Adaptive Multifilar Antenna

About

“With LTE, the demand for more and more bands on a smartphone has and will continue to increase, which has at present driven OEMs to simply include more antennas, each tailored for a specific frequency. Smartphones can contain as many as four or five antennas, which poses a considerable challenge for engineering a device, as number of antennas and their placement is often in direct competition with industrial design and other considerations. Actively tuned antennas aren’t anything new for antennas in other RF applications, but they are a relatively new thing in the smartphone and tablet space. In the past that was primarily because it was easy enough to tune a design to the handful of bands the handset was designed for. The challenge of getting an antenna with the right impedance increases. Description A multifilar antenna ( 200 ) comprises n spaced antenna filaments, where n is on integer greater than 1; a matching circuit ( 210 ) for matching the characteristic impedance of the antenna to that of a transmitting and/or receiving apparatus; a weighting circuit ( 240 ) for applying respective gain and phase adjustments to signals passed to or from the n filaments; switch means ( 310 ) associated with each filament for selectively altering the electrical length and/or interconnections of the filaments; means for detecting electrical properties of the multifilar antenna with respect to the frequency, polarisation and/or direction of propagation of a signal to be received or transmitted by the multifilar antenna and/or impedance matching of the antenna; and control means ( 230 ), responsive to the detective means, for controlling the operation of the matching circuit ( 210 ), the weighting circuit ( 240 ) and the switch means ( 310 ) to adjust the properties of the multifilar antenna ( 200 ) to suit better a current signal to be received or transmitted. US7034773 (B1) - Adaptive Multifilar Antenna