Wide tab electrodes are utilized for waveguiding the energy of anharmonic modes to lossy mounting at plate edges of monolithic crystal filters (MCFs). The effect of Z'-tabs on dual-resonator MCFs operating in the third-overtone thickness-twist mode is examined. The theoretical and experimental results show that while the unwanted mode suppression achievable with the Z'-waveguides is limited by the occurrence of untrapped modes, it is possible to attenuate both the strong (3, 1, 3) and newly excited modes below -20 dB. Experimental results for MCFs having wide Z'- and X-tabs are also presented.
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