Broadband And Multiband Antennas Based On Composite Right/Left Handed Structures

The internal mobile phone antennas should be compact and able to work at widebandand multi-band. Designing small wideband and multi-band antennas for small mobile phonesis one of the most challenging tasks. In general, it is more difficult for a conventional mobilephone antenna to operate efficiently at a lower frequency since the size of its ground size isnot big electrically. Besides, the antennas should be of a low profile because the modernmobile phones prefer to be thinner. Microstrip antennas are compact and of low profile, but itsbandwidth is too narrow to satisfy the wideband requirement. In this paper, we realize antennaminiaturization and wideband/multi-band operation by making use of the theory of compositeright/left handed (CRLH) transmission lines.We first introduce the background of the design for mobile phone antennas and somebasic theory of antennas and transmission lines. We systematically explain the theory ofCRLH transmission lines and its application to zero-order resonance antennas. The theoreticalanalysis shows that the CRLH structures can be used for antenna miniaturization.Second a small wideband planar antenna for DVB-H and GSM-900applications isproposed based on the theory of CRLH transmission lines. The resonant frequency iscontrolled by four CRLH parameters and is not relevant to the size of antenna. A bandwidthof70%is achieved for the frequency band from470MHz to960MHz. The gain andradiation pattern are also satisfy the requirement by DVB-H and GSM-900applications. Byusing the CRLH structures, this antenna not only has a wider bandwidth but also has a smallersize than a conventional antenna.Finally a small triple wideband planar antenna is proposed based on two CRLH units.The resonant frequencies are controlled by four CRLH parameters and a slot structure. Thebandwidths achieved cover the frequency bands685MHz-2.74GHz,3.15GHz-3.84GHz and4.9GHz-6.1GHz. It is shown that antenna miniaturization and wideband/multi-bandoperation can be realized by combining the CRLH and slot structures.