Showing papers on "Thin-film bulk acoustic resonator published in 1997"

A device incorporating a tunable thin film bulk acoustic resonator for performing amplitude and phase modulation

Abstract: A method for amplitude modulating signals, and a circuit that operates in accordance with the method. The method includes a first step of applying a modulating low frequency signal having a time-varying voltage to a tunable resonator. The tunable resonator exhibits parallel and series resonances at frequencies which shift as a function of the time-varying voltage. A second step includes applying an RF carrier signal having a frequency that is between the parallel resonant frequency and the series resonant frequency to the tunable resonator. In response thereto, the tunable resonator causes the RF carrier signal to be attenuated as a function of the time-varying voltage of the modulating low frequency signal. Also provided is a method for phase modulating signals, and a circuit that operates in accordance therewith. A first step includes applying a modulating low frequency signal having a time-varying voltage to a tunable resonator. The tunable resonator yields a maximum phase shift at one of a parallel resonant frequency and a series resonant frequency in response to the modulating low frequency signal. The amount of phase shift yielded is a function of a variation of the modulating low frequency signal voltage. A further step includes applying an RF carrier signal having a frequency that is substantially equal to the one of a parallel resonant frequency and a series resonant frequency. In response thereto, the tunable resonator phase shifts the RF carrier signal by the amount of phase shift yielded by the tunable resonator.

Sensitivity analysis of a thin film bulk acoustic resonator ladder filter

Abstract: In this paper, an analysis of sensitivity of the filter performance of a solidly mounted thin film bulk acoustic wave resonator ladder filter is presented. The ladder filter investigated consists of three series and two shunt resonators. Frequency sensitivity analysis of a single resonator and changes in out-of-band rejection, filter bandwidth, and insertion loss as a result of variation in thicknesses of piezoelectric layers and mounting interlayers is presented. Also, resonator and reflector layer thickness tolerances that must be held during filter fabrication are presented. Analysis of a single resonator shows that the thickness of the piezoelectric layer has the most dominant effect on the resonant frequency. For the acoustic stack, frequency sensitivity increases as the layers are traversed from the bottom layer to the topmost layer. The use of the multilayer acoustic stack resulted in increase in the Q of the resonator. Small variations in resonator material thicknesses show negligible effects on the out-of-band rejection level and an approximately linear relationship with filter bandwidth. Insertion loss sensitivity on the other hand indicated a non-linear relationship between thickness variations and corresponding effects on insertion loss.

Device containing controllable thin-film bulk acoustic resonator for amplitude and phase modulation

Abstract: PROBLEM TO BE SOLVED: To provide a low-frequency amplitude modulator or a low-frequency phase modulator by using a controllable BAW(bulk acoustic wave) resonator, which shifts the resonance frequency according to the applied voltage. SOLUTION: A BAW resonator 102 consisting of a piezoelectric layer and protective layer electrodes, etc., is constructed on a substrate by means of a prescribed material and process. Then the resonator 102 is built into an amplitude modulation circuit 91 as a modulator. When the modulating low-frequency signal, which is produced by an oscillator 96 is filtered by an LPF 98 and an RF choke 100 and applied between the electrodes 102a and 102b of the resonator 102, an electric field is generated on a piezoelectric layer 102c and vibration time-wise varying according to the signals is produced. A prescribed RF carrier signal that is produced by an oscillator 90 is filtered and applied to the resonator 102. The carrier signal is attenuated by the resonance frequency, as well as the impedance caused by the low-frequency signal of the resonator 102. Then the amplitude modulation is carried out. In a phase modulation mode, the oscillation frequency of the oscillator 90 is set almost equal to the parallel resonance frequency of the resonator 102. Then the phase shift is carried out.