声表面波四相单向叉指换能器

QUADRAPHASE UNIDIRECTIONAL SURFACE ACOUSTIC WAVE INTERDIGITAL TRANSDUCER

摘要: 四相单向换能器^[3]与三相单向换能器及群型单向换能器相比具有最佳的单向性,适宜用来制作宽带低插损声表面波滤波器。四相换能器的等效电路、声辐射导、静态电容以及频率响应等,还给出了简便的四相移相电路,计算了移相电路对频响的影响,从而得到了较完整的四相换能器的设计理论。用等指长不加权的四相换能器得到了插入损耗小于0.72dB的滤波器,在仪器分度为0.1dB的仪器上观察不到带内波纹。实测频响与理论频响符合良好。

Abstract: It is indicated that in comparison with three-phase unidirectional transducers and group-type unidirectional transducers the quadraphase unidirectional surface acoustic wave transducers (QPUT)^[3] are superior in directionality, suitable to the wideband low-loss filters. The equivalent circuit, acoustic radiation conductance, static capacity and frequency response of QPUT are derived, and the simple quadrature phase shift network and its influence on the frequency response are given. Thus, a rather complete design theory of QPUT are obtained.
A filter of insertion loss less than 0.72 dB is obtained by a uniform QPUT. The pas-sband ripple could not be observed by the instrument with division of 0.1 dB. The experimental frequency response agrees with the theoretical one very well.