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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 42581 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Medi, Ali
- Abstract:
- Phased array systems which are used for sending and receiving electromagnetic signals in mandatory directions are widely used in today’s wireless communication, satellite communication, and radar systems. Phased array systems are composed of units called transmitter/ receiver (TR) modules. These units are connected to antennas in one end and to the combiner/divider at the other end and are playing a major role in determining the quality of phased arrays. Transmitter/Receiver units include a phase shifting circuit for controlling the phase and an attenuator circuit for amplitude control of the signal being sent or received, solid state switches and a number of amplifiers. The aim of this thesis is to design and implementation of a 6bit phase shifting circuit at the frequency band of 7-10 GHz. Phase shifting circuits are usually implemented using III-V compound technologies such as GaAs and InP. Among the features of this processes that has made them suitable for our purpose is their very highly linear and low loss switches, high-quality passive elements (specifically, inductors) and the use of thicker conductors. These features enhance compression point and reduce loss in phased array system. But the important disadvantage of these processes is that they are expensive and unavailable to our country. Because CMOS technology is very low-cost and available, implementing phase shifting circuits in CMOS processes has been in much attention recently. By using CMOS technologies, it is possible to integrate RF circuits with other analog, base band, and digital circuits. But the problem is that CMOS processes have none of the features listed above for the III-V compound processes. For instance low quality factor of inductors and high on-resistance of switches lead to increasing circuit loss. Also components are not well modeled at frequencies above 1 GHz in these processes. In addition, due to the low control voltage levels for switches, the compression point of the system will be lower. This effect will make a confrontation between the NF of the system and its compression point, the two important parameters in a transceiver system. A 6-bit phase shifting circuit has been designed and fabricated in the TSMC’s 0.18µm CMOS technology. Performed measurements show good performance and high bandwidth of the circuit. One of the important features of this phase shifter is its low insertion loss compared to similar works which is even comparable with the phase shifters fabricated using GaAs technology
- Keywords:
- Phase Shifter Circuit ; Phased Array ; Phased Array Antenna ; Group Delay ; Complementary Metal Oxide Semiconductor Technology (CMOS)
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