Faculty Publications
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Publications by NITK Faculty
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Item Goubau-Line Leaky-Wave Antenna for Wide-Angle Beam Scanning from Backfire to Endfire(Institute of Electrical and Electronics Engineers Inc., 2018) Rudramuni, R.; Kandasamy, K.; Zhang, Q.; Tang, X.-L.; Kandwal, A.; Tharehalli Rajanna, T.R.; Liu, H.A Goubau-line leaky-wave antenna (LWA) with a large scanning angle is presented in this letter. In contrast to the conventional Goubau-line leaky wave with a small scanning angle range, this letter employed a periodically bending Goubau line, which not only brings in a periodic perturbation for leaky-wave radiation, but also enhances the scanning range due to the increased delay for each line element. The simulation and experimental results show that the proposed LWA provides 90 radiation efficiency and 7-10 dBi radiation gain from backfire to endfire through broadside as frequency changes. The proposed antenna features good radiation performance and has a compact and low-profile configuration. © 2011 IEEE.Item A 0.3?V, 56?dB DR, 100?Hz fourth order low-pass filter for ECG acquisition system(Elsevier Ltd, 2019) Polineni, S.; Hanumantha Rao, G.; Rekha, S.; Bhat, M.S.This paper proposes an extremely low voltage, low power bulk-driven voltage follower (BD-VF). As an application of the proposed BD-VF, a 4th order low-pass filter (LPF) with cutoff frequency adjustable from 50 Hz to 250 Hz is designed for electrocardiogram (ECG) acquisition systems. The filter is implemented in UMC 180 nm CMOS technology occupying only 0.03 mm2 area. Post layout simulation results show that the filter offers 56 dB dynamic range even with an extremely low supply voltage of 0.3 V. The total power consumption of the filter is 4.8 nW for a cutoff frequency of 100 Hz. The Figure-of-merit (FoM) and capacitance/pole of the filter are 5.7 × 10?15 and 2.2 pF respectively. The proposed filter offers the lowest FoM compared to the state-of-the-art nW-class filters. © 2019 Elsevier LtdItem An area-efficient, large time-constant log-domain filter for low-frequency applications(John Wiley and Sons Ltd vgorayska@wiley.com Southern Gate Chichester, West Sussex PO19 8SQ, 2020) Hanumantha Rao, G.; Rekha, S.This paper proposes a simple technique to increase the time constant of a log-domain filter. By using the proposed technique, the capacitor value can be reduced considerably; hence, overall area of the circuit can be reduced. A second-order log-domain low-pass filter (LPF) is implemented in UMC 65-nm complementary metal-oxide semiconductor (CMOS) technology to validate the proposed technique. It occupies an area as low as 0.005 mm2 and operates with a 0.5-V supply. For a cutoff frequency of 100 Hz, the filter consumes a power of 4 nW. By adjusting the bias current, the cutoff frequency can be linearly tuned from 10 to 500 Hz. The filter has the figure of merit (FoM) of 0.68×10?13 J, which is on par with many designs listed in the literature. The filter uses the lowest capacitance/pole (0.92 pF) among the similar designs given in the literature, which shows that the present design is area efficient. © 2019 John Wiley & Sons, Ltd.Item Time Constant Enhancement Technique for Low-Frequency Filters(Birkhauser, 2020) Rao, G.H.; Rekha, S.This paper presents a simple and novel technique to enhance the time constant of a source follower (SF)-based low-pass filter (LPF) for front-end processing of biomedical signals. The proposed technique reduces the capacitor value significantly, which in turn reduces the area of the circuit. Inherent negative feedback and lower number of transistors in this circuit result in good linearity and dynamic range even with low power supply of 0.8 V. A second-order LPF of cutoff frequency (f-3dB) of 100 Hz is designed by cascading the proposed NMOS and PMOS SF LPFs. Cutoff frequency can be tuned linearly from 10 Hz to 1 kHz by varying the bias current and, hence, can be fit into the desired frequency range of different bio-potentials. The filter, designed in UMC 65 nm process, occupies an area of 0.008mm2. It offers a dynamic range of 61.85 dB while consuming a power as low as 8 nW. Figure of merit of the filter is as low as 3.23?10-14J which is better than many other filter designs reported in the literature. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item A 0.3-V, 2.4-nW, and 100-Hz fourth-order LPF for ECG signal processing(John Wiley and Sons Ltd cs-journals@wiley.co.uk, 2020) Rao G, H.; Polineni, P.; Rekha, S.; Bhat, M.S.An ultra-low voltage, low power bulk-driven voltage follower (VF) is proposed in this paper. Further, it is exploited to design a fourth-order low-pass filter (LPF) for electrocardiogram (ECG) signal processing. The filter is designed in UMC 180-nm CMOS technology and operates with an ultra-low supply voltage of 0.3 V. It consumes an extremely low power of 2.4 nW for a cutoff frequency of 100 Hz. Results of post-layout simulation show that the proposed filter provides a dynamic range (DR) of 51.6 dB even from a 0.3-V supply voltage. The filter achieves a Figure-of-merit (FoM) of 4.7 × 10?15, which is better than many designs listed in the literature. © 2020 John Wiley & Sons, Ltd.Item A 0.8-V, 55.1-dB DR, 100 Hz Low-Pass Filter with Low-Power PTAT for Bio-Medical Applications(Taylor and Francis Ltd., 2022) Hanumantha Rao, G.; Rekha, S.This paper presents a power efficient transconductor-capacitor ((Formula presented.)) filter for front-end processing of bio-medical signals. A low voltage, low-power transconductor with improved output resistance is proposed. It offers a transconductance ((Formula presented.)) of 5.85 nS while operating at a supply voltage ((Formula presented.)) of 0.8 V. Furthermore, a low-power Proportional to Absolute Temperature (PTAT) current reference circuit is designed to bias the transconductor and to make (Formula presented.) independent of temperature. It follows PTAT characteristics in the temperature range of ?20 (Formula presented.) C to 70 (Formula presented.) C and is less sensitive to (Formula presented.) variations. A second-order Butterworth low-pass filter (LPF) with a cutoff frequency of 100 Hz is implemented to validate the proposed transconductor and the PTAT circuit. The filter is designed in UMC 65 nm CMOS process and it takes an area of 0.065 mm (Formula presented.). While consuming a power of 47 nW, it offers a dynamic range (DR) of 55.1 dB. Figure-of-merit (FoM) of the filter is as low as (Formula presented.) J, which is found to be on par with the filters reported in the literature. © 2022 IETE.Item An integrated frequency domain decomposition and deep neural network approach for short-term PV power forecast(Springer Science and Business Media Deutschland GmbH, 2025) Kumar, A.; Kashyap, Y.; Rai, A.Weather disturbances and atmospheric parameters significantly influence the fluctuations in PV power output, which in turn affect the stability of grid operations. The current study proposed short-term PV power forecasting based on appropriate cutoff frequency in frequency domain and artificial intelligence method. Initially, the actual PV power data are decomposed into the frequency domain, and optimal cutoff frequency is determined by minimizing the squared difference of correlation between the decomposed components. Subsequently, the PV power is separated into low-frequency components (LFC) and high-frequency components (HFC). Then, long short-term memory (LSTM) and light gradient boosting machine (LGBM) models are then employed to forecast the LFC and HFC PV power. The final forecast output is generated using various recombination methods. The proposed combined forecast model, LFC-LGBM + HFC-LGBM, based on frequency domain decomposition (FDD) and LGBM approach, demonstrates superior performance compared to models (LFC-LSTM + HFC-LSTM), (LFC-LGBM + HFC-LSTM), and (LFC-LSTM + HFC-LGBM). The best-performing model (LFC-LGBM + HFC-LGBM) achieves a MAE of 4.9420%, a RMSE of 7.1047%, and a correlation index (R) of 0.9734 for 15-min ahead timesteps. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.