Design Of Antennas Located On The Specific Airborne Platform And Dual-band Circularly Polarized Antenna

The research works are discussed with scientific projects. The thesis consists of two parts. With the project requirements of the arrangement of antennas on specific airborne platform, a layout scheme is presented in the first part. The simulated results show that the proposed scheme meets the project requirements and proves good application effect. In the second part, a dual-band circularly polarized (CP) antenna is introduced. The prototype of dual-band CP antenna is fabricated. The measured results show that the proposed antenna realizes the technical requirements.The main contexts of the thesis are as follows:1. According to the engineering requirements of the locations of antennas on specific airborne platform, the development history, the characteristics of airborne antennas and current state of layout design on airborne platform are introduced. The technical difficulties of layout design are discussed according to electromagnetic environment on the specific airborne and technical requirements of layout design. Firstly, isolated antennas are designed using FEKO based on some relevant theories of antenna. These isolated antennas agree with the technical requirements such as impedance, radiation and polarization characteristic. Then the specific airborne platform is built by the simulation software. Finally, the electrical parameters of 15 antennas are simulated when the antennas are located on the specific airborne platform surface. The positions of the antennas in local areas are adjusted in order to meet the requirements of pattern and isolation characteristic. The final simulated results indicate that the performance of all airborne antennas satisfy the requirements of the locations of antennas on specific airborne platform. Accordingly, it has proved the engineering feasibility of design proposal.2. According to the project requirements, a new design of dual-band CP slot antenna is proposed. Some difficulties in achieving antenna performance are pointed out such as broadband, low-profile, special frequency ratio and bidirectional radiation characteristics. By embedding a vertical stub, a T-shaped strip and a slit to the ground plane, the CPW-fed slot antenna can radiate right hand circularly polarized (RHCP) wave in two bands 3GHz±150MHz and 5GHz±300MHz. On the basis of simulated results, a prototype is fabricated and measured. According to the measured results, the VSWR is less than 2, the gain is above 2 dB and bidirectional radiation characteristics are obtained in the dual-band. The measured results show good agreement with the simulated results. Therefore, it can be proved that this design method is effective for application in engineering.