Research On Multimode Resonance Elliptic Patch Antennas

This thesis is devoted to the research on multi-mode elliptic patch antennas.The basic principle of an elliptic patch antenna is fully analyzed by means of mathematical tools such as the Mathieu functions.Based on the design techniques of patch antennas associated with the basic principle of the elliptic patch antennas,three kinds of multi-mode elliptic patch antennas are proposed.（1）A wide-beam,low cross-polarization,wide-band triple mode elliptic patch antenna design scheme is proposed.According to the relationship between magnetic current source and its far field,a semi-closed elliptical patch is selected as the main radiation patch.The dual mode resonance characteristics and low cross polarization are realized by shorting pin loading to make close to the resonance frequencies of the quasi _eTE₀₁ mode and quasi _eTE₁₂ mode.To broaden the radiation beam,a one-side opened parasitic patch is introduced to form triple-mode resonance.In principle,the parasitic patch eliminates the array factor of main radiation patch.This approach forms a single radiation element instead of the binary radiation elements of the main patch.The proposed antenna sample provides 14% bandwidth,a very stable gain and about 135°E-plane beamwidth,while the cross section is as low as 00.039λ.The maximum beam width reaches 150°and the minimum crosspolarization is only-13.11 d B.（2）A low-profile wideband triple mode elliptic patch antenna design scheme using non-radiative mode as impedance matching is proposed.Firstly,rectification is accomplished by loading shortcircuiting pins along the elliptical arc segment,and then loading elliptical slot to complete the coupling of the two radiation modes _eTM₃₁ and _eTM₅₁.In order not to destroy the current distribution of the two radiation modes and reduce the cross-polarization of the antenna,the resonant frequency point of the non-radiation mode _eTM₁₂ is pulled into between the two radiation modes to form a triple mode resonant characteristic by loading two slots in the ground plate.The finished antenna achieves a relative bandwidth of 13.52% with a profile thickness of 00.049λ,and obtains a more stable gain in the impedance bandwidth.（3）A simple structure low-profile broadband triple mode elliptic patch antenna design scheme is proposed.In the second design scheme,the non-radiative mode and raddition mode field distribution difference is large resulting in impedance bandwidth increasing is limited.Therefore,the elliptical arc segment short-circuit pin loading is abandoned,and a new scheme that can complete the coupling of the three radiation modes by loading only elliptical slot is proposed.Meanwhile,in order to obtain stable gain,the _eTM₁₂ mode gain enhancement is completed by using the proposed magnetic current enhancement stubs.After processing and measuring the antenna,the bandwidth of the finished antenna is as high as 20.57%,the profile thickness is only 00.052λ,and the antenna obtains a relatively stable gain in the impedance bandwidth range.