Research Of Pattern Regulation On Microstrip Patch Antenna Based On Multimode Resonances

Microstrip patch antennas（MPAs）with outstanding advantages have been popular in modern wireless communication systems.As a kind of cavity structure,the MPAs have a set of resonance resources from their high order modes.However,most of these high order modes have been suffered from the issue of distorted radiation patterns,which restricts the development and application of these high order modes.In this thesis,the main target aims to the radiation performances of the multimode patch antenna,which contains of improving deteriorative patterns and achieving special patterns for specific requirements.Meanwhile,the properties of the impedance have been also improved for wideband by utilizing the multi-resonant modes.The details of this communication are organized as follows.1.Studying the mechanism of the half-power beamwidth（HPBW）enhancement under low profile.The method of removing array factor has been proposed in order to achieve the wide HPBW.Furthermore,the two-resonance-mode patch antenna with wideband and widebeam under low profile has been designed,which has been different with conventional methods of introducing vertical current.In this section,firstly,the important factor of beamwidth at TM₁₀ mode has been calculated based on the cavity model and equivalent magnetic currents（EMCs）.And then,in order to effectively regulate the important factor,the shorted patch antenna（SPA）has been utilized and the beamwidth on E-plane could be widened to around140°.Thirdly,in order to reduce the cross polarization caused by SPA on H-plane,two analytical ways of“enhancement”and“suppression”have been proposed.By extending the length of radiative edge and loading suppressive shorted pins,the cross polarization has been reduced below-23.5 d B.Meanwhile,two resonant modes of SPAs have been combined aiming to acquire 12%wideband.Finally,the enhanced bandwidth,wide beamwidth,low cross polarization has been simultaneously achieved under low profile of around 0.029λ₀.2.Studying the method of beamwidth enhancement at TM₁₀ mode and simultaneously improving the high sidelobe at TM₃₀ mode.In this section,a low-profile aperture-coupled MPA under multiresonant modes for wide HPBW,high gain and enhanced-bandwidth is proposed.Firstly,the important factor in section one has been furtherly deeply studied and analysis,it seems that regulating the dielectric constant could simultaneously wide HPBW of TM₁₀ mode and improve the sidelobe of TM₃₀ mode.And then a linear radiative slot has been introduced,aiming to furtherly enhance the broadside radiation of the MPA at TM₃₀mode.Thirdly,in order to acquire wide impedance bandwidth in dual frequency band,a novel feeding network has been introduced,which yields two resonances around TM₁₀ and TM₃₀ mode,respectively.Finally,by only using a single radiative patch,the antenna has improved-bandwidths(|S₁₁|<–10 d B)with two-minimum poles in the range of 1.42–1.45GHz for the lower band and 3.95–4.13 GHz for the upper band,respectively,which is about two times wider than that of the traditional counterpart.Besides,the antenna maintains the small thickness of about 0.02λ_0.More importantly,the wide E-plane HPBW and broadside gain of the MPA are simultaneously enhanced to around 130°and 9.0 d Bi at the lower and upper bands,respectively.3.Increasing the number of high order modes and studying the comprehensive regulation of four resonant modes.In this section,a low-profile microstrip patch antenna（MPA）under multi-resonant modes for both bandwidth improvement and pattern diversity is proposed.Herein,the odd-order(TM₀₁ and TM₂₁)and even-order(TM₀₀ and TM₂₀)modes are employed for the generation of broadside-beam and dual-beam,respectively.Firstly,the resonant frequencies of the MPA at these four modes are extensively investigated aiming to reallocate these resonances for bandwidth enhancement.Secondly,the radiated fields of these modes are theoretically studied based on the equivalent magnetic currents.It demonstrates that the distorted radiation pattern of its TM₂₁ mode could be transformed into the broadside-beam by cutting these slots.Most importantly,by properly using these pins,the far-zone radiated fields of its TM₀₀ and TM₂₀ could be successfully reshaped as the dual-beam,especially with the same co-polarized electric-field component.Finally,the MPA has achieved an improved bandwidth(|S₁₁|<-10 d B)in the range of 3.63-3.87 GHz for the overlapped band,which is much wider than the traditional counterpart.Particularly,both of broadside-beam and dual-beam patterns with same polarization are gained under differential and common feeding schemes.Moreover,it holds the small thickness of about 0.056λ₀ while keeping stable gains of around 10.07 and 6.18 d Bi,low cross-polarization and single radiator.