Application And Design Of Miniature Printed Antennas In Broadband Communacations

Three kinds of planar printed antennas are designed and developed in this thesis and the main work is summarized as follows:An ultra-wide band antenna with coplanar waveguide feed has been designed, the work frequency band of the antenna is ultra wide band communication frequency(3.1 to 10.6 GHz). It has the characteristics of compact structure, small size and flat standing wave ratio. Besides, H plane is omnidirectional pattern. In order to avoid the interference from other communication standards to ultra-wideband communication, we design three stop-bands in the ultra-wideband antenna. The first stop band is realized by sculpture two inverted L type slots in the radiation patch which are symmetrical to feed line. The length of slot is about a quarter of wavelength for the center frequency and filter frequency band is WIMAX(3.3 to 3.6 GHz), the maximum VSWR is ten;The second stop-band is obtained by etching two slots on each side of the floor. The length of slot is approximately a quarter of wavelength for the center frequency and filter frequency band is WLAN(5.125 to 5.825 GHz), the maximum VSWR is ninet. By adding a split ring on the underside of the dielectric substrate, we design the third stop-band. The perimeter of the split ring is approximately a half of wavelength for the center frequency and filter frequency band is the maritime satellite communication frequency(7.25 to 7.75 GHz), the maximum VSWR is six.We design a multiband antenna by combining ultra broadband and narrowband. The antenna floor and radiation patch are on different sides of the antenna. The bandwidth is expanded by etching a rectangular slot on the upper edge of the floor and satisfies the ultra broadband communications(3.1-10.6 GHz).Two pass-bands out of ultra wide band are realized by etching slots on two edges of radiation patch. Through controlling the position, length and width of the slots, we make it meet the three communication standards GSM uplink frequency band(1.710 to 1.785 GHz) and WLAN(2.4 to 2.48 GHz).A frequency reconfigurable antenna is designed based on the planar slot antenna. The antenna size is 25?20?1 mm3. On the back of the antenna, we etch a main radiation slot in the middle. Then, we etch two rectangular slots on both sides of the main radiation slot and load the four diodes in the slots. There are three frequency work modes:(1) The working frequency is WIMAX(3.3 to 3.6 GHz).(2) The working frequency is WLAN(5.725 to 5.825 GHz).(3) The both of the mode one and two are working at the same time. By adjusting the diode on-off state to control the work modes, they can be switched freely. The patterns of three modes are very similar. It realizes the desired design goal.