Study And Design Of Compact And Broadband Antennas In Wireless Communication System

With the rapid development of modern wireless communication technology, the miniaturized and broadband antennas for various kinds of mobile equipment are requested. At the same time, considering multipath fading of antenna signal transmission, polarization diversity technology has been widely studied and used. In this thesis, the compact broadband antennas and ultra-wideband polarization diversity antenna are studied. The main contents of this paper are as follows:1) A multi-frequency broadband planar antenna is designed for modern ultra-thin mobile phone. It comprises some strip lines used to exciting three resonant frequencies,900 MHz,1800 MHz and 2400 MHz. The miniaturization of the antenna is achieved by bending the strip line. Also, by adjusting the gaps between the strips the bandwidth of antenna is broadened. The realized antenna is compact with a total size of 40 mm×100 mm×0.8 mm. Also, the antenna can operate at 825 MHz-975 MHz and 1450 MHz-2775 MHz.2) A small and broadband square monopole antenna is designed. It is composed of rectangle radiating patch with inverted H-slot and the ground plane with H-type conductor-backed plane. The measured results are in agreement with the simulated results. Antenna can operate at a bandwidth of 3.1 GHz-10.6 GHz. Moreover, in the whole band, the antenna basically keeps the same radiation pattern and the measured average gain is 4.8 dBi.3) A compact ultra-wideband polarization diversity antenna with high isolation is designed. It comprises a step-tapered slot antenna and a small square monopole antenna. In order to increase the bandwidth of the antenna, H-slot is etched on square radiating patch and H-shaped conductor-backed plane is added to ground plane. The step-tapered slot antenna is the horizontal polarization and square monopole antenna is vertically polarization. The isolation between the two ports is improved due to the orthogonal polarization mode. The simulated and measured S-parameters results show that the polarization diversity antenna can operate at a bandwidth from 3.1 GHz to 10.6 GHz and the average isolation between the two ports is better than 30 dB.