Chivapreecha, Sorawat

Preferred name

Alternative Name

Chivapreecha, S.

Chivapreecha, Sorwat

Main Affiliation

School of Engineering

sorawat.ch@kmitl.ac.th

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Generalized Pascal matrices, inverses, computations and properties using one-to-one rational polynomial s-z transformations
(2008-01-01)
Deng, Tian Bo
;
Chivapreecha, Sorawat
;
Dejhan, Kobchai
This paper proposes a one-to-one mapping between the coefficients of continuous-time (s-domain) and discrete-time (z-domain) IIR transfer functions such that the s-domain numerator/denominator coefficients can be uniquely mapped to the z-domain numerator/denominator coefficients. The one-to-one mapping provides a firm basis for proving the inverses of the so-called generalized Pascal matrices from various first-order s-z transformations. We also derive recurrence formulas for recursively determining the inner elements of the generalized Pascal matrices from their boundary ones. Consequently, all the elements of the whole generalized Pascal matrix can be easily generated through utilizing their neighbourhood, which can be exploited for further simplifying the Pascal matrix generations. Finally, we reveal and prove some interesting properties of the generalized Pascal matrices. © 2008 IEEE.
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Continuously Tunable Frequency and Phase Biquad Oscillator
(2026-05-01)
Chivapreecha, Sorawat
;
Suwannawach, Piyapan
This paper presents an improvement to the performance of a biquad oscillator, which is a recursive oscillator known for its excellent long-term stability. However, a significant limitation is that the oscillation frequency cannot be changed while the system is operating. Directly changing the frequency during operation causes the amplitude of the generated signal to vary significantly, either increasing or decreasing. A zero-input response analysis is used to understand the cause of this problem and to develop a solution that allows the amplitude of the generated signal to remain constant even when the oscillation frequency is changed during operation. In addition, this paper presents a method for controlling the phase of the generated signal by using a 1st-order IIR phase shifter structure. The proposed structure is specifically designed to allow the phase of the signal at the oscillation frequency to be adjusted continuously and independently of the frequency parameter. This integrated oscillator enables real-time, independent control of both signal frequency and phase without amplitude drift, making it suitable for applications requiring precise and dynamic signal synthesis.
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Internet network in space for small satellites: Concept and experiments
(2018-01-01)
Techavijit, Pirada
;
Sukchalerm, Polkit
;
Wongphuangfuthaworn, Natthapong
;
Plodpai, Aniwat
;
Manuthasna, Shariff
Currently, no wireless network service is being offered in space. This fact has caused satellite developers to establish their own wireless network with a low coverage area that does not function very well. These problems can be resolved by setting up an effective wireless network that can be offered as a service to satellites in orbit. This study is focused on designing a high-quality wireless-in-space network to connect satellites in orbit to the Internet. Such a network would enable satellites to be controlled through the Internet from the Earth without having their own ground stations. In this paper, various aspects of the design of a network setup standard are discussed. These aspects include appropriate wireless communication and the construction of a model satellite that can be connected to the network from space. The work also included testing the design by setting up the Internet network for use above Thailand's territory and launching the original model satellite for the demonstration of the principle. The sensor data was then transmitted in real time to audiences from all over the country and used to design an Internet network in space with global coverage, which is a target for further development.
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Bi-minimax design of even-order variable fractional-delay FIR digital filters
(2012-01-01)
Deng, Tian Bo
;
Chivapreecha, Sorawat
;
Dejhan, Kobchai
This paper proposes a new minimax method for designing even-order finite-impulse-response (FIR) variable fractional-delay (VFD) digital filters with both the peak errors (maximum absolute errors) of variable frequency response (VFR) and VFD response being minimized. We call such a new minimax design the bi-minimax design, which minimizes a mixed error function that contains both the VFR peak error and VFD peak error. A relative weighting factor is used in the mixed error function for adjusting the relative weightings of the two peak errors. The central part of the biminimax design is how to formulate the biminimax design with highly non-linear constraints on the VFD errors as a solvable one. After linearizing the highly non-linear constraints as linear ones, the biminimax design problem can be easily solved by using the well-known efficient software SeDuMi. As a result, both the VFR peak error and VFD peak error can be simultaneously suppressed and the resulting VFR errors and VFD errors are made nearly equiripple (bi-equiripple). As compared with the existing SOCP-based minimax design that minimizes only the VFR peak error, the proposed biminimax method can achieve a nearly biequiripple design for both the VFR and VFD errors. A design example is given to illustrate the effectiveness of the biminimax design method. © 2004-2012 IEEE.
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Microwave sensor for tangerine classification based on coupled-patch antennas
(2016-08-02)
Leekul, Prapan
;
Chivapreecha, Sorawat
;
Krairiksh, Monai
This paper deals with a microwave sensor for classifying tangerines by flavour using coupled-patch antennas. The operating frequency of the antennas is 2.45 GHz. The sensor determines the flavour of each tangerine by measuring the magnitudes of coupled signals of the antennas with the tangerine fruit at the centre. The sorting is carried out using an artificial neural network implemented on a field programmable gate array. The classification performance of the sensor is 95% accurate, so it has potential for use in sorting tangerines by flavour. In addition, the system uncertainty is analysed to determine optimal operating conditions.
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Unified Pascal matrix for first-order s-z domain transformations
(2009-06-16)
Deng, Tian Bo
;
Chivapreecha, Sorawat
;
Dejhan, Kobchai
The so-called generalized Pascal matrix is used for transforming a continuous-time (CT) linear system (filter) into a discrete-time (DT) one. This paper derives an explicit expression for a new generalized Pascal matrix called unified Pascal matrixfrom a unified first-order s-z transformation model and rigorously proves the inverses for various first-order s-z transformations. After deriving a recurrence formula for recursively generating the inner elements of the unified Pascal matrix from its boundary elements, we also show that the recurrence formula leads to computationally unstable solutions for high-order systems due to the so-called catastrophic cancellation in numerical computation, but the unstable problem can be solved through partitioning the whole unified Pascal matrix into several small matrices (submatrices) and then using the recurrence formula to compute the submatrices individually from their boundary elements. This operation almost retains the same computational complexity while guarantees numerically stable solutions. Moreover, an interesting property of the unified Pascal matrix is proved. © 2009 IEEE.
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A study and implementation of miniaturized satellite: CanSat for space activity enhancement
(2016-08-01)
Roeksukrungrueang, Chanathip
;
Chivapreecha, Sorawat
To build a satellite for countries with a modest research budget and little experience in space technology is very difficult. The concept of CanSat reach every country the opportunity to learn space technology of design, build, launch and operate a very small and simple satellite. This paper presents a CanSat which has been used to teach practical space engineering. The mission of our CanSat is to collect and transmit data from the sensors that are equipped in CanSat to ground station. But the problem of wireless communication is noise that make a lot of errors especially large data such as image. Therefore, channel coding, the extended Golay code, is applied to our CanSat for error correction. And with experienced from CanSat, we are ready to share CanSat education with space activity in our country. This is an excellent opportunity for students in Thailand to take their first steps practical in space technology.
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Pascal-interpolation-based noninteger delay filter and low-complexity realization
(2015-01-01)
Soontornwong, Parinya
;
Chivapreecha, Sorawat
This paper proposes a new method for designing the polynomial-interpolation-type noninteger-delay filter with a new structure formulation. Since the design formulation and the new realization structure are based on the discrete Pascal transform (DPT) and Pascal interpolation, we call the resulting filter Pascal noninteger-delay filter. The kth-order Pascal polynomial is used to pass through the given (k+ 1) data points in achieving the kth-order Pascal filter. The Pascal noninteger-delay filter is a realtime filter that consists of two sections, which can be realized into the front-section and the back-section. The frontsection contains multiplication-free digital filters, and the number of multiplications in the back-section just linearly increases as order becomes high. Since the new Pascal filter has low complexity and structure can adjust noninteger delay online, it is more suited for fast delay tuning. Consequently, the polynomial-interpolation-type delay filter can be achieved by using the Pascal approach with high efficiency and low-complexity structure.
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Low-Complexity and High-Modularity Structure for Implementing Transient-Free Pascal-Delay Filter
(2017-12-01)
Soontornwong, Parinya
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Deng, Tian Bo
;
Chivapreecha, Sorawat
The maximally flat variable-delay (VD) digital filter can be derived by using the discrete-Pascal-transform (DPT) and the DPT-based Pascal-polynomial interpolation. In this paper, we develop an efficient structure for the low-complexity and high-modularity implementation of this Pascal-type VD filter. As compared to other existing filter structures, this new structure greatly reduces the multiplication operations required in the filtering process. Roughly speaking, the proposed new structure can reduce the multiplication operations by almost one-third. Thus, this new filter structure has the lowest filter complexity among all the existing filter structures for the implementation of the maximally flat VD filter. As a result, signal interpolation can be efficiently performed through utilizing this new filter structure. As opposed to other existing structure with transient problem, we will show that the proposed new structure does not involve any transient problem. That is, it is a transient-free structure. Consequently, the proposed new filter structure can achieve more accurate signal-interpolation results than other structures that have the transient problem. Finally, we show that this proposed structure also has high modularity and it is suited for modularized hardware implementation.
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The matrix-based design and realization of digital parametric equalizer
(2021-05-01)
Jongsataporn, Thitaphan
;
Chivapreecha, Sorawat
This paper presents the design of a digital parametric equalizer based on matrix design equations and their corresponding digital filter structures. Matrix-based design equations are modified from the so called bilinear Pascal matrix for s-z transformation, appended with modifications in the feed-forward path of direct form-II digital filter structure based on consideration of standard biquadratic filters compared with peaking filter, lowpass shelving filter, and highpass shelving filter, as well as the proposed improvement procedures. Consequently, matrix design equations and their corresponding multiple outputs filter structure realizations for digital version of peaking, lowpass shelving, and highpass shelving filters can be achieved. The matrix-based design method and the proposed filter structure are consistent in terms of implementation because the main mechanism of a digital filter is determined by its filter structure, while filter coefficients are calculated from the matrix equation that corresponds to such structure. Digital filter characteristic can be determined or adjusted by updating new filter coefficients through matrix computation. The proposed peaking, lowpass shelving, and highpass shelving digital filters can be cascaded for use as a digital parametric equalizer. Design examples and the resulting frequency responses are shown as well as further explanation of hardware implementation for real-time digital parametric equalizer on STM32F769 processor. The simulation results and actual hardware frequency response measurements are compared to confirm the success of the proposed matrix-based design method and its implementation.

Chivapreecha, Sorawat

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