| Today, the demanding of antenna radiation pattern controlled has become increasingly flexible on airborne early warning radar, wireless communications and RFID, so that to meet these practical needs, the study of the new phased array antennas has been paid much more attention by many scholars. In this thesis, on the basis of a detailed analysis of bandgap properties of the C-shaped EBG structure, reflective analog phase shifter and controlled circuit which is based on STC89C51 single chip microprocessor, a four-element microstrip phased array antenna system with C-shaped EBG structure at the center frequency of 2.4GHz is fabricated and measured. The test results show that the antenna can steer beam from -30°to 30°, which establishes a good foundation for the application of phased array antenna system.First of all, this paper presents a kind of C-shaped high impedance surface EBG structure, the bandgap properties of the structure is analyzed in detail by using the 3D numerical simulation software and they are embedded between array elements for mutual coupling reduction. Because EBG structure can reduce the surface wave, the antenna radiation performance has been significantly improved.Then, the thesis introduces a microstrip reflection-type analog phase shifter and Wilkinson power divider, and the detailed design processes of them are presented. They are fabricated and measured. The measured results of the phase shifter show that continuous variable phase shifter is up to almost 230°within the change of voltage and the insertion loss is in the range of -1.45dB ~-3.5dB. The test results of Wilkinson power divider indicate that the input and output ports return loss are less than -20dB at the center frequency of 2.4GHz, the transmission loss between the input and output ports is -3.65dB, and the isolation between the two output ports is -21dB.Using STC89C51 MCU as the core component, control circuit is designed to achieve phase shift. By changing the four input digits to change the output voltages, it can produce the required voltages after being amplified by the integrated operational amplifiers. And the LED Digitron displays the current scanning angle.Finally, according to the reasonable structure, the EBG structures, microstrip four-element linear array, phase-shifting network, feed network and phase shifter control circuit are made up of the phased array antenna system. With the C-shaped EBG structure, the antenna main lobe gain has been increased from 11.45dBi to 12.28dBi, and the sidelobe level has been reduced from -0.77dBi to -3.04dBi, then front-back ratio is enhanced 3.1dBi. Mesurement results show that the antenna can be able to steer beam from -30°to 30°at the center frequency of 2.4GHz.In addition, a three-element H-shaped aperture coupling patch ESPAR phased array antenna is proposed in this paper. The center element has feed port while the side elements are passive. The reactance loading the two side passive patches can be controlled by tuning the DC voltages, respectively. Then, the beam of proposed antenna can be steered with wide-angle. The analysis of the antenna and EM simulation are given in details. The results show that the proposed antenna can steer beam from -20°to 20°and from -30°to 30°in H-plane when the reactance is varied in the range of capacitance and inductance, respectively. |
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