eLoran接收机的数字滤波器设计

Digital filter design of eLoran receiver

根据eLoran信号的特点,采用内插结构FIR带通滤波器与LMS自适应滤波器相结合的方法,滤除eLoran信号中频带内、外的噪声和干扰。首先利用内插结构FIR滤波器抑制带外干扰,在直接FIR滤波器的基础上介绍插值滤波器设计方法,根据eLoran信号的频谱特性设计出满足要求的内插结构FIR带通滤波器,通过比较发现:在相同的参数下,插值滤波器比直接FIR滤波器节省了很大的阶数,在工程应用上有很大的优势,而且所要求的频带越窄,采样率越大,节省资源的百分比就越大。其次,采用LMS自适应滤波器可以很好地滤除频带内的干扰和噪声,从而有效恢复理想eLoran信号。

According to the characteristics of eLoran signal, the interpolation FIR bandpass filter and adaptive noise canceller based on LMS algorithm are combined to filter out the noise and interference in and out of the intermediate frequency band of eLoran signal.Firstly, FIR filter with interpolation structure is used to suppress out-of-band interference.The design method of interpolation filter is introduced on the basis of direct FIR filter.According to the spectrum characteristic of eLoran signal, an interpolation FIR band-pass filter is designed.Through comparison, it is found that the interpolation filter can save a lot of orders than direct FIR filter under the same parameters, and has a great application in engineering.The narrower the required frequency band and the larger the sampling rate, the greater the percentage of resource saving.Secondly, the adaptive noise canceller based on LMS algorithm can filter out the noise in the frequency band very well.Thus, the ideal eLoran signal can be effectively restored.