HYBRID ULTRA-COMPACT 4TH ORDER BAND-PASS FILTERS BASED ON PIEZOELECTRIC ALN CONTOUR-MODE MEM RESONATORS

This work reports on the design, fabrication and te sting of a new class of hybrid (filter design using combined e lectrical and mechanical coupling techniques) ultra-compact (800◊120 m) 4 th order band-pass filters based on piezoelectric Alum inum Nitride (AlN) contour-mode microelectromechanical (MEM) resonators . The demonstrated 110 MHz filter shows a low insertion loss of 5.2 dB in air, a high out-of-band rejection of 65 d B, a fractional bandwidth as high as 1.14% (hard to obtain when onl y conventional electrical coupling is used in the AlN contour-mode technology), and unprecedented 30 dB and 50 dB shape factors of 1.93 and 2.36, respectively. All these are achieved in an extremel y small footprint and by using just half the space that any other 4 th order filter would have taken. In terms of nonlinearities, the 110 MHz filter shows a 1 dB compression point higher than +63 dBmV and input third order intercept point ( IIP 3) values well beyond +153 dBmV. This new hybrid design represents a net improvement over the state of the art and constitutes a very promising solution f or intermediate frequency (IF) filtering in many wireless communication systems.