磁聚焦电导率成像系统信号源与信号提取的实现

为了提高信号源的稳定度和实现扫频检测，以提取更可靠、更丰富的有用信号，信号源用直接数字频率合成器设计，输出频率为1～20 MHz的扫频正弦波信号，通过具有很好聚焦特性的平面螺旋线圈接成调幅电路输出。同时平面螺旋线圈采用差分线圈结构以检测和提取信号，其输出送往由集成乘法器MC1595组成的鉴相电路，使鉴相器输出相位变化随着输入信号的频差变化，利用低通滤波器滤除扫频载波从而提取线圈有目标以及目标变化时的频差信号。获得了足够的可靠数据，提高了系统的稳定度,提高了成像系统的空间分辨率。有利于系统软件进行电导率反演和成像。

Design and Implement of Signal Generator in Magnetic Focused Conductivity Tomography System

To improve stability of the signal source and perform sweeping detection, as well as extract abundance and reliable signal, the direct digital synthesis technology was employed to design the generator of source which formes a sweeping frequencies sine wave output from 1 MHz to 20 MHz. The planar spiral coil was connected as an amplitude modulation circuit. The same coil was made use of differential architecture for signal detection and extraction. The MC1595 was utilized to compose a phase detector, in which difference of phases varies with change of frequencies. A low pass filter was designed to filter the carry waves of the sweeping source. Thereby the system obtained abundance data and its stability was improved. Further, the spatial resolution of the system was enhanced. All of the above is in favor of using software in magnetic focused conductivity tomography system to reconstruct the image of conductivity within human body.