Vertically excited first-order antisymmetric mode plate wave resonator using X-113°Y LiNbO₃

This work proposes a new plate wave device composed of X-113°Y LiNbO₃ with a top interdigital transducer (IDT) and a bottom electrode. By the specially selected Euler angles of (90°, 90°, 113°), the first order anti-systematic (A₁) mode is vertically excited, meanwhile spurious modes are successfully suppressed without adding process complexity. Furthermore, the frequency is design-tunable via the IDT λ. The properties of the main mode and spurious modes are systematically analyzed by simulation, and several geometric parameters are optimized. Two groups of designs are studied by experiments, and an impedance ratio (Z-ratio) of 60 dB and 56 dB, bandwidth (BW) of 17.8% and 20.6% at 2 GHz and 4 GHz are demonstrated, respectively. The experimental results are also analyzed in terms of spurious modes and the use of reflectors. The measured temperature coefficient of frequencies (TCF) are as good as - 64 ppm/°C and -62 ppm/°C at resonance and antiresonance frequencies, respectively, regardless of a large BW of 18.3%. The proposed device shows great potential in the next-generation RF systems requiring ultra-wide BW at high frequency.