Chanchai Thongsopa

A single patch beam steering antenna

A single patch beam steering antenna is proposed. By using a one wavelength dual-feed patch, the beam direction of this antenna can be steered by adjusting the oscillating frequency at the feeds. Experimental results confirm the principle of this antenna and proved to be useful in microwave and millimeter wave applications.

Multilayer Strip Dipole Antenna Using Stacking Technique and Its Application for Curved Surface

This paper presents the design of multilayer strip dipole antenna by stacking a flexible copper-clad laminate utilized for curved surface on the cylindrical objects. The designed antenna will reduce the effects of curving based on relative lengths that are changed in each stacking flexible copper-clad laminate layer. Curving is different from each layer of the antenna, so the resonance frequency that resulted from an extended antenna provides better frequency response stability compared to modern antenna when it is curved or attached to cylindrical objects. The frequency of multilayer antenna is designed at 920 MHz for UHF RFID applications.

Effect of Antenna Patterns on Narrowband MIMO Capacity

In this paper, a model for MIMO capacity calculation with array element radiation patterns is proposed. The proposed model considers effect of radiation pattern, channel impulse responses and elements correlation separately. The effects of both directional and omni-directional antennas to the MIMO capacity are investigated. For the directional antenna case, horizontal polarized Dipole and Yagi-uda antennas are employed in the array. The omni-directional antennas case is considered to be an ideal MIMO capacity. We have shown that directional antennas reduce the narrowband MIMO capacity when the angle of arrival (AOA) is uniformly distributed. When the directional antennas with proper alignment to the mean AOA are used in a scenario where the AOA is Laplacian distribution, the capacity is increased. However, if the antenna alignment is off from the mean AOA, then the capacity is decreased.

CCCIIs-Based First-Order All-Pass Filter and Quadrature Oscillators

This paper introduces a current-mode first-order all-pass filter (APF) and its application in quadrature oscillator (QO) based on CCCII. The proposed filter can provide inverting and noninverting all-pass functions with a same circuit topology, it uses two CCCIIs and one grounded capacitor. Moreover, the first-order all-pass filter was applied in current-mode sinusoidal quadrature oscillators with the design based on block diagrams. The introduced oscillators can provide four phase-quadrature signals which independently control the condition of oscillation (CO) and frequency of oscillation (FO). The proposed oscillators consist of three CCCIIs and two grounded capacitors. The proposed APF and QOs have high output impedance which can directly drive load without additional current buffer. In addition, they use only grounded capacitors which are very appropriate to future development into an integrated circuit. The results of PSPICE simulation program correspond to the theoretical analysis.

VDBA-based floating inductance simulator with a grounded capacitor

This study presents the resistorless floating inductance simulator circuit based on employing voltage differencing buffered amplifier (VDBA) as new active component. The proposed floating inductance simulator circuit uses two VDBAs and only one grounded capacitor, which is suitable for integrated circuit design. The resulting equivalent inductance value of the proposed simulator can be tuned electronically through the transconductance parameter of the VDBA. As application example, the second-order RLC bandpass filter has been simulated using the proposed tunable floating inductance simulator. The simulation results using standard 0.35 μm BiCMOS process model are included to verify the theoretical analysis.

A U-Shaped cross sectional antenna on a U-shaped ground plane with an offset parabolic reflector for WLAN

This paper presents the increasing of the antenna performance, or made it to have high gain. Thus, it can be used for the outdoor transmission. The proposed antenna develops from the U-shaped cross-sectional antenna which typically it is used as an indoor antenna. By installing it with the offset parabolic reflector, many good characteristics antenna are achieved. The offset parabolic reflector is used for reflecting and concentrating an electromagnetic wave to the antenna. For this method, the antenna is easy to match, construct and safe cost in addition. The material is also easy to find.

Second Order Current-mode Quadrature Oscillators Using OTAs

This article presents new current-mode quadrature oscillator circuits using OTA which are designed from block diagram. The proposed circuits consist of three OTAs and two grounded capacitors. The circuits have high output impedance appropriate for cascade connection application in current mode technique which is capable to directly drive load. The oscillators use only grounded capacitor which is very appropriate for further development into an integrated circuit. In addition, the condition of oscillation can be adjusted orthogonally from the frequency of oscillation. The results of PSPICE simulation program are corresponding to the theoretical analysis.

DUAL-OUTPUT CURRENT DIFFERENCING TRANSCONDUCTANCE AMPLIFIERS-BASED CURRENT-MODE SINUSOIDAL QUADRATURE OSCILLATORS

This paper presents three current-mode quadrature oscillator (QO) circuits based on dual-output current differencing transconductance amplifier (DO-CDTA) which is designed from block diagram. The proposed circuits consist of two DO-CDTAs and two grounded capacitors. The circuits can provide two sinusoidal output currents with 90° phase difference. The condition of oscillation (CO) can be adjusted independently from the frequency of oscillation (FO) by adjusting the bias currents of the DO-CDTA. The proposed circuits have high output impedance appropriate for cascade connection application in current mode which is capable to directly drive load. The circuits use only grounded capacitors without any external resistor which is very appropriate for further development into an integrated circuit. Moreover, the oscillator circuits can also adjust amplitude of the output signal. The results of PSPICE simulation program are corresponding to the theoretical analysis.

Design of Double-Layer Copper Sheet for RFID Tags Antenna

This paper demonstrates a design of double-layer copper sheet suitable for RFID tags antenna called extended double-layer flexible strip dipole antenna. RFID tag antenna is widely used with different surfaces. The result found that RFID tag antenna can be bended or curved responding to the cylinder shape of the objects. Our proposed extended double-layer flexible strip dipole antenna has been technically designed to make changes on itself to obtain the result in increasing resonance frequency when it is being bended. The key concept of the study is the designed antenna which can freely change inside each layer when applying itself on curved object. The result of this design reveals that antenna has better performance than modern antenna. The extended double-layer flexible strip dipole antenna for RFID tags was designed for resonance frequency of 2.45 GHz. Consequently, the analysis of antennas efficiency will be affected by thickness. The designed antenna there will be considered and discussed to find out the relative value in order to use creating the design for the antenna that is suitable for the further study.

Development of magnetic shielding system for breast hyperthermia inductive heating

In this paper, the effect of cylindrical shield to heating area and location of induction heating for breast cancer hyperthermia treatment with hyperthermia inductive heating are presented. To determine heat distribution in the breast, which electric loss density is analyzed for various aperture sizes and radius of shielded cylindrical. It is a technique to control magnetic field intensity and relocate the heating area by using a cylindrical metal shielding with aperture. In the simulation, the inductive applicator is a ferrite core with diameter of 7 cm and excited by 4 MHz signal. The simulations show that the heating area can be effectively controlled by using the cylindrical shield with adjustable aperture size. The heating efficiency is reduced as the aperture size decreases. If the small heating area is needed, it may require longer treatment time. Nevertheless, the efficiency of heat can be increased by varying the radius size of shielding plate. Moreover, we investigate the position of heating region by varying the orientation of the ferrite core in x direction. The effect of horizontal position of the ferrite core to the heating location is also studied. Simulations show that the heating position can be relocated by changing the orientation of the ferrite core with cylindrical shield. The advantage of the magnetic shielding system is that it can be used to applied for prevent the effects of hyperthermia cancer treatment by induction heating.