Research On Microstrip Antenna Feed Network Based On Gap Waveguide

Gap waveguide represents a state-of-the-art transmission line structure that emerges in recent years.By utilizing the periodic electromagnetic bandgap(EBG)structure,it suppresses electromagnetic wave propagation in specific frequency band so as to eliminate electromagnetic leakage.Because of its full metal structure and the advantage of no need for electric contact,it boasts excellent properties such as low loss,large bandwidth,and convenient manufacturing,which makes it fairly suitable for millimeter-wave and other high frequencies.Based on the gap waveguide technology,this paper proposes a number of gap waveguide feed networks designed for microstrip antenna arrays,and the scientific research is outlined as follows:1.The structure of gap waveguide is analyzed.By studying the EBG element structure of the gap waveguide,and analyzing the influence that the parameters of the rectangular pin wield on the stopband,the Ka-band ridge gap waveguide(RGW)transmission line is designed.The transmission loss is compared with the common microstrip and rectangular waveguide.2.A microstrip array antenna fed by RGW is designed.The microstrip and RGW power divider are designed respectively.The comparison shows that the RGW power divider has the advantages of low loss,large bandwidth,and high output amplitude and phase balance.Then,the rectangular waveguide transition structure and the RGW coaxial transition structure are designed separately.By combining with the RGW power divider,an 8×8 feed network of microstrip array antenna has come into being.Compared with the conventional microstrip antenna,it features higher radiation efficiency.3.The RGW-microstrip differential transition structure is proposed.On the basis of the common rectangular aperture coupled microstrip antenna,the "H" slot is integrated into the RGW-microstrip differential transition structure,which not only improves the impedance matching and reduces the loss,but also produces more stable differential signals.Combined with the rectangular waveguide-ridge gap waveguide differential transition structure,a dual differential feeding network is formed to feed the 8×8 microstrip antenna array,thereby reducing the H-plane cross-polarization level from-18 d B to below-55 d B.Furthermore,it increases the antenna gain and enhances the symmetry of the E-plane radiation pattern.4.The gap waveguide monopulse comparator network is improved.By using a tapered groove width and triangular transition structure,it effectively boosts the impedance matching and bandwidth of the difference port.A ridge gap waveguide structure is developed to feed the sub-array through the aperture coupled of the bottom metal plate,which realizes the integration of the sum-and-difference network and the microstrip antenna array.Consequently,it inspires the design of a monopulse microstrip array antenna fed by gap waveguide,which possesses the properties of high gain and low profile.