WLAN Antenna For Terminal With Metal Boundary

With the massive application of wireless network communication,people now are available to access the Internet more efficiently and conviniently.Among many possible technical solutions,wireless local area networks(WLANs)are most ubiquitous in building reliable,speedy and secure connections between mobile terminals and the Internet,and its most frequently used standard includes IEEE 802.11a/b/g.The multi-functional,intelligent,ultra-thin,ultra-lightweight and metal texture mobile terminals lead the trend of its future development.Served as the transmitter and receiver for modulated WLAN signals in mobile terminals,antennas are particularly important for the overall performance of wireless systems,which brings enormous opportunities and challenges for the antenna design.Although it is gifted with excellent performance,the traditional WLAN antennas are large in size and are not applicable for the metal boundary conditions as well.In view of this,the research and design of WLAN antennas which are accord with the developing trend are practical and significant.Firstly,some WLAN protocols and related technologies are introduced,and then the state of the art of WLAN antennas,technical problems to be solved in this paper and related design techniques are detailed respectively.Secondly,two loop-based kinds of WLAN antennas with extreme low-profile and the capability to be suitable for the full metal boundary conditions,such as tablet applications,are proposed.The target tablet occupies a size of 10.1 inches(about 250 mm × 170 mm)and its screen size and screen thickness are 232 mm × 130 mm,3 mm,respectively.Hence,the reserved space for antennas is extremely limited.The prominent highlight and innovation of the proposed dual-band WLAN antennas should grant to its extreme low-profile(with thickness of only 3 mm);Resonant at 2.4 GHz and5.8 GHz respectively,the first antenna is a kind of double-loop structure and occupies an area of 26.8 mm × 8.5 mm.The second antenna structure incorporates the loop antenna and the IFA antenna.The resonance of 5.8 GHz originates from the loop structure and the lower resonance at 2.4 GHz can be attributed to the IFA structure correspondingly.The overall size of the second configuration is only 31.9 mm × 6 mm.The two structures generate some new ideas for future mobile terminals with low-profile and full metal boundaries.Thirdly,based on the previous two schemes,three novel dual-band omnidirectional WLAN antennas with symmetrical rings are presented.The first design is based on the double-loop antenna of the first scheme,which consists of six symmetrical ring antennas.its structure can be divided into two layers: the physical size of the upper layer corresponds to half a wavelength of the 2.4 GHz wave,and the physical size of the bottom layer is half a wavelength of the 5.8 GHz wave.The second design is actually a new type of the IFA antenna based on the second scheme.In this design,six IFA antennas are arranged in centrosymmetry.The second scheme and the third scheme share the same design mentality,to neutralize the influence from the ground plane and compress the profile of antennas.The three deigned centrosymmetric antennas perform pretty well in impedance matching and omnidirectional radiating within spherical or hemispherical space,and cover the operating frequencies of 2.4 GHz/5.8 GHz.Finally,A miniaturized circular microstrip antenna for unmanned aerial vehicles(UAVs)is proposed.It fully utilizes the bracket part of the UAV to stabilize the radiation pattern when its camera is in rotating.the antenna occupies a size of ? ×102mm2× 3mm and is with wide bandwidth and omnidirectivity in hemisphere domain It is indicated that the designed antenna is particularly suitable for 5.8 GHz WLAN communications.The designed two ultra-low-profile WLAN antennas with metal boundary,three omnidirectional antennas and an antenna for UAVs all possess good impedance characteristics and excellent omnidirectivity.Furthermore,the measurements show that the return loss is more than 10 dB in the whole bandwidth and the radiation efficient is greater than 60%,which totally meet the specified engineering requirements.