This paper presents a novel resonant energy detector (RED) based on MEMS-CMOS co-design for wake-up receivers (WuRX) so as to improve the anti-interference capability significantly. The proposed RED presents different down-conversion coefficient at different frequencies, and high-performance filtering can be achieved through the down-conversion process of RED. Using the same inductor-based matching network in the preceding stage, the proposed RED achieves 16 dB better signal to interferer ratio (SIR) and 0.5 dB better voltage gain when compared with a traditional ED. Furthermore, the 3-dB bandwidth (BW) of the radio frequency (RF) front-end is only 15 MHz which is comparable to that of MEMS matching networks and much lower than that of inductor based matching networks. The demonstrated RED significantly improves the WuRX’s filtering performance without sacrificing the sensitivity, which is proven to be an effective way to suppress interferers in WuRXs.

In this study, we carefully reduced the thickness of single-crystal Y128 degrees lithium niobate (LN) thin films to approximately 50 nm through low-power physical etching using argon gas. This process was adopted to construct a fin-mounted Lamb wave resonator operating above 30 GHz. The fabricated fin-mounted nanosheet LN resonator, operating at 36.84 GHz, achieved an electromechanical coupling coefficient (k(2)) of 33.82%, along with series and parallel 3-dB quality factors (Q(s) and Q(p)) of 13 and 83, respectively. These results demonstrate the highest figure of merit (FoM) of 28, surpassing other millimeter-wave (mmWave) resonators within the same frequency range.

In this work, a new kind of coupled shear SAW (CS-SAW) resonator based on LiNbO 3 /SiO 2 /Si substrate has been proposed and demonstrated. By designing and optimizing the interdigitated transducer (IDT) electrode geometries with respect to the piezoelectric thin-film layer thickness, two different shear piezoelectric coefficients, namely e 15 and e 16 , were utilized in one mode of vibration, so that the electromechanical coupling coefficient (k 2 ) was enhanced. The CS-SAW resonator operating at 5.8 GHz exhibits high k 2 of 8.94% and Bode-Q max of 120. This work not only achieves high performance of SAW resonators, but also discovers a new way of mode coupling.

This work presents A1-mode Lamb wave resonators based on Z-cut lithium niobate thin film to realize acoustic filters at 5 GHz. By using half-electrode reflectors and fin-type anchors, a high-performance resonator with excellent Figure of Merit (FoM) up to 316 has been implemented. The fabricated ladder-type filter achieves a 3-dB bandwidth (3dB-BW) of 990 MHz, equivalent to a fractional bandwidth (FBW) of 20% and an insertion loss (IL) of 1.85 dB at 4990 MHz. This demonstration proves great potential of Lamb wave acoustic filters based on lithium niobate for future 6G and Wi-Fi 7 applications.

This work reports on surface acoustic wave (SAW) piezoelectric resonators with high quality factor (Q) based on high-crystallinity aluminum scandium nitride (AlScN) thin films. The properties of surface acoustic wave modes were analyzed using finite element modeling (FEM) simulations. SAW resonators based on different AlScN composite substrates were fabricated and measured. Due to good crystallinity (FWHM < 1°) of the AlScN thin film, high quality factor over 1000 has been demonstrated based on the AlScN/AlN/sapphire composite substrate, which proves sapphire substrate is a good candidate to enable high $Q$ in AlN/AlScN SAW resonator development.

In this work, surface acoustic wave (SAW) resonators based on Z-cut LiNbO3/SiO2/Si substrate have been designed and fabricated. By optimizing the thickness of the SiO2 layer and the geometries of the interdigitated electrodes (IDT), the temperature coefficients of frequency of series (TCFs) and parallel (TCFp) resonant frequencies are effectively reduced to approach zero. The SAW resonator with lambda of 2.8 mu m operating at 1.37 GHz exhibits k(2) of 6.24% and high Bode-Qmax of 3115. The SAW resonator with lambda of 3.6 mu m operating at 1.1 GHz exhibits k(2) of 5.97% and Bode-Q(max) of 1793. The resonator with lambda of 3.6 mu m has the lowest TCF: TCFs = 1.08 ppm/degrees C and TCFp = -3 ppm/degrees C. This demonstration verifies the effectiveness of designing IDT wavelength together with the SiO2 thickness to minimize the SAW resonator TCF for oscillator and timing applications.

This paper reports an acoustic resonator with a high electromechanical coupling coefficient (k(2)) operating in the C-band, as a solution to meet the needs of next-generation high-speed communications. Firstly, the k(2) achievable for firstorder modes in different orientations of Y-cut LiNbO3 substrates is explored, showing the best combination of A1 modes in the X-axis direction in 128 degrees Y-cut LiNbO3. Then by optimizing the geometry design, a Lamb wave resonator with excellent performance was fabricated. The device in this work excites first-order asymmetric (A1) Lamb wave mode in the 128 degrees Y-cut lithium niobate film. A high k(2) of 57% is demonstrated by optimizing the electrode arrangement, exceeding the state-of-the-art.

This work presents a detailed study on the design of micro electromechanical system (MEMS) matching networks(MN) for low-power wake-up receivers (WuRX) operating inGHz frequency bands. To enhance the WuRX sensitivity, a co-design theory between the MN and CMOS energy detector(ED) is proposed and derived quantitatively to give the optimalcircuit topology and design under different scenarios of effectivequality factor (Q(e f f)), when the MEMS resonator is modeledas an effective inductive (L-e f f)matching element. To verify the proposed design theory as well as the high performance of MEMS MN (MMN), CMOS ED chips and various FBAR resonators of different sizes were fabricated and tested. Measurement results s how that the demonstrated MMN achieves relative sensitivitygain (Asens)and voltage gain (Gv)of 8.6 dB and 19.9 dB,respectively. The measuredAsensis the highest among all reported MMNs with similar ED input capacitance operatingat GHz frequencies

In this work, we propose a fin-mounted Lamb wave resonator design with half-electrode reflectors to achieve spurious mode suppression and quality factor enhancement at 12 GHz using Z-cut LiNbO3. Half-electrode reflectors and fin anchors are designed at both two sides of the resonator to effectively confine the acoustic energy. The fabricated spurious-free A1-mode resonator with half-electrode reflectors achieves coupling coefficient (k2) of 18.3%, parallel quality factor (Qp) of 1742, and Figure of Merit (FoM) of 319 at 11.7 GHz, demonstrating great potential of Lamb wave devices for next-generation wireless communications.

This work presents a fin-mounted A5-mode Lamb wave acoustic resonator based on Y128 degrees-cut lithium niobite thin film for millimeter wave (mmWave) frequencies. By using a new fin-mounted structure and optimized electrode geometry, we designed and fabricated a spurious-free A5-mode resonator at 27.58 GHz with k(2) of 4.4% and Q(p) of 448 to achieve a Figure of Merit (FoM) of 19.7, which is the highest in the frequency band around 30 GHz. In addition, a ladder-type filter for 3GPP Band n261 with a center frequency of 27.92 GHz was simulated based on the fin-mounted resonators. This demonstration provides a viable solution for high-frequency lithium niobate ( LiNbO3 or LN) acoustic resonators to be applied in the 5G Frequency Range 2 (FR2) frequency band.

In this paper, we employ a novel two-step approach combining metal-organic chemical vapor deposition (MOCVD) and physical vapor deposition (PVD) techniques to grow high-quality AlScN piezoelectric thin film. MOCVD was initially utilized to grow a seed layer of 100 nm high-crystalline AlN on a Si substrate. Magnetron sputtering—a technique known as PVD for its low deposition temperatures, simple process control and low cost—was employed to deposit another thick layer of 500 nm AlScN. This hybrid two-step approach yielded excellent crystal quality. Based on the high-crystalline AlScN thin film, we designed and fabricated SAW resonators to verify the device performance. The SAW resonator with wavelength of 800 nm operates at 5.35 GHz and demonstrates the highest Bode-Q max of 639. By using the two-step technique, this work demonstrates a feasible way to enable high-frequency, high-Q and especially low-cost AlScN SAW resonators for frequency control applications.

As wireless communication evolves into millimeter wave (mmWave) frequencies, it becomes extremely challenging to realize compact and integrated radio frequency (RF) front-end components with wide bandwidth and high energy efficiency. Here we propose a new fin-mounted acoustic resonator design based on nanosheet (thickness < 100 nm) Z-cut single-crystal lithium niobate (LiNbO3) thin film for large-bandwidth filtering applications in the 5G NR Frequency Range 2 (FR2) band. The fabricated fin-mounted acoustic resonator operating at 25.03 GHz exhibits a high electromechanical coupling coefficient ( k(2)) of 16% and quality factor ( Q(p)) of 132 at parallel resonant frequency (without any de-embedding), which achieves the highest Figure of Merit (FoM = k(2)xQ) in the 5G FR2 band among all reported resonators to date. This demonstration provides a new solution to the internal stress problem of nanosheet piezoelectric thin film devices and opens up more possibilities in enabling piezoelectric nanostructures for filtering, sensing, and timing applications.

This work presents a third-order asymmetric (A3) mode Lamb wave resonator based on 128° Y-cut lithium niobite (LiNbO 3 or LN) thin film operating at a super high frequency (SHF) up to 20.4 GHz. By exploring the possible electromechanical coupling coefficient (k 2 ) of A3-mode resonator in LiNbO 3 thin film of different orientations, we find that X-axis direction is the optimal direction to excite the A3-mode by applying horizontal electric field. Based on the analysis and simulation, spurious-free A3-mode resonator is designed and fabricated. The implemented device shows Q of 461 and k 2 of 6.95%, the highest reported FoM (Q•k 2 ) for piezoelectric MEMS resonators operating in this frequency range. The SHF operation and high k 2 of the A3-mode resonator show great potential of acoustic resonator technology for 5G millimeter wave (mm-Wave) applications.

This work reports on surface acoustic wave (SAW) piezoelectric resonators with high electromechanical coupling coefficient (k2eff) based on a-plane Aluminum Scandium Nitride (AlScN) films. The properties of surface acoustic wave modes were analyzed using finite element modeling (FEM) simulations. The influences of AlScN film thickness and in-plane propagation orientation on k2eff were evaluated. Due to good crystallinity (FWHM < 1°) and high Sc doping, optimized design parameters from FEM simulations were adopted to realize a high k2eff up to 5.17%, which is the highest among the reported AlScN SAW devices. These results demonstrate that the k2eff can be improved by using a-plane AlScN when compared to c-plane AlScN, which is highly needed for radio frequency (RF) filters.

This work presents a wideband radio-frequency micro-electro-mechanical system (MEMS) filter at 6.2 GHz that enables acoustic filters towards high frequencies beyond 6 GHz. The filter is comprised of resonators operating in the first-order antisymmetric (A1) Lamb wave mode and fabricated on Z-cut lithium niobate (LN) with 320-nm-thick suspended continuous thin film. Due to the spurious-free and high electromechanical coupling (k(2)) performance of the A1-mode LN resonators, the implemented MEMS filter demonstrates small in-band ripple and wide bandwidth (BW). Specifically, the measured result of the filter exhibits center frequency at 6.2 GHz, 3-dB fractional bandwidth (FBW) of 11.8% (BW = 734 MHz), insertion loss (IL) of 1.7 dB, and out of band (OoB) rejection of 25 dB.