SU790255A1 - Threshold device - Google Patents

Description

(54) THRESHOLD DEVICE

one

The invention relates to radio equipment and can be used in automated information processing systems for suppressing false alarms caused by side rails of processed signals and residual noise.

A threshold device is known which comprises a comparison device, an integrating device, two delay lines 10, a subtraction device and an attenuator fl.

At the input of the threshold device there are always residual noises due to both the input noise 15 of the primary information processing system, as well. and its general noise, the input noise can be essentially non-stationary, and its own noise can change its effective value during operation and differ for different samples of the same type, therefore it is important to minimize false alarms from noise and keep a constant likelihood. t-25 the availability of these operations at a sufficiently large interdigit of the implementation being processed, regardless of the noise level characteristic of the sample, In addition, if the pea- is processed; thirty

The input device of the threshold device is a set of signals, the amplitudes of the main lobes of which change randomly, and their temporal positions MaKcnNiyMOB also follow randomly relative to each other, which is typical for multichannel information processing, as a rule, the problem of temporary fixing the maximum of the main lobe of the largest of the signals.

The dependence of false alarms on residual noise on the time variation of their effective value or power, as well as the lack of fixation on the position of the maximum ejection, limit the application of this threshold device.

The closest in technical essence to the present invention is a threshold device comprising a delay line, an amplifier, a memory unit with a reset, and. the block is compared with 11I in the form of a limiter for level 2.

However, this device is also characterized by the dependence of false positives on the effective value of the pressure from the output of the primary processing system, although the number

these operations due to the fixation of the maximum release can be significantly reduced. .

In addition, the delay lines through which signals are sent to the comparator unit must have the required delay in sufficiently wide frequency bands to delay the signal without distortion, this complicates such devices, reduces their stability and leads to the presence of a fixed emission delay from the beginning. .

The purpose of the invention is to expand the functionality and increase the reliability of the threshold device, namely, simultaneously with suppressing false alarms from the side lobes of the signal being processed, to suppress false alarms from residual noise regardless of the behavior of their C power dispersion over time and eliminate the need for delayed signals. .

This goal is achieved by introducing a diode, a start pulse generator, a switch, a capacitor, and a low-pass filter into the threshold device containing a comparison unit and a peak detector connected to the input signal bus, the peak detector connected to the output of the low-pass filter which is connected to the bus input signals, and the output of the peak detector is connected via a diode to the output of the trigger pulse detector and via a serial switch to one of the plates of the additional capacitor and one of the inputs The second input of which is connected to the bus of the input signals and the output to the control input of the key, with the second plate of the additional capacitor connected to the common bus.

FIG. 1 is a functional diagram of the threshold device in FIG. 2 - time diagrams a, b, and c, which explain his work.

The threshold device contains a comparison unit 1 and a peak detector 2 assembled at an operational amplifier, the non-inverting input of which is connected to the input signal bus and with the output of low-pass filter 3 whose input is also connected to the input signal bus, the output of the peak detector and diode 4 and the cathode. via a serial key 5 about one of the plates of the additional capacitor b and with the second input of the comparison unit 1, and the first input is connected to the bus of the input signals. The second setting of the additional capacitor 6 is grounded, the anode of the diode 4 is connected to the generator 1, the start-up pulses, and the output of the comparison unit 1 is connected to the control input of the key 5.

FIG. 2 (digg. 11ma a) shows the input signal consisting of the Tzu section and part of the interval occupied by the many TC J signals. The same figure shows the same signal, but already at the output of peak detector 2, as with an open jumper (D-A) (so when Uc- and Uca are closed, where UCA is the voltage at the peak detector load, and Uc2 is the voltage at the additional capacitor 6, i.e. at the second input of the comparator unit 1. Pulses corresponding to the beginning and end of fixation of the main lobe are shown in Fig. 2 (diagram b). The impulses of the operations Kf, and for pain On a larger scale, the change in the voltage of Uc-f and sa is shown in Fig. 2 (diagram c).

The device works as follows.

The start of the processing of the input implementation is preceded by a start pulse, which, through diode 4, charges the load capacitor of the peak detector 2 to the value needed to provide the selected (low) probability of false alarms for residual noise at the beginning of processing Uci. In the absence of an operation signal Kf, key 5 is open all the time, its resistance can be neglected and the load capacitance consists of a peak capacitor of the detector 2 and an additional capacitor b, that is,

G C + C z peak. lop

"J

This total capacitor begins to discharge with a time constant tpcfi, which is determined by the feedback resistance of the operational amplifier and the parallel, e: / iy load resistance, i.e. input impedance unit 1 sravt neni.

At the same time, after the termination of the trigger pulse, the filter of the lower frequencies begins to accumulate a constant noise component with a constant time Tf, which is selected from the condition f f tpof: (l). In case of presence only. residual noise (T value of this constant component Jout is related to (dispersion) noise power by some coefficient f, depending on the distribution pattern of the envelope at the output of the primary processing system

 D 2)

and in the case of the presence of a signal (Tc)., its value is related to some degree -1 coefficient X with the effective value of this signal and which

depends on the behavior of its duty cycle and the change in the amplitude in the processing interval, i.e.

U, 9CUJ,

Sending the component Uo is summed with the instantaneous values of the input realization Ugj and, if the link (L-A) in FIG. 1 .. was open, then at the output of the peak detector 2 at point (A), a total signal would be generated

,, mU, (4)

moreover, by selecting the values of the summing resistors and the splitter in the feedback of the operational amplifier, the summation scale for Ugx is equal to 1, and for the constant component Uo in (2) and (3) is equal to m.

As soon as ugxa exceeds the value of voltage Uc / i on the total capacitor C, the latter will begin to change according to the law

yyyy ju (t) dt, ()

3apCj

 the time constant of the charge circuit, which is determined by the output impedance of the operational amplifier Rf, t, i; (, the diode resistance in the open state R and the value of C, i.e.

(,,, C6)

moreover, the relation between this time constant and the time constant of the low-pass filter is selected from the condition

,, SG)

fT

where I, (J is a priori known, the longest signal duration at the input of the processing system,

In this case, the expression (5) in view of (6) and (7) can be written in the form

one

mU

. c,, "- ®From the Lme dia in (Fig. 2. it can be seen that the condition for the absence of noise operation, taking into account (8), will be

, lou,

v), t ;;;,

and taking into account 121

5c, ps

, (t) di, cg) Jdpcj

8X1

if we mark the first addend

on the right side of the inequality through and „or.

i.e

-

and

)

pore iCSpCj;

This will be the threshold, the Transformation of which is the difference

8X /) -, Us ..-%

and will trigger.

If we consider that the distribution of the envelope noise at the input of the threshold device is Rayleigh, then the probability of false alarms is determined, as shown, for example, in (4) by

, 2

-and

pore

 C-fZ)

Substituting in (12) the expression

ipo

dl (10x we get

25

CI3)

whence it is seen that for this device the magnitude of the probability of false

operations depends on the scale of summation of the constant component m in (4) and the constant charge time “P Cg C6) chosen for it and does not depend on the (variance) power

residual noise.

If there is a signal, the constant component of its Doc / due to the presence of a delay in the low-pass filter (two-link filter) at the initial moment will be equal to

Wash noise accumulated in the previous part of the implementation at the input of the threshold device and at the moment when

.

)

(i)

VHG Jtapct

the signal from the output of the comparison unit 1 will close the key 5 and the Additional capacitor b (if the key resistance is sufficiently large in the closed state and the resistance value is large. Lenin) will keep the value of DC I which was at cy F ap capacity at the moment of exceedance (Fig. 2, diagram c), and the peak detector load capacity continues to charge with a constant time

YO sapc peakAt. you; (b (if you choose

.A.C. „„ 1 US)

65

Claims (1)

j.on then, in practical terms, Cs. At the moment when L} g; {(t) becomes smaller and then the signal from the output of the comparison circuit opens the key and the additional capacitor (C oop) quickly charges to a value that will at that moment on the load capacitor of the peak detector (Crtwv.em By the next signal-ala emission, its constant component Uoc and under the conditions of operation (11) already begins to grow (w) it is necessary to add the CKESSR from (3), i.e. from (10) it follows that Thus, due to the peak detector and the two-link low-pass filter with the ratio between their constant time (7) and (1), the last response from the signal will correspond to the main lobe of the largest signal, the position of the maximum of which can be easily determined by measuring half the pulse duration Kcp for the output of the comparison circuit (Fig. 2, diagram b). And the delay relative to the beginning This device is absent in this device. The use of the proposed device allows, along with the suppression of false alarms on the side lobes of the signal being processed, which By fixing the maximum burst, to stabilize the probability of false alarms in noise with their non-stationary nature, and to fix the burst of the signal that did not resort to its delay relative to the reference point. Claims of the invention nopoi oBoe device comprising a comparator unit and a peak detector connected to the input signal bus, characterized in that, in order to expand its functionality and increase reliability, a diode, a trigger generator, a key, a capacitor and a frequency filter are inserted into it the peak detector is connected to the output of the low-pass filter, the input of which is connected to the bus of the input signals and the output of the peak detector is connected via a diode to the output of the trigger pulse generator and, via a serial key, to one second electrodes of the additional capacitor and to one input of a comparison unit, a second input coupled to a bus input signals and The output - to the control input of a key, wherein said second electrode is connected to an additional capacitor common bus. Sources of information taken into account in the examination 1. USSR author's certificate number 530445, class, H 03 K 5/20, 30 .11.76. 2, Ipatov V.P. KazarinoB Yu.M. Kolomensky Yu.A. Uhl Uitsky Yu.D. Search, detection and measurement of signal parameters in radio navigation systems. M., Sov.radio, 1975, p.234, rice, 7.18a (prototype).