Wideband Circularly Polarized Antennas with Broadside and End-Fire Radiations 


Student thesis: Doctoral Thesis

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Award date26 Nov 2021


This thesis presents investigation of a series of wideband circularly polarized (CP) antennas with unique radiation characteristics for microwave and millimeter-wave (mm-wave) applications. In this thesis, CP antennas with broadside and end-fire radiation performances are analyzed. Recently, wideband CP antennas attract more and more attention due to its large operating spectrum which can provide high speed data transmission rate for wireless communication. In addition, their CP radiation performance can improve receiving flexibility of signals with different polarizations. For such a purpose, wideband CP antennas are always welcome for communication industry. A significant challenge associated with such antennas is significantly extending its bandwidth while maintaining wide axial ratio (AR) bandwidth, which is a performance to evaluate CP realization, especially in mm-wave band. In this thesis, novel complementary radiators are proposed to extend operating bandwidth of CP antenna at microwave and mm-wave band. Based on this proposal, novel techniques are proposed to realize CP antennas with enhanced performances such as wide AR bandwidth, high antenna gain, high operating frequency and compact size.

My study begins with extending operating bandwidth of CP antenna at microwave band. We introduce a novel complementary radiator. By using such antenna structure, good impedance matching can be realized within a large frequency range. Based on this proposed radiator and feeding network, a wide band CP antenna operating at X-band is designed. Compared with other recently reported CP antenna, the proposed antenna illustrates wideband, low profile and low-cost characteristics.

Furthermore, we design another novel CP antenna element for mm-wave application with ultra large operating frequency bandwidth. The radiator is composed of a diagonally placed patch dipole and a mirrored S-shape patch, which acts as the E-dipole and M-dipole, respectively. To further enhance the antenna gain for the proposed antenna, we use it as an element and propose a wideband 8×8 CP antenna array with high gain radiation within a wide AR bandwidth.

Finally, to find a novel technique to enhance the operating bandwidth and realize compact size of end-fire CP antenna at mm-wave band, a new design method for end-fire CP dielectric rod waveguide antenna at 30 GHz is presented with a rotated tapering rod which consists of a matching taper and a radiation taper. The proposed antenna achieves a wide impedance bandwidth throughout the whole Ka band as well as a wide 3-dB axial ratio bandwidth (ARBW) of 37% from 27.5 to 40 GHz. The main advantages for this antenna design are its wide impedance bandwidth and 3-dB ARBW, simple structure, and easy fabrication.

The output of this research work produces two journal papers published in the journal of IEEE Transactions on Antennas and Propagation and a submitted manuscript in the journal of IEEE Antennas and Wireless Propagation Letters.