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Notch Filter Software4/24/2021
In designing an analog notch lter, a number of notch lter topologies were explored.It provides a reference guide with the most commonly used second order analog circuit topologies, having different advantages.
Also, a simple and efficient algorithm is suggested for implementing fixed-point second order IIR filters on digital controllers. The theoretical simulations are compared with responses obtained in practice. Twin T Fliege Sallen-Key Magnitude-frequency and phase-frequency diagrams 1 Sallen-Key analog notch filter response; channel 1-input signal V IN, channel 2-output signal V OUT Figures - uploaded by Mircea Susca Author content All figure content in this area was uploaded by Mircea Susca Content may be subject to copyright. Notch Filter Software For Free Public FullDiscover the worlds research 17 million members 135 million publications 700k research projects Join for free Public Full-text 1 Content uploaded by Mircea Susca Author content All content in this area was uploaded by Mircea Susca on May 12, 2018 Content may be subject to copyright. It provides a refer - ence guide with the most commonly used second order ana- log circuit topologies, having different advantages. Also, a simple and efcient algorithm is suggested for implementing xed-point second order IIR lters on digital controllers. Keywordslter; notch; analog; digital; Sallen-K ey; bilin- ear transform; difference equation. I. I NTRODUCTION Notch lters are a key component to remove undesired radio frequency signals in a wide range of applications, such as radar sys- tems, broadband wireless networks, and satellite communications 1, 2. T otal harmonic distortion (THD) measure- ments are one of the most commonly quoted in audio. This is tuned to reject the fundamental frequency, and any signal that gets through is a combination of the ampliers noise (including any hum) and the distortion. The distortion shows up as a signal that is harmonically related to the signal fed into the amp, which will be subsequently measured 4. Also, in tone-signalling, audio-signal, hearing-aid feedback, or mains-rejection systems active bandstop lters have been used to remove noise, the most common being the elimination of 50 and 60 Hz hum components from electrical equipment 5. As such, band-reject and notch lters have been used in various situations for the past years and are still being developed. The purpose of this paper is to make a comparative study of different notch lter implementations in the analog and digital domains alike. Analog implementations consume less bandwidth, but the signals are more likely to get deteriorated during transmission. In contrast, digital lters are generally noise-immune and exible in implementation, although consume a lot more bandwidth to carry the same information. Any given transfer function can be achieved by a cascade of simpler circuits of this kind and one or more passive RC networks 6. The classic transfer function of a second order notch lter is: H ( s ) s 2 2 0 s 2 0 Q s 2 0, (1) where: 0 natural frequency, and Q quality factor of the lter (tied to the lter bandwidth after Q f 0 f ). The natural fre- quencies of the zero pair and pole pair must coincide to guarantee balanced gains in the passband, and great attenuation at the desired frequency. The pair of complex conjugate zeros placed on the imaginary axis involve the so-called blocked transfer, which gives the cir- cuit its band-reject characteristic 7. At 0 angular frequency the system has a pronounced minimum, accompanied by a large shift in its oscillation phase.
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