SU1320883A1 - Device for recovering time intervals of digital signals received from channel with limited bandwidth - Google Patents

Abstract

The invention relates to a pulse technique, in particular to devices for extracting digital signals from digital transmission channels with limited bandwidth, and Thebes. 2 can be used to reproduce digital signals from a magnetic carrier with frequency modulation — modulation in digital video recording systems, audio recordings, information accumulators in a computer. The purpose of the invention is to improve the accuracy of the recovery of time intervals of digital signals received from a channel with a limited bandwidth. The device comprises an input signal bus 1, a matching unit 2, a delay block 3 and 4, a relative averaging block 5, a comparison block 6 and 7, a pulse shaping block 8, a trigger block 9. The accuracy of the time interval allocation provided by this device is determined by the characteristics of the unit of comparison 6. 4 Il. (L with to about 00 00 with

Description

The invention relates to a pulse technique and can be used to extract digital signals from digital transmission channels with a limit of 1 bandwidth, which can be used to reproduce digital signals from FM magnetic modulation magnetic media in digital video recording, sound recording, storage systems. x information in the computer.

The purpose of the invention is to improve the accuracy of the recovery of time intervals of digital signals received from a channel with a limited bandwidth.

Fig, 1 shows the timing diagram of the signals; in fig. 2 - functional device diagram; in fig. 3 - the corresponding schematic diagram; in fig. 4 shows analytical plotting of the vertices of the pulses showing the properties and limitations of the signals of the recovery device.

The device contains (Fig. 2) bus

1 input signal, matching unit 25 of OR 35, whose output is 2, delay blocks 3 and 4, relative averaging block 5, comparison blocks 6 and 7, pulse shaping unit 8 and trigger block 9. Input bus 1 is connected to the input of matching block 2, made (see fig. 3) of the input amplifier 10 connected in series, the matching resistor 11 with the first output of the block 2 and the alphabet 12 on the voltage divider made on the resistors 13 and 14 and having the second output of the block 2, First the output of block 2 is connected to the input of the first second delay unit 3 including delay line 15 and a first input of relative averaging unit 5 containing a voltage divider on resistors 16 and 17; second input unit 5 is connected to the output of a second delay unit 4 including serially connected delay line 18 and a load resistor 19, the input of the delay unit 4 is connected to the output of the delay unit 3 and to the first inputs of the comparison unit 7 and the comparison unit 6, which is made on the comparators 20 and 21 with differently combined inputs. The first and second outputs of the comparison unit 6 are connected to the corresponding information inputs of the pulse shaper unit 8 comprising a pulse shaping circuit 22 and 23 on the falling edge of the information signal. The second output of matching unit 2 with equalizing circuit 12 is connected to a second input of comparison block 7, in which a negative bias circuit 24 is connected to the second input of a common bus, including a parallel-connected negative voltage source 25 and a voltage divider on resistors 26 and 27, and a positive bias circuit 28 comprising in parallel a positive voltage reference source 29 and a voltage divider across resistors 30 and 31. The output of the bias circuit divider 24 is connected to the first inverting input of the comp Rathore 32 comparing circuit 33, and output divider bias circuit 28 is connected to a first inverting input of comparator 34, comparing circuit 33, second inputs of the comparators 32 and 34 soy; They are connected to the first input of the comparison unit 7, the outputs of the comparison circuit 33 are connected to the inputs 5

The transmitter of the comparator unit 7 is connected to the prohibition bus of the formers 22 and 23 of the pulse shaping unit 8, the outputs of which are connected to bus 36 and 37. intended for further processing in the self-synchronization circuits, and to the inputs of the trigger block 9, comprising a trigger 38, the output of which is connected to the bus 39, which is the output of the recovered binary information at the original time intervals.

In the device for restoring time intervals (as well as binary information) of digital signals received from a channel with a limited bandwidth, the input signal (Fig. 16) is twice delayed equally (Fig. 1 g, the solid line is the input signal, and the point is once delayed , dotted - twice delayed, without distortion and with the same amplitude, relative amplitude is performed over the amplitude (for example, by a voltage divider

0

five

0

resistors) between the input signal

and twice the delayed signal (FIG. 1 g, dash-dotted line), separate the difference signals using comparing devices, namely the difference signal between a relatively average and once delayed (figure 1 f) and the difference signal between the input and once delayed

(Fig. 1). The selected signals from the first comparing device (Fig. 1, I) are fed to the input busbars of the pulse formers on the falling edge, and from the second comparing device (Figs, 1e, jt, j) to the information inputs of the formers, as a result of false pulses arising at the output of the second comparing device (Fig. 1,.) when there are long pulses on the input signal that are longer than the comparison time, which with a given threshold (Fig. 1) of the bias circuits 24 and 28 separates the difference signal leveled at you The open circuit 12 is an input signal and a signal at the output of the block 3 delay and combines the signals of the comparison circuit 33 on the OR element 35 (Fig. because the control signal to the control input JQ of the block 8 is missing ... From the output of the shaping unit to the busbar. 36 and 37, the units are cleared corresponding to the initial time intervals of the strobe pulses, and zero therefore the binary information is easily supplied by the usual RS trigger 38 The accuracy of the time interval allocation is determined by the characteristics of the comparison unit 6 that the docks of the channel front rise (Fig .1, 6.8, the third unit and the next j followed by zero with a label exceeding the amplitude of the digital signals, do not pass at the output of the drivers (Fig. 1 to , ).

The shaper signals use Q as the following theorem, for further processing in the chains. Consider simultaneously plots.

mosynchronization and serves to trigger devices, the output of which removes the original binary signal with the restored temporal relations (Fig. 1 m, ").

Restoring time intervals and binary information is as follows.

From the bus 1 to the input of the matching unit 2 a composite digital signal is received, received from a channel with a limited bandwidth (Fig. 1b). An example of the signal is shown.

10100111 1010110

 having impulses

the length t, the longer the rise time of the channel front, i.e. (in this case, the rise time is equal to the duration of two bits, i.e.

t, 2Tg). From the input amplifier 10, through the terminating resistor 11, the signal goes to delay blocks 3 and 4 and is halved in block 5 relative averaging on resistors 16 and 17 relative to the delayed signal at the output of delay block 4. In the comparison block 6, the difference between the signals at the output of the relative averaging block 5 and the output signal of the delay block 3 affects the comparators 20 and 21 and at their outputs the signals are intersected relative to the differential signal horn, which arrive at the information inputs of the formation block 8 pulses on the falling edge. False pulses (Fig. 1, J-) are suppressed by signals.

20883

block

7, which, with predetermined thresholds (FIG. 1) of the bias circuits 24 and 28, separates the difference signal between the input signal equalized on the equalization circuit 12 and the output signal of the delay unit 3 and Combines the comparison circuit signals 33 on the OR element 35 (FIG. 1 and), since the control signal at the input JQ of control of block 8 is absent, .. From the output of the formation unit to the buses. 36 and 37, the unit and zero are cleared corresponding to the initial time intervals of the strobe-pulses, therefore the binary information is easily transmitted by the usual RS flip-flop 38. The accuracy of the selection of the time intervals is determined by the characteristics of the comparison unit 6, which is dock j

thirty

 .

35

p

the vertices of the input signal, once and twice delayed signal of one amplitude with a rise time w 25 of the channel front equal to or longer than a bit (Cf / Tg), and using a linear approximation of the rising edge, we have (Fig. 4) three parallel broken straight lines: ABC is for the input signal, DEF is for once delayed and HI is for double delayed signal, in which parallel direct AB, DE, H, having a slope oi relative to the time axis of the abscissa, intersect with three parallel direct waves, EF, HI inclined to the x-axis. At points B and H, we make sections that are parallel to the ordinate axis, which, according to the theorem on the intersection of parallel lines, form similar triangles BIN and KKN. Let us draw in these triangles the line LNM, equidistant from the lines BNK and INH. The LNM lines are nothing more than the median of the BIN and NHM triangles, which divide the BI and NK sides in half, but the BLN and HMN triangles lying on the LNM median are also similar and have the medians straight LE and EM, therefore, for any inclinations d and fl points L and M will always belong to BI and NK sections, respectively

40

45

50

Similarly, for broken straight lines corresponding to extended impulses ABP, DEP, GHP and OBC, OEF, OHI, which respectively form triangles BHL and OWC, in which the middle lines LH and VM are also 513

dianes, but in the triangles BHL and VNM, the direct LE and EM are also medians, therefore, in these cases, the points L and M belong to the sections BI and NK, regardless of the slopes d and ft. Thus, the intersection points L and M of the middle line LM corresponding to a relatively averaged signal, and the direct LE and VM, which are part of the once delayed signal, regardless of the steepness of and. the pulse decays are not connected on the time axis and are reference points for restoring the original digital signal intervals. At the same time, I and K must be present in the active zone, amplitudes, otherwise, with increasing steepness of the fronts (Fig.4.4 S lines of the near-average averaged and once delayed signal are shifted to the depth of the zone between the BI and NK sections, and the relative averaging line acquires an additional break RT. When the steepness of the pulse front becomes equal to infinity (Fig.48), i.e., when rectangular pulses arrive at the input, the intersection points S and S of the polyline are relative averaging: UARTHB K t IQ between the UAB CQ input line and UGHH IQ broken lines are twice delayed - but to the broken line UDEb) FQ once the delayed signal. Thus, in order to preserve the immobility of the intersection points L and M, regardless of the change in the steepness of the pulses, it is necessary to exceed or equal the duration of the rise time of the channel 7 with respect to the total delay of the 2Tj signals, i.e. With f 2T, and, therefore, with the direct reception of digital signals, a mine channel, the input signal is passed through the channel equivalent, for example, through an integrating circuit.

Claims (1)

Invention Formula An apparatus for recovering time slots of digital signals received from a channel with a limited bandwidth, comprising a matching unit made j O 5 0 5 o Q five 0 6 B in the form of a series-connected input amplifier, a matching resistor and an input voltage equalization circuit, two delay blocks with a load resistor, the first comparison block, made in the form of two comparators, to the opposite inputs of which two bias circuits from the voltage dividers are connected reference voltage, characterized in that, in order to improve the accuracy of the restoration of time intervals, a second comparison unit, made in the form of two comparators, is additionally introduced into it, neither pulses, made in the form of two pulse formers on the back edge, output RS-flip-flop, OR element to the first comparison unit and relative averaging unit, with the first input of the relative averaging unit connected to the input of the first delay unit, and the second input to the output The second delay block, the output of the first delay block is connected to the first inputs of the first and second comparison blocks, and the output of the relative averaging block to the second input of the second comparison block, the outputs of which are connected to the inputs of the block Formation of pulses, respectively, with the information inputs of the first and second pulse formers on the falling edge, the outputs of which are connected to the first and second output buses and the inputs of the output trigger, the output of which is connected to the third output bus, the output of the voltage equalization of the input voltage in the matching unit with the second input of the first comparison unit, in which the second input is connected to a common bus of bias circuits, the positive and negative outputs of which are connected respectively to the inverting and the non-inverting inputs of the comparators, the second inputs of the KQ-tors are connected to the first input of the first comparison unit, and the outputs are connected to the inputs of the OR element, the output of which is the output of the first comparison unit and connected to the prohibition input of the pulse shaping unit. Have but Jb kw r t V-7 ijrKj  -Vv / / 7 / (U - / b LVyy -. M r L, / V v OK tlL 3 i nOmHhiu and / f l lg M r v  . A A A Jjofffhmu  f J n h d Jtil fie. /. ADC, Q AT Ven A B C fie. Compiled by G. Brynsky Editor M. Dshin Tehred A. Kravchuk Order 2666/55 Circulation 901 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35r Raushsk nab. 4/5 Production and printing company, r 5, p. Project, 4 In e n F I Proofreader A. Obruchar