Loaded series resonators for adjusting frequency response of acoustic wave resonators

An acoustic wave filter device comprising:

• an acoustic wave filter element comprising input electrodes and output electrodes located on a top surface of a piezoelectric layer;
• a first resonator comprising a first resonator top electrode on the top surface of the piezoelectric layer and a first resonator bottom electrode on a bottom surface of the piezoelectric layer, the first resonator having a first notch in resonator impedance at a first frequency, wherein one of the top and the bottom electrodes of the first resonator is electrically connected to the acoustic wave filter element;
• and
• a second resonator coupled to the acoustic wave filter element and comprising a second resonator top electrode on the top surface of the piezoelectric layer, a second resonator bottom electrode on the bottom surface of the piezoelectric layer, wherein the second resonator has a second thickness that is different from a first thickness of the first resonator such that the second resonator has a second notch in resonator impedance at a second frequency that is different from the first frequency, and wherein one of the top and the bottom electrodes of the second resonator is electrically connected to the acoustic wave filter element,
• wherein the first frequency is an anti-resonance frequency of the first resonator, and the second frequency is an anti-resonance frequency of the second resonator, and
• wherein both the first and the second frequencies are within a sideband of resonator impedance of the acoustic wave filter element.