Search

This work presents an acoustic platform using solidly mounted thin-oriented lithium niobate (LiNbO3) film on silicon (Si). A thin layer of amorphous Si eliminates a conductive layer generated in the thin-film bonding processes and contributes to acoustic energy confinement and thermal frequency stability. The gigahertz operating frequency is achieved by resorting to the guided acoustic wave shear-horizontal wave (SH0) in a 400-nm-thick X-cut LiNbO3 thin film. Due to the elimination of the parasitic surface conduction (PSC) effect, the electromechanical coupling of the guide acoustic wave is maximized in the Si-based heterogeneous wafer. Due to the minimized acoustic impedance mismatch between surface material and substrate, longitudinal and higher order spurious modes are suppressed. Due to the stiff substrate with a small temperature expansion coefficient (TEC), the solidly mounted structure features a reduced temperature coefficient of frequency (TCF) and improved power handling. The fabricated resonator shows an extracted electromechanical coupling coefficient of 22.8%, a high loaded $Q$ of 1208 at 1.6 GHz, and a TCF of −36 p/min/K. The compressed filter is demonstrated with a minimum insertion loss (IL) of 0.6 dB, a fractional bandwidth (FBW) of 8%, an out-of-band rejection of 30 dB, a TCF of −38.5 p/min/K at roll-off, and a miniaturized footprint of 0.4 mm2. The performance has shown the strong potential of the LiNbO3–Si platform for front-end applications in 5G. [ABSTRACT FROM AUTHOR]

This work presents a class of micro-electro-mechanical system (MEMS)-driven radio frequency filters in the X-band. The X-band center frequencies are achieved by resorting to the third-order antisymmetric Lamb wave mode (A3) in a 650-nm-thick Z-cut lithium niobate thin film. A novel bandwidth (BW) widening technique based on using the self-inductance of the top interdigital transducers and bus lines is proposed to overcome the limitations set by the electromechanical coupling (${k} _{t}^{2}$) and satisfy the demands in miniaturization and wide BW. Four different designs of the filters are designed and fabricated to show the trade-off among BW, insertions loss (IL), out-of-band rejections, and footprint. Due to the spurious-free and high- ${Q}$ performance of the A3 lithium niobate resonators, the fabricated A3 lithium niobate filters have demonstrated small in-band ripples and sharp roll-offs. One of these fabricated has demonstrated a 3-dB BW of 190 MHz, an IL of 1.5 dB, and a compact footprint of 0.56 mm2. Another design is fabricated to demonstrate a 3-dB BW of 170 MHz, an IL of 2.5 dB, an out-of-band rejection of 28 dB, and a compact footprint of 1 mm2. [ABSTRACT FROM AUTHOR]

This work presents a new class of microelectromechanical system (MEMS) resonator toward 60 GHz for the fifth-generation (5G) wireless communications. The wide range of the operating frequencies is achieved by resorting to different orders of the antisymmetric Lamb wave modes in a 400-nm-thick Z-cut lithium niobate thin film. The resonance of 55 GHz demonstrated in this work marks the highest operating frequency for piezoelectric electromechanical devices. The fabricated device shows an extracted mechanical $Q$ of 340 and an $f\times Q$ product of $1.87\times 10^{13}$ in a footprint of $2 \times 10^{-3}$ mm2. The performance has shown the strong potential of LiNbO3 antisymmetric mode devices for front-end applications in 5G high-band. [ABSTRACT FROM AUTHOR]

This paper demonstrates the first nonreciprocal network based on switched low-loss acoustic delay lines. The four-port circulator is built upon a recently reported frequency-independent, programmable, nonreciprocal framework based on switched delay lines. The design space for such a system, including the origins of the insertion loss (IL) and harmonic responses, is theoretically investigated, illustrating that the key to better performance and low-cost modulation signal synthesis lies in a large delay. To implement a large delay, we resort to in-house fabricated low-loss, wideband lithium niobate (LiNbO3)SH0 mode acoustic delay lines employing single-phase unidirectional transducers. The four-port circulator, consisting of two switch modules and one delay line module, has been modularly designed, assembled, and tested. The design process employs time-domain full circuit simulation, and the results match well with measurements. An 18.8-dB nonreciprocal contrast between IL (6.6 dB) and isolation (25.4 dB) has been achieved over a fractional bandwidth of 8.8% at a center frequency 155 MHz, using a record low switching frequency of 877.19 kHz. The circulator also shows 25.9-dB suppression for the intramodulated tone and 30 dBm for IIP3. Upon further development, such a system can potentially lead to future wideband, low-loss chip-scale nonreciprocal radio frequency systems with unprecedented programmability. [ABSTRACT FROM AUTHOR]