The Design Of Antenna Worked On The Mental Surface In UHF Band

Many highly integrated miniature systems are required to communicate at RF wavelengthsmuch larger than their own physical size, requiring an “electrically small antenna”(ESA). As thetrend towards miniaturization and multifunctionality in wireless devices progresses, the need forrelatively effcient and environmentally agnostic electrically small antennas in every frequencyband becomes more acute.First, the center frequency of470MHz for electrically small antenna is designed in this thesis;the improvements of capacitive loading PIFA antenna successfully met the design requirements.The volume of the antenna is50mm26mm9.2mm，and-10dB bandwidth of the antenna is6MHz. A reconfigurable electrically small antennas is designed on the basis of the electrically smallantenna, it can work properly in free space and on the metal surface in the center frequency of470MHz.Second, a novel antenna worked on the mental surface for ultrahigh frequency (UHF) bandradio frequency identifcation (RFID) is designed in this thesis. The antenna is fabricated on a verythin substrate with thickness of0.8mm.The capacitive coupled feeding technique is used toperform a broadband operation. Bending a long patch into four half-wavelength radiating elementsmakes the surface currents of all radiating elements in phase, thus achieving an enhanced antennagain and a good reading range performance. Finally, the antenna is analyzed with HFSS and theReturn Loss (less than-10dB) cover the902-928MHz UHF RFID systems. The antenna is made ofinexpensive FR4board, fully planar structure, it is easy to process. Through the measurement: tagantenna in free space maximum reading distance of3.2m, maximum reading distance of the metalsurface1.9m, which achieved the expected results.