A theoretical and experimental study on strip reflection coefficient of different crystal symmetry class

The closed-form expressions of strip reflection coefficients of tetragonal 4/mmm, hexagonal 6/mm and trigonal 3m crystal etc are derived, which are different from that of cubic m3m crystal published. The reflection coefficients for short-circuited Al grating and groove grating on 112° rotated X-cut Y-propagation LiTaO₃ are then given by our theory. The reflection property of the groove grating on 112°LiTaO₃ in which short-circuited Al grating was placed has been studied by an experimental method and the condition that internal reflection is close to zero was achieved. It concluded that the structure of single finger without internal reflection can be realized by placing short-circuited Al strip in groove grating on 112°LiTaO₃ and thereafter a pass-band filter with central frequency 255 MHz, bandwidth about 10 MHz, pass-band ripples less than 0.4 dB are yielded by utilizing those results in the study of single finger without internal reflection.