Analysis And Design Of Printed Antenna Based On Open Slot

Printed slot antenna is widely used in modern wireless communication systems,especially mobile terminals for its low profile and other characteristics such as easy to integrate.In this paper,the effect of the feeding structure on the open slot antenna is discussed.A tri-band slot antenna and a four-port slot antenna are constructed to apply in the mobile terminal as well as indoor base station systems.As far as the open slot antenna is concerned,especially the narrow substrate slot antenna,the feed structure can easily affect the antenna's radiation characteristics.If we use the microstrip line to feed the open slot antenna,the terminal short-circuit microstrip line can maintain the performance of slot antenna and carry out the effective excitation.However,if take the coaxial line as the feedline,the inner conductor of the coaxial line should be tilted 45° with the slot lengthwise direction to easily meet the resonant requirement of the open slot.These two kinds of feeding methods can ensure that the slot antenna shows high polarization purity.On the other hand,applying the SMA connector directly on the open slot as feed port,although it helps to simplify the antenna structure,can reduce the polarization purity of the slot antenna.The multi-frequency slot antenna structure can be realized by loading other slots in the narrow slot radiating element.And halved processing,by feeding the slot structure using slotline,can realize its multi-frequency characteristics under the premise of reducing the antenna size and maintaining its characteristics.The antenna based on this construction can work in three wide bands of WLAN and WIMAX.In fact,the enhancement of the operating bandwidth is caused by the multi-cavity coupling between the slots,in comparison to the slot directly loading into the feedline.As for the printed four-port antenna of quadrature slot elements,due to the difference in polarization,the port isolation between two adjacent slot elements is larger than that of the diagonal two slots,although the former two have smaller distance.In order to further improve the isolation between ports,a cross shape closed slot structure is introduced in the metal layer center of the antenna,which helps reducing coupling between ports with its band rejection resonance characteristic.This structure antenna of 2.26-2.63 GHz band can provide larger than 24 dB isolation.