High Frequency Surface Acoustic Wave Research Articles

Epitaxial growth of LiNbO3 thin films by excimer laser ablation method and their surface acoustic wave properties

ABSTRACTWe have formed epitaxial LiNbO3 thin films on sapphire substrates (001),(110) and (012) using an excmer-laser ablation technique. We have fabricated surface acoustic wave (SAW) filters on the films and evaluated SAW properties. It is demonstrated that the LINbO3 thin films on the sapphire substrates are candidates for a high frequency SAW filter because of their high velocities of propagation (5300–5600m/s).

Phase-preserving imaging of high frequency surface acoustic wave fields

Measurements of the acoustic wave field of high frequency surface acoustic wave (SAW) devices have to be performed in order to develop and improve the computer modelling of SAW propagation. We introduce a method which detects the angle deflection of a laser beam due to the mechanical undulation of the substrate surface and in addition has a high temporal resolution capability by the use of a picosecond laser source. The shortness of the optical pulses (3 ps) in the time domain transforms to a large bandwidth (greater than 10 GHz) of the measurement limited only by the jitter of the driving electronics.

Surface‐acoustic‐wave digitized angular accelerometer

An angular accelerometer utilizing a sensing element 10 comprising a strain member 18 and a crosswise torsion member 24, both substantially comprising flat beams 18 and 25, respectively. The strain member 18 is affixed at each end to the object whose angular acceleration is to be measured, the angular acceleration vector lying along the axis of the strain member 18. The torsion member 24 is formed with an end mass 26,26' at each end. The strain member 18 is formed from a material such as quartz whose elasticity changes in proportion to the torque it experiences. A high-frequency surface acoustic wave is sent along the strain member and the change in its frequency due to the torque in the strain member 18 is measured.

Effect of Electrode Resistance on Insertion Loss and Triple Transit Echo in Surface Acoustic Wave Filter

The electrode resistance greatly influences the insertion loss and the triple transit echo for high frequency surface acoustic wave filters. A new equivalent circuit model in which a resistance is arranged in series at the electrical port for periodic section of the transducer is used to analyze this influence and the accuracy of the theoretical results is verified by experiments. A new design technique which suppresses the triple transit echo in the high frequency range by stretching a non-overlapped aperture of the transducers is reported.

Rare-earth substituted piezoelectric PbTiO3 ceramics for acoustic wave applications

Electromechanical and surface acoustic wave (SAW) properties of PbTiO3, ceramics modified by partial substitution of rare-earth for the Pb, specifically (Pb, Ln) (Ti, Mn)O3 (Ln=La, Ce, Pr, Nd, Sm, Eu, or Gd) ceramics, are extensively investigated. The SAW delay time temperature coefficient is found to be minimum when Ln=Nd. A zero temperature coefficient can be achieved in the (Pb, Nd) (Ti, In, Mn)O3 system with appropriate compositions. High frequency SAW filters are fabricated using these ceramics. It is also found that (Pb, Sm) (Ti, Mn)O3 ceramics have exceptionally large electromechanical anisotropy (ratio of electromechanical coupling factor for thickness vibration to that for planar vibration is above 15). A 7.5MHz linear array ultrasonic probe employing these ceramics is developed for medical use.

Tungsten bronze family crystals for acoustical and dielectric application

Abstract Ferroelectric SBN single crystals Sr.61Ba.39Nb2O6 approximately one inch in diameter have successfully been grown. Piezoelectric, high frequency dielectric and surface acoustic wave properties of the SBN crystals have been examined and are reported.

<title>Development of a Two-Step E-Beam Lithography Process For Submicron Surface Acoustic Wave (SAW) Device Fabrication</title>

A two-step fabrication process was developed which has produced previously unobtainable high frequency surface acoustic wave (SAW) devices. In addition, the design-to-test cycle time has been shortened significantly to allow an effective interactive design procedure. The SAW structure places some of the most stringent precision requirements on current electron-beam lithography, since finger placement errors are directly related to phase errors in the electrical performance of bandpass or pulse compression filters. A form of double precision is implemented in the interface software to enable successful patterning of the monotonic variation in line width from less than 0.4 pm to more than 0.9 pm required for a 1 to 2 GHz pulse compressor. Compensation for proximity effects due to the electron beam profile was also implemented. Alignment accuracy within a field is controlled to within ±250 A and field placement is accomplished via a laser interferometer controlled stage. Several alternative processes, including direct slice writing, reverse liftoff, and x-ray lithography are compared. Once the E-beam master is generated, large area contact replication is achieved using a modified conformable mask printer. This process has extended the range of SAW device performance beyond 2 GHz in a fundamental mode which, represents a significant advancement in microfabrication. Three-day turnaround from design to packaged devices was demonstrated using this technique.

Phase sensitive laser probe for high-frequency surface acoustic wave measurements

Field measurements of surface acoustic waves can be performed by coherent light in several ways. A method is described where a laser beam is focused to a small spot on the surface to obtain phase and amplitude infomation. A modified knife-edge technique has been applied in combination with amplitude modulation of the laser beam and single-side-band modulation of the surface wave. The apparatus has proven to be a powerful and flexible analytical tool. It is able to retieve phase and amplitude information from a traveling wave, and a partially standing wave can be characterized in terms of phase and amplitude of its two haveling wave components. The apparatus has been used up to 450 MHz.