摘要
目的 研究一种用于电阻抗多频及参数成像数字采集系统的具有高抗噪性能和快速的解调方法 .方法 提出一种新解调方法正交序列解调法 ,通过构造一对正交的正弦序列 ,计算所采序列与这两个序列的内积 ,从而得出相应频率成分的实部和虚部 .结果 在 n频率成分 ,每周期采样点为 N的情况下 ,从采样结束到解调完成共需 2 n次加法和 2 n次乘法运算 ,随机噪声可被衰减 (N/ 2 ) 1 /2 倍 .除特定频率点外 ,高次谐波被有效抑制 .结论 正交序列解调法具有系统资源占用少、计算速度快、抗噪性强的优点 。
AIM To develop demodulation methods with high anti-noise ability and high speed for data acquisition system inelectrical impedance multi-frequency and parameter tomography. METHODS By using of "orthogonal sequential demodulation" we developed, a pair of orthogonal sinusoidal sequences was built and the inner products between these sequences and the sequence we acquired from measuring signal were calculated. Thus the real part and imaginary part of corresponding frequency component was got. RESULTS For the signal which consisted of n frequency components, when we sampled N points per period, total operations we needed after sampling finished were 2n times multiplication operations and 2n times addition operations. And the random noise rejection ratio was (N/2) 1/2 . Except for particular frequencies, the harmonic components were rejected effectively. CONCLUSION The orthogonal sequential demodulation has the advantages of both the high calculating speed and the high noise rejection ability. It also has the advantage of less resource needed these can meet the needs for data acquisition system in electrical impedance multi-frequency and parameter tomography very well.
出处
《第四军医大学学报》
2000年第7期S164-S166,共3页
Journal of the Fourth Military Medical University
基金
国家自然科学基金!资助项目 ( 3 9870 2 17)
"九五"国家重点攻关课题!( 96-92 0 -12 -0 4)
关键词
多频电阻抗成像
电阻抗参数成像
正交序列解调法
multi-frequency electrical impedance tomography
electrical impedance parameter tomography
demodulation
orthogonal sequence
signal noise ratio
