Filter anti-aliasing

In addition, vibration data collected with a microprocessor-based analyzer is filtered and conditioned to eliminate non-recurring events and their associated vibration profiles. Anti-aliasing filters are incorporated into the analyzers specifically to remove spurious signals such as impacts. While the intent behind the use of anti-aliasing filters is valid, however, their use can distort a machine s vibration profile. 

Fig. 6.7. Block diagram of the differential mixed-signal architecture. AAF Anti-aliasing filter BF Buffer MUX Multiplexer...

Anti-aliasing filters (considered part of Analog Conditioning ) are needed at the input to remove out of band energy that might alias down into baseband. The antialiasing filter at the output removes the aliases that result from the sampling theorem. 

After the anti-aliasing filter, the analog/digital converter (ADC) quantizes the continuous input into discrete levels. ADC technology has shown considerable improvement in recent years due to the development of oversampling and noise-shaping converters. However, a look at the previous technologies [Blesser, 1978] [Blesser and Kates, 1978][Fielder, 1989] will help appreciate the current state-of-the-art. 

Besides the elimination of the sample-and-hold, oversampling converters also reduce the complexity of the anti-aliasing filter. Previous anti-aliasing filters required the use of high order active filters (11th order elliptic for example) that resulted in phase... 

Analysis/synthesis, 51 Analytic signal definition, 409 Anti-aliasing filter, 196, 200 Array misalignment, 270 Articulation Index, 264 Articulatory speech synthesis, 419 Asymmetry of masking, 17 Attack time ANSI, 260 compression, 255 Attack, 319, 322 Audio codec quality, 37 Audio quality, 1-2 Audio restoration (See Restoration)... 

Examples of analogue processing include anti-aliasing filters for the conversion stage. In situations where real-time processing power is limited, there may also be benefits in implementing analogue filters. 

Aperture IR blocking Shutter anti-aliasing. filter... 

Few weeks after the execution of the second AVT, a simple dynamic monitoring system was installed in the tower. The system is composed by a 4-channel data acquisition system (24-bit resolution, 102 dB dynamic range, and anti-aliasing filters) with three piezoelectric accelerometers (WR model 731A, 10 V/g sensitivity, and 0.50 g peak). The response of the tower is measured in three points, belonging to the cross section at the crowning level of the tower. Furthermore, a temperature sensor is installed on the S-W front, measuring the outdoor temperature. 

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