The narrow slot loop antenna and linear slot antenna fed by microstrip line are designed for dual frequency at 2.44 GHz and 5.25 GHz on the standard of IEEE 802.11b/g (2.4{2.4835 GHz) IEEE 802.11j/a (5.15{5.35 GHz) and IEEE 802.16d (5.7{5.9 GHz). These structures are easy to adjust the length of slot antenna for dual frequency band. It can control the higher frequency band around 4.9 GHz to 5.8 GHz by linear slot antenna. Adjusting some parameters of narrow slot loop antenna will influence on the resonance frequency and bandwidth. By using IE3D software [1] the characteristics of antenna are investigated and analyzed including instance input impedance return loss and far field radiation patterns.

This thesis presented the design and construction of an adaptive active band-pass filter by using a tachometer circuit. The main part was the multi voltage-mode filter circuit based on an operational transconductance amplifier which could automatically adjust the center frequency to adapt to the input signal frequency by the tachometer circuit. The frequency error value in the center frequency was set to be ≤ 3% of the input signal. Furthermore the proposed filter could support the input signal in the frequency range of 10 Hz - 10 kHz. From the simulation and experimental results of the proposed prototype filter it could respond to the frequency according to the theory of the band-pass filter and the error in choosing the center frequency which was 1.45 % and 2.6 % respectively (below the set error value of 3 %). Therefore the proposed filter could be used for real application. The working principles of the proposed prototype filter could also be applied to the noise attenuation circuit of an electrocardiogram machine. Moreover this research could be used as a guideline study for those who want to develop other types of adaptive active filters for higher efficiency.

In this paper the printed loop antenna is proposed for high frequency radio frequency identification (HF-RFID) systems (13.56 MHz). The proposed antenna is designed on the printed circuit board (PCB). The antenna structure consists of printed semi-spiral loop with rectangular structure patch at the middle of loop. It can provide the magnetic field distribution to cover the operating area with various directions that can improve the communication performance between reader and various tag orientations. From the measured results the proposed antenna has more efficient than the printed spiral loop antenna

This paper presents risk assessment of damages for equipments in the building based on IEC standards and ITU-T recommendations. The study of risk assessment of damages for equipment in the building includes of 6 main topics: calculation of frequency of damages due to lightning discharges calculation of risk of damage calculation of risk areas estimation of probability factors consequential damage factor acceptable risk levels and mitigation methods to reduce the influence of power line induction affecting to equipment. Also the implementations of surge protective devices (SPDs) at the entrance of power lines into the building contribute to a further decrement of damage.