Guofeng Chen

Cross-Sectional Lamé Mode Ladder Filters for UHF Wideband Applications

This letter reports on the first demonstration of ladder filters based on the recently demonstrated cross-sectional Lamé mode resonator (CLMR) technology. These filter prototypes show a fractional bandwidth (BW3dB) as high as 3.3% and an insertion loss as low as 0.4 dB. As the resonance frequency of CLMRs can be lithographically controlled without significantly degrading their electromechanical coupling coefficient (k2t), multiple contiguous frequency bands can be covered by this filter technology without adding fabrication complexity. This unique feature addresses one of the most crucial challenges associated with the development of miniaturized mobile platforms adopting carrier-aggregation. Furthermore, the capability of achieving large BW3dB, around lithographically defined center frequencies, enables the fabrication of transmit and receive modules of the next-generation radio-frequency front ends on the same chip without adding fabrication steps.

RF Passive Components Based on Aluminum Nitride Cross-Sectional Lamé-Mode MEMS Resonators

This paper presents a new class of monolithic integrated RF passive components based on the recently developed aluminum nitride (AlN) MEMS cross-sectional Lamé-mode resonator (CLMR) technology. First, we experimentally demonstrate a 920-MHz CLMR showing the values of electromechanical coupling coefficient (k_t²) and quality factor (Q_load) in excess of 6.2% and 1750, respectively. To the best our knowledge, the resulting figure of merit (= Q·k_t²), in excess of 108, is the highest ever reported for AlN-based piezoelectric resonators using interdigitated metallic electrodes (IDTs) and operating in the same frequency range. Second, we report the measured performance of an 870-MHz ladder filter, synthesized using three degenerate CLMRs. This device shows the values of fractional bandwidth (BW_3dB) in excess of 3.8% and an insertion loss of ~1.5 dB. Finally, we report the performance of the first piezoelectric transformer (PT) based on the CLMR technology. This device, dubbed “cross-sectional Lamé-mode transformer,” exploits the high-k_t² of the CLMR technology to achieve high values of open-circuit voltage-gains (G_v) in excess of 39. To the best of our knowledge, such a high G_v-value is the highest ever reported for MEMS-based PTs operating in the microwave frequency range.

Low impedance arrays of coupled Cross-Sectional Lamé mode resonators with high figure of merit in excess of 100

We report on novel high electromechanical coupling coefficient (kt2) and large input capacitance (C0) Cross-Sectional Lamé mode resonators (CLMRs). We show that, by coupling multiple 3-fingers CLMRs, it is possible to simultaneously achieve high Figure of Merit (FoM, namely the product between quality factor, Q, and kt2) and large C0-values. The use of this design approach permits to evade the intrinsic reduction of FoM, occurring in traditional single-plate CLMRs at increasing C0-values. In addition, we report on the performance of a 3-finger 730 MHz CLMR, showing a FoM in excess of 147. Such a record high FoM is the highest reported in AlN resonators operating in the same frequency range.

A microelectromechanical AlN resoswitch for RF receiver application

Resonant switches (resoswitches) using a novel design and fabrication process are reported. A folded beam structure compensates for the stress-gradient-induced bending in the sputtered AlN material and ensures that the free end of the center actuated beam is in plane with the anchor beams. A 21.14 kHz resoswitch with a Q of over 2000 and an actuation gap of 1.3 μm is turned on at the resonant frequency with a 0.5dBm 800MHz carrier that is square wave modulated at 21.14 kHz. This demonstration shows the feasibility of monolithically integrating a high gain RF piezoelectric transformer with a high-Q electrostatic resoswitch for a zero stand-by power RF wake-up receiver.

Aluminum Nitride cross-sectional Lamé mode resonators with 260 MHz lithographic tuning capability and high kt 2 > 4%

We experimentally demonstrate Aluminum Nitride (AlN) cross-sectional Lamé mode resonators (CLMRs) operating in the microwave frequency range and showing high Qkt2 products (FoM) in excess of 85. Such feature enables low motional resistance (Rm) values (37 Ω) in CLMRs characterized by low static capacitance (Co) approaching 66 fF. In addition, the ability of CLMRs to simultaneously achieve high kt2 (> 4%) and a lithographic frequency tunability (> 260 MHz around 900 MHz) is experimentally demonstrated, for the first time, in this work. Such important feature renders CLMRs promising candidates to replace off-chip Surface Acoustic Wave (SAW) devices in lithographically defined filters for next-generation wireless communication platforms.

Cross-sectional Lamé mode filters for UHF wideband applications

We demonstrate the first ladder filter based on the use of the recently demonstrated cross-sectional Lamé mode resonators (CLMRs). This device shows a fractional bandwidth (BW3db) as high as 3.3% while enabling an insertion-loss as low as 2.5 dB. As the resonance frequency of CLMRs can be controlled lithographically without significantly degrading their electromechanical coupling coefficient (kt2), this novel filtering technology permits to cover multiple frequency bands without adding fabrication complexity. In particular, as demonstrated in this work, this feature enables the use of CLMFs in platforms adopting carrier-aggregation. In addition, the capability of achieving large BW3dB around lithographically defined center frequencies permits to build transmitter and receiver modules of next-generation Radio-Frequency (RF) front-ends on the same chip and without adding fabrication steps.