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四相单向换能器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。
Compared with three-phase unidirectional transducer and group unidirectional transducer, four-phase unidirectional transducer has the best unidirectional property and is suitable for making broadband low insertion loss surface acoustic wave filter. The equivalent circuit of four-phase transducer, acoustic radiation guide, static capacitance and frequency response are also given. The simple four-phase phase-shift circuit is also given, and the effect of the phase-shift circuit on the frequency response is calculated. Four-phase transducer design theory. A filter with an insertion loss of less than 0.72 dB was obtained with a four-phase transducer of equal length and non-weighting. No in-band ripples were observed on an instrument graduated to 0.1 dB. The measured frequency response is in good agreement with the theoretical frequency response.