Medina Huamán, Víctor ManuelLoi, DanteRombouts, PieterHernández Corporales, Luis2023-07-252023-07-252023-07-21Medina, V., Loi, D., Rombouts, P. & Hernandez, L. (21-25 May, 2023). Analysis of in-band Spurious Tones of VCO-based Analog Filters and Mitigation Techniques [proceedings]. 2023 IEEE International Symposium on Circuits and Systems (ISCAS), Monterey, USA.2158-1525https://hdl.handle.net/10016/37979Proceedings of: 2023 IEEE International Symposium on Circuits and Systems (ISCAS), 21-25 May 2023, Monterey, USA.Recently VCO-based filters have been used to implement feature extraction in voice recognition systems. Typically implemented filter structures embed the VCOs in a feedback loop. In these implementations, harmonic distortion has been observed in the output signal. This harmonic distortion has been attributed to ring oscillator nonlinearity but its origin stems from a system level problem. In this manuscript we will analyze this problem by looking at the cross modulation of Pulse Frequency Modulation (PFM) side-bands and we will explain how this creates the previously misunderstood harmonic distortion. Moreover, we will propose efficient techniques to mitigate these harmonic components and show that they can easily be implemented in hardware.5eng© 2023 IEEEVCO-ADCPulse frequency modulationAnalog filtersVoice feature extractionconference proceedingsElectrónicahttps://doi.org/10.1109/ISCAS46773.2023.10181860open access152023 IEEE International Symposium on Circuits and Systems (ISCAS)CC/0000034124