The invention provides a tunable surface acoustic wave (SAW) resonator and a filter. The semiconductor piezoelectric layer comprises an embedded type or lifted type electrode doping area. The tunable SAW resonator adjusts the resonant frequency through the characteristic that the metallization ratio and mass load changes along with the change of DC bias. A mobile phone and a wireless system of the provided tunable RF filter can cover a plurality of communication frequency bands or frequency ranges, the required filters are reduced, and the size and price of the RF filter are reduced.

Tunable surface acoustic wave resonator

An acoustic wave filter having thermal sensing acoustic wave resonator comprises a substrate, a plurality of series acoustic wave resonators formed on the substrate, at least one shunt acoustic wave resonator formed on the substrate and a thermal sensing acoustic wave resonator. The thermal sensing acoustic wave resonator is one of a series acoustic wave resonator and a shunt acoustic wave resonator. Thereby the thermal sensing acoustic wave resonator plays dual roles of thermal sensing and acoustic wave filtering.

Thermal sensing acoustic wave resonator and acoustic wave filter having thermal sensing acoustic wave resonator

Electrode-width-controlled (EWC) single-phase unidirectional transducers (SPUDT) contribute to reduction of insertion loss of surface acoustic wave (SAW) devices due to their strong unidirectional properties. In this work, we propose a method to optimize the unidirectionality of EWC-SPUDT based on our research results that the unidirectionality of the EWC-SPUDT cell is strongly related to its reflectivity and its unidirectional angle. Furthermore, in order to ensure strong unidirectionality to achieve low insertion loss, a simulator based on the finite element method (FEM) is used to study the relationship between geometrical configuration of the EWC-SPUDT cell and its reflection coefficient, as well as its transduction coefficient. Simulation results indicate that the reflection coefficient of the optimized EWC-SPUDT cell composed of 128° YX lithium niobite (LiNbO3) substrate and Al electrodes with thickness of 0.3μm reaches the optimal value of 5.17% when the unidirectional angle is designed to be −90°. A SAW delay line is developed with the optimized EWC-SPUDT cell without weighing, and the simulation results are verified by experiments. The experimental results show that the directivity exceeds 30 dB at the center frequency and the insertion loss is just 6.7 dB.

Analysis and Design of Single-Phase Unidirectional Transducers with High Directivity

The invention relates to a BAW resonator with reduced heat build-up. The heat build-up is reduced by a thermal bridge which dissipates heat from the electro-acoustically active region to a support substrate, without impairing the acoustics of the resonator.

Baw resonator with reduced heat build-up, hf filter comprising baw resonator, duplexer comprising hf filter, and production method

This article proposes a robust method for the synthesis and design of optimal linear group delay filters with prescribed bandwidth and dispersion properties. The proposed filters are based on a cascade of second-order all-pass filter cells, for which all the parameters are optimized in order to reach the desired wideband linear group delay characteristic with positive slope. Compared to the previously published synthesis method, the proposed approach offers appropriate initialization enabling convergence and aiming for the optimal solution. The method’s convergence and robustness are proved through a 21-cells synthesis, which is the highest number of cascaded cells reported to date, due to the usual convergence problem. Then the electronic feasibility is illustrated through the measurement results of a lumped-elements linear group-delay filter prototype dimensioned with this method. The measured group delay presents a positive slope of 8 ns GHz−1 in the frequency range [100–725] MHz. It is, to the best of our knowledge, the highest positive slope reported to date with an electronic implementation (i.e except SAW and waveguide devices).

A Robust Algorithm for the Design of Wideband Positive-Slope Linear Group Delay Filters

A surface acoustic wave (SAW) device comprising a piezoelectric substrate having a working surface with an active zone capable of propagating an acoustic wave on said working surface; at least one interdigital transducer on the working surface, having interdigital fingers aligned in the active zone for inducing or receiving surface acoustic waves in the active zone; and a heating element on the working surface; wherein the transducer, heating element and preferably a temperature sensor are monolithically formed on the substrate.

Monolithically applied heating elements on saw substrate

A surface acoustic wave (SAW) device comprising at least one heating element formed on the substrate; at least one temperature sensor having a first electric component on the substrate whose resistance varies with the temperature of the substrate and a second electric component whose resistance does not vary; and a temperature controller including an operational amplifier bonded in thermally conductive relationship to the substrate. The operational amplifier is responsive to the output of the temperature sensor to apply power to the heating element and thereby maintain the temperature of the substrate within a predetermined temperature range. The transducer, heating element, and first component are monolithically formed on the substrate, and only three electrical connections are on the substrate at voltage to off-SAW die points.

SAW Device With Heat Efficient Temperature Controller

Many of today's radar systems rely on digital processing for pulse compression. The future of SAW LFM pulse compression systems depends on achieving at least comparable performances to all-digital solutions. SAW-based pulse compression systems can consume less power and have higher dynamic range than all-digital systems, properties important for portable and long-range radars. The future market for SAW dispersive devices depends on development of larger time-bandwidth (BT) product device structures. Currently a BT of 10,000 is achievable, with a goal of > 20,000 in a single SAW device.

Improved SAW Slanted Array Compressor structure for achieving > 20,000 time-bandwidth product

A family of Electrode-Width-Controlled (EWC) SPUDT filters for a miniature SAW channelizer was presented in the 1993 IEEE Ultrasonics Symposium. The effort reported was expanded, and led in 1996 to the successful development of a full-fledged compact high-performance SAW Channelizer module. To commemorate the passing of Clinton S. Hartmann, this paper presents previously unpublished techniques for the SAW channelizer filters. The first area concerns the implementation of the transduction and reflection tap weights of the SPUDT design. Here a highly accurate yet practical scheme involving a modified EWC structure with three equal-width electrodes was devised. Desired reflectivity is achieved in part by varying the separation between the two transduction electrodes, whereas the distance from the centerline of these two to the center of the nominally “wide” reflecting electrode remains λ/2. This leads to a wide range of net reflectivity, and enables a fabrication insensitive electrode pattern. The second concerns the design of a frequency selective multi-strip coupler (MSC). The MSC was conceived from the perspective of basic short transducer sections with λ/8 wide electrodes placed on λ/4 centers. The sections are electrically interconnected, with each section odd multiple of λ/4 long. Without incurring excessive loss, the MSC suppresses the strong second harmonic response of the EWC/SPUDT effectively. The third area concerns various techniques for spurious signal reduction in both time and frequency domains. These are by way of judicious SAW die layout, wire bonding scheme, and processing of both the top and bottom surfaces of the SAW chip. The channelizer module has 7 unshielded SAW filters in a single multi-chip module with no electrical matching for the SAW transducers. The filters are centered 20 MHz apart from 267.5 to 387.5 MHz. Results of the channelizer performance will be presented to illustrate the success enabled in part by the techniques discussed.

Tom A. Martin

Papers

Monolithically applied heating elements on saw substrate

SAW Device With Heat Efficient Temperature Controller

Improved SAW Slanted Array Compressor structure for achieving > 20,000 time-bandwidth product

A compact high-performance EWC/SPUDT SAW Channelizer