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Amplifiers and Filters
Published in Clarence W. de Silva, Sensor Systems, 2016
Filtering can be achieved by digital filters as well as analog filters. Before digital signal processing became efficient and economical, analog filters were exclusively used for signal filtering and are still widely used. An analog filter is typically an active filter containing active components such as transistors or op-amps. In an analog filter, the input signal is passed through an analog circuit. Dynamics of the circuit will determine which (desired) signal components would be allowed through and which (unwanted) signal components would be rejected. Earlier versions of analog filters employed discrete circuit elements such as discrete transistors, capacitors, resistors, and even discrete inductors. Since inductors have several shortcomings such as susceptibility to electromagnetic noise, unknown resistance effects, and large size, today they are rarely used in filter circuits. Furthermore, due to well-known advantages of IC devices, today analog filters in the form of monolithic IC chips are extensively used in modem applications and are preferred over discrete-element filters. Digital filters, which employ digital signal processing to achieve filtering, are also widely used today.
Digital Signal Processing
Published in Richard L. Shell, Ernest L. Hall, Handbook of Industrial Automation, 2000
The classic analog filter types, called Cauer, Butterworth, Bessel, and Chebyshev are well studied and have been reduced to standard tables. Analog filters are historically low order (≤ 4) and are often physically large devices. High-precision high-order analog filters are notoriously difficult to construct due to the inexactness of the analog building-block elements and inherent parameter sensitivity problems. Currently analog filters have been routinely reduced to electronic integrated circuits (IC) which adjust their frequency response using external resistors and capacitors.
Temperature Control in Large Buildings
Published in William S. Levine, Control System Applications, 2018
Clifford C. Federspiel, John E. Seem
The purpose of the analog filter is to remove high frequency noise before sampling by the analog-to-digital (A/D) converter. This filter is commonly called an anti-aliasing filter or an analog prefilter. It is especially important to use an anti-aliasing filter when controlling flow or pressure in a duct or pipe because turbulence can generate a large amount of noise. The bandwidth of the analog filter should be selected based on the sampling period for the A/D converter. In the HVAC industry, a sampling period of 1 second is typical.
First order universal filters employing single DV-EXCCCII
Published in International Journal of Electronics Letters, 2023
Analog filter circuits have applications in areas of communications, signal processing, control system and instrumentation. The circuit designs using the current-mode approach emerged as an important topic in the research with inherent features, such as large bandwidth and dynamic range, high slew rate, greater linearity, simple circuitry and low power supply. A number of high performance active analog blocks are discussed in the literature. Some of the most popular active elements are CCII (Horng, 2010a; Shah et al., 2004), DVCC (Horng, 2010b), OTRA (Cam et al., 2004), OTA (Sotner et al., 2014), CDTA (Shah et al., 2007; Shah et al., 2008a; Shah et al., 2008b; Tangsrirat et al., 2010), CCTA (Pandey et al., 2011), OFCC (Pandey et al., 2014), DO-CCII (Yuce & Minaei, 2016), CFA (Shah et al., 2005), DX-MOCCII (Beg et al., 2011), and many more.
Development of wireless smart sensor network for vibration-based structural health monitoring of civil structures
Published in Structure and Infrastructure Engineering, 2022
Niusha Navabian, Sherif Beskhyroun, Justin Matulich
This low-power and low-cost chip has an ultralow noise density of 25 µg/√Hz in three axes and an integrated analogue, low-pass, antialiasing filter with a fixed bandwidth of approximately 1.5 kHz. The analogue filter reduces out of the band noise to limit bandwidth for a high-resolution signal. Further filtering option integrated in the accelerometer chip is a digital filter to maintain excellent noise performance at various bandwidths. This filtering option includes low-pass digital decimation filter and a bypassable high-pass filter providing output data rates between 3.9 Hz to 4 kHz. To digitise the filtered analogue signals, this accelerometer has an integrated 20-bit ADC that is an ideal resolution for SHM applications.