Research On Wide Beam-Coverage Microstrip Antenna And SSPP-Based Leaky-Wave Arrays

With the rapid development of modern science and technology,various wireless systems have increasingly higher requirements on the performance of antennas in complex environments,and traditional antennas have become increasingly difficult to meet the needs of modern wireless systems.In various scenarios,the requirements for antennas are also diverse,such as wide beam coverage,multi-polarization,low cost,miniaturization,easy fabrication,modularization,and intelligence.Generally,when an antenna have a wider beam,the antenna can effectively transmit or receive electromagnetic waves in a larger angular range.With the development of modern wireless communication and radar technology,antennas with wider beams or wider beam scanning ranges are needed to improve the coverage of the entire system.MPAs(Microstrip Patch Antennas)are widely used in various wireless systems owning to their advantages such as low profile,low cost,easy fabrication,and easy integration with microwave circuits.At the same time,LWAs(Leaky-Wave Antennas)have been paid much attention,due to their wide angle scanning characteristics without expensive and complicated beam control network.Therefore,research on a MPA with wide beam coverage and LWAs with wide-angle scanning is of great theoretical significance and practical engineering value.This dissertation is mainly concerned with design of the pattern-reconfigurable MPA with wide beam coverage and wide angle scanning LWAs.The major works and main contributions of this dissertation are outlined as follows.1.Design of a TM₃₀/TM₄₀-mode pattern-reconfigurable MPA for wide beam coverage.A novel two-state multi-lobe pattern-reconfigurable MPA for wide beam coverage is proposed,where two states are realized by two higher modes,and a multi-lobe pattern is employed for each state.First,the equivalent transmission line model is used to analyze input impedances of the dual-mode MPA.By adjusting sizes of the capacitive coupling patches and profile of the MPA,the frequency bands of TM₃₀ and TM₄₀ modes are controlled,yielding a band intersection.Then,the cavity model is used to analyze complementary patterns of these two higher modes.By controlling length of the radiating patch,the beam-level differences of TM₃₀-mode and TM₄₀-mode patterns are reduced,respectively.In addition,the directivities of the dual mode MPA are studied.Two parasitic patches are also loaded.As a result,the mode-gain difference between TM₃₀ and TM₄₀modes is small.Finally,these two patterns are combined through reconfigurable technology to achieve a wide 3-dB beam coverage,which is wider than 141°.The three-lobed pattern and the four-lobed pattern in the two states have 7 beams with all the beam overlap levels greater than-3 dB.Experimental results verify that the novel two-state pattern reconfigurable method for wide beam coverage is effective.2.Design of dual-linearly polarized frequency-controlled beam-scanning microstrip LWAs based on S-SSPPs(Symmetrical-Spoof Surface Plasmon Polaritons)lines.Based on S-SSPPs transmission lines and radiation patches with different types,two LWAs with dual-linearly polarized radiation are designed.First,differential and common mode excitations are used to effectively separate the electric-couplings and magnetic-couplings between S-SSPPs transmission lines and TM₁₁-mode circular microstrip patch array,which make the patch array radiate V-pol(Vertical Polarization)and H-pol(Horizontal Polarization)electromagnetic waves,respectively.In addition,the cross polarization levels for each polarization state are suppressed at the same time.Then,a square microstrip patch array fed by S-SSPPs transmission lines are also excited by differential and common modes.In this case,TM₁₀ and TM₀₁ modes of the square patch array excited by the separated electric-couplings and magnetic-couplings radiate V-pol and H-pol waves,respectively.Finally,two high-purity dual-linearly polarized frequency-controlled beam-scanning microstrip patch arrays are designed.Measured results of the circular microstrip patch array show that the antenna radiate H-pol waves with common mode excitation.In 11.5?14.4 GHz band,the main beams scan from-24°to+25°with cross polarization levels less than-30 dB.The maximum gain is 13.0 dBi.With differential mode excitation,the scanning range of the V-pol array is-44°?+23°in 10.5?14.2 GHz band.The maximum gain and cross polarization level are 13.1 dBi and-30 dB,respectively.The performance of the dual-linear polarized LWA is good.3.Design of a dual-linearly polarized frequency-controlled beam-scanning microstrip LWA based on SSPPs(Spoof Surface Plasmon Polaritons)and SIW(Substrate integrated Waveguide).First,a circular patch array antenna with a suppressed OSB(Open-Stop Band)is fed by SIW slots.This V-pol antenna scans from backward to forward,and the scanning characteristics can be adjusted by parameters of the SIW feeding network.Then,a circular patch array antenna fed by a double-side SSPPs transmission line radiates H-pol waves.It also scans from backward to forward,and its scanning characteristics can be adjusted by parameters of the SSPPs transmission line.Finally,by using the shared aperture technology,the V-pol antenna fed by the SIW and the H-pol antenna fed by the SSPPs are combined to design a dual-linearly polarized LWA.Isolations of the dual-polarized LWA are higher than 22 dB.For the H-pol state,the LWA scans from-26°to+32°in 11.4?14.5 GHz band,and its maximum gain is 14.1 dBi.For the V-pol state,the operating band is 10.3?15.1 GHz.The LWA scans from-39°to+24°with gain less than13.4 dBi.It is worth mentioning that the scanning characteristics of each polarization state are freely and independently adjustable.4.Design of a high radiation efficiency and polarization purity LWA based on double-asymmetrical SSPPs.First,the effect of the array structure on the H-plane cross-polarization level and the radiation efficiency of the antenna are analyzed in detail.Then,double-asymmetrical technology are utilized to suppress the OSB.Finally,a high radiation efficiency and polarization purity LWA is proposed.The maximum radiation efficiency of the proposed LWA is as high as 81%.Measured results show that,the LWA can scan from-15.7°to+77.6°in 10.7?14.3 GHz band,and its maximum gain is 12.9 dBi.The E-plane cross-polarization levels are less than-26 dB.In addition,the H-plane cross-polarization level at the broadside frequency(11.4 GHz)is less than-25 dB.5.Design of wide-angle scanning circularly polarized microstrip LWAs based on SSPPs.A circularly polarized elliptical patch array is excited by the electromagnetic couplings between the SSPPs transmission line and the patch array.The LWA scans from-36oto+43owithin 11.0?15.0 GHz.In the operating band,the ARs are less than 3 dB.The maximum gain and radiation efficiency are 13.3 dBic and 87%,respectively.Based on this,a method for redistributing the excitation distribution of the radiation patch array is proposed to realize a tapered distribution.At the same time,the inter-element phase differences,which control the beam directions,change a little.Thus,the maximum SLLs of the radiation pattern are reduced without changing the beam scanning characteristics.The circularly polarized LWA scans from-14oto+38o,and its SLLs are lower than-20 dB.