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A bespoke signal processing algorithm for operational modal testing of post-tensioned steel and concrete beams
Published in Nigel Powers, Dan M. Frangopol, Riadh Al-Mahaidi, Colin Caprani, Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges, 2018
D. Noble, M. Nogal, A.J. O’Connor, V. Pakrashi
The main component of noise in the data is electrical noise. The sources of accelerometer noise can be broken down into the electrical noise from the circuitry that converts the mechanical vibration into a voltage signal that is thus correlated against a given acceleration, and the mechanical noise from the accelerometer itself. Ambient vibration of the system will also contaminate the pure structural signal. The A/C mains by which the accelerometer is powered has an alternating current with a frequency of 50Hz. This 50Hz signal, including all of its harmonics, is represented in the output data. This 50Hz electrical noise and its harmonics are filtered out by means of a ‘notch’ filter. A notch filter is a high order bandpass filter that removes specifically defined frequencies, while passing all other frequencies. Figure 6 shows the result of applying a series of notch filters of 50Hz and its multiples to the data. The blue signal in Figure 6 represents the raw signal, whereas the red signal represents the raw signal following removal of the electrical noise.
Design of Actuator Servo Controller
Published in Abdullah Al Mamun, GuoXiao Guo, Chao Bi, Hard Disk Drive, 2017
Abdullah Al Mamun, GuoXiao Guo, Chao Bi
It is shown in the previous section how notch filters can be used to eliminate unwanted resonant oscillations of the actuator. Notch filter can also be used to eliminate sensor noise whose energy is concentrated in a narrow band of frequencies. When different signals are measured in a control system, the process of measurement often contribute to noise entering into the system. These measurement noises are usually random in nature containing wide band of frequencies. However, in many practical systems, the noise from a sensor either can be sinusoidal or has its energy concentrated in a narrow band of frequencies. Such noise has severe detrimental effects on the performance of the closed loop. A method useful for elimination of the effects of narrow band sensor noise is explained next.
Mixing and Processing Equipment
Published in Hilary Wyatt, Tim Amyes, Audio Post Production for Television and Film, 2013
Notch filters have a high Q and allow a specific frequency to be selected and attenuated. They are used to reduce such problems as camera noise and can be ‘tuned’ to the appropriate frequency. The offending noise can often be removed without completely destroying the basic sound quality. A depth of at least 20dB is necessary for successful noise rejection. Tuned to 50/60Hz rejection, the filter can reduce mains frequency hum, with a further 100/120Hz notch for its audible second harmonics. A 15kHz notch filter can be used to reduce the 625-line sync pulse interference noise, radiating from domestic televisions in Europe.
Designing and Validation of Miniaturized CPW Based Microwave Notch Filter Using Loaded Modified Multiple Split Ring Resonator (MSRR)
Published in IETE Journal of Research, 2021
The notch filter (NF) rejects a narrow band of frequencies and passes all other frequencies on either side of this band unaltered. The notch filter can be extensively used in antennas, mixers, and amplifiers to attenuate the unwanted higher frequency signals. In this article, the main intention has been given to design a low-cost CPW NF with a highly compact size, sharp rejection, low loss, and high roll-off factor. This work presents an array of conventional MSRR structures using lumped elements. But to enhance the performance of the filter, it was replaced by an array of modified MSRR structures loaded above the transmission line [22] in the bottom layer of CPW. The relationship amid the resonating frequency and the loaded MSRR ring perimeter is parametrically studied and a single band NF is designed at resonating frequency of 2.56 GHz. An equivalent lumped LC circuit is also derived for the proposed NF and simulated. It has been inferred that there is a well-matched behavior among EM frequency simulated, measured and circuit simulated responses. In the second part of this paper, the metamaterial properties of the modified MSRR structure have been presented. The metamaterial properties are justified by extracting several parameters of it. Lastly, DBNF is designed using this array of modified MSRR. The performance comparison is done with the previous related works and the proposed filter in the last section.
Time-efficient fault detection and diagnosis system for analog circuits
Published in Automatika, 2018
Qiwu Luo, Yigang He, Yichuang Sun
The notch filter is popularly used in the fields of radar and sonar, communication, measuring instruments, etc. owing to the selective characteristic for specific frequency band [25–27]. In order to evaluate the real-time efficiency and computing capacity of the realized system, we have diagnosed the notch filter circuit in Figure 5 [27], the component parameters are given in Figure 5 and the parameter precision is 1%, the trap centre frequency is 275.6 Hz. The input node 7 and output node 9, together with intermediate nodes 1, 2, 3, 4 and 8 are selected as accessible nodes, thus, the voltage of accessible nodes V7, V9, V1, V2, V3, V4, V8 constitute a kind of test signal. And the A–F and P–F characteristics are captured by the MAX12529 as another two kinds of test signals. Consequently, the value of the circuit parameters N defined in (9) equals 9. The photograph of its actual circuit has given in Figure 6.