Thin film plate acoustic resonators for integrated microwave power oscillator applications

Abstract

Two-port film plate acoustic resonators (FPAR) devices operating on the lowest order symmetric Lamb wave mode (S0) in C-oriented AlN membranes on Si were fabricated and tested for their power handling capabilities in a feedback-loop power oscillator circuit. The FPAR was operated at an incident power level of 24 dBm for several weeks without performance degradation. Its flicker noise constant was calculated from close-in phase noise data as a R ¼ 2.1 × 10 236 /Hz. The results indicate that IC-compatible S0 FPARs are well suited for integrated microwave oscillators with thermal noise floor (TNF) levels below 2175 dBc/Hz. Introduction: Film plate acoustic resonator (FPAR) devices using the lowest order symmetric Lamb wave mode (S0) in C-oriented aluminium nitride (AIN) membranes on Si [1] for future telecom applications have enjoyed considerable interest recently since they allow on-chip integration of the acoustic device with the semiconductor circuitry and seem to be fully compatible with existing integrated circuit (IC) technology [2]. In addition, the S0 mode provides some very attractive features, such as high propagation velocity of about 10 000 m/s, weak dispersion and moderate coupling coefficient up to 3% [3]. In this Letter we report on two new features opening the way for FPAR technology into lownoise integrated microwave oscillators. We show that FPAR devices can dissipate substantial amounts of RF-power without performance degradation and have very low residual flicker phase noise.

Polymer coated thin film plate acoustic resonators (FPAR) for gas sensing applications

“…Two-port FPARs have demonstrated insertion losses of around 5dB and an unloaded Q of 3000 at a frequency of 0.9GHz [10]. Also, 0.9GHz FPAR-based oscillators have exhibited low phase noise [11]. These results, along with the expected high mass sensitivity of the S0 Lamb mode in acoustically thin plates, motivated us for the present study.…”

Thin film Lamb wave resonators in frequency control and sensing applications: a review

“…Here we discuss the specific realization of a grating-type LWR-stabilized clock in the 900 MHz range running at up to 27 dBm (0.5 W) loop power and exhibiting a phase noise of −92 dBc Hz −1 at 1 kHz [32]. The close-in phase noise 1 Hz intercept point of the oscillator was measured as £(1 Hz) = −2 dBc Hz −1 which was then used to determine the LWR flicker noise constant α R = 2.1 × 10 −36 /Hz [36]. This value is comparable with some of the best SAW resonators built to date and suggests that the LWR technology is a low noise one.…”

“…The two-port LWR shown in figure 10 is connected in a feedback oscillator loop, as shown in figure 13, with a sustaining RF amplifier capable of generating 27 dBm (0.5 W) of RF power at the 880 MHz resonant frequency. In this power oscillator configuration, the FPARs were operated at an incident power level of 24 dBm (250 mW) for 5 weeks [36]. The power dissipated resulted in a moderate temperature increase of about 6-7 • K. An inspection under an optical microscope and a detailed analysis of their electrical characteristics prior to and after the power test did not show any measurable performance degradation or any evidence of electro-migration and aging effects.…”

An intermode-coupled thin-film micro-acoustic resonator

“…Lamb wave-based thin-film resonators employ the FBAR technological platform while employing the robust design principles of the commercial surface acoustic wave (SAW) technology. High-quality factors combined with moderate piezoelectric couplings and robust compensation of the temperature coefficient of frequency make these devices attractive for low-loss and low-noise applications [10,11]. More specifically, Lamb wave resonators employing the lowest order symmetric Lamb wave S0 have attracted considerable interest owing to their low dispersive nature and very high 1 Author to whom any correspondence should be addressed.…”