Search for: All records

This work demonstrates a passive low-insertion-loss (IL)RF filter with periodic passbands and capable of sparsifying the spectrum from 238 to 526 MHz for sparse Fourier transform (SFT)based spectrum sensing. The demonstrated periodic filter employs LiNbO 3 lateral overtone bulk acoustic resonators (LOBARs)with high-quality factors (Qs), large electromechanical coupling (k t 2 ), and multiple equally spaced resonances in a ladder topology. The fabricated LOBARs show k t 2 larger than 1.5% and figure of merits (k 2 Q) more than 30 for over 10 tones simultaneously and are both among the highest demonstrated in overmoded resonators. The multi-band filter centered at 370 MHz have then been obtained with a passband span of 291 MHz, a spectral spacing of 22 MHz, an IL of 2 dB, FBWs around 0.6%, and a sparsification ratio between 7 and 15. An out-of-band rejection around 25 dB has also been achieved for more than 14 bands. The great performance demonstrated by the RF filter with 14 useable periodic passbands will serve to enable future sparse Fourier transform-based spectrum sensing. 

This work reports the first lithium niobate (LiNbO 3 ) lateral overtone bulk acoustic resonator (LOBAR) with a high figure-of-merit (FoM) for each overtone. We exploit electrode offset as a key parameter to excite both the even-order and the odd-order modes with uniform k t 2 . The fabricated device shows Qs (1966, 1215, and 1513) among the highest reported for LiNbO 3 resonators at the equally-spaced resonances (446.4, 599.8, and 757.3 MHz). As a result, high FoMs of 83.6, 102.6 and 63.1 have been obtained simultaneously for aforementioned resonances. These FoMs significantly surpass those of the state-of-the-art overtone devices. With these qualities, frequency-hopping oscillators based on LiNbO 3 LOBARs can be enabled for low power and phase-continuous frequency-hopping applications.