Research And Design Of Antenna In Mobile Terminal System

In recent years, with the rapid progress of the wireless communication technology, the demand for the mobile terminal antennas becomes increasingly higher. Nowadays, the trend of mobile terminal systems is tend to be miniaturization, multi-functionalization and this not only increases the complexity of the electromagnetic environment around the antennas but also requires antennas to cover more frequency bands for terminal applications. The design of mobile terminal antennas put emphasis up on the properties of multi-frequency, multi-polarization and miniaturization of the antennas. In this thesis, we mainly focus on the design of different kinds of antennas used in different field and how to realize the multi-frequency, multi-polarization and miniaturization of these antennas.1. A dual-frequency and dual-polarization Beidou satellite navigation antenna is presented. In the design, the dual-layer of dielectric-slab is used to realize the dual-band and dual-polarization of the antenna. The material of the dielectric-slabs is FR4 and the thickness of it is 1mm. The S parameters of the Beidou satellite navigation antenna meet the requirements in the transmitting frequency band(1611-1621MHz) and receiving frequency band(2487-2497MHz). The polarization of the transmitting antenna is left-hand circular polarization and the polarization of the receiving antenna is right-hand circular polarization. The proposed antenna has been successfully simulated and measured. Comparisons between the simulation and measurement results show a good agreement, the antenna has good far field radiation characteristics and the isolation between the transmitting antenna and receiving antenna can meet the requirement.2. A novel rectangle-shaped aperture antenna for ultrawideband(UWB) applications with triple band-notched characteristics is presented. By attaching a frequency selective surface(FSS), triple notched frequency bands centered at 3.5, 5.7 and 8.2 GHz are obtained. The frequency selective surface(FSS) is loaded in the aperture over the microstrip feed line. The proposed antenna has been successfully simulated and measured. Experimental results indicate that the proposed antenna yields an impedance bandwidth of 2.55-12 GHz with VSWR ￡2, except the triple notched bands of 3.15-3.85 GHz(Wi MAX band), 5.4-6.1 GHz(WLAN band) and 7.8-9.3 GHz(X-band satellite communication). Moreover, the overall dimension of the proposed antenna is 30′35′1.5 mm3. Comparisons between the simulation and measurement results show that the UWB antenna has broadband matched impedance values and stable radiation patterns for all radiating frequencies.3. A wireless local area network(WLAN) external antenna which can be used for the 3G/4G communication is presented. The proposed antenna has been successfully simulated and measured. Experimental results indicate that the proposed antenna yields impedance bandwidth of 700-960 MHz and 1710-2700 MHz with VSWR ￡3. The antenna adopts the form of planar monopole antenna with a compact and low profile structure. Comparisons between the simulation and measurement results show a good agreement, we can find that the antenna has good far field radiation characteristics.4. A multi-antenna system of the multifunctional interphone is presented and the external antenna of it is designed according to the proposed external antenna in the previous section. There are other three antennas in the multi-antenna system, such as the main built-in antenna, GPS antenna and Wi-Fi antenna. The external antenna is a representative planar monopole antenna and the measurement results indicate that the external antenna can cover 380-400 MHz, 400-470 MHz, 1447-1467 MHz, 1785-1805 MHz and 2300-2400 MHz bands. The main built-in antenna is a PIFA antenna and it can cover 791-960 MHz, 1447-1467 MHz and 1710-2170 MHz bands. The GPS antenna and the Wi-Fi antenna are very close and the measurement results indicate that they have good performance in their working frequency bands. Comparisons between the simulation and measurement results show a good agreement and we can find that the antennas has good far field radiation characteristics and the isolation between the antennas can meet the requirement.