S/C Band Low Profile Circularly Polarized Shared-Aperture Antenna

As a device for missile-borne system to transmit and receive electromagnetic waves, the functions of missile-borne antenna are becoming more and more abundant. The shared-aperture antenna can improve the aperture utilization rate of missile seeker and can avoid radiation interference between antennas. This paper proposes a low profile circularly polarized shared-aperture antenna for missile seeker antenna based on the theory of microstrip circular polari-zed antenna. More specifically, the sequential rotation feed technology is adopted for the rectangular microstrip antenna in the high-frequency C-band part, while the orthogonal double feed technology is adopted for the cross microstrip antenna in the low-frequency S-band part. The nested shared-aperture antenna structure is adopted to realize the design of shared aperture antenna of 63 mm×63 mm×1.574 mm. The reflection coefficient is less than -10 dB in the frequency bands of 4.87~5.13 GHz and 2.49~2.51 GHz. The relative bandwidth of high-frequency antenna is 8.1% and that of low-frequency antenna is 0.4%. The axial ratio of the two antennas in the maximum radiation direction at the center frequency is less than 3 dB. The experimental data show that the shared-aperture antenna designed and applied to the missile-borne antennacan significantly improve the aperture utilization of the missile seeker, and can also eliminate the deterioration of the radiation performances caused by the mutual coupling of antennas.