RESUMEN
Linear equations derived from the scattering matrix approach to the two-port resonator were solved, and analytical expressions for the normalized SAW amplitudes were obtained. Asynchronous and synchronous resonators were analyzed numerically. It was shown that the output of the two-port resonator is a sum of two signals. In the case of the asynchronous resonator, these signals are in phase at a resonance frequency; for the synchronous resonator, they are in phase quadrature, which causes the higher insertion loss of the synchronous resonator.
RESUMEN
The scattering matrix method was used to derive an expression for the reflection coefficient of a one-port SAW resonator. This expression was applied to calculations of an input admittance of a synchronous resonator on ST-cut quartz. Very good agreement was obtained between calculated and measured parameters of the resonator.
RESUMEN
Surface acoustic wave (SAW) resonators on ST cut quartz, with synchronous placement of the interdigital transducers (IDT), were designed, fabricated, and measured. The basic structure of the resonators was a two-port one. The one-port resonators were obtained by parallel connection of the two IDT or by short circuiting one of them. The IDT were apodized to eliminate coupling to spurious modes. The transfer function of the two-port resonators was calculated by using the scattering matrix method. Several models of these resonators were investigated in the frequency range from about 300 to 715 MHz. By matching the theoretical and experimental transfer functions, the loss coefficient as a function of frequency and the SAW velocity in the reflector area as a function of aluminium layer thickness were determined. The responses of the resonators were free of any spurious modes.
RESUMEN
The synchronous two-port resonator can be used for the determination of SAW parameters, including velocity, electromechanical coupling coefficient, and reflection coefficient of one strip. These parameters can be determined from a comparison between the measured and calculated transfer functions of the resonator. Using this technique, the SAW free surface velocity of the 45 degrees XZ-cut of lithium tetraborate (Li(2)B(4)O(7)) crystal was found to be equal to 3436 m/s. The other measured parameters agree well with the values found in the literature.
RESUMEN
A surface acoustic wave (SAW) two resonator filter with coupling interdigital transducers (IDTs) located inside the reflectors, was designed, fabricated, and tested. In the filter, electrodes of the coupling IDTs are in spatial synchronism with the reflectors' electrodes. The filter, fabricated on ST-cut quartz, had a center frequency of 302.6 MHz, insertion loss about 13 dB, and minimum rejection in the stopbands of about 40 dB.
RESUMEN
The admittance matrix of a surface acoustic wave interdigital transducer (IDT) is derived from the impulse response model and circuit theory. It is shown, that Y(23)=Y(13) for a symmetrical IDT and Y(23)-Y(13) for an antisymmetrical one. A simple algorithm for the input admittance calculation of apodized IDTs is given. The proposed algorithm is also capable of analyzing withdrawally weighted, withdrawally weighted and apodized, and unapodized IDTs. Calculations of an apodized IDT input admittance are compared with measurements.