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New hybrid of PTS-CAPPR methods using GA for PAPR reduction in OFDM systems
(2009-12-01)
Pradabpet, Chusit
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Yoshizawa, Shingo
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Miyanaga, Yoshikazu
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Dejhan, Kobchai
In this paper, we propose a new PAPR reduction by using the hybrid of partial transmit sequences (PTS) and cascade adaptive peak power reduction (CAPPR) methods with coded side information (SI) technique design by genetic algorithm(GA). These methods are used in an Orthogonal Frequency Division Multiplexing (OFDM) system. The OFDM employs orthogonal subcarriers for data modulation. These sub-carriers unexpectedly present a large peak to average power ratio (PAPR) in some cases. A proposed reduction method consists of these two methods and realizes both advantages at the same time. In order to obtain the optimum condition on PTS for PAPR reduction, a quite large calculation cost must be demanded and thus it is impossible to obtain the optimum PTS. In the proposed method, by using the pseudo-optimum condition with a coded SI technique designed by GA, the total calculation cost becomes drastically reduced. In simulation results, the proposed method shows the improvement on PAPR and also reveals the high performance on bit error rate (BER) of an OFDM system. ©2009 IEEE.
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Sensorless speed control of DC servo motor using Kalman filter
(2009-12-01)
Praesomboon, Sukanya
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Athaphaisal, Santi
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Yimman, Surapun
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Boontawan, Rodjarin
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Dejhan, Kobchai
This research aims to study speed sensorless DC motor control using Kalman filter. Kalman filter considers the DC motor mathematical model. The model will start from a continuous state space into a discrete state space form. Inputs of the system are the armature voltage and the armature current with noises. The output of the system is the estimated speed. Kalman filter is used to estimate the speed without noise interference. The result from the estimated speed will be compared with the reference speed and the speed error will be used by the controller to control the linear amplifier. The final output is the constant speed of the DC motor. Even though the load of the DC motor changed the speed of the DC motor remains constant under the control. The experiment shows that Kalman filter can reject the noise from the system and can estimate the speed of the DC motor with a high accuracy. The estimated speed will be feedback to control the system for constant speed. ©2009 IEEE.
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High-input and low-output impedance voltage-mode all-pass networks
(2009-12-01)
Kumngern, Montree
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Dejhan, Kobchai
In this paper, two new voltage-mode first-order all-pass networks are proposed. Each of proposed networks employs two differential difference current conveyors (DDCCs), one grounded capacitor and one grounded capacitor. No passive component matching conditions are required. The networks offer high-input and low-output impedances; hence it can be directly employed as a subsystem of monolithic circuits. The use of only grounded capacitor and resistor makes the proposed networks ideal for integrated circuit implementation. The characteristics of the proposed all-pass networks are simulated using PSPICE to verify the theory.
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Electronically tunable current-mode quadrature oscillator using current differencing transconductance amplifiers
(2009-12-01)
Kumngern, Montree
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Dejhan, Kobchai
A new electronically tunable single-element-controlled current-mode quadrature oscillator circuit using current differencing transconductance amplifiers (CDTAs) is presented. The proposed oscillator is consisted of two CDTAs, two grounded capacitors and one grounded resistor, which is beneficial to monolithic integrated circuit implementation. The oscillation condition and oscillation frequency of the circuit are independently controllable. Also, the oscillation frequency can be controlled by a bias current of CDTA. The realized of the circuit provides four quadrature current outputs at high output impedance nodes. PSPICE simulation results that confirm the theoretical predictions are given. © 2009 IEEE.
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Medical image compression and DICOM-format image archive
(2009-12-01)
Suapang, Piyamas
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Dejhan, Kobchai
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Yimmun, Surapun
In general, the image formats from radiological modalities are incompatible with the standard DICOM-format. Our system is developed to convert images into DICOM-format that are ready to implement in the medical teleradiological system. The system can process and record the image signal sent to the display unit in the single frame and multiframe image modes. The later mode keeps the set of images in windows bitmap file with .BMP file extension. The resulting images are then compressed with two different techniques - JPEG and JPEG2000. The significant advantage of JPEG2000 over normal JPEG is that the error from JPEG2000 compression is smaller than the error from JPEG. Nevertheless, both methods share a similar mishap; when the compression ratio increases, they both generate more error than the processes on lower compression ratio do. In addition, our system can also convert the image data in normal or automatic DICOM process into the standard DICOM 3.0 format without altering the image data. The final image data can then be used in any radiological modality. © 2009 SICE.
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Single-resistance-controlled current-mode quadrature sinusoidal oscillator
(2009-10-22)
Kumngern, Montree
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Knobnob, Boonying
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Dejhan, Kobchai
A new single-element-controlled current-mode quadrature oscillator circuit using second-generation current conveyors (CCIIs) is presented. The proposed oscillator is consisted of two CCIIs, two grounded capacitors and three grounded resistors. The circuit is beneficial to monolithic integrated circuit implementation by the use of grounded passive components. In addition, a new current-controlled sinusoidal oscillator using two second-generation current-controlled conveyors (CCCIIs), two grounded capacitors and one grounded resistor can be achieved by replacing CCIIs and resistors series at X terminals with CCCIIs. The oscillation frequencies of the CCII-based can be controlled by a grounded resistor while the CCCII-based can be controlled by a bias current. The realized of both circuits provide four quadrature current outputs at high output impedance nodes. PSPICE simulation results that confirm the theoretical predictions are given. ©2009 IEEE.
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Current-mode multiphase sinusoidal oscillator using translinear conveyors
(2009-10-22)
Kumngem, Montree
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Junnapiya, Somyot
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Dejhan, Kobchai
A current-controlled current-mode multiphase sinusoidal oscillator employing translinear current conveyors is presented. The proposed oscillator circuit, which uses ~nly one translinear current conveyor and one grounded capacitor for each phase and can generate arbitrary n signals which are equal in amplitude and equally spaced in phase. The oscillation frequency of each phase is independently tuned through bias current while the oscillation condition is controlled by current gain of current conveyor. The proposed circuit also enjoys having simple structure, very low-component count and it is highly suitable for IC implementation. ©2009 IEEE.
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Voltage-mode multifunction biquadratic filter based on simple CMOS OTAs
(2009-10-19)
Kumngern, Montree
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Dejhan, Kobchai
A voltage-mode versatile multifunction filter with four inputs and three outputs biquadratic filter based on simple CMOS operational transconductance amplifiers (OTAs) is presented. By appropriately connecting the input and output terminals, the proposed circuit can work as either a single-input multiple-output (SIMO) or a multiple-input single-output (MISO) filter without changing the circuit topology. When the circuit functions as a SIMO filter, it provides bandpass (BP), lowpass (LP) and bandstop (BS) voltage responses with grounded capacitors. When it functions as a MISO filter, the circuit can realize all the standard non-inverting and inverting second-order filter functions. The parameters ω<inf>o</inf> and Q can be set orthogonally by adjusting the circuit components. For realizing all the filter responses, no critical matching condition is required, no inverting-type input signal is imposed and all the incremental parameter sensitivities are low. The simulation results confirm the theoretical analysis. ©2009 IEEE.
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Current-tunable current-mode universal filter using minimum elements
(2009-10-22)
Kumngern, Montree
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Chanwutitum, Jirasak
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Dejhan, Kobchai
In this paper, a new electronically tunable current-mode universal filter with three inputs and single output employing only two translinear current conveyors and two grounded capacitors is presented. The proposed configuration provides lowpass, bandpass, highpass, bandstop and allpass current responses by choosing appropriate input signals without any component matching conditions, all at a high impedance output which enables easy cascading in the current-mode operation. The filter also offers independent electronic control of the natural frequency (ω<inf>0</inf>) and the quality factor (Q) through adjusting of the bias current and the current gain of the CCCII. The parameter sensitivities are all very low and the structure is very suitable for IC implementation. The characteristics of the proposed circuit are simulated using PSPICE to confirm the theory. ©2009 IEEE.
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An FPGA-based implementation of variable fractional delay filter
(2009-10-19)
Nithirochananont, Ussanai
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Chivapreecha, Sorawat
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Dejhan, Kobchai
A variable fractional delay (VFD) filter is widely used in applications such as symbol timing recovery, arbitrary sampling rate conversion and echo cancellation. This paper presents an implementation of variable fractional delay filter on FPGA. The implementation utilizes an efficient structure so called Taylor structure. The main advantage of this structure is to reduce number of multiplier and adder when compared with Farrow structure or modified Farrow structure. The result of implementation will be reported as throughput and area utilization. ©2009 IEEE.

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