Low Rcs Microstrip Array Antenna

In this thesis, radar cross section (RCS) reduction of microstrip planar patch antenna array is introduced and researched.In Chapter One, the concept and application background of RCS are briefly introduced. And the differences between antenna RCS and ordinary RCS are emphasized in this chapter.In Chapter Two, the methods of reducing array antenna RCS are discussed. These methods are divided into two classes according to the conformation. The first one is reducing RCS of each element of an array. The second one is treating an array as an integer to reduce RCS. These methods can also be sorted into two types as RCS full-time reduction and part-time reduction according to performing time. In this thesis, the latter is mainly discussed.In terms of RCS full-time reduction methods, the effects of circular apertures, defected ground structures (DGS) and shorting posts are introduced in Chapter Three. Finally, a rectangular patch antenna with two circular apertures, a DGS and a shorting post is optimized. Compared with the original patch antenna, the RCSs of the new antenna are reduced in a large frequency band. At the same time, the return loss and radiation pattern are maintained, and the decrease of gain is acceptable.In terms of RCS part-time reduction methods, a novel reconfigurable Yagi-Uda substrate is proposed in Chapter Four. This structure is composed of Yagi-Uda microstrip arrays etched on a substrate. When the structure is put directly on the top of a metal ground or a planar patch antenna, the reflection of normal incidence radar wave is deflected at certain frequencies. Thus, the monostatic RCS is reduced. To guarantee antenna's working, a reconfiguration technique is used to maintain radiation. Using the reconfiguration technique further, the resonant frequency can be shifted to broaden the lowest-RCS bandwidth. So the target's RCS can be reduced in a broad frequency band with this reconfigurable Yagi-Uda substrate.In Chapter Five, the thesis is summarized. And the improvability and potential applications of the reconfigurable Yagi-Uda substrate for array RCS reduction are forecasted.