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ABSTRACT
A method to evaluate the performance of a wide type of analog filters is proposed. This method requires only a Microcontroller Unit (MCU), low-cost peripheral components, circuitry, and a mobile device, so it can be set up readily with an easily available development platform. This eliminates the cost of acquiring the expensive instruments that are usually used for such testing. Moreover, this performance evaluation platform can be used as a communication interface and bridge to an Internet of Things (IoT) system. The feasibility and extended scope of application of this platform represent a significant advance in the ability to conduct such testing. The measurements obtained by using the proposed method to evaluate analog filters show good agreement with the desired functionalities.
Nomenclature
| A | = | amplitude of pulse |
| Ab,pi | = | estimated passband output amplitude of band-pass filter |
| Ab,si | = | estimated stopband output amplitude of band-pass filter |
| Ah,p | = | estimated passband output amplitude of high-pass filter |
| Ah,s | = | estimated stopband output amplitude of high-pass filter |
| Al,p | = | estimated passband output amplitude of low-pass filter |
| Al,s | = | estimated stopband output amplitude of low-pass filter |
| At | = | amplitude of triangle waveform |
| Db,pi | = | Digitization of Ab,pi, i = 1 and 2 |
| Db,si | = | Digitization of Ab,si, i = 1 and 2 |
| Dh,p | = | Digitization of Ah,p |
| Dh,s | = | Digitization of Ah,s |
| Dl,p | = | Digitization of Al,p |
| Dl,s | = | Digitization of Al,s |
| DUTbpf | = | band-pass filter device under test |
| DUThpf | = | high-pass filter device under test |
| DUTlpf | = | low-pass filter device under test |
| fb,pi | = | passband frequency of band-pass filter, i = 1 and 2 |
| fb,si | = | stopband frequency of band-pass filter, i = 1 and 2 |
| fh,p | = | passband frequency of high-pass filter |
| fh,s | = | stopband frequency of high-pass filter |
| fp | = | passband frequency of low-pass filter |
| ftriangle(t) | = | triangle waveform |
| ft | = | frequency of triangle waveform |
| fs | = | stopband frequency of low-pass filter |
| kl,p | = | parameter that defines passband characteristic of low-pass filter |
| kl,s | = | parameter that defines stopband characteristic of low-pass filter |
| n | = | index of harmonic |
| PS | = | digitized passband-to-stopband amplitude ratio for low-pass filter |
| PSbi | = | digitized passband-to-stopband amplitude ratio for band-pass filter, i = 1 and 2 |
| PScritical | = | critical passband-to-stopband amplitude ratio for low-pass filter |
| PScritical,bi | = | critical passband-to-stopband amplitude ratio for band-pass filter, i = 1 and 2 |
| PScritical,h | = | critical passband-to-stopband amplitude ratio for high-pass filter |
| PSh | = | digitized passband-to-stopband amplitude ratio for high-pass filter |
| Sn | = | parameter that indictaes attenuation, n = odd = 1,3,5, … |
| t | = | time |
| vout,b,pi | = | passband output of band-pass filter, i = 1 and 2 |
| vout,h,p | = | passband output of high-pass filter |
| vout,h,p_1,3 | = | partial passband output of high-pass filter |
| vpeak,b,pi | = | peak passband output of band-pass filte, i = 1 and 2 |
| vpeak,b,si | = | peak stopband output of band-pass filter, i = 1 and 2 |
| vpeak,h,p | = | peak passband output of high-pass filter |
| vpeak,h,s | = | peak stopband output of high-pass filter |
| vpeak,l,p | = | peak passband output of low-pass filter |
| vpeak,l,s | = | peak stopband output of low-pass filter |
| αatt,n | = | attenuation at the n-harmonic frquency |
| αattl,p | = | attenuation at the large harmonic that is related to fp of low-pass filter |
| αattl,s | = | attenuation at the large harmonic that is related to fs of low-pass filter |
| αmax | = | the maximum attenuation for the passband corner of low-pass filter |
| αmax,bi | = | the maximum attenuation for the passband corner of band-pass filter, i = 1 and 2 |
| αmax,h | = | the maximum asttenuation for the passband corner of high-pass filter |
| αmin | = | the minimum attenuation for the stopband corner of low-pass filter |
| αmin,bi | = | the minimum attenuation for the stopband corner of band-pass filter, i = 1 and 2 |
| αmin,h | = | the minimum attenuation for the stopband corner of high-pass filter |
| ϕ1 | = | phase shift |
Disclosure statement
No potential conflict of interest was reported by the authors.