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Journal of the acoustical society of America
Arrays of parametric receiving Berktay, H. O., Muir, T. G. 53 (May 1973) 1377-1383
functions is possible. Recent developments have yielded results where the loss from input to output is of the order of 30 dB.
arrays
Theory is presented to describe the response of arrays whose elements consist of parametric end-fire receivers The results of measurements on arrays containing up to four elements are presented in support of the theory. Electronic steering of this type of array is also discussed. The use of very small transducers in the formation of narrow receiver beams at low frequencies is demonstrated Vapour bubble dynamics Finch, R. D., Neppiras, E. A. 53 (May 1973) 1402-1410 The principles underlying the dynamics of a bubble filled with condensable vapour in a thermally conducting liquid are set out and the equations governing the radial motion of a spherical bubble in an unbounded liquid at a fixed temperature are derived. A linearized solution of these equations is then found assuming an harmonic acoustic drive. It is shown that the effective stiffness of the bubble is a complicated function of bubble radius and frequency; consequently it is possible for bubbles of two distinct sizes to resonate at the same frequency. Numerical values are presented for vapour bubbles in liquid Helium 1, nitrogen, water, and for a liquid with the same effective thermal conductivity as liquid Helium II.
SONICS AND ULTRASONICS Acoustic surface wave recirculating memory van de Vaart, H., Schissler, L. R. SU-20 (April 1973) 154-161 An acoustic surface wave memory is described operating at a bit rate of 220 MHz and a storage capacity of 1 280 bit per recirculation loop. The transducers are coded using orthogonal pairs of Golay complementary sequences to obtain pulsein pulseout behaviour. The shape of the delayed pulse is analysed and compared with the pulse shape that is obtained using a simple single finger pair transducer. The recirculation electronics uses standard MECL-HI logic for both the amplifier and the write, read, inhibit and reclocking functions The cost of this recirculating memory and the feasibility of constructing larger capacity stores are discussed Signal processing by parametric interactions in delay-line devices Kino, G. S., Ludvik, S., Shaw, H. J., Shreve, W. R., White, J. M., Winslow, P. K. SU-20 (April 1973) 162-173 A new type of signal-processing device which employs the parametric interaction between surface or volume acoustic waves passing in opposite directions through an acoustic delay line is described The devices are capable of giving real-time convolution of two modulated signals, and the time inversion of an arbitrary signal. As one signal acts as the reference for the other a vi.rtualIy infinite range of electronically variable signal-processing
ULTRASONICS.
NOVEMBER
1973
Signal processing by electron-beam interaction with piezoelectric surface waves Bert, A. G., Epsztein, B., Kantorowicz, G. XI-20 (April 1973) 173-181 A new type of device is described in which an acoustoelectric surface wave interacts with low-energy free charges created on the surface of a piezoelectric material. The experimental results show that one of the most promising applications is an analogue rf storage device for which several minutes of storage time have been achieved at 30 MHz on quartz with an internal insertion loss of 63 dB. Application of acoustic surface wave technology to spread spectrum communications Bell Jr, D. T., Holmes, J. D., Ridings, R. V. SU-20 (April 1973) 181-189 Spread spectrum transmission is being proposed for an increasing number of digital communication, navigation and radar systems. One of the reasons is the simplicity and availability of surface wave devices for performing the necessary signal generationand processing. The properties of spread spectrum signals, the operation of SAW devices and their advantages and limitations when used in communication systems are discussed. Spread spectrum terminology and basic concepts are defined in terms common to both systems engineers and device designers. Ranging and data transmission using digital encoded fm-‘chirp’ surface acoustic wave filters Burnsweig, J., Wooldridge, J. SU-20 (April 1973) 190-197 A digital encoded multislope chirp modem/ demodem unit has been built using two three-port SAW filters Each filter, operating at 30 MHz centre frequency, provides either positive or negative slopes as digital Is or OS with a time-bandwidth product of 280, an unweighted bandwidth of 3.6 MHz and a time dispersion of 50 ps. The modems were used to calibrate and compare the operational performance of a conventional multitone CW ranging system with a multislope chirp ranging system. The significant advantage of the chirp system is the ability to obtain continuous range data from a satellite repeater simultaneously while other modes of information are being transmitted, and to combine the ranging and data-link transmission on a time-order basis using digital encoded chirp sequences. A review of device technology for programmable surface wave filters Staples, E. J., Clairborne, L. T. SU-20 (April 1973) 197-205 A review of programmable surface acoustic wave filters is presented. The elementary theory, fabrication procedures, and device performance are described in the light of recent technological advances. Both hybrid and monolithic structures are considered. The relative
advantages of programming techniques which utilize diode switching are compared to those that make use of solid state three terminal, and acoustic wave detectors. Potential applications of acoustic matched filters to air-traffic control systems Grant, P. M., Collins, J. H., Darby, B. J., Morgan, D. P. SU-20 (April 1973) 206-218 The potential role of acoustic matched filters in the demanding field of civil and military air-traffic control (ATC) systems is examined. Highlighted are the problems of current ATC systems and the significant aspects of acoustic matched filters and their expeditious usage in modems employing band spreading for a multisubscriber environment and certain envisaged ATC systems deemed necessary for future traffic growth that could benefit greatly from acoustic technology. Surface elastic wave bandpass filters for frequency synthesis Hickernell, F. S., Kline, A. J., Allen, D. E., Brown, W. C. SU-20 (April 1973) 218-220 Surface elastic wave bandpass filter techniques have been applied to the development of a miniaturized frequency synthesizer for satellite communications systems. A bandpass filter centred at 247 MHz has been developed exhibiting less than 7 dB insertion loss over a 6 MHz 1 dB band with sidelobe rejection greater than 45 dB. Bandpass filters using a non-linear wave transducer Worley, J. C. SU-20 (April 1973) 220-221
fm surface
A generalized fm method of obtaining bandpass filters using surface wave delay lines is discussed. Two identical fm transducers are used as input and output. The fm function of the transducers is determined by the required passband. A programmable surface acoustic wave matched filter for phase-coded spread spectrum waveforms Hagon, P. J., Micheletti, F. B., Seymour. Wrigley, C. Y. SU-20 (April 1973) 221-224
R. N.
A programmable surface acoustic wave matched filter for biphase-coded spread spectrum waveforms has been constructed using a temperature-stable St-cut quartz tapped delay line and silicon-on-sapphire integrated central circuits. Programming (code changing) can be achieved with a serial data input at 10 MHz rates over a wide temperature range (-23°C to +85”(Z). Generation of pseudonoise sequences using surface acoustic waves Morgan, D. P., Sutherland, J. G. SU-20 (April 1973) 224 Pseudonoise sequences can be generated by using a surface acoustic wave delay line in place of a shift register. Module-2 addition is achieved by combining the outputs of two transducers and using envelope detection. A 3 l-bit pseudonoise sequence was generated with a bit period of 1.1 ps.
295
functions is possible. Recent developments have yielded results where the loss from input to output is of the order of 30 dB.
arrays
Theory is presented to describe the response of arrays whose elements consist of parametric end-fire receivers The results of measurements on arrays containing up to four elements are presented in support of the theory. Electronic steering of this type of array is also discussed. The use of very small transducers in the formation of narrow receiver beams at low frequencies is demonstrated Vapour bubble dynamics Finch, R. D., Neppiras, E. A. 53 (May 1973) 1402-1410 The principles underlying the dynamics of a bubble filled with condensable vapour in a thermally conducting liquid are set out and the equations governing the radial motion of a spherical bubble in an unbounded liquid at a fixed temperature are derived. A linearized solution of these equations is then found assuming an harmonic acoustic drive. It is shown that the effective stiffness of the bubble is a complicated function of bubble radius and frequency; consequently it is possible for bubbles of two distinct sizes to resonate at the same frequency. Numerical values are presented for vapour bubbles in liquid Helium 1, nitrogen, water, and for a liquid with the same effective thermal conductivity as liquid Helium II.
SONICS AND ULTRASONICS Acoustic surface wave recirculating memory van de Vaart, H., Schissler, L. R. SU-20 (April 1973) 154-161 An acoustic surface wave memory is described operating at a bit rate of 220 MHz and a storage capacity of 1 280 bit per recirculation loop. The transducers are coded using orthogonal pairs of Golay complementary sequences to obtain pulsein pulseout behaviour. The shape of the delayed pulse is analysed and compared with the pulse shape that is obtained using a simple single finger pair transducer. The recirculation electronics uses standard MECL-HI logic for both the amplifier and the write, read, inhibit and reclocking functions The cost of this recirculating memory and the feasibility of constructing larger capacity stores are discussed Signal processing by parametric interactions in delay-line devices Kino, G. S., Ludvik, S., Shaw, H. J., Shreve, W. R., White, J. M., Winslow, P. K. SU-20 (April 1973) 162-173 A new type of signal-processing device which employs the parametric interaction between surface or volume acoustic waves passing in opposite directions through an acoustic delay line is described The devices are capable of giving real-time convolution of two modulated signals, and the time inversion of an arbitrary signal. As one signal acts as the reference for the other a vi.rtualIy infinite range of electronically variable signal-processing
ULTRASONICS.
NOVEMBER
1973
Signal processing by electron-beam interaction with piezoelectric surface waves Bert, A. G., Epsztein, B., Kantorowicz, G. XI-20 (April 1973) 173-181 A new type of device is described in which an acoustoelectric surface wave interacts with low-energy free charges created on the surface of a piezoelectric material. The experimental results show that one of the most promising applications is an analogue rf storage device for which several minutes of storage time have been achieved at 30 MHz on quartz with an internal insertion loss of 63 dB. Application of acoustic surface wave technology to spread spectrum communications Bell Jr, D. T., Holmes, J. D., Ridings, R. V. SU-20 (April 1973) 181-189 Spread spectrum transmission is being proposed for an increasing number of digital communication, navigation and radar systems. One of the reasons is the simplicity and availability of surface wave devices for performing the necessary signal generationand processing. The properties of spread spectrum signals, the operation of SAW devices and their advantages and limitations when used in communication systems are discussed. Spread spectrum terminology and basic concepts are defined in terms common to both systems engineers and device designers. Ranging and data transmission using digital encoded fm-‘chirp’ surface acoustic wave filters Burnsweig, J., Wooldridge, J. SU-20 (April 1973) 190-197 A digital encoded multislope chirp modem/ demodem unit has been built using two three-port SAW filters Each filter, operating at 30 MHz centre frequency, provides either positive or negative slopes as digital Is or OS with a time-bandwidth product of 280, an unweighted bandwidth of 3.6 MHz and a time dispersion of 50 ps. The modems were used to calibrate and compare the operational performance of a conventional multitone CW ranging system with a multislope chirp ranging system. The significant advantage of the chirp system is the ability to obtain continuous range data from a satellite repeater simultaneously while other modes of information are being transmitted, and to combine the ranging and data-link transmission on a time-order basis using digital encoded chirp sequences. A review of device technology for programmable surface wave filters Staples, E. J., Clairborne, L. T. SU-20 (April 1973) 197-205 A review of programmable surface acoustic wave filters is presented. The elementary theory, fabrication procedures, and device performance are described in the light of recent technological advances. Both hybrid and monolithic structures are considered. The relative
advantages of programming techniques which utilize diode switching are compared to those that make use of solid state three terminal, and acoustic wave detectors. Potential applications of acoustic matched filters to air-traffic control systems Grant, P. M., Collins, J. H., Darby, B. J., Morgan, D. P. SU-20 (April 1973) 206-218 The potential role of acoustic matched filters in the demanding field of civil and military air-traffic control (ATC) systems is examined. Highlighted are the problems of current ATC systems and the significant aspects of acoustic matched filters and their expeditious usage in modems employing band spreading for a multisubscriber environment and certain envisaged ATC systems deemed necessary for future traffic growth that could benefit greatly from acoustic technology. Surface elastic wave bandpass filters for frequency synthesis Hickernell, F. S., Kline, A. J., Allen, D. E., Brown, W. C. SU-20 (April 1973) 218-220 Surface elastic wave bandpass filter techniques have been applied to the development of a miniaturized frequency synthesizer for satellite communications systems. A bandpass filter centred at 247 MHz has been developed exhibiting less than 7 dB insertion loss over a 6 MHz 1 dB band with sidelobe rejection greater than 45 dB. Bandpass filters using a non-linear wave transducer Worley, J. C. SU-20 (April 1973) 220-221
fm surface
A generalized fm method of obtaining bandpass filters using surface wave delay lines is discussed. Two identical fm transducers are used as input and output. The fm function of the transducers is determined by the required passband. A programmable surface acoustic wave matched filter for phase-coded spread spectrum waveforms Hagon, P. J., Micheletti, F. B., Seymour. Wrigley, C. Y. SU-20 (April 1973) 221-224
R. N.
A programmable surface acoustic wave matched filter for biphase-coded spread spectrum waveforms has been constructed using a temperature-stable St-cut quartz tapped delay line and silicon-on-sapphire integrated central circuits. Programming (code changing) can be achieved with a serial data input at 10 MHz rates over a wide temperature range (-23°C to +85”(Z). Generation of pseudonoise sequences using surface acoustic waves Morgan, D. P., Sutherland, J. G. SU-20 (April 1973) 224 Pseudonoise sequences can be generated by using a surface acoustic wave delay line in place of a shift register. Module-2 addition is achieved by combining the outputs of two transducers and using envelope detection. A 3 l-bit pseudonoise sequence was generated with a bit period of 1.1 ps.
295