5 GHz Lamb wave Wi-Fi channel filters

Lamb-wave resonators offer the possibility to adjust their resonance frequency by varying the period of their inter-digitated electrodes. Leveraging the high frequency operation of the first antisymmetric mode in thin film lithium niobate membranes, this opens perspectives towards the cointegration of several filters operating in the 4–7 GHz range on the same die. To demonstrate this, we designed and fabricated a set of channel filters for the 5 GHz Wi-Fi standard. Resonators exhibit frequencies varying from 5.1 to 5.6 GHz and electromechanical coupling ranging from 5.5 to 9% for electrodes pitches varying from 1.1 µm to 800 nm, with quality factors in the 400–600 range. 3 and 5-resonator ladder filters exhibit insertion losses close to 2 (resp. 4) dB and rejection of 20 (resp. 30) dB, mostly limited by the frequency positionning of the resonators and feedthrough capacitances.