In a typical orthogonal frequency division multiplexing (OFDM) broadband wireless communication system, a guard interval using cyclic prefix is inserted to avoid the inter-symbol interference and the inter-carrier interference. This guard interval is required to be at least equal to, or longer than the maximum channel delay spread. This method is very simple, but it reduces the transmission efficiency. This efficiency is very low in the communication systems, which inhibit a long channel delay spread with a small number of sub-carriers such as the IEEE 802.11a wireless LAN (WLAN). To increase the transmission efficiency, it is usual that a time domain equalizer (TEQ) is included in an OFDM system to shorten the effective channel impulse response within the guard interval. There are many TEQ algorithms developed for the low rate OFDM applications such as asymmetrical digital subscriber line (ADSL). The drawback of these algorithms is a high computational load. Most of the popular TEQ algorithms are not suitable for the IEEE 802.11a system, a high data rate wireless LAN based on the OFDM technique. In this thesis, a TEQ algorithm based on the minimum mean square error criterion is investigated for the high rate IEEE 802.11a system. This algorithm has a comparatively reduced computational complexity for practical use in the high data rate OFDM systems. In forming the model to design the TEQ, a reduced convolution matrix is exploited to lower the computational complexity. Mathematical analysis and simulation results are provided to show the validity and the advantages of the algorithm. In particular, it is shown that a high performance gain at a data rate of 54Mbps can be obtained with a moderate order of TEQ finite impulse response (FIR) filter. The algorithm is implemented in a field programmable gate array (FPGA). The characteristics and regularities between the elements in matrices are further exploited to reduce the hardware complexity in the matrix multiplication implementation. The optimum TEQ coefficients can be found in less than 4µs for the 7th order of the TEQ FIR filter. This time is the interval of an OFDM symbol in the IEEE 802.11a system. To compensate for the effective channel impulse response, a function block of 64-point radix-4 pipeline fast Fourier transform is implemented in FPGA to perform zero forcing equalization in frequency domain. The offsets between the hardware implementations and the mathematical calculations are provided and analyzed. The system performance loss introduced by the hardware implementation is also tested. Hardware implementation output and simulation results verify that the chips function properly and satisfy the requirements of the system running at a data rate of 54 Mbps.

In a typical orthogonal frequency division multiplexing (OFDM) broadband wireless communication system, a guard interval using cyclic prefix is inserted to avoid the inter-symbol interference and the inter-carrier interference. This guard interval is required to be at least equal to, or longer than the maximum channel delay spread. This method is very simple, but it reduces the transmission efficiency. This efficiency is very low in the communication systems, which inhibit a long channel delay spread with a small number of sub-carriers such as the IEEE 802.11a wireless LAN (WLAN). To increase the transmission efficiency, it is usual that a time domain equalizer (TEQ) is included in an OFDM system to shorten the effective channel impulse response within the guard interval. There are many TEQ algorithms developed for the low rate OFDM applications such as asymmetrical digital subscriber line (ADSL). The drawback of these algorithms is a high computational load. Most of the popular TEQ algorithms are not suitable for the IEEE 802.11a system, a high data rate wireless LAN based on the OFDM technique. In this thesis, a TEQ algorithm based on the minimum mean square error criterion is investigated for the high rate IEEE 802.11a system. This algorithm has a comparatively reduced computational complexity for practical use in the high data rate OFDM systems. In forming the model to design the TEQ, a reduced convolution matrix is exploited to lower the computational complexity. Mathematical analysis and simulation results are provided to show the validity and the advantages of the algorithm. In particular, it is shown that a high performance gain at a data rate of 54Mbps can be obtained with a moderate order of TEQ finite impulse response (FIR) filter. The algorithm is implemented in a field programmable gate array (FPGA). The characteristics and regularities between the elements in matrices are further exploited to reduce the hardware complexity in the matrix multiplication implementation. The optimum TEQ coefficients can be found in less than 4µs for the 7th order of the TEQ FIR filter. This time is the interval of an OFDM symbol in the IEEE 802.11a system. To compensate for the effective channel impulse response, a function block of 64-point radix-4 pipeline fast Fourier transform is implemented in FPGA to perform zero forcing equalization in frequency domain. The offsets between the hardware implementations and the mathematical calculations are provided and analyzed. The system performance loss introduced by the hardware implementation is also tested. Hardware implementation output and simulation results verify that the chips function properly and satisfy the requirements of the system running at a data rate of 54 Mbps.

A controlled column experiment was conducted to investigate the geophysical response of gasoline spills into the partially saturated sand column. The column was 0.61 diameter (ID) and 2 m high cylindrical polyvinyl chloride, which was packed with the Borden sand to a height of 1.95 m, flushed with CO2, saturated, and drained to a height of 0.73 m. The monitoring techniques used for this experiment was DC resistivity and time domain reflectometry (TDR) methods. The column was equipped with resistivity electrodes and TDR probes, which were placed on the column wall vertically with 3 cm intervals, on opposite sides, two monitoring wells, an injection well, a manometer, an outlet/inlet system, and a vent. A total amount of 5 liters of standard API 91-01 gasoline was added to the system in steps of 1, 2, and 2 liters to examine the geophysical response to different amounts of gasoline. Measurements were taken before and after each injection and also during subsequent fluctuation of the water table. Both monitoring techniques were able to record even the minor changes in the trend of conductivity and permittivity profiles due to the addition of the small amount of gasoline during the first spill. The conductivity and permittivity profiles obtained before lowering the water level below the original level and those obtained after the water level reached to the original level do not match, which is an indication of entrapped gasoline inside the pores. Two core samples was taken from the sand symmetrically after each water table fluctuation and analyzed for total petroleum hydrocarbon (TPH) analysis and the results were compared to the conductivity and permittivity results. The conductivity profile obtained using DC resistivity method was compared to that of obtained using TDR method. The profiles match in the saturated zone where all of the pores are connected with water and therefore electrolytic conduction is predominant. In the unsaturated zone, where there is low pore water connectivity, TDR measured conductivity values are higher than those measured using the resistivity method. Water saturation values were calculated using conductivity and permittivity values before and after each injection. Different values of saturation exponent (n) were tested for Archie’s law until an appropriate value was found which gave the best water saturation from conductivity data for clean Borden sand. Then, the water saturation obtained from permittivity values using Topp’s equations for different materials were compared to that of obtained from conductivity values using Archie’s equation. Topp’s equation for 30 µm glass beads provided the best match. Furthermore, other equations developed by other researchers were examined to obtain water saturation profiles from the permittivity values; all of them overestimate the water saturation for Borden sand. The water saturation profiles after the gasoline spills obtained using both Archie’s law and Topp’s equation do not match, perhaps because both equations were developed for three-phase (water-solid-air) systems.

Photonic Crystal (PC) devices are the most exciting advancement in the field of photonics. The use of computational techniques has made considerable improvements in photonic crystals design. We present here an ultrahigh quality factor (Q) photonic crystal slab nanocavity formed by the local width modulation of a line defect. We show that only shifting two holes away from a line defect is enough to attain an ultrahigh Q value. We simulated this double heterostructure nano cavity by using Finite Difference Time Domain (FDTD) technique. We observed that photonic crystal cavities are very sensitive to the frequency, size and position of the source. So we must choose the right values for these parameters.

A controlled column experiment was conducted to investigate the geophysical response of gasoline spills into the partially saturated sand column. The column was 0.61 diameter (ID) and 2 m high cylindrical polyvinyl chloride, which was packed with the Borden sand to a height of 1.95 m, flushed with CO2, saturated, and drained to a height of 0.73 m. The monitoring techniques used for this experiment was DC resistivity and time domain reflectometry (TDR) methods. The column was equipped with resistivity electrodes and TDR probes, which were placed on the column wall vertically with 3 cm intervals, on opposite sides, two monitoring wells, an injection well, a manometer, an outlet/inlet system, and a vent. A total amount of 5 liters of standard API 91-01 gasoline was added to the system in steps of 1, 2, and 2 liters to examine the geophysical response to different amounts of gasoline. Measurements were taken before and after each injection and also during subsequent fluctuation of the water table. Both monitoring techniques were able to record even the minor changes in the trend of conductivity and permittivity profiles due to the addition of the small amount of gasoline during the first spill. The conductivity and permittivity profiles obtained before lowering the water level below the original level and those obtained after the water level reached to the original level do not match, which is an indication of entrapped gasoline inside the pores. Two core samples was taken from the sand symmetrically after each water table fluctuation and analyzed for total petroleum hydrocarbon (TPH) analysis and the results were compared to the conductivity and permittivity results. The conductivity profile obtained using DC resistivity method was compared to that of obtained using TDR method. The profiles match in the saturated zone where all of the pores are connected with water and therefore electrolytic conduction is predominant. In the unsaturated zone, where there is low pore water connectivity, TDR measured conductivity values are higher than those measured using the resistivity method. Water saturation values were calculated using conductivity and permittivity values before and after each injection. Different values of saturation exponent (n) were tested for Archie’s law until an appropriate value was found which gave the best water saturation from conductivity data for clean Borden sand. Then, the water saturation obtained from permittivity values using Topp’s equations for different materials were compared to that of obtained from conductivity values using Archie’s equation. Topp’s equation for 30 µm glass beads provided the best match. Furthermore, other equations developed by other researchers were examined to obtain water saturation profiles from the permittivity values; all of them overestimate the water saturation for Borden sand. The water saturation profiles after the gasoline spills obtained using both Archie’s law and Topp’s equation do not match, perhaps because both equations were developed for three-phase (water-solid-air) systems.

The operation speed of power delivery system of packages has been upgraded to GHz. The instant current will pass to the power plane of the mother board by way of the IC pins and result in electromagnetic wave propagation between the power plane and the ground plane, then to produce the programs of electromagnetic interference. In this thesis, we will analyze the EMI of power delivery system of packages by finite-difference time-domain in two dimensions structure in three sections. In firist section, to computing EMI in finite-difference time-domain in two dimensions structure. In second section, to analyze more complicated power delivery plane, ex: EBG, in finite-difference time-domain in two dimensions structure. In three section, to add property of capacitors on power plane to reduce EMI in two dimensions structure. Above all, we hope to built a fast computing method to compute EMI to solve the time-consuming problems of full-wave simulated software. And to supply the engineer to deal with the similar problems in packages efficiently.

In modern high-speed digital circuits, the space of the traditional single-layered or double-layered circuit board is not enough, therefore multi-layered circuit and stacked distribution technology are widely applied to many applications. The signal via is a vertical interconnection structure to communicate different signal layers, which will be seriously interfere with the simultaneous switching noise by via through the parallel plate cavity that consists of power and ground plane. It is an important issue to minimize the influence from noise. In multi-layered printed circuit boards, shorting vias are usually utilized to interconnect the planes with the same voltage level. The major theme of this thesis is the placement of shorting vias affecting plane cavity mode. And we propose a design rule of the shorting vias to significantly decrease the simultaneous switching noise and improve the power integrity of multi-layered circuit board.

When we want to solve electromagnetic problems, the Finite Difference Time Domain (FDTD) method is a very useful numerical simulation technique to solve these problems. However, the traditional FDTD method is an explicit finite-difference scheme, so the method is limited by the Courant-Friedrich-Levy (CFL) stability condition. In other words, the minimum cell size will limit the maximum time-step size in a computational domain. Therefore, while simulating structures of fine scale dimensions, it will relatively result in a prohibitively high computation time generated by the maximum time-step size. The WLP-FDTD is based on the Weighted Laguerre Polynomials technique and the traditional FDTD algorithm. It is an implicit finite-difference equations. Therefore, it can completely avoid the stability constraint, and then improve calculation time by choosing relatively large time-step. In this thesis, we incorporate non-uniform grid method into the WLP-FDTD. By using them to simulate the structures of fine scale dimensions can reduce the computation time and memory usage. Further, we extend this method from two-dimensional to three-dimensional and add loss media into original formulations that will make the application of this method more widely.

In this thesis, we will discuss aging line detection and electrical fire precaution by using powerline communication technique. Fire is always a serious disaster which endangers our lives and property. Electrical fire is a major proportion of fire disaster. Even every house generally setup circuit breaker and fuse in time, electrical fire still occurred oftentimes. Current powerline communication technology is using household powerline as a medium of signal transmission, whose channel characteristic will be affected by surrounding environment. We hope that we can analyze the change of transmission characteristic in high frequency of household powerline, which deterioration during long time. At the same time, we will detect variation of high frequency characteristic of powerline as the basis for judgment of aging line, to prevent electrical fire further. Finally, we combine our approach into PLC system, which can also diagnose the line while transmission of powerline at the same time, adding the value without having too much cost.

In this thesis, we propose and demonstrate a simple and precise method for measuring mm scaled cell gap by using terahertz time domain spectroscopy (THz-TDS) system. This method allows us to measure the cell gap from 15mm to 1.5mm. In addition, the accuracy of measured thickness for the proposed method is also discussed and analyzed. Meanwhile, a nematic liquid crystal BL006 with birefringence as high as 0.27 in THz frequency range and its optical properties of cholesteric liquid crystal (CLC) as mixing chiral materials are investigated and reported. The ordinary refractive index and average effective refractive index at 20oC are from 1.52 to 1.56 and from 1.61 to 1.64, respectively, in THz frequency ranging from 0.2 THz to 1.4THz. In addition, we also demonstrate that cell filled with CLC is with polarization independent property for THz radiation. Through the 5mm cell filled CLC with diluted concentration of the dopant chiral material for decreasing the critical voltage, an electric controlled polarization independent phase shifter with the modulation depth exceeding 2pi is demonstrated. Furthermore, we also investigate the driving field dependence of phase retardation and discuss the reliability.