SU1071985A2 - Device for measuring pulse time position - Google Patents

Abstract

DEVICE FOR MEASURING THE TEMPORAL POSITION OF A PULSE according to the ed. St. 576553, characterized in that, in order to measure accuracy under coherent interference conditions, which overlap in spectrum and partially in time with the signal, a second accumulator and a threshold unit are introduced into it, and the input of the second accumulator is connected to the notch filter output, the output The second storage device is connected to the control input of the bandpass filter through the threshold unit, to the second control input of the switch and to the second input of the registrar, and the control input of the second storage device is connected to the third output of the registrar. ra.

Description

WITH

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SP The invention relates to radionavigation, can be used in pulse-phaeo radionavigation systems with indicators. According to the main author. Guards No. 576553, a device for measuring the pulse temporal position is known, comprising a series-connected band-pass filter, a notch filter, a reference point forming unit and a recorder, successively connected signal error parameter analyzer, a drive and a switch, and the signal analyzer character analyzer input is connected to the output of the forming unit reference point, the switch output is connected to the control input of the reference point generation unit, and the control inputs analysis However, in a known device LZ for measurement errors, the value of which depends on the amplitude of the surface signal to the ionospheric signal, the accuracy of determining the temporal position of the pulse decreases. The purpose of the invention is to improve the accuracy of measurement under the conditions of coherent interference, r overlap the spectrum and partially in time with the signal. The goal is achieved in that a device for measuring the temporal position of a pulse containing a series-connected band-pass filter, a notch; a filter, a measuring point forming unit and a recorder connected in series by a signal parameter error sign analyzer, a drive and a switch. the signal is connected to the output of the reference point forming unit; the switch input is connected to the control input of the i forming unit of the reference point The glasses, and the control inputs of the signal mismatch analyzer for the signal switch and switch are connected to the corresponding recorder outputs, a second accumulator and a threshold unit are entered, the input of the second accumulator is connected to the output of the notch filter, the output of the second accumulator is connected to the control unit via the threshold unit the input of the bandpass filter, with the second control input of the switch and the second input of the recorder, and the control input of the second accumulator is connected to the third output of the recorder. On the fig. Figure 1 shows the structural electrical circuit of the proposed device; in fig. 2 shows an embodiment of the registrar / in FIG. 3, temporary diagrams that explain the operation of the device; in fig. 4 - amplitude-frequency (a) characteristic and phase-frequency (b) characteristic of a band-pass filter. The device (Fig. 1) contains a co-axial filter 1, a notch filter 2, a reference point forming unit 3, a recorder 4, a signal parameter mismatch analyzer 5, a first drive 6, a switch 7, a threshold block 8 and a second drive 9. A recorder (Fig. 2) contains a search and additional search unit 10, a phase tracking unit 11, a polysemy resolution unit 12, a time position measurement unit 13, a synchronizer 14 and a reference oscillator 15. The device operates in the following way. The input mixture of the signal and interference enters the band 1 and notch 2 filters (Fig. 3 a, B). In this case, in the initial state, the bandwidth of the bandpass filter 1 is equal to kHz (Fig. 4o (-0). The filtered signal arrives at the measuring point forming unit 3 (Fig. Sound) and then to the recorder 4. The recorder 4 measures the temporal position of the pulse In this case, at the search stage, the combination of the voltage of the reference generator 15 in the synchronizer 14 of the reference gating pulses 16 to 19 (FIG. 3 g) with any point on the radio pulse is made. For this, in the search and additional search block 10, accumulation is made at points strobe If the temporal position of the gating pulses 16 to 19 does not coincide with the time of arrival of the signal, then the accumulation of noise is on average close to zero and after some time (analysis time) from block 10 the command is sent to the synchronizer 14 to move the gating pulses. is chosen so as to avoid signal skipping.When the arrival time of the signal coincides with the gating moments, efficient accumulation occurs in block 10 and pf: the az1y search step ends. At the second stage, the combination of 16 19 19 pulsed pulses with the front of radio pulses is carried out. This procedure is performed by moving the gating pulses rigidly interconnected to the beginning of the signal in increments equal to the period of high-frequency filling until the gating pulse 19 turns out

at the very beginning of the radio pulse. In this case, the accumulation in it becomes close to zero and the search ends.

The next procedure — timing synchronization — consists of precisely matching the gating pulses 16, 17, 18 to the high-frequency filling phase. In this case, in block 11, the tracking of the phase 8) of the Register 4 is analyzed for the sign of accumulation of the signal / m at the time of the action of the strobe pulse 18 and is adjusted using the tracking system in phase. With zero accumulation, the synchronization process ends. In connection with the possible ambiguity of choosing a period of high-frequency filling before the measurement, the procedure of placing the ambiguity of the phase measurements, consisting in the combination of gating pulses 16 and 17 with half-waves 20 and 21 in the region of the formed envelope reading point (Fig. 2, c, d), is performed. . In addition, in block 12 of elimination of ambiguity, the sign of accumulation in gate pulses 16 and 17 is analyzed relative to the reference point tjj. When the impulse 18 is correctly set in phase of the high-frequency filling, the accumulation in the pulses 16 and 17 will have corresponding different signs, and the disambiguation unit 12 generates a control command in the unit 13 for measuring the time position in the production of measuring the time interval. Otherwise, the gating pulses 16 through 19 are shifted by the period of high-frequency filling and n {the erectile resolution resolution procedure is repeated. The measurement of the time interval in block 13 is carried out as described in the operation of the known device.

When subjected to partially overlapping tsix in time of coherent interference, the type of signals reflected from the ionosphere, the shape of the resulting pulse, starting from a time equal to the spatial wave delay, is distorted. A change in the pulse formula at L to leads to the appearance of a mismatch between the true t-Q and the actual position tp of the temporal position of the reference point (Fig. 33). as a result of accumulation in the accumulator 6, the switch 7 operates, the weight coefficient K changes, and a false correction occurs. At the same time, gating pulses 16 to 19 are shifted to the right along the time axis (Fig. 3 Z) Depending on the ratio of the amplitudes of the surface and spatial signals, the offset of the reference point can reach several periods of high-frequency filling.

In this case, the correction does not eliminate the time position measurement errors at all. The proposed device uses information about the presence of a signal reflected from the ionosphere, which appears due to the fact that the strobe pulse 19 appears on the signal front. For this purpose, a pulse 19 strobe arrives at the control input of the second accumulator 9. Result

0 accumulation in the second accumulator 9 is fed to the input of the threshold unit 8, which generates on its control signal simultaneously arriving at the second input of the recorder 4 (to control the synchronizer 14), to the second control the input of the switch 7 and to the control input of the bandpass filter 1. Under the action of this control signal of syncro, the lowlator 14 displaces the gating pulses 16-19 to the left by a predetermined value 4 -t and (Fig. Zi), changing the parameters of the band-pass filter 1 (as will be shown below), thus

5 that the steepness of the front of the radio pulse at the output of the filter filter 1 increases (Fig. 3), and the switch 7 connects to the control input of the unit 3 forming the reference point

0 reference voltage E, changes the weighting factor K so that the reference point is also shifted to the left by 4-t (Fig. 33), All values величины1, ut have certain values. Calculated in advance from the known value of the maximum possible delay ionospheric signal. The gating pulse 19 is thus transferred to the start of the pulse, with the result that the output of the second accumulator 9 again sets a voltage close to zero. For this, the control voltage at the output of the threshold unit 8 has not changed, it uses a series-connected comparator and a trigger that is clocked by a front.

Consider the processes occurring in bandpass filter 1.

0

Band-pass filter 1 with a controlled characteristic contains cascade-connected 2nd order links and controlled feedback circuits such that this is realized

5 transfer function of a fractional bandpass filter of the form NorM (p2 |

H (R / -777-7-7-77 - (1 /

Nfp2 |. (. N,

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: where P is the complex frequency; “(, N (even values relative to N, (p2), N (p) .Ho P;

HQ is a constant gain;

| Jj are the feedback coefficients.

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The filter delay control is described as follows.

It is known that the group delay of the filter is determined by the slope of the phase-frequency characteristic (FPH) in the passband of the filter.

In accordance with formula (1), the frequency response of the filter is described by the relation

f (

f (w) -c (rctgU, M, ((uj2, | 3.)

group delay time

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This shows that, with an increase in ft, the denominator (3) increases, and the f-p%) decreases. The appearance of the frequency response and the frequency response at different values is shown in Figs. 4a, 5. A decrease in the delay can also be associated with a change in the duration of the first half-wave of the impulse response. This results in an increase in the steepness of the front of the radio impulse (Ja at the filter output and a decrease in the error due to interference at the position of the spatial signal. 1 The positive effect of the invention is the following. It is known that measuring the temporal position of the envelope reading point is the least robust procedure, Because Complicated 11} with interfering installation requirements for increasing measurement accuracy lead to the need to achieve potential characteristics of a receiver For white noise and lumped noise, this problem is solved by applying matched filtering. Usually, the floor: square-wave frequency response filters, under these conditions, should have a down-width bandwidth of 4 to 4, Pulsed RNS Loran-S signals with a duration T (200 µs bandwidth should be about 7-10 kHz. The minimum measurement error is achieved when a reference point is formed near the maximum of the radio pulse. When deleting objects n distances,

and more kilometers, the reception conditions are characterized by the presence of interfering ionospheric signals, the magnitude of which is delayed relative to the surface; shorter than their duration; what

makes it impossible to apply matched filtering. In existing receivers, for this reason, the bandwidth of the band-pass filter is 2-3 times wider,

0 ie within 20-30 kHz, and the formation of the reference point occurs closer to the beginning of the radio pulse, where the signal amplitude is (0.3-0.5) ,. Due to

5 of this, the loss in the ratio: signal / noise is achieved 2-3 times as compared with the matched filter without taking into account the increasing number of interferences that fall into a wider transmission band.

In the proposed device, the introduction of a second accumulator and a threshold unit, as well as the use of a bandpass filter with a special shape of the frequency characteristic, allowed increasing the accuracy of measuring the temporal position of the pulse signal by providing a mode close to matched filtering in the absence of signals reflected from the ionosphere; an increase in the steepness of the signal front with a permissible (up to 30%) increase in noise errors and a decrease in interference with the reflected signal. In the first case, the filter band

 (Fig. 4a 0) is in the order of 10-12 kHz, and the pulse response envelope is close in. form to the radio pulse envelope.

In the second set of frequency form

The 0 characteristic is changed so that the effective bandwidth of the filter is increased approximately 2 times (Fig. 4a), and the slope of the phase characteristic in the passband (Fig. 4a, / 5/0) is close to zero, which leads to decrease of the filter delay in the region of the main part of the signal spectrum. The leg is equivalent to increasing the 1TH GROSS OF the signal at the output of the filter. Increasing the front allows the reading point to be formed closer to the beginning of the radio pulse without reducing the signal amplitude. Only the signal-to-noise ratio deteriorates due to an increase in the effective bandwidth, i.e.

72 times or 30%.

one

The use of the proposed device, for example, in the well-known KPI-5F receiver-indicator, will allow the receiver's range of radionavigation signals to be expanded without decreasing the accuracy characteristics and provide moving objects with data on the months of tonnage.

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Claims (1)

DEVICE FOR MEASURING TIME PULSE POSITION by ed. St. No. 576553, characterized in that, in order to understand the measurement accuracy under the influence of coherent noise overlapping in the spectrum and partially in time with the signal, a second drive and a threshold unit are introduced into it, and the input of the second drive is connected to the output of the notch filter, the output of the second drive through the threshold block is connected to the control input of the bandpass filter, with the second control input of the switch and the second input of the recorder, and the control input of the second drive is connected to the third output of the recorder .