用于CATV的SAW加解密芯片的设计

DESIGN OF SAW SCRAMBLER CHPS FOR CATV

为了得到用于CATV信号加解扰的非线性相位、非对称幅频特性的声表面波(SAW)滤波器,本文采用面向对象的程序设计语言C++,编制了可以设计和综合任意幅频特性、任意相频特性的本表面波滤波器的计算机设计软件.本文在一个设计中同时采用了多种本征函数综合所要求的幅频和相频特性.结果用非常少的叉指对数的加权换能器实现了在38MHz图象载频上倒相,并使38MHz到39.25MHz的平台,相对31.25MHz到33.57MHz的平台衰减某个电平XdB.与之对应的一个器件则将图象载频再倒相,并使被衰减的平台升高电平XdB.在网络分析仪上实测结果与理论设计的结果一致.

To obtain the Surface Acoustic Wave (SAW) Fllters with uulinear phase and unsymmetrical amplitude applied in CATV ecrambler , we use Borland C+ + language to invent a computer program, which can be utilized to design SAW filters with any phase and phase and any amplitude characteristes. This paper also gives a method to employ a series of eigen functions in one design. At theend, a SAW device with a few fingers weighting transducer achieves that the phase reverses at 38MHz, and the amplitude of region from 38MHz to 39. 25MHz decays XdB than that from 31.2SMHz to 33. 25.MHz, while the counterpart device reverses in phase and amplitude . the result tested by the vector network analyzer is identical to the theory.