Browsing by Author "Jebeli Haji Abadi, Ali"

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    Design of Phase Shifters for Phased Array Antenna Applications
    (2024-10-24) Jebeli Haji Abadi, Ali; Ghannouchi, Fadhel M.; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Belostotski, Leo; Fapojuwo, Abraham
    This thesis presents a method for reducing the complexity of the I-Q phase shifter. This new method is based on the I-Q phase shifter architecture, where the input signal is divided into two orthogonal paths. By adjusting the amplitude of these two signals and then combining them, a signal with a phase difference relative to the input signal is obtained. The variable attenuators used in this method must be adjusted based on the required phase shift, and these attenuators are controlled by the system's control unit through multiple control lines. By reducing the number of control lines in this phase shifter, we effectively decrease the complexity and load on the control section. In this work, we first introduce a Voltage Variable Gamma Phase Shifter. This phase shifter requires only one control line and provides continuous phase variation. In this approach, the input divider is replaced with a circulator, and the two attenuators are replaced with a single variable resistor. The variable resistor is a PIN diode, controlled by a single control line. This phase shifter was fabricated and tested at 3.45 GHz with a bandwidth of 300 MHz. It provided approximately 95 degrees of phase change, with insertion loss less than 14 dB. The limitation of this method is the circulator, which prevents its use in Microwave Monolithic Integrated Circuits (MMIC). To address this issue, we have developed the next version of this phase shifter. The second step in this thesis involves modifying the Voltage Variable Gamma Phase Shifter to make it suitable for MMIC applications. To achieve this, we replace the input circulator with a coupler. This method has its own pros and cons. Although this version can be used in MMIC applications, we do not have control over both paths, which means we will lose the ability to vary the phase. In this configuration, since we have control over only 50 percent of the input signal, we will lose at least 50 percent of the phase variation. This phase shifter has been fabricated and tested at 3 GHz with a bandwidth of 400 MHz. The final step is the MMIC version of this phase shifter. Using a GaN substrate and 250 µm technology, we designed the MMIC phase shifter using the process design kit (PDK) from United Monolithic Semiconductor (UMS).This phase shifter provides a phase variation of 40 degrees and a bandwidth of 400 MHz at 3.5 GHz, with an insertion loss of less than 8 dB. The dimension of the final version of this phase shifter is 2 by 1.6 mm.