Research And Design Of Dual-band Circularly Polarized Microstrip Antenna

This dissertation mainly focuses on the research and design of dual-band circular polarized microstrip antenna.It begins with an overview of the reseaerch background and significance of the selected subject and the current development at home and abroad.The dissertation sums up the basic theories of the microstrip antenna,including the principle,parameters and feeding technologies.The procedure of rectangular and circular microstrip antennas based on the cavity model theory is analyzed.Then,the key technologies of realizing dual-band circular polarized are studied.Among it,the production conditions and synthesis methods of circular polarized wave are analyzed in detail.When the axial ratio of the antenna is 3dB,the difference of the corresponding LHCP power and the RHCP power is at least 15.340 dB.Based on the principle of single-feed method,cavity model theory and high frequency structure simulator(HFSS),three novel microstrip antennas with simple structure and good circular polarization performance are designed while one of these is manufactured and measured.The axial ratio of the first design is less than 3dB both in the two working bands of the global navigation satellite system(GNSS),and the measured axial ratio bandwidths are 150 MHz and 100 MHz at low frequency and high frequency,respectively.However,the lobe characteristic of the high frequency shows that the polarization separation is not very good,and the circular polarization characteristic of the antenna is only in very small angle with the Z axis direction.Meanwhile,the second design of the dual-band circularly polarized microstrip antennas is designed in this dissertation.The antenna operates at 1.25 GHz and 2.8GHz,and the axial ratio bandwidths are 950 MHz and 750 MHz.But the lobe characteristic of the high frequency can not achieve the desired results either.Based on the theory,the third design of the dual-band circularly polarized antennas is designed.The antenna operates at 2.7GHz and 4.4GHz,and the axial ratio value is 2.3dB and 0.5dB and shows the good circularly polarized radiation characteristics.