الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
MEMS (Micro-Electro-Mechanical Systems) refer to devices or systems integrated with electrical and mechanical components in the scale of microns. Due to its small size, low cost, low power consumption and high efficiency, MEMS technology had been widely used in many fields.
One of the most important fields that had started to use MEMS as a fundamental structural-base component is the micro communication systems. The marketing trend of using MEMS in communication system shows an exponential growth especially in the direct conversion RP modulations.
The demand for light and low-power wireless communication systems has been growing rapidly in recent years with a relentless push for higher speeds and increased functionality. The modem wireless communication systems employ.
The conventional complex indirect conversion modulation methods such as Quadrature Phase Shift Keying (QPSK) and Quadrature Amplitude Modulation (QAM) for increased band width and spectrum efficiency such modulation schemes have been traditionally implemented using the indirect conversion heterodyne modulators, since it was difficult to design direct-conversion digital RP modulators with adequate modulation accuracy for low bit error rates (BER) and reliable data transmission. However the continuous scaling and developments microelectromechanical system (MEMS) makes it now possible to realize direct¬conversion digital modulators with improved performance, higher conversion efficiency and data throughput.
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Direct modulation has significant advantage of eliminating the need for IF modulation and up/down conversion stages by Modulating the RF carrier directly with a digital bit stream, consequently reducing size, complexity of circuits, and cost.
In this thesis, a novel direct-digital PSK modulators are proposed with new RF components and circuits devised in low-cost MEMS technology for portable wireless applications. A new direct-digital PSK modulator concept is introduced where the carrier is modulated directly using MEMS as a basic structure of the electric circuits.
The MEMS-BPSK is composed of a rat-race hybrid coupler and a single-pole double-throw MEMS switch controlled by a digital baseband signal. Also, the concept of the proposed MEMS-BPSK modulator is introduced to construct a MEMS-QPSK modulator using Microstrip Couplers (Branch Line Quadrature Hybrid coupler and Hybrid ring rat-race coupler) with two single-pole double-throw MEMS switches controlled by a digital baseband signal.