Research On Novel High Performance Artificial Magnetic Conductor-Based Microstrip Patch Antennas

Low profile,light weight,low cost,compact and planar configurations are among the requirements for antennas to be used in modern wireless communication systems,such as wireless local area networks(WLAN),radio frequency identification(RFID),global positioning systems(GPS),etc.Moreover,antennas with wide impedance bandwidth(IBW)and good radiation patterns are preferable in many modern mobile and wireless broadband communication systems,as they increase these systems data transfer speed.Although a conventional microstrip patch antenna(MPA)is planar,low profile and compact when printed on a high ?r material,it has a narrow IBW(<5%),low gain(<6 dBi),low aperture efficiency and large size at lower frequency.In this dissertation,surface wave(SW)propagating on an artificial magnetic conductor(AMC)surface is employed to improve the IBW and radiation performances of the MPA,whereas the in-phase reflection property of the AMC is used to greatly reduce the MPA profile.Four AMC-based novel MPAs,namely,thin-profile,high-gain and wideband AMC-based U-slot cut MPA;compact wideband AMC-loaded MPA with high gain and higher aperture efficiency;AMC-based MPA with wide 3-dB gain bandwidth;and AMC-inspired single-layer low-profile microstrip antenna are modeled,designed and experimentally validated.The simulations and measurements show a very good consistency between them.The main contributions of this work can be summarized as below:1.The historical background of the MPA and that of the artificially engineered material with electromagnetic(EM)properties that are not otherwise obtainable with natural materials,as well as the state-of-the art of the AMC-loaded microstrip antennas,are thoroughly presented.Analytical methods utilized to analyze the in-phase reflection and surface wave properties of the AMC structure,the effect of the surrounding material on the AMC properties,and the different techniques employed to the measure the AMC properties are also discussed.2.A thin-profile,high-gain and wideband AMC-based U-slot cut MPA is developed to overcome the high profile of the conventional U-slot cut MPAs printed on a PEC-GND.To achieve a wider IBW,two rectangular slots are cut on the AMC near the two radiating edges of the rectangular MPA to free the fringing E-fields,which decreases the antenna total quality factor(Qt),and thus enhancing the resultant antenna IBW.Moreover,four strips and a defected ground structure(DGS)are introduced on the AMC and PEC-GND,respectively,to improve further the IBW and gain at the upper band edge.With this design strategy,an antenna with a profile of h?0.03?0 can realize an IBW of above 30%,a peak gain of 10 dBi and a very low weight,making it a good candidate for conformal wideband applications3.A compact(lateral size S<?0:is the wavelength in free space)wideband,high-gain and improved aperture efficiency AMC-loaded MPA is realized by suppressing the deleterious effect of the parasitic overlay capacitor created between the AMC and the MPA on the IBW,and introducing a set of shorting pins at the AMC center.By integrating the shorting pins into the AMC structure,the AMC becomes a composite right-left hand transmission line,leading to more in-phase current distributions on the AMC-surface,which improves the antenna gain.The antenna achieved a measured IBW of more than 25%,peak gain of better than 9.5 dBi and a simulated peak aperture efficiency of higher than(100%).The proposed antenna is good candidate for closely spaced antenna systems,such as radar,multiple-input multiple-output(MIMO),dish feed antenna,etc.4.The effects of the antenna(top)substrate on the SW travelling along the interface between the bottom and top substrates is investigated for the first time.It is shown that the loading of the upper substrate increases the effective permittivity of the AMC,which in turn,reduces the resonance and the transverse magnetic TM S W propagation constant of the AMC,respectively.By truncating the top(antenna)substrate,the TM SW propagation constant and effective permittivity are reduced,which enhances the antenna IBW and 3-dB gain BW to about 40%.The wide IBW is due to the reduced(Qt)and closely spaced multi-resonant modes,while the enhanced 3-dB gain is due to the reduced propagation constant of the TM SW.5.A new planar and printed wideband AMC-inspired antenna excited using a thin microstirp line feed network in the form of a crossed dipole is developed.The feed network act as an electric dipole,whereas the AMC cells behave as a magnetic dipole,and together they form a low profile(0.05?0)printed complementary antenna(magneto electric dipole antenna)with wide IBW of(>40%),stable gain and radiation pattern with identical 3-dB beam widths in E and H-planes,low cross-polarization and back radiation levels.