针对测试环境中常存在的超声波频段的有色干扰噪声, 设计了一种基于横向滤波器和最小均方误差自适应滤波算法的自适应对消器结构, 并提出了固定步长和自适应步长相结合的自适应滤波算法流程。该方法增设了一个接收环境噪声的专用探头来自动跟踪噪声特性的改变, 无需手动设置自适应滤波器参数和期望信号。通过自适应步长调整算法与固定步长方法结合, 该方法能够在实现良好滤波效果的同时兼顾快速跟踪环境的变化。实验表明, 提出的方法可以有效滤除目标超声波信号频带之外频率点处的有色干扰噪声, 信噪比改善幅度可达16 dB; 时间复杂度为O(n), 可实现实时处理。本文方法可以在无人工干预下自动、实时、有效地滤除与超声波信号频率接近的有色干扰噪声, 已被成功地应用于气体超声波流量测量中。

For colored interference noise in digital ultrasonic signals at ultrasonic frequency band, an adaptive canceller was designed based on a transversal filter and the least mean square adaptive filtering algorithm. An adaptive filtering algorithm was proposed combining the fixed and adaptive step lengths. The proposed method could track automatically the changes of noise characteristics by adding a special probe to receive the environment noise without manually setting the parameters and the expected signals of the adaptive filter. By combining adaptive step method and fixed step method, the proposed method has good tracking and steady-state properties. Experiment results show that proposed method filters effectively out the colored noise located outside the frequency band of the target ultrasonic signal in real time and the signal-to-noise has improved up to 16 dB and the time complexity is O(n). The method has been successfully applied to gas ultrasonic flow measurement and filters out the colored noise in real time automatically and effectively without the manual intervention.