On The Ultra-wideband Dual-polarized And The Dual-band Circularly Polarized Antennas

The research works are presented with scientific projects. The main research works can be divided into two parts: In the first part, the ultra-wideband dual-polarized feed prototype for the reflector antenna is introduced and analyzed in detail. Besides, the simulated and measured results of the proposed antenna are given and realize the project requirements. Then the single-feed dual-band circularly polarized microstrip antenna is introduced and fabricate. The measured results show the proposed antenna realizes the technical requirements.The main contexts of the thesis are as follows:Firstly, according to the technical indicators of the ultra-wideband dual-polarized feed for the reflector antenna, the related concepts and current state of the ultra-wideband antenna are elaborated. The difficulties in designing the ultra-wideband dual-polarized feeding antenna are pointed out. Based on comparative analysis on all kinds of ultra-wideband antennas, the cascading log-periodically scaled floded dipole antennas called ELEVEN antenna is proposed with low profile, ultra-wide operating band, dual-polarized and constant phase center location. ANSYS HFSS is used to simulate the performance of the proposed antenna. On the basis of simulation and analysis by ANSYS HFSS, the antenna prototype is fabricated and measured. The measured results show the impedance and radiation characteristic have good consistency in the f-4f operating band, the voltage standing wave ratio(VSWR) is less than 2.5. In addition, the beamwidth and gain can satisfy the requirements of feed antennas for the reflector.Secondly, according to the technical indicators of the dual-band circularly polarized microstrip antenna, the related concepts and realization method of the dual-band dual-polarized antenna are elaborated. The difficulties are also pointed out to design the dual-band dual-sense circularly polarized microstrip antenna. And the single-feed dual-band circularly polarized microstrip antenna is designed against the difficulties. ANSYS HFSS is used to simulate and optimize the performance of the proposed antenna and the antenna prototype is fabricated. The measured results show that the VSWR of the designed antenna is less than 2.0, the gain is over 7 d Bic in the operating bands and dual-band circularly polarization is obtained. The measured results indicate that the proposed antenna has high engineering application value.