Circularly Polarized Antennas Based On Substrate Integrated Waveguide

Substrate Integrated Waveguide(SIW) technique which can be fabricated using PCB, LTCC process is a novel planar guided-wave structure which is similar to the rectangular metal waveguide developed in recent years. SIW inherits a lot of merits of the conventional rectangular waveguide devices, such as high Q, high power capacity,low insert-loss and low radiation-loss and many other advantages, but also can be compensate for disadvantages of the rectangular waveguide devices such as difficult to integrate with other devices, large volume, the three-dimensional structure and other shortcomings. SIW which has a lot of merits of light weight, low cost, mass production is very suitable for the designing and mass-production of microwave and millimeter-wave integrated antenna and circuits. Owing to its resistance to polarization mismatch and multi-path effects, circularly polarized(CP) antennas are widely used in wireless communications. Consequently, how to use the substrate integrated waveguide technology to design circularly polarized antennas fabricated on SIW has become a central issue for many scientists. In this thesis, after reading the related literature at home and abroad, and understanding the related principles and methods, some kinds of SIW CP antenna are presented, and the major work and contributions of the author are as follows:1. A circularly polarized antenna based on eighth-mode substrate integrated waveguide is designed; Due to SIW antenna used at the low frequency, its size is relatively large, so in order to reduce the size of the antenna, a linearly polarized antenna elements based on eighth mode substrate integrated waveguide(EMSIW) is designed. To achieve circular polarization, sequential rotation technique(SRT) is a favored choice, where antenna elements are fed by uniform magnitude and progressive phase shifts of 90 o. The measured 10-dB return loss and 3-dB axial ratio bandwidths at the center frequency 5.2GHz are 10.96% and 21.53 %, respectively. It can be used in WLAN operating at 5.2GHz.2. A broadband circularly polarized planar antenna based on a quarter-mode substrate integrated cylindrical cavity sub-array is presented in this chapter. Due to SIW antenna having a high Q value, so that it has a narrow bandwidth. To achieve wideband circular polarization SIW antenna, sequential rotation technique(SRT) is a favoredchoice. It is composed of two layers: a quarter-mode substrate integrated cylindrical Cavity(QMSICC) sub-array and the feeding network comprised of three Wilkinson power dividers. The measured 10-dB return loss and 3-dB axial ratio bandwidths at the center frequency 5.2GHz are 40% and 25.5%, respectively. The gain measured for right-hand circular polarization(RHCP) is 4.6 dBi at 5.2GHz. And it will be used in WLAN operating at 5.2GHz.3. A circularly polarized antenna based on substrate integrated waveguide which is applied for WLAN(5.15-5.825GHz) is designed. Bandwidth enhancement of the proposed SIW Antenna using a substrate removal under the slot and using the SIW hybrid modes, and the proposed antenna can be applied for WLAN(5.15-5.825GHz).The proposed antenna radiate circularly polarized electromagnetic by inspiring the cavity two orthogonal mode TE120 and TE210, at 5.8GHz. Simulation results show that:The 10-dB return loss bandwidths at the center frequency 5.5GHz is 17.63%. The 3-dB axial ratio bandwidths at the center frequency 5.8GHz are 1.55%. The antenna can be applied to WLAN(5.2-5.8GHz).