Unidirectional surface-acoustic-wave transducers with a ZnO film on glass substrate

A unidirectional surface-acoustic-wave transducer with a sputtered ZnO film on a glass substrate is presented, consisting of interdigital electrodes and a plate electrode on both sides of the film. Experiments are in good agreement with the equivalent-network approach, which is similar to Smith's networks for the normal interdigital transducer.     

New phase-shifting technique for group-type unidirectional transducers used in surface-acoustic-wave filters

The letter reports a novel method of phase shifting useful in the group type of unidirectional transducers used for the design of low-loss SAW filters. This technique utilises the thin-film capacitance present between the newly described configuration of the feed-electrode layers as an essential element of the required phase shifter. The stray capacitance existing between the feed electrodes is used to advantage. The theoretical and experimental results of one of the filters fabricated are presented.     

High-frequency operation of lateral hot-electron transistors

The high-frequency operation of a lateral hot-electron transistor (LHET) with near ballistic transport in the base and collector is considered. The high-frequency efficiency of the hot-electron transport in the base and collector are evaluated. It is shown that due to two-dimensional electron gas the high-frequency properties of the LHET collector are quite different from the properties of the hot-electron transistors with vertical structure     

Miniature surface-acoustic-wave filters

An introduction to Surface-Acoustic-Wave (SAW) devices-their operation, advantages, and applications--is presented. The process of design and realization of high-performance SAW filters is examined from initial specifications to final device operation. Several techniques drawn from a variety of disciplines illustrate the implementation of finite impulse response SAW frequency functions. Material properties, transducer weighting, and computer-aided design are treated. An example of the design and testing of a 321-MHz 0.35-percent bandwidth, 65-dB sidelobe, 15-dB insertion loss filter is presented.     

Monolithic surface-acoustic-wave phase shifter

A monolithic surface-acoustic-wave phase shifter is described. The device consists of a distributed Schottky-barrier varactor junction capable of varying the electrical boundary conditions seen by a surface acoustic wave propagating on a piezoelectric medium. Almost 180° of phase shift is achieved in 55 acoustic wavelengths of interaction region at 54 MHz.     

Design criteria for surface-acoustic-wave convolvers

The effect of acoustic dispersion and attenuation on the performance of surface acoustic wave convolvers is shown to be equivalent to an ideal convolver in cascade with a linear time-invariant filter. Using this result calculations of the implementation loss due to acoustic dispersion and attenuation, transducer bandpass response, and input/output matching networks are given showing the effects of phase and amplitude responses which are representative of typical convolver designs.     

Helical surface-acoustic-wave delay line

A 2-port helical surface-acoustic-wave delay line operating at 50 MHz and having a 182 ?s time delay on a thin Bi12GeO20 plate with face dimensions slightly under 5 × 2.5 cm is described, in which crosstalk suppression of more than 50 dB is achieved without introducing loss into the desired output signal.     

Laser probing of a surface-acoustic-wave resonator

An acoustic surface-wave resonator was studied using a heterodyning laser probe. The resonator consists in two periodic gratings ion-implanted in an ST cut-quartz substrate and an interdigital transducer deposited between gratings. The positioning of the transducer with respect to the standing wave pattern was investigated, the frequency being about 125 MHz. The variation of the transducer impedance around the resonance frequency is a function of this positioning and it was established that the greatest impedance change is obtained when the transducer fingers are in coincidence with the standing wave antinodes of the displacement perpendicular to the surface.     

Narrow-band filters employing surface-acoustic-wave resonators

It is possible to utilize a surface-acoustic-wave (SAW) interdigital transducer (IDT) with a large number of electrodes as a resonator-a SAW resonator. Band-elimination filters and bandpass filters with a narrow bandwidth have been developed employing SAW resonators.     

Electrically cascaded surface-acoustic-wave resonator filters

Three nearly identical surface-acoustic-wave resonator filters at ? 35 MHz have been fabricated with aluminium metallisation on yz LiNbO3 substrates. The filters are electrically cascaded to yield a combined frequency response that exhibits 80 dB sidelobe suppression, Q ? 3000, no spurious responses in the range 1?500 MHz and an insertion loss in a 50 ? system of only 13 dB.     

Efficiency of the surface-acoustic-wave diode convolver

The diode convolver performs signal processing, for example correlation, by mixing two input waveforms in an array of diodes, each diode being connected to a tap on a surface acoustic wave delay line. This paper gives the theory for the device efficiency, for a parallel circuit arrangement of taps and diodes. The effect of stray capacity is also analyzed. An experimental 31-tap device used hybrid circuitry in order to allow close spacing of the taps, giving a tap-to-tap propagation time of 90 ns. The efficiency agrees well with theory, showing that the bilinearity factor is maximized for an intermediate value of the bias current. The maximum bilinearity factor, relating external powers, was -34 dBm.     

Mode conversion in surface-acoustic-wave reflective arrays

We have investigated the possibility of the conversion of surface acoustic waves to other modes in a reflecting-array structure, such as that employed in the reflective-array compressor (r.a.c.). As the angle of incidence on the reflectors is reduced from normal incidence, we find that the mode-conversion possibilities become more restricted. However, for a 45° inclined array of reflectors on LiNbO3, coupling to a strongly piezoelectric pseudo-surface-wave is still allowed. Using metal reflectors, conversion to this mode is observed at frequencies only 19% above the s.a.w. reflection frequency. Comments are made on the relevance of the observations to the fabrication of dispersive filters for pulse-compression systems.     

70 MHz surface-acoustic-wave resonator notch filter

A 70 MHz notch filter employing a surface-acoustic-wave resonator in a hybrid-coil circuit to produce a notch depth of 50 dB has been developed. The notch frequency is tunable over a 40 kHz range and the passband attenuation is approximately 7 dB.     

An integrated piezoelectric-insulator DMOST surface-acoustic-wave convolver

A detailed investigation and analysis of a new device, the PI-DMOST convolver, is presented. The feasibility of this type of convolver has been previously demonstrated [1]. In this paper, we present the experimental results of another configuration of the device, fabricated with a new process. The theory is presented in detail for operation of the convolver using first-order Rayleigh-mode waves, and then extended to include other SAW modes.The convolver measures 100 μm by 1 cm, has a dynamic range of 70 dB, and is realized using ZnO piezoelectric films on a planar-processed silicon wafer.     

Improvements in surface-acoustic-wave pulse-compression filters

Computer simulations have been used to compare the performance of two common surface-acoustic-wave pulse-compressor geometries. Experimental results demonstrate that the desirable properties of both are achieved in a single device by using `inclined? transducers, which give improved performance over large fractional bandwidths.     

A thin-membrane surface-acoustic-wave vapor-sensing device

An integrated silicon-based vapor sensor is realized with a ZnO-on-Si surface-acoustic-wave (SAW) oscillator containing an absorptive polymer located on a thinned, membrane region of the device. If the membrane thickness is comparable with or smaller than a SAW wavelength, wave energy is present at both membrane surfaces. Thus the SAW transducers and associated amplifiers can be protected by an enclosure, leaving only the polymer exposed to the ambient atmosphere. Experiments on a 30 MHz, ZnO-on-silicon thin-membrane temperature-compensated SAW oscillator for vapor sensing are described. The use of the multi-channel device for solubility parameter sensing is discussed.     

Magnetically tuned surface-acoustic-wave phase shifter

A novel technique for achieving variable phase shift in surface-acoustic-wave devices is demonstrated. By depositing a thin film of magnetostrictive material onto the surface of a conventional surface-acoustic-wave delay line, the wave velocity can be varied by adjusting an externally applied magnetic field. Experimental results are presented for a nickel film on a lithium-niobate substrate, and several possible applications are mentioned.     

Band-elimination filter employing surface-acoustic-wave resonators

A surface-acoustic-wave (s.a.w.) band-elimination filter has been developed employing s.a.w. resonators composed of interdigital transducers with a large number of electrodes, exhibiting more than 80 dB stopband rejection with a passband attenuation of less than 1 dB.     

Triple-transit suppression in surface-acoustic-wave devices

Two techniques are described for the reduction of triple-transit signals in surface-acoustic-wave devices. Both have been tested experimentally and found to work satisfactorily.     

Analysis of the surface-acoustic-wave crossbar coupler

An analysis of the scattering of surface acoustic waves at a region of periodic surface mass loading is presented. Experimental measurements of the scattered-wave amplitudes show close agreement with theoretical calculations.