WO1999010988A2 - Spread spectrum communication device - Google Patents

Spread spectrum communication device

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Publication number
WO1999010988A2
WO1999010988A2 PCT/RU1998/000248 RU9800248W WO1999010988A2 WO 1999010988 A2 WO1999010988 A2 WO 1999010988A2 RU 9800248 W RU9800248 W RU 9800248W WO 1999010988 A2 WO1999010988 A2 WO 1999010988A2
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WO
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Patent type
Prior art keywords
input
output
phase
signal generator
carrier signal
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Application number
PCT/RU1998/000248
Other languages
French (fr)
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WO1999010988A3 (en )
Inventor
Gennady Fedorovich Degtyarev
Leonid Nikolaevich Aman
Anatoly Yakovlevich Demidov
Vitaly Andreevich Kachalin
Gennady Andreevich Kosin
Artur Viktorovich Kostin
Viktor Nikolaevich Leshkov
Alexei Viktorovich Pugovkin
Leonid Yakovlevich Serebrennikov
Alexandr Nikolaevich Umnov
Original Assignee
Gennady Fedorovich Degtyarev
Leonid Nikolaevich Aman
Anatoly Yakovlevich Demidov
Vitaly Andreevich Kachalin
Gennady Andreevich Kosin
Artur Viktorovich Kostin
Viktor Nikolaevich Leshkov
Alexei Viktorovich Pugovkin
Serebrennikov Leonid Yakovlevi
Alexandr Nikolaevich Umnov
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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation

Abstract

The communication device comprises, connected in series, a binary information source, a carrier pulse generator, a transmitter, a communication link, a high-frequency signal receiver, a correlation-phase demodulator, a decision-maker, a binary information receiver as well as a fast starting pulse generator, an input of which is coupled to the output of the binary information source and an output is connected to the pulse input of the carrier signal generator which is provided with different, for each of information value, phase of constituents of one out of two similar noise-like signals delayed one relative to another by a predetermined time period T exceeding their correlation interval. Here the correlation-phase demodulator is provided base on received signal compression with subsequent synchronous (quasi-coherent) response processing at an input of a matched filter which ensures unique correspondence of transmitted and received information.

Description

COMMUNICATION DEVICE

This invention relates to information transmit-receive means, where information is presented in a discrete (binary) form, over high-frequency communication lines using broadened spectrum signal (noise-like signals).

So-called active correlation receivers form the basis for most common communication means operating on noise-like signals (NLS) and to generate respective high-frequency signals at the transmitting end of communication links various types of modulators are generally utilised (see L.E.Varakin Communication Systems Operating on Noise-Like Signals. - Moscow, Radio I Svyaz, 19850. Here, in order to transmit binary data, various modulating code pseudorandom sequences can be used characterised in that a maximum value of auto-correlation function of a predetermined sequence defining each of data bit states is greater than a similar value of mutual correlation function of these sequences (see EPO application No.366 086, IPC H 04 K 3/00, publ. 02.05.90).

However, capabilities of componentry employed and strict requirements to receiver timing circuits restrict the spectral width if signals used here to units or several dozens of MHz.

In using matched filters, timing availability, in a general case, is not a prerequisite for detecting (discerning) receiver input signals. At the same time, the difficulty of conforming modulator and matched filters characteristics renders implementing advantages of such receivers a rather complicated technical problem which substantially limits classes of broadened-spectrum signals used and, consequently, capabilities of communication systems. Each of such systems becomes unique, oriented either to the use of pseudo-noise (pseudorandom) signals of specific types and having specific characteristics (see Japanese application No.63-31 127, IPC H 04 J 13/00, publ. 22.06.88; EPO application No.O 263 687, IPC H 04 K 3/00, publ. 13.04.88) or to the use of matched filtering to enhance timing circuits operation at multi-stage processing of receiver input signals (see German application No. OS 37 40 665, IPC H 04 J 13/00, publ. 16.06.88). As a result, the spectral width of practically used NLS, at the best, is 10 to 20 MHz at their rather limited real base, whilst in communication systems of a sufficiently large throughput and in multi-station access system NLS advantages manifest themselves the more, the broader the spectrum of signals used therein. Here problems arise associated with providing secure discernment of binary signals while maintaining high efficiency of data transmit-receive systems.

In a binary information transmit-receive device using signals modulated by direct and reversed pseudorandom pulse wave-trains (see application PCT No.92/02997, IPC H04 B 15/00, published 20.02.92), their correlation processing (convolution) is performed by a filter on ASW-elements matched by one of its outputs with direct, and by another with reversed modulation formats of received signals. Here, depending on the logical state of transmitted data, one of correlator output forms a radio pulse whose envelope corresponds to auto-correlation function (ACF) of the modulating code sequence while another output forms its convolution function (CF). When the transmitted data logical state changes, signals at the correlator outputs accordingly change their places.

The class of code sequences for which ACF and CF have sufficient distinctiveness is rather restricted. Given actual characteristics of the signal generating, transmit-receive and processing trunk lines, advantages of this device become even more insignificant which limits bands of NLS used here to units and several dozens of MHz.

Out of known analogues, the closest by technical essence and implementation is a communication device wherein separating digital streams corresponding to logical "0" and "1 " of transmitted data is carried out due to phase change (by 180°) of one of signals delayed with respect to another by a predetermined amount, each of the signals being a sample of the same non-periodic sequence (see US patent No.4.363.130, IPC H04 K 1/00, published 07.12.82). The device is composed from, connected in series, a binary information source, a carrier signal generator, a transmitter, a communication link, a high-frequency signal receiver, a correlation-phase demodulator, a decision-maker and a binary information receiver.

Here the carrier signal is generated by alternate strobing of reference sequence and, depending on the value of the transmitted data, of direct or inverse non-periodic sequence delayed by a half inter-bit time interval. At a receiver end of the device, corresponding delay compensation is performed and the source information is retrieved due to signal phase (correlation) processing.

In the used version of the carrier signal generator such implementation of presenting logical levels of transmitted message, using time correlational processing of received signal, results in reducing throughput of such communication systems. As the band of signals transmitted on the communication link increases, losses on their conversion in processing sharply increase resulting in substantial reduction of radio systems efficiency. Signal bands actually obtainable here are several MHz.

The invention is directed to broadening the spectrum for a larger class of noiselike signals used in digital communication links.

The above task is attained due to the fact that a communication device comprising a carrier signal generator, a control input of which is coupled to an output of binary information source and an output of which is connected to an input of transmitter whose output is connected, via communication link, with an input of a high- frequency signal receiver, as well as a correlation-phase demodulator, an input of which is coupled to an output of the high-frequency signal receiver, and an output of which is connected to a decision-maker input, an output of the decision-maker is, in turn, connected to the input of the binary information receiver, and in contrast to the prototype device, it is provided with a generator of fast delta-shaped starting pulses whose input is coupled to the output of the binary information source and whose output is connected to the pulse input of the carrier signal generator made with different for each of information value phase of constituents of one of two duration-limited similar noise-like signals delayed with respect to one another by a predetermined time period T exceeding their correlation interval, and the correlation-phase demodulator is adapted to compress received signals.

In this case, the carrier signal generator may be made as a noise-like signal generator an input of which forms a pulse input of the carrier signal generator while an output of which is connected to first combined inputs of multipliers, whereby a second input of one of the multipliers is coupled to one of outputs of a two-phase generator and a second input of another of the multipliers is coupled to an output of a switch one input of which forms the control input of the carrier signal generator while two other inputs are coupled to the outputs of the two-phase generator, whereby an output of one of the multipliers is connected to one of summator inputs directly and an output of the other of the multipliers is connected to another summator input through a delay line for delaying by a predetermined time T, whereby a summator output is an output of the carrier signal generator.

Said carrier signal generator may be made as a noise-like signal generator an input of which forms a pulse input of the carrier signal generator and an output of which is connected to first inputs of the two multipliers, respectively, via a delay line and directly, whereby the second input of one of the multipliers is coupled to one of the outputs of the two-phase generator via a phase corrector, while the second input of the other multiplier is coupled to the output of the switch one input of which forms the control input of the carrier signal generator and the other two are coupled to the outputs of the two-phase generator, the outputs of the multipliers are connected to respective summator inputs, and the summator output is the output of the carrier signal generator.

The correlation-phase demodulator may be provided as a matched filter an input of which forms an input of the correlation-phase demodulator and an output of which is connected to one of inputs of a synchronous detector, another input of which is connected to an output of the matched filter through a delay line for delaying by the predetermined time T, whereby an output of the synchronous detector forms the output of the correlation-phase demodulator. Said carrier signal generator according to one of possible embodiments has a two- phase generator, three strobe members, a summator, a switch, a 90 degrees phase- shifter, a delay member for delaying by the predetermined time T, a passive phase- code manipulator, whereby one of outputs of the two-phase generator is connected to a high-frequency input of the first strobe member a pulse input of which is coupled to one of switch outputs, another output of which is connected to a pulse input of the second strobe member, a high-frequency input of which is connected to another output of the two-phase generator, whereby a high-frequency input of the third strobe member is coupled, through the phase-shifter, to one of the two-phase generator outputs, while a pulse input of the third strobe member is combined with the input of the delay member for delaying by the predetermined time T and forms a pulse input of the carrier signal generator, whereas the delay member output is connected to the switch pulse input another input of which forms the control input of the carrier signal generator, whereby outputs of each of the strobe members are connected to respective summator inputs, a summator output being connected to the input of the passive phase-code manipulator whose output, in turn, is the output of the carrier signal generator, respectively, wherein a phase correction member is connected in series in one of the outputs of the synchronous detector of the correlation-phase demodulator.

The correlation-phase demodulator may be provided also as a matched filter an input of which forms an input of the correlation-phase demodulator and an output of which is connected, via a delay line for delaying by the predetermined time T, to combined inputs of the summator and a first subtracter and other inputs of which are also combined and coupled to the matched filter output, whereby outputs of the summator and the first subtracter, via its own amplitude detector each, are connected with respective inputs of a second subtracter an output of which is the input of correlation-phase demodulator.

The above carrier signal generator may be made as a acoustic surface-wave element comprising three in-phase and one reversed phase signal band matched interdigit transducer positioned on a piezo substrate to one side of the modulating interdigit transducer an output of which is the output of the carrier signal generator, whereby input converters of the acoustic surface-wave member are combined in pairs and coupled to corresponding switch outputs, switch inputs forming, respectively, a pulse and a control inputs of the carrier signal generator, whereby spacings between the converters of each input pair, in a direction of the member acoustic conductor, are equal to each other and are defined as a product of the predetermined delay time T multiplied by the propagation velocity of the acoustic surface-wave.

The correlation-phase demodulator may be provided as an acoustic surface- wave member comprising two identical output signal band matched interdigit transducers positioned on a piezo substrate to one side of the demodulating interdigit transducer an input of which forms the input of the correlation-phase demodulator, whereby the spacing between output converters, in a direction of acoustic conductor of the acoustic surface-wave member, is defined by a product of the predetermined delay time T multiplied by the wave propagation velocity, wherein each of the output transducers is connected to a corresponding input of a synchronous detector an output of which is the output of the correlation-phase demodulator.

The correlation-phase demodulator may be made as an acoustic surface-wave element comprising a demodulating interdigit transducer placed on a piezo substrate which forms an input of the correlation-phase demodulator as well as equally spaced from one side of an input converter, in a direction of the member's acoustic conductor, two groups consisting of an in-phase and in-phase as well as of in-phase and reversed phase output signal band matched interdigit transducers, whereby the spacings between output converters of each group, in a direction of the member's acoustic conductor, are defined as a product of the predetermined delay time T multiplies by the propagation velocity of the acoustic surface-wave, while differently spaced from the input converter, in a direction of the member's acoustic conductor, output converters are combined in pairs and are connected, via separate amplitude detectors to corresponding subtracter inputs, an output of which is the output of the correlation- phase demodulator.

According to a still further embodiment, the above carrier signal generator is made as a acoustic surface-wave element comprising two input signal band matched interdigit transducers positioned on a piezoelectric to one side of the modulating interdigit transducer which is an output of the carrier signal generator, whereby a first input converter is coupled to a switch output, a first input of which forms a control input of the carrier signal generator, a second input combined with an inverter input forms a pulse input of the carrier signal generator and is connected with a second input converter, while a third input is coupled to the inverter output, whereby the spacing between the input converters, in a direction of the member's acoustic conductor, is defined as a product of the predetermined delay time T multiplied by the propagation velocity of the acoustic surface-wave.

The distances between the signal band matched interdigit transducers, determined in a direction of the member's acoustic conductor as a product of the predetermined delay time T multiplied by the propagation velocity of the acoustic surface-wave, are equal to an odd number of quarters of its length.

The above carrier signal generator may also be provided in the form of acoustic surface-wave member comprising a modulating interdigit transducer placed on a piezoelectric being an output of the carrier signal generator, as well as an input signal band matched interdigit transducer coupled to a summator output, one summator input being coupled to an output of a delay member for delaying by the predetermined time T, another summator input being coupled to a switch output, a first input of the switch forming a control input of the carrier signal generator while a second input combined with inputs of inverter and delay member forms a pulse input of the carrier signal generator, and a third input is coupled to the inverter output.

The present invention is based on the fact that determining features of most noise-like signals used for information transmission are mainly concentrated in a time period close to their correlation interval which is objectively characterised by a low relative level of lateral self-correlation function lobes when using NLS as compared to its main maximum.

A flow-diagram of the device to be patented is presented on Fig.1 ; Fig.2 and Fig.3 show embodiments of the carrier signal generator; Fig.4 and Fig.5 show embodiments of the correlation-phase demodulator; Fig.6 shows and embodiment of the carrier signal generator using an acoustic surface-wave element where the waves are induced by single-polarity pulses; Fig.7 and Fig.8 show embodiments of the correlation-phase demodulator using acoustic surface-wave elements; Fig.9 shows an embodiment of the carrier signal generator using an acoustic surface-wave element where the waves are induced by dual-polarity pulses; Fig.10 shows an embodiment of the carrier signal generator using an acoustic surface-wave element and an external timing circuit; Fig.1 1 and Fig.12 show an initial noise-like signal and its ACF, respectively; Fig.13 shows a voltage oscillogram at the carrier signal output; Fig.14 and Fig.15 show signals at the inputs and output of the synchronous detector, respectively, per one data bit; Fig.16 and Fig.17 show signals at the inputs and output of the synchronous detector, respectively, defined by source information.

The device consists (see Fig.1 ) of, connected in series, binary information source 1 , carrier signal generator 2 having constituent phase of one out of two similar noise-like signals separated by a predetermined time period T, said phase being different for each of information value, transmitter 3, communication link 4, high- frequency signal receiver 5, correlation-phase demodulator 6, decision-maker 7, binary information receiver 8 as well as fast starting pulse generator 9 an input of which is coupled to an output of the binary information source 1.

The carrier signal generator 2, in turn, comprises a noise-like signal generator 10 an input of which forms a pulse input 1 1 of the carrier signal generator 2 and is coupled to an output of the fast starting pulse generator 9, and an output of which is connected to first combined inputs of multipliers 12 and 13. A second input of the multiplier 12 is coupled to one of outputs of a two-phase generator 14, while a second input of the multiplier 13 is coupled to an output of the multiplier 15 whose two inputs are coupled to outputs of the two-phase generator 14 and a third input forms a control input 16 of the carrier signal generator and is coupled to an output of the binary information source 1. An output of the multiplier 13 is connected with one of inputs of summator 17 another input of which is coupled, through a delay line 18 for delaying by the predetermined time T, to an output of the multiplier 12. An output of the summator 17 is, in turn, an output 19 of the carrier signal generator 2.

Correlation-phase demodulator 6 is a matched filter 20 whose input forms an input 21 of the demodulator 5 and whose output is directly connected to one of inputs of synchronous detector 22 to a second input of which the output of demodulator 6 is connected via a compensating delay line 23 for delaying by the predetermined time T, whereby an output of the synchronous detector 22 is simultaneously an output 24 of the correlation-phase demodulator 6.

The device to be patented can operate with any NLS modulation formats: with linear frequency modulation (LFM) or chirp signals, phase-shift-keyed (PSK) and discrete-(digital)-time (DT) signals, coded pulse pseudorandom wave-trains (PRW), etc. The matched filter is designed for optimum signal processing generated by the NLS generator of the carrier signal generator and a known version of its implementation cam be determined for each specific case (see L.E.Varakin, "Communication Systems Operating on Noise-Like Signals", Moscow, Radio I Svyaz, 1985; D.Morgan "Acoustic Surface-Wave Signal Processor", translated from English, Moscow, Radio I Svyaz, 1990). Fig.4 demonstrates an example of providing a matched filter intended to process PRW and PSK signals.

The fast starting pulse generator is provided based on a differentiating circuit using active TT-logic elements of corresponding speed of response.

Any two-phase sinusoidal generator forms at its outputs two reversed-phase high- frequency voltages necessary to transfer NLS spectrum to the operating part of RF- range. A switch is made according to a diode-resister scheme using TT-logic elements. The level of spurious passing through the switch is not worse than minus 20 dB.

Depending on the type of signals generated by the NLS generator, multipliers may be provided both as a balanced modulator and as a mixer with additional two- phase generator frequency signal rejection. The device is based on the Gilbert circuit with additional phasing of multiplier inputs/outputs. Suppression level of two-phase generator signals is not less than 20 dB.

Summator is of any type. In the simplest case (see Fig.1 and Fig.2), it is provided as a common selective load of the multipliers.

In the simplest case, the transmitter is a power amplifier having transition (matching) circuits for the communication link being used.

The high-frequency signal receiver may be both of heterodyne type and with direct amplification, depending on the type of the matched filter being used.

The synchronous detector is a multiplier having at its output low-frequency filtering circuits optimum with respect to ACF envelope of the NLS being used, for example, a Wien bridge.

The decision-maker, in the simplest case, is a differential amplifier-limiter with an RS-trigger at its output.

Delay lines are designed to function in its own frequency band each and are made taking into account recommendations set forth in monographs (see L.E.Varakin, "Communication Systems Operating on Noise-Like Signals", Moscow, Radio and svyaz, 1985, pp.352-361 ; A.I.Morozov, V.V.Proklov, B.A.Stankovsky, "Piezoelectric Converters for Radio- Electronic Devices", Moscow, Radio I Svyaz, 1981 , pp.102-105).

With increasing the NLS spectrum average frequency, providing the required characteristics of the delay line 18 for delaying by the predetermined time T may prove a complicated technical problem. To eliminate arising problems (see Fig.2), the delay line 18 is coupled to the first input of the multiplier 18 whose output is directly connected to a corresponding summator 17 input (see Fig.2). Here the input of the delay line 18 for delaying by the predetermined time T is coupled to the output of the noise-like signal generator 10, while the multiplier 12 second input is coupled to a phase corrector 25 of any type for a changeable angle range not less than 90 degrees.

In all other respects, the circuit and operation of the carrier signal generator 2 do not undergo any alterations.

Duration of noise-like signals generated by the generator 10 in the above embodiments of the carrier signal generator 2 (see Fig.1 and Fig.2) is limited to minimum value of the inter-bit time interval in the transmitted data stream supplied by the source 1 output.

In order to remove this limitation, the carrier signal generator (see Fig.3) comprising the two-phase generator 23 has included therein three strobe members 27, 28, 29 as well as summator 30, switch 31 , 90 degrees phase shifter 32, delay member 33 for delaying by the predetermined time T, passive phase-code manipulator 34. One of outputs of the two-phase generator 26 is connected to a high-frequency input of the first strobe member 27, a control input of which is coupled to one of outputs of the switch 31. Another output of the switch 31 is connected to a control input of the second strobe member 28, a high-frequency input of which is coupled to another output of the two-phase generator 26.

A high-frequency input of the third strobe member 29 is coupled, via the phase- shifter 32, to one of the outputs of the two-phase generator 26 while a control input of the third strobe member 29 is combined with an input of the delay member 33 and forms the pulse input 11 of the carrier signal generator 2. An output of the delay member 33 is connected to a pulse input of the switch 31 , another input of which forms the control input 16 of the carrier signal generator 2. Outputs of each of the strobe members 27, 28, 29 are connected to corresponding inputs of the summator 30. An output of the summator 30 is connected with an input of the passive phase- code manipulator 34 which, in this case, is provided based on a multi-tap delay line 36 with a discrete equal to pulse duration at outputs of the strobe members 27, 28, 29. In turn, outputs of the multi-tap delay line 36 are connected, through a weighting coefficient matrix 37, with corresponding inputs of the summator 38 whose output forms an output of the manipulator 34 and is the input 19 of the carrier signal generator 2.

Simultaneously, an input of the synchronous detector 22 of the correlation- phase demodulator 6 (see Fig.4) is additionally coupled to the phase correction member 35 an input of which is combined with an input of compensating line 23 for delaying by the predetermined time T and is coupled to an output of the matched filter 20. An input of the matched filter 20 forms the input 21 of the demodulator 6.

Inputs of the compensating delay line 23 and of the phase correction member 35 are coupled to corresponding inputs of the synchronous detector 22 whose output is the output 24 of the demodulator 6.

The matched filter 20 of the correlation-phase demodulator 6, in the present case, is the multi-tap delay line 39 outputs of which are connected, via the weighting coefficient matrix 40 reversed as compared to the matrix 37 of the phase -code manipulator 34, with inputs of the summatior 41 whose output is connected, via the band-pass filter 42 optimal with respect to pulses at outputs of strobe members of the generator 2, with an input of the compensating delay line 23.

The strobe members are provided as a pin-diode switch. In order to control the diode states and to generate high-frequency pulses of a predetermined duration at the strobe member outputs, biased multivibrators based on TT-logic are employed. The level of spurious passing through the closed switch is not worse than minus 30 dB, setting time is not more than one period of the two-phase generator output voltage.

The delay member is of any type, for example, an integrating RC-circuit having a TT- logic element generator.

The 90 degrees phase-shifter is provided on delaying RC-circuits, accuracy of setting a predetermined phase shift is not worse than plus/minus 10 degrees.

Time discretes of the multi-tap delay line of the phase-code manipulator and matched filter is equal to the pulse duration at the strobe member outputs. The matched filter pass-band, by the output signal, is defined as the unit divided by pulse duration at the strobe member outputs.

The phase correction member is of similar construction as the 90-degrees phase- shifter.

With NLS bandwidth comparable to its average frequency value, when the number of periods of filling correlation peaks at an output of the matched filter 20 is several units, efficiency of synchronous detector 22 operation is significantly reduced.

With the aim of relative broadening the spectrum of signals being processed, the correlation-phase demodulator 6 comprising, connected in series, matched filter 20 and compensating delay line 23, has introduced thereto (see Fig.5) the summator 43, first subtracter 44, second subtracter 46, amplitude detectors 46 and 47. Here the matched filter 20 input forms the input 21 of demodulator 6, and its output is connected, via the compensating delay line 23 for delaying by the predetermined time T, with combined inputs of summator 43 and the first subtracter 44, other inputs of which are also combined and coupled to the matched filter 20 output. Outputs of the summator 43 and the first subtracter 44, each via its amplitude detector 46 and 47, are connected to corresponding inputs of the second subtracter 45 whose output is the output 24 of the correction-phase demodulator 6.

Summators and subtracters are provided based on a current addition circuit on a common load and differ from each other only by the presence of an inverter at one of member outputs.

Amplitude detectors are provided according to any scheme of high-frequency-filled pulse envelope extraction. At their output the detectors comprise low-frequency filtering circuits, optimal with respect the ACF envelope of NLS being used, for example, Wien bridges.

The above-discussed embodiments of the device to be patented allow to utilise noise-like signals with a band up to 30-50 MHz and an average frequency up to 100- 150 MHz. in order to further broaden the NLS band, with corresponding increase of its average frequency, the carrier signal generator 2 is made on acoustic surface waves (see Fig.6) and includes three in-phase and one reversed phase input interdigit transducers 48, 49, 50, 51 located on a piezo substrate 52 to one side of an encoding interdigit transducer 53 an output of which is the output 19 of the carrier signal generator 2. The input converters 48 and 49, as well as 50 and 51 are combined in pairs and coupled to corresponding outputs of the switch 54 whose outputs form, respectively, the pulse input 1 1 and control input 16 of the carrier signal generator 2. Distances L between converters 48 and 49, 50 and 51 are equal to the product of the predetermined delay time T multiplied by the propagation velocity of acoustic surface wave V. In one of the combined pairs, transducer pins of the same name are differently directed.

For the same purpose of broadening the frequency spectrum of noise-like signals being processed, the correlation-phase demodulator 6 (see Fig.7) is provided on acoustic surface waves and comprises two identical output interdigit transducers 55, 56 disposed on a piezo-substrate 57 to one side from the demodulating pin back-to- back converter 58, an input of which is the input 21 of demodulator 6. Each of the output pin back-to-back converters 55 and 56 is connected with a corresponding input of the synchronous detector 59 whose output is the output of demodulator 6. The distance L between the output transducers is defined as a product of multiplication of the predetermined delay time T by the propagation velocity of acoustic surface wave V. In order to reduce the influence of secondary effects within piezo-electric transducers on the result of processing demodulator 6 input signals, this distance is selected as a multiple of an odd number of quarters of acoustic wavelength.

Further broadening the spectrum of NLS being processed, at average frequency values comparable to their band, is provided by the correlation-phase demodulator 6 (see Fig.8) made on acoustic surface waves and comprising a demodulating interdigit transducer 61 located on a piezo-substrate 60, the converter forming an input 21 of demodulator 6, as well as two equally spaced from the demodulating interdigit transducer 61 groups of successive in-phase, in-phase and in-phase, reversed phase output interdigit transducers 62, 63, 64, 65. The distances L between the output transducers 62, 63 and 64, 65 in each of these groups are equal to each other and are defined as a product of multiplication of the predetermined delay time T by the propagation velocity of acoustic surface wave V. Output interdigit transducers 62, 63 and 64, 65 equally spaced from said transducer 61 are combined in pairs and connected, via amplitude detectors 66, 67, with corresponding inputs of subtracter 68 an output of which is the output 24 of demodulator 6.

For the purpose of reducing secondary effects within acoustic surface-wave transducers with simultaneous simplification of ASW-element design, the carrier signal generator 2 (see Fig.9) includes two input interdigit transducers 69 and 70 positioned on a piezo-substrate 71 to one side from modulating interdigit transducer 72 whose output is the output 19 of the carrier signal generator 2. Here the first input transducer 69 is coupled to an output of the switch 73 one input of which forms the control input 16 of the carrier signal generator while its other input is coupled to an output of inverter 74. Inverter 74 input is combined with a third input of the switch 73 which at the same time is the pulse input 1 1 of the carrier signal generator 2, and is coupled to the second input interdigit transducer 70. The distance between the input transducers 69 and 70 is defined as a product of the predetermined delay time T multiplied by the propagation velocity V of acoustic surface wave.

In carrier signal generators operating on acoustic surface waves, the predetermined delay time T is determined by mutual arrangement of input interdigit transducers which is very difficult to change after a ASW-element has been fabricated.

In order to enhance functional capabilities with respect to setting the delay time T, the carrier signal generator 2 made using an acoustic surface-wave element which comprises a modulating interdigit transducer 76 disposed on piezo-electric 75, said converter being the output 19 of the carrier signal generator 2, as well as a second, signal band matched interdigit transducer 77, has introduced thereto a summator 78 one input of which is coupled to an output of the delay member 79 for delaying by the predetermined time T, and another input is coupled to an output of switch 80 whose first input forms the control input 16 of the carrier signal generator 2, a second input combined with inputs of inverter 81 and delay member 79 forms the pulse input of the carrier signal generator 3, while a third input is coupled to an output of inverter 80.

Here an output of summator 78 is connected to the input interdigit transducer 77.

The communication device (see Fig.1 ) operates as follows. At each change in the signal logic level at the output of the source 1 , the generator 9 generates sufficiently fast pulses the front of which effects triggering of generator 10 with a result that a noise-like signal is developed in a predetermined modulation format (see Fig.1 1 ) with a delta-shaped envelope of its self-correlation function on first inputs of multipliers 12 and 13. At the same time, control signals from the source 1 output are supplied to the input of switch 15 and, depending on the transmitted data logical state, at the second input of multiplier 13 either in-phase or reversed phase voltage from the output of generator 14 with respect to a signal at the first input of the multiplier 12 is set up. According to this, also phase interrelations of constituents of converted signals supplied to inputs of summator 17 change. Using the line 18, the output signal from multiplier 12 is delayed by the predetermined time T generally exceeding correlation interval of the noise-like signal generated by the generator 10, and at the output of the generator 2 a noise-like carrier signal is also generated (see Fig.13) one of constituents of which undergoes phase changes in strict correspondence with transmitted information.

From the output of transmitter 3 a signal that has passed communication link 4 and initial processing in the receiver 3, is fed to the input of correlation- phase demodulator 6 and, consequently, to the input of the matched filter 20 at the output of which a correlation response is formed whose constituents, being shifted by the time T, are either in-phase or reversed phase, depending on transmitted information logical state. An output signal from the matched filter 20 is fed to one of inputs of the synchronous detector 22 directly, and is fed to another input through the compensating delay line 23 for delaying by the time T, whereby portions of synchronous detector 22 input signals overlapping in time (see Fig.14) are phased differently, depending on the value of transmitted information which predetermines video-pulse polarity at its output (see Fig.15). As a result, at the output of correlation-phase demodulator 6 variable polarity pulses are generated (see Fig.16 and 17) which are thereafter selected and registered in the decision-maker 7 from where restored digital data are fed to the receiver 8.

Operation of the communication device having the generator 2 according to the circuit of Fig.2 is performed as above with the same result since the phase discrepancy between the envelope spectra and ACF filling of carrier signal constituents conditioned by the presence in the circuit of the first input of one of the multiplier 12 (13) of the delay line 18 is eliminated using the phase corrector 25 connected in the circuit of the second input of one of these multipliers.

The carrier signal generator 2 according to the scheme of Fig.3 operates as follows.

For each of starting pulses at the input 1 1 , the output of strobe member 29 generates a signal having a rectangular envelope and fill the frequency of which is equal to the frequency of the two-phase generator 26. Depending on the logical state of transmitted information, a similar high-frequency pulse is generated having a T-time delay driven by the member 33, with different fill phase at the input of one of strobe members 27 or 28. Thus generated signals are fed to inputs of summator 30 from the output of which the resulting pair of radio-pulses is supplied to the input of the passive phase-code manipulator 34 which, in the simplest case, is a multi-tap delay line 36 whose outputs are connected, via the weighting coefficient matrix 37, with corresponding inputs of summator 38. Thus, the output 19 of the generator 2 forms a high-frequency signal of which a part of constituents changes according to transmitted information. Using the 90-degrees phase shifter 32 provides a better peak-factor of the generator 2 output signal and additional orthogonality of its constituents due to quadrature interrelations of high-frequency fills of phase-code wave-trains. Here elimination of fill quadratures of time-coinciding pulses at the input of synchronous detector 22 of the correlation-phase demodulator 6 (see Fig.4) is effected with the aid of phase correction member 35. In all other respects, operation of the communication device does not differ from that discussed above.

Demodulator 6 according to flow-chart 5 operates as follows.

Noise-like signals coming to the input 21 of demodulator 6 from the output of receiver 5 are compressed in the matched filter 20 into two correlation bursts separated by the time interval T. This pulse pair a relative fill phase of one of which changes according to transmitted information at the output of source 1 is fed to the inputs of summator 43 and subtracter 44. Simultaneously, the same pulse pair delayed by the time T comes to other inputs of summator 43 and subtracter 44 from the output of compensating line 23. as a result, one of outputs of the detector 46 or 47 forms three video-pulses separated by the time interval T, whereby the central pulse amplitude is two times of that of the side pulses. Simultaneously, at the output of the other detector two video-pulses appear of the same amplitude separated by the time interval 2T. When transmitted information changes, the output states of detectors 46 and 47 change their places. Side pulses are compensated for in the subtracter 45 and at the output 24 of demodulator 6 pulses are generated of one or another polarity, in strict correspondence with the source information.

Carrier signal generator 2 operates on acoustic surface waves (see Fig.5) as follows.

Depending on the logical state of control signals at the input 16, delta-shaped starting pulses from the input 1 1 of generator 2 are fed from one of the outputs of switch 54 to a corresponding group of the converters. Under their effect, two short acoustic trains are formed within the sub-surface layer of the piezo-electric 52 (see D.Morgan above) which coming to the modulating structure of the transducer 53 generate at the output 19 of generator 2 a composite carrier signal in a predetermined format, PSK, LFM, DT and others. Lengths of acoustic waves excited by pulses coming from the outputs of switch 54 differ by variable fill phase of one of the trains in pair. Thereby uniqueness of correspondence of output signals characteristics from the generator 2 with logical levels at its input is provided. Correlation-phase demodulator 6 made on acoustic surface waves (see fig.7) operates as follows.

A signal coming to the input 21 of demodulator 6 is convoluted with its replica formed under its influence by the spatial structure of the interdigit transducers provided in such a way (see V.I.Rechitsky "Acoustic Radio Components: Circuits, Technology, Designs", Moscow, Radio I Svyaz, 1987, pp.90-1 13; Ya.D.Shirman, V.N.Manzhos, "Theory and Technology of Radio Radar Information Processing on Interference Background", Moscow, Radio I Svyaz, 1981 , pp.129-131 ), that in a result of superimposing acoustic surface waves, each of the output transducers 55 and 56 forms two correlation pulses separated by the time interval T. Due to a certain difference in the spatial bias of the output transducers 55 and 56 with respect to the input transducer, the signal is delayed by the time T at one of the inputs of synchronous detector 59, whereby time-overlapping portions of these signals are differently phased depending on the value of transmitted information resulting in different polarity video-pulses being generated at the output 24 of demodulator 6.

When the input transducers 55 and 56 are spaced apart by the distance L, multiple of an odd number of quarters of the wavelength, secondary signals caused by wave re- reflections from the pins come to the inputs of the synchronous detector in a quadrature interrelation to the basic one which substanrially reduces their effect on the result demodulator 6 input signal processing.

Correlation-phase demodulator 6 made according to the circuit of Fig.8 operates as follows.

Noise-like signals coming to the input 21 of demodulator 6 are compressed by the input transducer 61 and each of the input transducers 62, 63, 64 and 65 generates two correlation bursts separated by the time interval T a relative fill phase of one of which changes according to transmitted information. As a result of in-pair combination of L spaced apart output transducers one of the outputs of detector 66 or 67 forms three video-pulses separated by the time interval T, whereby the central pulse amplitude is two time as that of the side pulses, and at the output of the other detector two video-pulses appear of the equal amplitude separated by the time interval 2T. When transmitted information changes, the output states of detectors 66 and 67 change their places. The side pulses are compensated for in the subtracter 68, and pulses of one or another polarity, in unique correspondence with transmitted information are generated at the output 24 of demodulator 6.

Carrier signal generator 2 shown on Fig.9 operates on acoustic surface waves as follows.

Delta-shaped starting pulses from the input 1 1 of generator 2 come to the second input transducer 70. Simultaneously, the same pulses but with polarity depending on the logical state of control signals at the input 16 are fed to the first transducer 69. Under their effect, two short acoustic trains are formed in the subsurface layer of piezo-electric 71 separated by the time interval T which, coming into the modulating structure of transducer 72, generate at the output 19 of the generator 2 a composite carrier signal in a predetermined format, PSK, LFM, DT and others. Depending on polarity of pulses coming to the input transducers 69 and 70, lengths of acoustic waves differ by a variable fill phase of one of trains in pair. This provides the uniqueness of correspondence of generator 2 output signals with logical levels at its input 16.

Carrier signal generator 2 made according to the circuit shown in Fig.10 operates as follows.

Delta-shaped signals coming to the input 11 of carrier signal generator 2 are fed, via switch 80 and summator 78, to the input transducer 77 of ASW-element. The same pulses come to the same converter 77 from the output of summator 78 but delayed by the member 79 by the predetermined time T. Under their influence, two short acoustic trains form in the sub-surface layer of piezo-electric 75 separated by the time interval T, which coming into the modulating structure of transducer 76, generate at the output 19 of generator 2 a composite carrier signal in a predetermined format, PSK, LFM, DT and others. Depending on the state of switch 80, defined by the data bit value at the input 16 of the carrier signal generator, polarity of pulses coming to the input transducer 77 is different. As a result, lengths of acoustic waves in the subsurface layer of piezo-electric are characterised by the variable fill phase if one of the trains in pair. This provides unique correspondence of generator 2 output signals with logical levels at its input 16.

Experimental researches conducted with respect to radio-telephone and technological (fire and security alarms) communication systems as well as for building local computer networks (ARCNET, IOLA, ETHERNET) have confirmed the promising nature of technical solutions forming the basis of the device to be patented (see Fig.1 1 to Fig.17).

With the spectral density of the used NLS of 10"16 J/Hz, at the speed up to 3 Mbit/sec, in the radius over 20 km, the bit error rate was not worse than 10"6. Within closed rooms of reinforced-concrete building, at distances in excess of 150 m, with the same communication link parameters of throughput and errors, the signal strength at the transmitter antenna output was 0.5 - 10 mW.

To produce ASW elements under industrial conditions, photolithography was employed having resolution of 2 - 3 μm on substrates from lithium niobate and thermally stable quartz ST-cuts. Technological scatter was not more than 5% (less than 0.5 dB by signal level) for bands of NLS used up to 200 - 250 MHz at average frequencies 400 - 600 MHz with signal bases up to 100. Sizes of IC on ASW-elements (without case) are 3.0 x 3.5 mm.

Claims

1. A communication device comprising a carrier signal generator, a control input of which is coupled to an input of a binary information source and an output of which is connected to an input of a transmitter whose output is connected, via a communication link, with an input of a high-frequency signal receiver, as well as a correlation demodulator, an input of which is coupled to an output of the high-frequency signal receiver and an output of which is connected to an input of a decision-maker, an output of which is connected to the input of binary information receiver, distinguished in that said communication device is provided with a fast delta-shaped starting pulse generator, an input of which is coupled to the output of said binary information source and an output of which is connected to a pulse input of the carrier signal generator made with different for each of information values constituent phase of one of two duration-limited similar noise-like signals delayed one relative to the other by a predetermined time interval T exceeding their correlation interval, while the correlation- phase demodulator is provided with the possibility of compressing received signals.
2. A device as claimed in claim 1 , distinguished in that said carrier signal generator is provided as a noise-like signal generator, an input of which forms a pulse of the carrier signal generator, and an output of which is connected to first combined inputs of multipliers, wherein the second input of one of the multipliers is coupled to on of outputs of a two-phase generator, and the other input of the other multiplier is coupled to an output of a switch whose one input forms a control input of the carrier signal generator and whose two other inputs are coupled to inputs of the two-phase generator, wherein an output of one of the multipliers is connected with one of summator inputs directly while an output of the other multiplier is connected with another summator input through a delay line for delaying by a predetermined time T, wherein summator output is the output of the carrier signal generator.
3. A device as claimed in claim 1 , distinguished in that said carrier signal generator is provided as a noise-like signal generator, an input of which forms the pulse input of the carrier signal generator and another input is connected to first inputs of the two multipliers, respectively, via the delay line for delaying by the predetermine time T and directly, wherein the second input of one of the multiplies is coupled to one of outputs of the two-phase generator via a phase corrector, while the second input of the other multiplies is coupled to an output of the switch, one input of which forms the control input of the carrier signal generator, and other two inputs are coupled to inputs of the two-phase generator, multiplier outputs are connected with corresponding summator inputs, and summator output is the output of the carrier signal generator.
4. A device as claimed in claim 1 , distinguished in that said correlation-phase demodulator is provided in the form of a matched filter, an input of which forms the input of the correlation-phase demodulator, and an output of which is connected to one of inputs of a synchronous detector, another input of which is coupled to the input of the matched filter via a delay line for delaying by the predetermined time T, wherein an output of the synchronous detector forms the output of the correlation-phase demodulator.
5. A device as claimed in claim 1 , distinguished in that said carrier signal generator comprises a two-phase generator, three strobe members, summator, switch, 90-degrees phase shifter, delay member for delaying by the predetermined time T, passive phase-code manipulator, wherein one of outputs of the two-phase generator is connected to a high-frequency input of the first strobe member whose pulse input is coupled to one of switch outputs, another output of which is connected to the pulse input of the other strobe member, the high-frequency input of which is coupled to another output of the two-phase generator, wherein the high-frequency input of the third strobe member is coupled, via the phase shifter, to one of outputs of the two- phase generator, and the pulse input of the third strobe member is combined with the input of the delay member for delaying by the predetermined time T and forms the pulse input of the carrier signal generator, the output of the delay member is connected to one switch input, another input of which forms the control input of the carrier signal generator, wherein the output of each of the strobe members is connected with a corresponding summator input, the output of the summatior being connected to an input of the passive phase-code manipulator, an output of which, in turn, is the output of the carrier signal generator.
6. A device as claimed in claim 1 , distinguished in that the correlation-phase demodulator is provided in the form of a matched filter whose input forms the input of correlation-phase demodulator and whose output is connected, via the delay line for delaying by the predetermined time T, with combined inputs of the summator and the a first subtracter, other inputs of which are also combined and coupled to an output of the matched filter, wherein the outputs of the summator and first subtracter are connected, each through its own amplitude detector, with corresponding inputs of the subtracter whose output is the output of the correlation-phase demodulator.
7. A device as claimed in claim 1 , distinguished in that said carrier signal generator is provided in the form of an acoustic surface-wave element comprising three in-phase and one reversed phase input signal-band matched interdigit transducers located on a piezo-substrate to one side of a modulating interdigit transducer, an output of which is the output of the carrier signal generator, wherein input interdigit transducers of the acoustic surface-wave element are combined in pairs and coupled to corresponding switch outputs, switch inputs forming, respectively, the pulse and control inputs of the carrier signal generator, wherein spacings between transducers of each input pair, in a direction of the element's acoustic conductor, are equal to each other and are defined as a product of the predetermined delay time T multiplied by the propagation velocity of acoustic surface wave.
8. A device as claimed in claim 1 , distinguished in that the correlation-phase demodulator is provided in the form of an acoustic surface-wave element comprising two identical output signal-band matched input interdigit transducers located on a piezo-substrate to one side of the demodulating interdigit transducer, an input of which forms the input of the correlation-phase demodulator, wherein the spacing between the output interdigit transducers, in a direction of the acoustic surface-wave element's acoustic conductor, is defined as a product of the predetermined time delay T multiplied by the wave propagation velocity, wherein each of the output interdigit transducers is connected with a corresponding input of the synchronous detector whose output is the output of the correlation-phase demodulator.
9. A device as claimed in claim 1 , distinguished in that the correlation-phase demodulator is provided in the form of an acoustic surface-wave element comprising a demodulating interdigit transducer located on a piezo-substrate and forming the input of the correlation-phase demodulator, as well as equally spaced from one side of the demodulating interdigit transducer, in a direction of the element's acoustic conductor, two groups consisting of in-phase and in-phase as well as in-phase and reversed phase output signal-band matched interdigit transducers, wherein spacings between output interdigit transducers of each group, in a direction of the element's acoustic conductor, are defined as a product of the predetermined delay time T multiplied by the propagation velocity of acoustic surface wave, while differently spaced from the demodulating interdigit transducer, in a direction of the element's acoustic conductor, output interdigit transducers are combined in pairs and connected, via separate amplitude detectors, with corresponding inputs of a subtracter whose output is the output of the correlation-phase demodulator.
10. A device as claimed in claim 1 , distinguished in that said carrier signal generator is provided in the form of an acoustic surface-wave element comprising two input signal-band matched interdigit transducers located on a piezoOelectric to one side of the modulating interdigit transducer, an output if which is the output of the carrier signal generator, wherein the first input interdigit transducer is coupled to the output of the switch, a fist input of which forms the control input of the carrier signal generator, a second input combined with an inverter input, forms the pulse input of the carrier signal generator and is connected to the second input interdigit transducer, and a third input is coupled to an inverter output, wherein the spacing between the input interdigit transducers, in a direction of the element's acoustic conductor, is defined as a product of the predetermined delay time T multiplied by the propagation velocity of acoustic surface wave.
1 1 . A device as claimed in any one of claims 8 to 10, distinguished in that the spacing between signal-band matched interdigit transducers, defined in a direction of the element's acoustic conductor as a product of the predetermined delay time T multiplied by the propagation velocity of acoustic surface wave are equal to an odd number of quarters of its length.
12. A device as claimed in claim 1 , distinguished in that said carrier signal generator is provided in the form of an acoustic surface-wave element comprising a modulating interdigit transducer located an a piezo-electric and being the output of the carrier signal generator, as well as an input signal-band matched interdigit transducer coupled to a summator output, one input of said summator being coupled to the output of the delay member for delaying by the predetermined time T, and another input being coupled to a switch output, a first input of which forms the control input of the carrier signal generator, another input, combined with inputs of the inverter and delay member, forms the pulse input of the carrier signal generator, and a third input is coupled to an inverter output.
13. A device as claimed in any one of claims 1 , 4, 6, distinguished in that it is provided with a phase correction member connected between one of inputs of the synchronous detector of correlation-phase demodulator and an output of the matched filter thereof.
PCT/RU1998/000248 1997-08-06 1998-07-31 Spread spectrum communication device WO1999010988A3 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4363130A (en) * 1960-03-18 1982-12-07 Lockheed Missiles & Space Company, Inc. Binary digital communication system
EP0360476A2 (en) * 1988-09-20 1990-03-28 AT&T Corp. Homodyne-type spread spectrum transmitter/receiver
US5341396A (en) * 1993-03-02 1994-08-23 The Boeing Company Multi-rate spread system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4363130A (en) * 1960-03-18 1982-12-07 Lockheed Missiles & Space Company, Inc. Binary digital communication system
EP0360476A2 (en) * 1988-09-20 1990-03-28 AT&T Corp. Homodyne-type spread spectrum transmitter/receiver
US5341396A (en) * 1993-03-02 1994-08-23 The Boeing Company Multi-rate spread system

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