signal and the other received signal are averaged. A signal processing method characterized by (2) A reflected wave from a target based on a transmission pulse train of a constant period is received in the envelope line M, and the target is irradiated by the first reception signal received by the reflected wave and the transmission pulse. At least one other received signal having a smaller gap than the collective range of received signals obtained at the same time is extracted, the average value of the first received signal and the other received signal is obtained, and this average value is used as the transmit pulse. A signal processing method characterized in that sample-and-hold processing is performed based on a reference point that is smaller than the collection range of simultaneously obtained received signals from a reference point in time. (3) Receive the reflected wave from the target object by the emitted beam of the transmitted pulse train of a constant period in the form of its envelope, and the target object is irradiated by the first received signal received by the reflected wave and the transmitted pulse. At least one other received signal having a smaller gap than the collective range of received signals obtained at the same time is extracted, the average value of the first received signal and the other received signal is obtained, and this average value is used as the transmit pulse. The signal processing method is characterized in that signal processing is performed based on an angular reference that is separated from the reference direction of the emitted beam by an angular distance that is smaller than the collection range of the simultaneously obtained received signals. (4) Receive the reflected wave from the target based on the transmitted pulse train of a constant period through a logarithmic amplifier in the form of its envelope, and use the first received signal received by the reflected wave and the transmitted pulse to target the target. is irradiated and obtained at the same time, and extracts at least one other received signal having a smaller gap than the collective range of received signals obtained at the same time, and calculates the first received signal from the average value of the first received signal and the other received signal. or a signal processing method characterized by subtracting the average value of a plurality of amplitudes of other received signals. (5) Receive a reflected wave from a target based on a transmission pulse train of a constant period in the form of its envelope via a linear amplifier with STC, and generate a first reception signal received by the reflected wave and the transmission pulse. At least one other received signal having a smaller gap than the collection range of the received signals obtained simultaneously when the target is irradiated by is extracted, and the first received signal is calculated from the average value of the first received signal and the other received signal. A signal processing method characterized in that the average value of a plurality of amplitudes of the received signal or other received signals is subtracted. Applicant's agent Patent attorney Takehiko Suzue 3-

Claims (3)

[Claims] (1) Receive reflected waves from a target based on a transmission pulse train of a constant period in the form of its envelope, and simultaneously receive a first reception signal received by the reflected waves and the target object illuminated by the transmission pulses. A signal processing method characterized in that at least one other received signal having a gap smaller than a signal collection range is extracted, and the first received signal and the other received signal are subjected to average processing. (2) Receive the reflected wave from the target based on the transmission pulse train of a constant period in the form of its envelope, and the target is irradiated by the first reception signal received by the reflected wave and the transmission pulse, and the target is simultaneously obtained. at least one other received signal having a smaller gap than the collection range of the received signals to be received, obtain an average value of the first received signal and the other received signal, and use this average value as a reference to the transmitted pulse. A signal processing method characterized in that sample-and-hold processing is performed from the point in time based on a criterion that is smaller than the collection range of the simultaneously obtained received signals. (3) Receive the reflected wave from the target object by the emitted beam of the transmitted pulse train of a constant period in the form of its envelope, and the target object is irradiated by the first received signal received by the reflected wave and the transmitted pulse. At least one other received signal having a smaller gap than the collective range of received signals obtained at the same time is extracted, the average value of the first received signal and the other received signal is obtained, and this average value is used as the average value of the transmitted pulse. An angle that is smaller than the collection range of simultaneously obtained received signals from the reference direction of the emitted beam! 1. A signal processing method characterized in that signal processing is performed simply based on 1. <4) Receive the reflected wave from the target based on the transmission pulse train of a constant period in the form of its envelope via a linear amplifier with STC, and then receive the first received signal received by the reflected wave and the front! l[! At least one other received signal having a smaller gap than the collection range of the received signals obtained simultaneously when the drift is irradiated by the transmitted pulse is extracted, and the average value of the first received signal and the other received signal is calculated. A signal processing method characterized in that the average value of a plurality of amplitudes of a first received signal or other received signals is subtracted.