Abstract The breakthrough technology in dry fiber fabrication has opened the possibility for using fiber bandwidths all the way from 1.3 to 1.6 £gm. The fiber amplifier that is in common use can not fully cover the whole, which its range is from 1.3 to 1.6 £gm. Recently, the Cr4+-doped fiber has shown a broadband emission from 1.3 to 1.6 £gm. Therefore, it is eminently suitable for super-wideband optical source. In this study, we first propose and fabricate a Cr4+-doped fiber by employing a commercial drawing-tower method, which has good core diameter uniformity, the growth speed is up to 200 m/min, and the core diameter is less than 10 £gm. The central wavelength of the ASE spectrum is at 1310 nm, and a 3-dB bandwidth is 300 nm. The divergent angle of the Cr-doped fiber is 17 o ¡Ñ 15 o and it¡¦s also similar to a single mode fiber of 16 o ¡Ñ 16 o. Low-loss fusion splice can readily be done with the standard single mode fiber, and is beneficial when integrated with the broadband WDM couplers. Therefore, it is good for commercial production and application to light wave systems.

Abstract The thesis comprises two different IC design projects, which are briefly introduced as follows. The first part is the NIC (Network Interface Controller) design. The NIC implements all of the Media Access Control (MAC) layer functions for transmission and reception of packets in accordance with the IEEE 802.3 standard. The design is compatible with CSMA/CD type Local Area Network, i.e, 100/10 Mbps Ethernet. The second part is a post-amplifier for a 16Mbps infrared transceiver module. We presents a design of the post-amplifier to convert the pre-amplifier output into digital pulses such that the baseband digital codec can further translate the pulses into the format of IrDA protocols. The design of the amplifier is aimed at the VFIR (very fast infrared) which is supposed to provide a 16 Mbps data transmission rate. The circuit design is carried out by TSMC 0.35 um 1P4M CMOS technology. The simulations results of the design meet the required specification of IrDA VFIR.

This thesis utilizes the digital predistortion technique to improve the linearity of high power amplifiers for WiMAX basestation applications. The power amplifier with the proposed technique can achieve higher output power and efficiency than with the conventional output power backoff technique. Owing to a very high PAPR value of the OFDM modulation signals applied to WiMAX basestation, the linearity requirement for the basestation power amplifiers is very strict. This thesis adopts a look-up table predistorter based on a polar scheme and realizes the digital predistorter circuitry using FPGA. As a result, the implemented digital predistorter successfully enhances the linearity of a 15W Lateral MOSFET Class-AB power amplifier operating in 2.6 GHz WiMAX band. Under the conditions that satisfy the spectrum mask and EVM requirement, the power amplifier with the digital predistorter can operate at higher output power and conversion efficiency than without the digital predistorter.

In this thesis, a low-power current-mode instrumentation amplifier is proposed for the portable physiological signal recording system. This proposed instrumentation amplifier is used as a front-end amplifier of physiological signal recording system. In general, the physiological signal is very small, for example, the electrocardiogram (ECG) signals. Therefore, the system needs a front-end amplifier to amplify small physiological signals so that it is easier to analyze the signals. Besides, the system will be operated for a longer period because of the proposed amplifier¡¦s low-power property. The circuit theorem, design process and simulation, circuit layout as well as the measurement results all have detailed description in this study. Moreover, a specific physiological signal recording system prototype is proposed. This proposed instrumentation amplifier has used TSMC 0.35 £gm 2P4M CMOS process technology.

In this paper, a distributed Electroabsorption Modulator (EAM) monolithically integrated with Semiconductor Optical Amplifier (SOA) is analyzed. Using the distributed effects on the optical modulation and amplification, several advantages have been found in this work, such as high-speed modulation, microwave performance, low nose properties, and low chirp, which is quite fitted to the requirements of optical fiber communications. EAMs have been widely used due to high-speed, high extinction ratio, the compactness, and the capability of integration. However, due to the highly loaded capacitance in the waveguide, EAMs generally suffer from high microwave reflection and thus low modulation efficiency during high-speed modulation. By the distributed structure, SOA-integrated EAMs can not only enhance the impedance match by adopting distributed high impedance transmission line (HITL), but also offer optical gain. By the optical processing scheme of re-amplification and re-modulation, it also has been found that the extra amplified spontaneous emission (ASE) noise coming from SOA can be reduced to get lower noise figure (NF). Appling the saturation on SOA, the positive frequency chirp of EAM can be compensated to give overall low chirp. By the distributed structure, chirp compensation has been realized by this characterization. In this work, the distributed EAM-SOA scheme and the traditional single section EAM-SOA scheme are used for comparison, higher speed and lower NF are observed in distributed scheme. Due to impedance matching improvement in distributed scheme, a -3dB bandwidth of higher than 40GHz and 40Gbit/s data transmission is achieved, while a 15GHz of -3dB bandwidth is obtained in single device. Also, in 10Gbit/s data transmission, a 3dB lower of power penalty occurs in distributed scheme, while the lower NF is the mainly dominating mechanism.

A fiber amplifier is constructed at 1014.8nm and then frequency doubled to produce 507.4nm. This could then be frequency doubled again to produce 253.7 radiation. The fiber amplifier consists of Ytterbium doped double-clad fiber cooled to low temperatures and incorperates a diode laser as the seed source. The amplifier is built in a two stage configuration with high power diode lasers at 980nm pumping each stage. The output of the fiber amplifer is then doubled in a PPLN crystal and redoubled in a BBO cavity. Measurements are taken throughout the system to determine ouput powers from the first stage and from the fiber amplifier as a whole.

No description available.

No description available.

Medical hyperthermia refers to heating of tumors to temperature levels which are lethal to the cells for sufficient periods of time or rendering the cancerous cells more sensitive to ionizing radiation or chemotherapy. In order to increase the temperature in cancerous tissues, high power solid state microwave amplifiers need to be used. Recently ultra wide-band and continuous wave microwave methods have received increasing attention. Using adaptive focusing annular phase array applicators the radiation pattern can be adjusted according to tumor size and seating depth. For this purpose power amplifiers operating across 300MHz-1000MHz having a minimum output power of 150W needed to be designed. By varying the operating frequency the penetration depth can be controlled. Since currently 12 (with plans to increase the number to 18) of these amplifiers will be operating simultaneously in the designed system, the power added efficiency of the amplifier will be important both to regarding the cost of electricity and also allow for easier cooling requirements and thus a more compact system. The aim in this project is to have an efficiency of 60% across the band. In this thesis a power amplifier working in a push-pull configuration, designed using an NXP LDMOS device (BLF-647P) capable of delivering 200W RF power is demonstrated. During this thesis, different power combining topologies were studiedusing a nonlinear model that was developed in ADS using basic data provided by NXP. Using the developed model, load pull simulations have been performed and the input, two output matching networks are designed based on results from the load pull simulations. The design was manufactured and mounted on a copper base plate designed for this work which allowed efficient water cooling as well as serving as a fixture to firmly attach the matching circuits to the transistor and connectors. The measurements show that the design is capable of delivering more than 125 W from 360-940 MHz in pulsed mode operation with a mean efficiency of 50% which was measured in continuous mode. This work has demonstrated a high power wideband amplifier with high efficiency needed to drive future hyperthermia systems. The high efficiency of the amplifier allows for modern hyperthermia systems to be built in a more compact configuration with lower operating cost, which would not be possible with commercially available amplifiers.

With the growth of smart phones, the demand for more broadband, data centric technologies are being driven higher. As mobile operators worldwide plan and deploy 4th generation (4G) networks such as LTE to support the relentless growth in mobile data demand, the need for strategically positioned pico-sized cellular base stations known as ‘pico-cells’ are gaining traction. In addition to having to design a transceiver in a much compact footprint, pico-cells must still face the technical challenges presented by the new 4G systems, such as reduced power consumptions and linear amplification of the signals. The RF power amplifier (PA) that amplifies the output signals of 4G pico-cell systems face challenges to minimize size, achieve high average efficiencies and broader bandwidths while maintaining linearity and operating at higher frequencies. 4G standards as LTE use non-constant envelope modulation techniques with high peak to average ratios. Power amplifiers implemented in such applications are forced to operate at a backed off region from saturation. Therefore, in order to reduce power consumption, a design of a high efficiency PA that can maintain the efficiency for a wider range of radio frequency signals is required. The primary focus of this thesis is to enhance the efficiency of a compact RF amplifier suitable for a 4G pico-cell base station. For this aim, an integrated two way Doherty amplifier design in a compact 10mm x 11.5mm monolithic microwave integrated circuit using GaN device technology is presented. Using non-linear GaN HFETs models, the design achieves high effi-ciencies of over 50% at both back-off and peak power regions without compromising on the stringent linearity requirements of 4G LTE standards. This demonstrates a 17% increase in power added efficiency at 6 dB back off from peak power compared to conventional Class AB amplifier performance. Performance optimization techniques to select between high efficiency and high linearity operation are also presented. Overall, this thesis demonstrates the feasibility of an integrated HFET Doherty amplifier for LTE band 7 which entails the frequencies from 2.62-2.69GHz. The realization of the layout and various issues related to the PA design is discussed and attempted to be solved.