Reconfigurable antenna design for mobile handsets including harmonic radiation measurements

The design of a reconfigurable antenna with good load matching and covering a wide frequency range presents a practical challenge when the antenna size is tightly constrained. A procedure is presented for the design of a reconfigurable mobile antenna, which overcomes the antenna size limitations. Tuning is achieved by placing a varactor diode at a specific position across a slot in the radiator conducting surface. The fabricated antenna is designed to cover a wide band, between 1700 and 2040 MHz, at a return loss better than 10 dB. The radiation of harmonics generated because of the varactor non-linearities are simulated and measured. The experimental set-up ensures that the low levels of radiated harmonics are reliably validated. The experimental results show good agreement with that computed using the Friis equation.