Study On Broadband Array Antenna And Wireless Terminal Antennas

Space division multiple access techniques, broadband adaptive antenna array techniques, frequency-hopping and spread-spectrum techniques, and satellite communication techniques become more prevalent in the modern military secure communication systems, which makes the design and manufacture of broadband omnidirectional miniature antennas and broadband adaptive antennas to be an urgent and important issue. Being associated with three research projects, this dissertation makes deeply insight into the fast and accurate analysis, optimal design and manufacture of a 100-400MHz broadband omnidirectional miniature antenna, a 225-800MHz broadband circular array antenna, seven wireless terminal antennas and a submarine antenna. The author's major contributions are as follows:1. The design and realization of a composite structure cage antenna are presented. Two novel techniques are used for the broadband omnidirectional miniature cage antenna. First, the antenna has a composite structure of cage and asymmetric biconical structure. The impedance bandwidth and radiation pattern bandwidth are enhanced, and the tilting and ripping of radiation patterns are eliminated. Second, a helical shorting wire is used to reduce the antenna height effectively. The helical shorting wire leads to more convenience for routing the feeding wires of array antennas and plays a function of lightning protection.2. A novel wide-band two-element center-fed cage array antenna is investigated. By using the PSO-based impedance matching optimization technology, according to the measured impedance of the antenna, a broadband matching and dividing network is designed. A 100-400MHz matching and dividing network is manufactured and used as the feeding network of the two-element array antenna. The impedance of the array element is improved, and equal amplitudes and same phases are achieved in the broad frequency band. Second, by reusing the feeding coaxial-cable shield as the shorting line of the array element, the problem of routing the feeding wires is solved effectively.3. A 225-800MHz broadband adaptive antenna array is studied. First, particle swarm optimization (PSO) is investigated for the optimal design of the broadband adaptive array antenna beam forming procedure. The 60-degree half power beam width (HPBW), low side lobe level, as well as small front to back ratio, are established as a versatile objective function and optimized simultaneously. Proper radiuses of 225-450MHz and 450MHz-800MHz four-layer circular array antennas are selected for decreasing the effect of the mutual. Second, the feeding networks of the array antenna are presented and studied. The feeding network includes a diplexer (225- 450- 800MHz) and two power dividers (225- 450MHz and 450- 800MHz) using lumped components. The power dividers are designed using the PSO-based impedance matching optimization technology mentioned previously. Third, according to the requirements of wide-band frequency-hopping and spread-spectrum techniques, the cubic spline interpolation (CSI) method is utilized to efficiently obtain the complex excitations at arbitrary frequency points within the working frequency band. An eight-layer circular array antenna working in 225-800MHz is designed successfully.4. Two novel antennas are investigated for small satellite communication. One of them is a multilayer microstrip antenna which can realize right circularly polarized radiation and left circularly polarized radiation simultaneously at receiving frequency band and transmitting frequency band by using the Lange-coupler as an orthogonal feeding network, respectively. The patch coupled feeding and additional lumped filtering network techniques achieve a high port-to-port isolation. Another one is a tapered meander line turnstile dipole antenna. The designed antenna has a size reduction rate of 96% compared with a traditional turnstile dipole antenna, and the impedance is improved by using the matching network optimized by PSO.5. Three mobile phone antennas are investigated for multiband application. A planar meander sleeve monopole antenna is studied for DVB-H/GSM mobile handsets. Another two antenna using combined PIFAs are studied for GSM/DCS and WLAN mobile handsets. By using the meander and reused structure, the antenna size is miniaturized. The reused structure and notching slot improve the port-to-port isolation effectively.6. A Dual-band Toroidal Beam Antenna for WLAN Communications is presented. The antenna mainly consists of six dual-band inverted-L radiating elements and is fed by a two-section six-way microstrip power divider. The effects of the length of two strips, the height of the antenna and the size of ground are analyzed. The two-section microstrip power divider is investigated by analytical method.7. A novel design of ultra-wideband (UWB) antenna for wireless USB (WUSB) flash disk is presented. The baseband module shielding box and the RF module shielding box, two necessary parts for a WUSB flash disk, are subtly used as the radiators, which means that no other radiators are needed for the antenna. A shorting tube is used as the signal wire channel to connect the baseband and the RF modules, which also is a shorting wire of the antenna. 8. A multi-band combined three-in-one antenna for submarine communication is proposed. The three-in-one antenna includes a Beidou dual-band circularly-polarized antenna, an X-band horizontally-polarized omni-directional antenna and a VHF perpendicularly-polarized omni-directional antenna.