New algorithms for the detection and elimination of sine waves and other narrow-band signals in the presence of broadband signals and noise (original) (raw)
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Adaptive subband notch filter for rfi cancellation in low interference to signal ratio
eurasip.org
In this paper, an adaptive-subband-based Radio Frequency Interference (RFI) cancellation method for VDSL systems is developed. The use of subband adaptive IIR notch filter with a specific developed excision algorithm offers a solution in low Interference to Signal Ratio (ISR) environment. The division of a fullband problem into several subbands improves the tracking ability of the Fullband Adaptive Notch Filter (FANF) in low ISR, since the noise variance is reduced in each subband and offers faster convergence speed, due to decimation. In this paper, we compare the performances of the subband method with the classical fullband method using the normalized-stochastic-algorithm-based IIR Adaptive Notch Filter (ANF).
IMPLEMENTATION OF INTERFERENCE CANCELLATION BY ADAPTIVE FILTERS
This paper investigates on the development and implementation of adaptive noise cancellation (ANC) algorithm meant for mitigating the high machinery noise in factory plants ,which makes the speech signal unintelligible.This opens up the need for an adaptive filter that cancels this interference of noise.An adaptive filter is computational device that attempts to model the relationship between two signals in real time in an iterative manner.An adaptive filter self adjusts the filter coefficients according to an adaptive algoritm.A comparative study of Gradient based adaptive Infinite Impulse Response(IIR) algorithm and its modified version is performed using MATLAB simulator interms of converging speed.From the simulation result the best IIR algorithm is used for implementation in Performance Optimized with Enhanced RISC PC ( Power PC) 7448.
A new adaptive line enhancer using a recently advanced digital biquadratic filter section and a modified least-squares based algorithm is proposed in this paper. The new structure is having an independent tuning of the central frequency and the bandwidth of the bandpass/bandstop realizations, permitting a considerable reduction of the computations (by eliminating the matrix inversion operation), while ensuring very small residual error in low frequency applications, due to the very low sensitivity for poles near z=1. All theoretical results are verified experimentally.
A powerful notch filter for PLI cancelation
2021
In this work, we present a powerful notch filter for power-line interference (PLI) cancelation from biomedical signals. This filter has a unit gain and a zero-phase response. Moreover, the filter can be implemented adaptively to adjust its bandwidth based on the signal-to-noise ratio. To realize this filter, a dynamic model is defined for PLI based on its sinusoid property. Then, a constrained least square error estimation is used to emerge the PLI based on the observations while the constraint is the PLI dynamic. At last, the estimated PLI is subtracted from recordings. The proposed filter is assessed using synthetic data and real biomedical recordings in different noise levels. The results demonstrate this filter as a very powerful and effective means for canceling the PLI out.
Adaptive noise cancelling: Principles and applications
Proceedings of The IEEE, 1975
This paper describes the concept of adaptive noise cancelling, an alternative method of estimating signals corrupted by additive noise or interference. The method uses a "primary" input containing the corrupted signal and a "reference" input containing noise correlated in some unknown way with the primary noise. The reference input is adaptively filtered and subtracted from the primary input to obtain the signal estimate. Adaptive filtering before subtraction allows the treatment of inputs that are deterministic or stochastic, stationary or time variable. Wiener solutions are developed to describe asymptotic adaptive performance and output signal-to-noise ratio for stationary stochastic inputs, including single and multiple reference inputs. These solutions show that when the reference input is free of signal and certain other conditions are met noise in the primary input can be essentiany eliminated without signal distortion. It is further shown that in treating periodic interference the adaptive noise canceller acts as a notch filter with narrow bandwidth, infinite null, and the capability of tracking the exact frequency of the interference; in this case the canceller behaves as a linear, time-invariant system, with the adaptive filter converging on a dynamic rather than a static solution. Experimental results are presented that illustrate the usefulness of the adaptive noise cancelling technique in a variety of practical applications. These applications include the cancelling of various forms of periodic interference in electrocardiography, the cancelling of periodic interference in speech signals, and the cancelling of broad-band interference in the side-lobes of an antenna array. In further experiments it is shown that a sine wave and Gaussian noise can be separated by using a reference input that is a delayed version of the primary input. Suggested applications include the elimination of tape hum or turntable rumble during the playback of recorded broad-band signals and the automatic detection of very-low-level periodic signals masked by broad-band noise.
An approach of adaptive notch filtering design for electrocardiogram noise cancellation
Indonesian Journal of Electrical Engineering and Computer Science
An electrocardiogram (ECG) is a means of measuring and monitoring important signals from heart activity. One of the major biomedical signal issues such as ECG is the issue of separating the desired signal from noise or interference. Different kinds of digital filters are used to distinguish the signal components from the unwanted frequency range to the ECG signal. To address the question of noise to the ECG signal, in this paper the digital notch filter IIR 47 Hz is designed and simulated to demonstrate the elimination of 47 Hz noise to obtain an accurate ECG signal. The full architecture of the structure and coefficient of the IIR notch filter was carried out using the FDA Tool. Then the model is finished with the help of Simulink and the MATLAB script was to filter out the 47 Hz noise from the signal of ECG. For this purpose, the normalized least mean square (NLMS) algorithm was used. The results indicate that before being filtered and after being filtered it clearly shows the eli...
Noise Cancellation Using an Adaptive Filtering Technique
Acoustic “Noise” is becoming a major problem in the field of engineering and digital signal processing. The problem that is being faced by engineers is how to decrease this noise level to a minimum or to eradicate it in total. Then came the idea of noise cancellation; a mechanism of cancelling out an unwanted noise by introducing a secondary anti-noise. To achieve this they need a special type of filter “adaptive filters”, just as the name, it is kind of filter that has the ability to adjust its position to adjust to a change in the external environment. This project is based on ways we can achieve this noise cancellation using an adaptive filter. Three adaptive filtering algorithms were implored, the LMS, RLS and Block LMS, which were all implemented both in the MATLAB and Simulink environment. A GUI was designed to allow a user to use the implemented adaptive filters, listen to an audio play back of the processing audio signals and view the processing graphics. The only shortcoming of the project is the absence of the real time workshop on the student version of MATLAB, so the GUI to synchronize with the Simulink models was displaying processing graphics in non-real time
An Efficient Adaptive Noise Cancellation Scheme Using ALE and NLMS Filters
International Journal of Electrical and Computer Engineering (IJECE), 2012
The basic theme of our paper is to implement a new idea of noise reduction in the real time applications using the concepts of adaptive filters. Our model which is presented as one of the solutions is based on two stages of operation with the first stage based on the ALE (Adaptive Line Enhancer) filters and the second stage on NLMS (Normalized Least Mean Square) filter. The first stage reduces the sinusoidal noise from the input signal and the second stage reduces the wideband noise. Two input sources of voice are used; one for the normal speech and the other for the noise input, using separate microphones for both signals. The first signal is of the corrupted speech signal and the second signal is of only the noise containing both wideband and narrowband noise. In the first stage the narrowband noise is reduced by using the ALE technique. The second stage gets a signal with ideally only the wideband noise which is reduced using the NLMS technique. In both the stages the concerned algorithms are used to update the filter coefficients in such a way that the noise is cancelled out from the signal and a clean speech signal is heard at the output.
Novel algorithm for sinusoidal interference cancellation
2011
A simple and efficient method for canceling sinusoidal interference is presented in this paper. The interference of known frequency is modeled as a sum of unknown amplitude and zeros phase sine and cosine components. The amplitude of those components are sequentially estimated interms of Wiener-Hopf solutions using cumulative average system. Additionally, in order to avoid any look-up tables for generating the sine and cosine signals, the coupled-digital oscillator is employed instead. It has been demonstrated that the proposed method can efficiently and rapidly cancel sinusoidal interference as compared with the previous method.
AN ADAPTIVE MIXED-SIGNAL NARROWBAND INTERFERENCE CANCELLER FOR WIRELINE TRANSMISSION SYSTEMS
Narrowband radio transmitters like radio amateurs and broadcast radio stations are considered to be a serious problem for highbitrate data transmission over twisted pairs. Due to its high power level, radio frequency interference (RFI) has the potential of overloading the receiver's analog-to-digital converter (ADC). Once the ADC is in saturation, any countermeasure taken in digital domain will fail, so the problem has to be faced at least partly in the analog domain. This paper proposes an adaptive, mixed-signal, narrowband interference canceller employing a modified recursive leastsquares (RLS) algorithm which is split into an analog and a digital part. The mixed-signal approach enables the circuit to generate an interference-cancelling signal of several MHz while operating the adaptive algorithm at some kHz. The structure is fast enough to prevent the ADC from overloading due to radio amateur interference, thus protecting the data transmission from interruption. Simulation results as well as measurements indicate a practical disturbance rejection potential of about ¢ ¡ ¤ £ ¦ ¥ § ¡ dB.