X-Band Miniature Filters Using Lithium Niobate Acoustic Resonators and Bandwidth Widening Technique

Abstract

This work presents a class of micro-electromechanical 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 2 t) 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 mm 2. Another design is fabricated to demonstrate a 3-dB BW of 170 MHz, an IL of 2.5 dB, an outof-band rejection of 28 dB, and a compact footprint of 1 mm 2 .

Near-Zero Drift and High Electromechanical Coupling Acoustic Resonators at > 3.5 GHz

“…This alignment is mode-dependent resulting in high insertion loss at S 2 and S 4 modes. Note that those modes are fairly separated from A 3 mode and can be mitigated with lumped elements [51], [52].…”

Chip-Based Brillouin Processing for Microwave Photonic Phased Array Antennas

“…For example, approximately 350 mW of coupled pump power was used by McKay et al to generate 4 dB of Brillouin gain over a 400 MHz bandwidth [73] in a Ge:SiO 2 -As 2 S 3 PIC [94]. By analysing (13), the magnitude of Brillouin gain generated for a fixed pump power is related to the figure of merit (FOM), G S BS L e f f , and determines how effective a material platform is at generating Brillouin gain [63]. Increases to both the Brillouin gain coefficient and the effective waveguide length are needed to reduce the required pump power.…”

“…The inset shows a silicon photonic integrated circuit, a candidate hybrid platform for integrated Brillouin processing. they are not suitable for millimeter wave frequencies due to large acoustic losses [12], [13]. Reconfigurable filters based on cascaded banks of high-pass and low-pass filters offer discretely reconfigurable bandwidths and central frequencies [14].…”

Multi-Band and Frequency-Agile Chip-Based RF Photonic Filter for Ultra-Deep Interference Rejection

“…Large stopband rejection is required to mitigate agile frequency hopping interference used for wireless communications [2] and to prevent damage to sensitive electronics from high power jamming signals. Conventional RF electronic filters that rely on fixed cavities [3] or surface acoustic waves [4], [5] are typically limited to a single RF resonance and are fundamentally unable to demonstrate wideband response reconfigurability and flexibility. On the other hand, filters that are based on digital signal processing may be easily reconfigured, however, their operating bandwidth is limited by the sampling rate of commercially available analog-digital converters [6].…”