SU1474850A1 - Delta-modulator - Google Patents

Abstract

The invention relates to automation and communication technology. Its use in signal transmission systems makes it possible to increase the accuracy of the conversion by expanding the dynamic range of the signals being converted. The delta modulator comprises a comparator 1, a shaper 4 of the information pulse sequence, an integrator 5, a pack 9 for extracting symbols and a block 10 for expanding packs of symbols. Thanks to the introduction of comparators 2.3, integrators 6.7, amplitude-pulse modulator 8, multiplexer 11, switching unit 12, and source 13 threshold levels in a delta modulator, the compression is performed over packs of identical symbols, the number of which changes signal. 2 Il.

Description

(21) 4240321 / 24-24

(22) 05/05/87

(46) 04.23.89. Bul Number 15

(71) Leningrad Electrotechnical Institute of Communications. Prof. M.A.Eonch-Bruevich

(72) A.Yu. Bukhinnik, B.E. „Trofimov and P.E. Scherbatii

(53) 621.376.56 (088.8)

(56) USSR Author's Certificate No. 349080, cl. H 03 M 3/02, 1970.

Electroslap, 1979, No. 11, p. 38-40, fig. one.

USSR Author's Certificate No. 1129732, cl. H 03 M 3/02, 1983.

(54) DELTA MODULATOR

(57) The invention relates to automation and communication technology. It is used / 5

The signaling in the signal transmission systems makes it possible to increase the accuracy of the conversion by expanding the dynamic range of the converted signals. The delta modulator comprises a comparator 1, a shaper 4 of the information pulse sequence, an integrator 5, a pack 9 for extracting symbols and a block 10 for expanding packs of symbols. Thanks to the introduction of comparators 2 and 3, integrators 6 and 7, amplitude-pulse modulator 8, multiplexer 11, switching unit 12 and source 13 threshold levels in the delta modulator, compression is performed on packs of identical symbols, the number of which changes as the input signal. 2 Il.

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The invention relates to automation and communication technology and can be used in signal transmission systems.

The purpose of the invention is to improve the accuracy of the conversion by expanding the dynamic range of the converted signals.

FIG. 1 shows a block diagram of a delta modulator; in fig. 2 is a graph of the signal-to-noise ratio (s / w) for different types of delta modulation.

The delta-modulator contains the first - the third comparators 1-3, the imaging unit 4 of the information pulse sequence (PHIL), the first - the third integrator 5-7, the amplitude-pulse modulator (AIM) 8, the pack selection unit 9, the pack expansion unit 10 EFROL , multiplexer 11, switching unit 12 and source 13 threshold levels. The delta-modulator has informational 14 and clock 15 inputs and output 16. The FIEP4 can be implemented as a trigger.

A symbol allocation block 9 may be executed on a shift register, to the direct and inverse outputs of which equivalence elements are connected. At the same time, on the first output of block 9, the signal appears when a packet is selected from N + 1 identical symbols (pulses or pauses), on the second output — with N, and on the third — with N-1 symbols in the packet (SW).

The block 10 of expanding packs of symbols can be implemented, for example, on a four-bit shift register (for N 4), the outputs of the first two bits of which are connected to the inputs of the OR element, and the outputs of the last two bits — through elements AND, whose other inputs The control inputs of the block, the fifth input of the AND element, is combined with the information input of the register and is the information input of the block.

Blocks 2, 3, 5-13 form a local demodulator, similar to the delta demodulator on the receiving side. The local demodulator and delta-demodulator on the receiving side form an approximating signal from the same digital signal, therefore, if the compression factor M is applied to the transmitting side using a local demodulator, the delta-demodulator will

work with the expansion coefficient M (U6x), since in relation to the input analog signal the local demodulator is connected to the feedback circuit of the delta modulator, and the delta demodulator on the receiving side is switched on directly.

The delta modulator operates as follows.

The input analog signal U, is fed from input 14 to comparator 1, where it is compared with the restored value of the analog signal and the previous clock fed from integrator 5 (from the output of the local demodulator). If ,, then the output of the comparator is a logical signal 1

what if

U, 1 - logical O. Comparator 1 has a narrow partitioned zone, the width of which is 3-4 times less than the minimum quantization step of a delta modulator. The output signal of the comparator 1 is supplied to the information input of the imaging device 4, which, with a clock frequency FT, coming from the input 15, forms the output digital information

a sequence of logical symbols O and 1,

which carries

information about the analog input signal U1, from the output of the PFTI 4 signal is fed to the output 16 of the delta modulator, as well as to the input of the local demodulator, which is the feedback circuit of the delta modulator.

The digital compression of the input analog signal in the delta modulator is performed in this way.

As the slope of the input analog signal increases, a pack of uniform characters appears at the delta-modulated (DM) signal at the output of the FIIP 4. Prior to the appearance of packs of N + 1 or more homogeneous symbols, the AIM 8 operates with a constant initial value of the signal from the output of integrator 6 in accordance with the digital DM signal received at its input. In this case, the delta modulator operates in the linear delta modulation mode with a quantization step d ,. When packs of N + 1 or more homogeneous symbols appear, the delta modulator begins to work in compression mode. At the same time, up to the estimated level of the input speech signal, lower P1, the compression is carried out by packs of N + 1 or more uniform symbols, at P1 P per Ј P2, the compression is driven by packs of N and more uniform SYMBOLS. bundles of N-1 or more uniform characters.

The quantization step of the delta modulator depending on the estimated level of the input speech signals is controlled by blocks 2, 3, 7, 9-13. In this case, the integrator 7 can be both analog and digital. Depending on this, respectively, comparators 2 and 3 should be analog or digital. In the latter case, the number of bits of the comparator corresponds to the size of the digital integrator 7. Source 13 must form four levels P ,, P t, P2 | pЈ in analog or digital form. Accordingly, the switching unit 12 must contain either digital switches of the appropriate size two-channel switches or analog ones.

Consider an example of analog shaping of signal level estimates. Then, the integrator 7 is implemented as a double integrator, on which an estimate of the level of the input analog signal is formed from the packs of uniform symbols separated by block 10 from the output DM signal.

Consider the process of adapting the quantization step in a delta-modulator to the value of the level of the input analog signal. With an increase in the level of this signal at the output of FISH 4 in the DM signal, bundles of uniform symbols appear. The DM signal enters a block 9 of the selection of symbols, where it is fed to the information input of the five-bit shift register. To the value of the estimated input signal level, equal to Р,, block 9 works on the selection of packs of more than characters. On the fifth clock after the arrival of a pack of five homogeneous symbols, the same logical symbols appear on the five bits of the register. At the output of the corresponding equivalence element of block 9, a signal appears. In this way, bundles of uniform characters are extracted, however, the duration of the selected packs is reduced to one clock cycle. The total signal flow corresponding to packs of N + 1 homogeneous

0

five

0

five

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five

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five

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five

characters, is fed to the multiplexer 11, which is controlled by the signals from the outputs of the Comparators 2 and 3.

Comparator 2 compares the estimated value of the input analog signal with the level P ,, and the comparator is the 3rd level Pg until P per is P P. If Preg7, pf, a logical 1 signal appears at the output of the comparator 2, which , controlled by the switching unit 12, connects to the input of the comparator 2 a signal P, from the source 13.

Thus, if P reg, Pr, at the output of the comparator 3, a logical signal 1 appears, which, by controlling the switching unit 12, connects the signal Pa to the input of the comparator 3. Since in this situation, P per, the outputs of Comparators 2 and 3 are accessed by the logic O signals. The inputs to the control inputs of multiplexer 11, they control the connection of the signal from the first output of block 9 to extension 10 of the symbol packs. At the same time, the signal of the logical comparators 2 and 3, arriving at the control inputs of block 10, permits the passage of characters from all bits of its shift register to the OR element, with the result that the output of the latter, i.e. at the output of block 10, the initial duration of the pack of uniform symbols is restored.

With a further increase in the input analog signal level, the number and duration of the packs increase, and consequently, the estimated value of the level P reg generated by the integrator 7 increases. If P per P, then the output of comparator 2 is a logical signal 1. This signal connects the second output block 9 (packs of characters) to the information input of block 10, in which the output of the last bit of the shift register is turned off from the OR element. In this case, block 10 recovers the initial duration of only packs consisting of uniform symbols. The logical 1 signal from the output of the comparator 2 enters the switching unit 12 and connects to the input of the comparator 2 a signal of the level Pi, generated by the source 13. Depending on the initial quantization step, clock frequency and circuit design features,

In a delta modulator, this level should be P 2 (0.9-0.95) P. Connecting a P-level signal instead of a P is necessary because analyzing the level of more or more homogeneous symbols increases the signal level at the output of the second integrator 5, which, accordingly, increases the level of the output pulse of the AIM 8 and thereby increases the quantization step of the delta module Torah. This increase in pitch causes a decrease in the density and length of packs of uniform

DM-signal symbols at the output of FIEP 4, 15 by companding on N + 1 packs

which, in turn, reduces the estimated value of the speech signal level Reg. In this case, the delta modulator can return to the analysis of a digital signal using N + 1 uniform symbols, and then again to analysis using N uniform symbols, etc. This situation can occur, for example, with homogeneous symbols; III - delta modulation with digital companding by N-1 KiN + 1 packs of uniform characters. The linear delta modulation of Qi operates with a constant quantization step LL and reaches maximum security at an input signal level equal to Pft. Delta-modulation with digital companding by scaling up the level of the input analog signal. For its prevention, from the N + 1 uniform symbols, to the input of the comparator 2, connects the input digital DM signal to the level P, instead of P, if,.

For the same reason, at P ftr i P, instead of level P 2, the signal of logic 1 is connected to the input of comparator 3 by means of block 12 and a signal of level P i is connected to the input of comparator 3. In this case, the corresponding switchings also occur in the multiplexer 11 and the pack expansion unit 11T. Thus, in this situation, level analysis is carried out on the basis of packs of homogeneous symbols of the DM signal, consisting of more homogeneous symbols.

At the output of the pack 10 expansion packs, packs of uniform symbols, extracted from the output DM signal, are obtained in the form of packs of logical 1,

with and the change is made on the basis of the analysis of the DM signal by N + 1 homogeneous symbols, with the PE RSIGN PP analysis

50

In which laid the information about the level of the input analog signal. In the case of a 45-yes signal, it is conducted on N uniform than, depending on the magnitude of this character, and on P c Ј P g P c - on

The level of analysis and the allocation of packs are conducted on a smaller number of simultaneously analyzed homogeneous symbols within N-14K Ј N + 1. This batch signal is fed to the inputs of integrators 6 and 7, where it is converted into a level signal, and, acting on AIM 8, controls the level of the output pulses of AIM 8 and the quantization step size, and consequently, the compression value in the delta modulator ( in the delta demodul torus). From the output signal of the AIM 8 ina at Pp Ј RStsGN g with N-1 uniform symbols; at point P, maximum protection is achieved, which theoretically corresponds to protection at points Rl and Pb when using the same integration scheme in delta-demodulators.

5, - Thus, the proposed delta modulator allows the dynamic range of the transmitted voice signals to be expanded, thereby improving the conversion accuracy.

Tegrator 5 forms a reconstructed voice input analog signal, which is fed to the second input of comparator 1 (in a delta-demodulator - an analog signal receiver) „

FIG. Figure 2 shows the qualitative dependences of the signal-to-noise ratio on the level of input analog signals for various types of delta modulation: I — linear delta modulation (without companding); II - delta modulation with digital

homogeneous characters; III - delta modulation with digital companding by N-1 KiN + 1 packs of uniform characters. The linear delta modulation of Qi operates with a constant quantization step LL and reaches maximum security at an input signal level equal to Pft. Delta-modulation with digital companding by bundles of N + 1 uniform symbols in the output digital DM signal to an input signal level of 7 e works with a constant quantization step L, and when P.Q is exceeded, the quantization step value changes. Companding is carried out on N + 1 uniform symbols, while maximum protection is achieved at the input signal level (Pb). In the proposed delta-modulator, dependence III has four sections where the quantization step varies according to different laws. PJJ values of the input analog signal, the delta modulator operates with a constant quantization step. &,

PD P CWI-H

The pg quantization step changes and the change is made on the basis of the analysis of the DM signal using N + 1 homogeneous symbols, with the PE RSIGN Pp analysis

da-signal is conducted on N uniform symbols, and when P c Ј P gig R c - on

da-signal is conducted on N uniform symbols, and when P c Ј P gig R c - on

and when Rr RSGG g with N-1 homogeneous characters; at point Pc, maximum protection is achieved, which theoretically corresponds to protection at points Rl and Pb using the same integration schemes in the delta demodulator ah.

Thus, the proposed delta-modulator allows the dynamic range of the transmitted voice signals to be expanded, thereby improving the conversion accuracy.

Claims (1)

Claims A delta modulator containing a first comparator, the first input of which is the information input of the delta modulator, the output is connected to the information input of the information pulse shaper, the clock input of which is combined with the clock inputs of the symbol selection block and the expansion unit packs of symbols is the clock input of the delta modulator, the first integrator, the output of which is connected to the second input of the first comparator, the output of the information pulse generator the sequence is connected to the information input of the block selection of symbols and is the output of the delta module torus, characterized in that, in order to increase the accuracy of the conversion by expanding the dynamic range of the converted signals, a pulse-amplitude modulator, a second and third comparators, a second and a third integrator, a multiplexer, a switching unit and a source of threshold levels are introduced into the delta modulator whose outputs are connected to RA Q 0 five corresponding information inputs of the switching unit, the first - the third outputs of the block selection of packs of characters are connected to the multiplexer information inputs of the same name, the output of which is connected to the information input of the character extension block, the output of which is connected to the inputs of the third and second integrators, the outputs of which are connected respectively to the first inputs of the second and the third comparators and the first input of the amplitude-pulse modulator, the second input of which is combined with the information input of the expansion unit bursts of symbols and connected to the output of the information pulse sequence generator, the output of the pulse amplitude modulator is connected to the input of the first integrator, the outputs of the second and third comparators are connected respectively to the first and second control inputs of the extension pack of the symbols, multiplexer and switching unit, the first and second the outputs of which are connected to the second inputs of the second and third comparators. PC Rsign, 30b