Research On Compact Tunable Antennas And Diversity Characteristics For Mobile Devices

The rapid growth of portable device market has increased the need of multi- function and small-sized devices. As a new growth point in the market, terrestrial digital television broadcasting services are used in various consumer electric products. For its low frequency and wideband operation, the integrated DTV antenna for mobile handset has become a new challenge in antenna design.In this thesis, three aspects are studied. First of all, a compact PIFA antenna element prototype with varactor tuning is designed. Through software simulation and manual adjustment, the tuning function of this DTV antenna is realized. The antenna covered most of DTV band, and the feasibility of tuning scheme is verified.Secondly, the prototype antenna is ameliorated to deal with its shortage. A new monopole integrated antenna structure is developed within the limited interior space of the device. At the mean time, a novel switchable matching scheme is proposed. This scheme is verified with parameter simulation.Next, the electrically controllable matching circuit is developed. Some related topics including effects of parasitic parameters are also studied. The layout of the circuit is optimized to reduce effects of parasitic parameters, and two stages of the circuit are compensated by adjustment. An ameliorated scheme for future development is also proposed.Last, a series of measurements have been carried out. Two diversity antennas are measured respectively. The return loss characteristics, pattern and peak gain of each antenna are measured and studied.