| With the rapid development of satellite navigation system and modern communication technology, the electronic equipment has become more and more small, wideband operation and functional, the circularly polarized antenna for the GNSS and satellite communication has become a hot topic, and the demand for CP antenna is enhanced. Based on practice of the project, the wideband CP antenna, dual band CP antenna, quadrifilar helix antenna, low side-lobe CP antenna array and shaped beam antenna array for earth coverage have been studied intensively in the thesis for GNSS applications. The author’s major contributions are as follows:1. Wideband and dual-band CP antennas with dual feeds are studied. A wideband CP microstrip antenna is designed in this paper based on the global navigation satellite system applications. The proposed antenna adopts the annular radiation patch with air as its gap. By adjusting the inner and outer radius of the patch, the antenna is able to cover the L2 and L5 bands of GPS, as well as the E5 a and E5 b frequencies of Galileo navigation system(1164-1215MHz). With two feeds mutually perpendicular to the proposed antenna, the operation bandwidth is broadened. The feeding network consists of a broadband 90o phase shifter and a Wilkinson power divider, with the help of which the antenna achieve about 26% VSWR bandwidth. In order to meet the requirement of multi-band operation of GPS, another dual-band CP microstrip antenna is designed. This antenna employs two radiation patches stacked together with two probe feeds. By adjusting the feeding points and the radius of the patch to fit the resonance frequencies. A slot is cut at the surface of the radiation patch for the perturbation of the surface current so as to optimize the axial-ratio. The measured results demonstrate the proposed antenna could realize right hand circular polarization radiation at the L1, L2 and L5 bands of GPS with axial-ratio less than 3dB.2. Electromagnetic coupling feed CP antennas are investigated. To make further improvement of the operation bandwidth to cover all the frequencies of GNSS, electromagnetic coupling feed is adopted. First of all, a slot-coupling CP antenna with lotus-shaped slots is designed. With the help of these slots, the energy is coupled to the concentric radiation patches. A broadband phase shifter is used in the feeding network. And the measured bandwidth of VSWR is as much as 41.7%. The axial-ratio is less than 3dB within the whole band. So as to obtain the CP antenna with characteristics of miniaturization, a strip line feeding network divided into two layers is adopted. The size of the antenna is reduced greatly. By adjusting the dimension of the slots and patches, the gain and axial-ratio of the low observation angle enhanced. The proposed antenna realizes a bandwidth of 50%, and the measured axial-ratio within the operation frequencies is less than 2dB.3. Quadrifilar helix antenna is presented and studied. The quadrifilar helix antenna adopts the open circuit form at its top with parasitism arms loaded. By adjusting the radius of the helix and the length of the arms, the width of the radiation pattern is broadened as well as the gain of low observation angle is enhanced. The output of the feeding network maintain stable within the whole band through the use of broadband phase shifter. The proposed antenna is processed and measured. The simulated results confirm well with the measured ones.4. Linear arrangement CP antenna array is investigated. A wideband antenna array with right hand circular polarization for WiMax applications is designed. The array element uses the slot-coupling technology to broaden the operation bandwidth. The proposed antenna array is required to own the radiation patterns with low side lobe. The amplitude and phase to the array elements is optimized. Through a comparative of all the simulated results, the optimal amplitude and phase distribution is determined. Based on the distribution, we designed the feeding network. The antenna array is manufactured and measured, and meets the design requirements.5. Shaped beam antenna array for earth coverage is studied. Through the research of shaped beam antenna array for earth coverage for the Galileo navigation satellite system use. The thesis presents a design of a CP antenna array with 24 antenna elements. The requirement for this antenna array is the radiation patterns should be shaped for earth coverage. In view of the dual band operation of Galileo navigation satellite system, a dual-band right hand CP antenna is designed as the element. The amplitude and phase distribution for these 24 elements are optimized through the Genetic Algorithm. Then we modeled the antenna array with simulation software, and the simulated results proved the validity of the Genetic Algorithm.
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