This book gives the fundamental principles and device design techniques for surface acoustic wave filters. It covers the devices in widespread use today: bandpass and pulse compression filters, correlators and non-linear convolvers and resonators. The newest technologies for low bandpass filters are fully covered such as unidirectional transducers, resonators in impedance element filters, resonators in double-mode surface acoustic wave filters and transverse-coupled resonators using waveguides.The book covers the theory of acoustic wave physics, the piezoelectric effect, electrostatics at a surface, effective permittivity, piezoelectric SAW excitation and reception, and the SAW element factor. These are the main requirements for developing quasi-static theory, which gives a basis for the non-reflective transducers in transversal bandpass filters and interdigital pulse compression filters. It is also needed for the reflective transducers used in the newer devices. It is a thorough revision of a classic on surface acoustic wave filters first published in 1985 and still in print. It uniquely combines easy-to-understand principles with practical design techniques for all the devices in widespread use today. It includes complete coverage of all the latest devices which are key to mobile phones, TVs and radar systems; and, a new foreword by Sir Eric Albert Ash.

Surface Acoustic Wave Filters: With Applications to Electronic Communications and Signal Processing

The coupling-of-modes approach for modeling and analyzing surface-acoustic wave devices is reviewed. We discuss the established formalism and survey the modifications introduced to account for phenomena such as resistivity, dispersion and in particular, the effects related to surface transverse wave and leaky surface-acoustic wave devices. The extraction of the COM parameters from experiments and theoretical simulations are considered. The design of various SAW devices such as resonators and resonator filters as well as practical aspects are discussed. Finally, the unresolved modeling problems are addressed.

Coupling-of-modes analysis of saw devices

The most frequently used models for surface acoustic wave (SAW) devices are the impulse model, the equivalent circuit models, the Coupling-of-Modes model, and the matrix models. While the impulse-model is only a first order model the other models include second order effects, e.g. reflections, dispersion, and charge distribution effects. The influence of diffraction and refraction on the transfer function of a SAW filter can be described by the angular spectrum of straight-crested waves model. A survey of these different models will be given. The simulation of low-loss filters requires flexible analysis tools, which can cope with different geometries and substrates. Operating with a parameter set, which depends only on the substrate crystal and not on the specific geometry of the SAW filter, is advantageous. Due to the high insertion attenuation of conventional transversal filters the requirements on the accuracy of the analysis are focused on S21, whereas for low-loss filters all elements of the S-matrix are important. The comparison of simulations with a P-matrix model, which fulfills the above mentioned prerequisites, and measurements of different types of low-loss filters, e.g. SPUDT, DMS, and transverse-mode coupled resonator filters are presented

Review of models for low-loss filter design and applications

A modeling method is described for using coupling-of-modes to model each transverse mode of a surface acoustic wave (SAW) transversely coupled resonator filter (TCF). Closed-form expressions are obtained which accurately describe the characteristics of this device class. The derivation of the model is described, a comparison between theory and experimental device performance is given, and the use of the model to synthesize optimized SAW TCFs is illustrated. The model is compared to experimental results in which excellent agreement is obtained over a 60- to 80-dB range, depending upon the device design. The accuracy of the model combined with closed-form expressions for filter performance allows for the use of nonlinear least-squares fitting techniques for experimentally determining coupling-of-modes (COM) model parameter values. >

Modelling of SAW transversely coupled resonator filters using coupling-of-modes modeling technique

A novel surface acoustic wave (SAW)-based gyroscope with an 80 MHz central frequency was developed on a 128° YX LiNbO 3 piezoelectric substrate. The developed sensor was composed of a SAW resonator, metallic dots, and two SAW delay lines. A SAW resonator was employed to generate a stable standing wave with a large amplitude, metallic dots were used to induce a Coriolis force and to form a secondary SAW, and two delay lines were formed to extract the Coriolis effect by comparing the resonance frequencies between these two delay lines. Coupling of modes (COM) modeling was conducted to determine the optimal device parameters prior to fabrication. According to the simulation results, the device was fabricated and then measured on a rate table. When the device was subjected to an angular rotation, resonant frequency differences between the two oscillators were observed because of the secondary wave, generated by the Coriolis force, perturbed the propagation of the SAW in the sense element. Depending on the angular velocity, the difference of the resonance frequency was linearly modulated. The obtained sensitivity was approximately 172 Hz deg −1  s −1 at an angular rate range of 0–500 deg/s. Device performances depending on different mass weights and temperatures were also characterized. Good thermal and shock stabilities were observed during the evaluation process.

Development of SAW based gyroscope with high shock and thermal stability

An analysis model for surface acoustic wave (SAW) transversely coupled resonator filters has been developed by use of the coupling-of-mode theory. To make the model work properly, an approach based on a transversely coupled six-port test structure has been designed which, in conjunction with a computer-aided multiport data manipulation and fitting program, enables the experimental determination of all necessary parameters. The experimental approach and the associated theoretical background are described. Key features of the computer-aided data fitting program are summarized. A comparison between theory and experimentally measured results shows excellent agreement over an 80-dB range. >

Experimental determination of COM model parameters for SAW transversely coupled resonator filter

The conventional coupled resonator filters, widely used in mobile communication systems, usually work with unbalanced termination conditions in both input and output electrical ports. However, there are increasing demands from systems engineers to have compact SAW filters which are able to operate with differential input and/or output termination. To meet these demands, two kinds of new innovative structures have been developed. In this paper the basic idea on which the new innovative structures are based are first discussed. This is followed by the presentation of the new structures in detail as experimental devices. The first is a 6-pole transversely coupled resonator filter at 150 MHz with a more than 100 kHz of 3 dB working bandwidth and very low shape factor (the transition bandwidth from -3 dB to -35 dB is less than 40 kHz), built on 34/spl deg/YX-quartz. It works with both input and output terminals in differential conditions. The other is a longitudinally coupled resonator filter built on 36/spl deg/YX-LiTaO/sub 3/ substrate and working at 860 MHz with a fractional bandwidth of about 1.5%. It operates with unbalanced input but differential output.

Coupled resonator filters with differential input and/or differential output

The design of transversely coupled SAW resonator filters is more complex than conventional SAW's because of its two dimensional nature. Previously, an innovative COM modeling technique for TCF's was proposed along with the method of experimentally determining the COM and electrostatic parameters necessary for the model. In this paper detailed design examples are given which are based on this modeling technique and the parameter database. The paper gives all design information (number of electrodes, beam width, grating and transducer periods, etc.) and corresponding COM model parameters. Also, the complete measured and predicted electric performances are presented. An excellent agreement is found between the theoretical predictions and the experiments over a wide frequency range. As a practical design tool this approach has shown an excellent accuracy and high efficiency for optimum design procedures

D.P. Chen

Papers

Modelling of SAW transversely coupled resonator filters using coupling-of-modes modeling technique

Experimental determination of COM model parameters for SAW transversely coupled resonator filter

Coupled resonator filters with differential input and/or differential output

Precise design technique of SAW transversely coupled resonator filters on quartz