An apparatus is disclosed for a double-mode surface-acoustic-wave (SAW) filter having a modulated interdigital transducer. In example aspects, the apparatus includes a double-mode surface-acoustic-wave filter that has at least one interdigital transducer. The interdigital transducer includes a first busbar, a second busbar, and multiple fingers extending from the first busbar toward the second busbar. The multiple fingers include a first set of fingers having a first spatial property. The multiple fingers also include a second set of fingers having a second spatial property different from the first spatial property. The second spatial property includes at least two fingers of the second set of fingers being positioned adjacent to each other.

A mechanism for suppression of spurious signals or modes in FBAR resonators and filters, incorporating the effects of the electromagnetic (EM) cavity resonance physical field model. The suppression of spurious signals is achieved by modifying the characteristics of the EM cavity resonance of the FBAR resonator. This is achieved by keeping the fundamental piezoelectric resonance frequency of the resonator constant and shifting the EM cavity resonance to a lower frequency. This shift of the EM cavity resonance frequency ensures that the sub-spurious signals generated from the interaction between the piezoelectric resonance frequency and the EM cavity resonance frequency, are shifted to a lower-frequency, which advantageously lies in a rejection band area outside the passband of the piezoelectric resonance. The FBAR resonator is modified to include a zipper edge top electrode which includes a series of local ridges or peaks and valleys being generally between adjacent ridges or peaks.