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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 54721 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Khavasi, Amin; Fakharzadeh, Mohammad
- Abstract:
- A phase shifter is a microwave element that changes the phase of the input signal at a specific center frequency and bandwidth and, ideally, produces a signal with the same amplitude and a modified phase at the output. In practice, this phase change in the passive phase shifter is accompanied by a decrease in amplitude due to different factors. Various use cases can be described for phase shifters in telecommunication circuits, but its most important application is in regulating the relative phase of each antenna in a phased array system, which is the most common method of beam steering and forming. A phased array system is one of the leading solutions to achieve beamforming and high directivity at millimeter-wave frequencies that will soon be used in 5G. Engineers prefer to use passive phase shifters due to more linearity, smaller noise figure, and lack of DC power consumption in many applications. High insertion loss in passive phase shifters reduces the signal-to-noise ratio at the output, and its variations also cause the array gain to be unequal for different input angles. This thesis provides methods for compensating the response by focusing on the reflective type phase shifter. The central part of the RTPS is a varactor diode, so a circuit is designed to characterize it correctly. Also, we introduce a procedure for designing the optimal reflective load, including appropriate architecture and selecting the best characteristic impedance. As a result, the phase changes of 〖360〗^∘ and the minimum insertion loss variations are achieved. The following methods are used to design narrowband and wideband phase shifters for the 2.45GHz ISM band on the FR4 and RO4003C substrates. Measurements show that using introduced methods causes an average insertion loss of 1.57dB over 37 % relative bandwidth and more than 〖360〗^∘ phase changes. Finally, non-coherent beamforming methods are introduced to transform the response compensation into an optimization problem for finding the best bias voltage, and for a 2-element standard array, 0.6dB improvement is obtained
- Keywords:
- Characteristic Impedance ; Phased Array ; Phase Shifter Circuit ; Reflective Type Phase Shifter ; Optimum Reflective Load ; Non-Coherent Beamforming
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