Tuwanut, Panwit
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Tuwanut, Panwit
Alternative Name
Tuwanut, P.
Tuwanuti, Panwit
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panwit.tu@kmitl.ac.th
28 results
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Item type:Publication, Breathing sound detection from the external auditory canal with condenser microphones(2021-05-19); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Simplified Derivative-Based Carrierless PPM Using VCO and Monostable Multivibrator(2025-06-01); ; ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, New pulse oximetry detection based on the light absorbance ratio as determined from amplitude modulation indexes in the time and frequency domains(2022-05-01); ; The Pandemic COVID-19 situation, a pulse Oximetry is significant to detect a varying blood oxygen saturation of a patient who needed the device to operate with continuous, rapid, high accuracy, and immune of moving artifacts. In this article, three main schemes for low-complexity pulse oximetry detection are proposed. In the first scheme, the light absorbance ratio (R) is obtained by separating the red and infrared photoplethysmography (PPG) amplitude modulation (AM) signals from the frequency-division multiplexing (FDM) signal with two different bandpass filters (BPFs), determining the ratio of modulation index of red and infrared PPG AM signals. In the second scheme, the output PPG AM signals for the red and infrared light wavelengths from the BPFs are transformed into the frequency domain such that the AC components of both PPG AM signals are the magnitudes of the highest peaks in their respective sidebands, while the DC components are the magnitude of their carrier frequencies; then, the AC/DC ratio of the red PPG AM signal is divided by the AC/DC ratio of the infrared PPG AM signal is R. In the last scheme, the FDM signal is transformed into the frequency domain without being passed through any BPF, and R is obtained in the same way as in the same second scheme. Experimental results obtained by using the first scheme have an average error of about 0.7138%, for the second and the last scheme have an average error of about 1%, and all the methods agree with the corresponding mathematical model. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Pulse Oximetry Based on Quadrature Multiplexing of the Amplitude Modulated Photoplethysmographic Signals(2023-07-01); ; ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A Practical Circuit of Cyclic Chirp Spread Spectrum Modulation for Long Range Communication(2022-01-01); ; ; Various technologies have been utilized in long range communication to satisfy increasing usage of the internet of things in a wide large area. Recently, a modulating technique called cyclic chirp spread spectrum (CSS) modulation has attracted attention due to its low power usage and long-range coverage. However, a cyclic CSS circuit is complex to build. Hence, the objective of the work is to propose a practical circuit of cyclic CSS modulation. The proposed circuit is designed to complicated-free creation. To prove that the presented circuit is pragmatic, a simulation test is performed. The simulation results have illustrated that the designed circuit well generates a chirp modulating signal. Also, the proposed circuit is flexibly configurable. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A Simplified Analog Implementation of Cyclic Shift Chirp Encoding and Decoding for LoRa Communications(2026-06-01); Currently, LoRa wireless communication technology has become widely adopted in IoT systems due to its long-range capability and low power consumption. However, LoRa is a technology developed by Semtech, which does not disclose the details of the Cyclic Shift Chirp encoding process, a core component of LoRa signals. This lack of transparency prevents users from accessing the physical-layer structure of the signal or freely customizing key parameters such as bandwidth and spreading factor. Although such customization can enhance system flexibility, there is currently no officially disclosed method to achieve it. This research proposes a Cyclic Shift Chirp encoder/decoder circuit built from basic analog components, including adders, subtractors, comparators, and ramp generators, based on a Pulse Width Modulation (PWM) principle. This approach enables researchers and developers to generate LoRa-like signals independently and customize various parameters without introducing limitations. Moreover, the proposed circuit is simple, low-cost, and easy to understand, making it suitable for advanced research, educational experiments, and the design of communication systems that require high flexibility at the LoRa PHY layer. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, An Image Resizing Function Embedded in an Inverse Discrete Cosine Transform(2022-01-01); Image resizing is an everyday activity and can be done in either a spatial domain or a transform domain. This work realizes that an image is commonly stored in the transform domain and the transformed image must be converted back to the spatial domain to display. This work hence proposes embedding an image resizing function based on a scaled frequency (SF) in a matrix operation of inverse discrete cosine transform (IDCT) for the sake of convenience. By adopting the proposed technique called as the SF-IDCT is not only capable of resizing the transformed image to a given resolution, but also acquiring the IDCT as a by-product. Image data can be shortened or lengthened in proportion to their frequencies by varying the frequencies of the DCT basis functions. Besides, the effects of modifying the pattern of the image data are also studied. The experimental results indicate that the SF-IDCT functions well. The proposed technique reconstructs an upsized image of equal or better visual quality than those produced by existing methods. For a downsized image, the performance of the presented approach is competitive with other available methods. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Influence of Light Intensity on a Motion Artifact Signal in a Photoplethysmographic Signal(2018-11-27); ; A photoplethygraphic (PPG) signal acquired from a commercial pulse oximeter is habitually disfigured by a motion artifact (MA) signal while any motion takes place. Inherently, the MA signal can either be additive or multiplicative, By having the MA signal intertwined with the PPG signal, the estimate of the oxygen saturation (SpO2) value is unreliable. The computation of SO02 value is based on proper red and infrared (IR) PPG signals measured by the pulse oximeter. Generally, the frequency components of the red and IR PPG signals as well as the MA signal are in the same range. To overwhelm this problem, the frequency components of the red and IR PPG signals are severed from the frequency band of the MA signal. To implement the separation, a legacy source of driving red and IR LEDs in the pulse oximeter is replaced by two alternating current sources having different frequencies. With this solution, the additive MA signal is no longer involved but the multiplicative MA signal is yet not concluded. In this work, change in light intensity fed to both red and IR LEDs is studied whether the changed light intensity has any impact on the multiplicative MA signal. According to the study, it is found that change in light intensity does not affect the multiplicative MA signal. The multiplicative MA signal still exists since the overall calculated SpO2 values have some error up to 1 %. Besides, change in light intensity does not improve the quality of the estimated SpO2 values while resting. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, New analytic solution of second-order oscillator using multi-time variables technique(2005-01-01); ; In this paper, a new analysis of sinusoidal oscillator amplitude controlled by forced response using the second order differential equation (ODE) is proposed. In general, the amplitude of the complete response is derived where forced response slope is normally assumed to be zero. The value of forced response only at initial time is thus employed to determine the amplitude. But if forced input is dynamic signal the amplitude of complete response gained by using such assumption is different from the experimental result. Thus, a new analysis of amplitude for a dynamic forced response is proposed in this paper. It is found that the forced response at any arbitrary time (not only at the initial time) is presented in a term of natural response magnitude. Magnitude of natural response is therefore directly controlled by forced response. To confirm the theoretical analysis, experimental results have been demonstrated and agreed well with the analysis results. © 2005 IEEE. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A simple and economic PWM and ΣΔ modulator circuit based on modified source-couple oscillator(2006-01-01); ; In this article, a simple and economic Pulse Width Modulator (PWM) and Sigma Delta Modulator (ΣΔ) circuit which is based on the modified CMOS source couple voltage-control oscillator is presented. The circuit can work either as PWM or ΣΔ modulator, depending on the condition of the two bias currents which are forced of the source couples. Namely, the circuit is a PWM when these two bias currents are out of phase. Otherwise, it is a ΣΔ modulator when both bias currents are identical. In addition, another feature of the proposed circuit is that the modulated signal can be either in voltage or current format. Moreover, the proposed circuit provides wide range of frequency operation because of few numbers of CMOS in the circuit. Furthermore, the circuit is very suitable for realization in integrated circuits (ICs) form and can be employed for optical communication application. The simulation results of the circuit are demonstrated and agreed well with theoretical anticipation. © 2006 IEEE.