Tunable dipole antennas

The concept of extending the operating bandwidth of a dipole has been investigated, and two bandwidth extension approaches were studied. The first approach involves the use of parasitic elements to physically change the length of the dipole. The second approach involves capacitively loading a dipole via varactor diodes to produce a travelling-wave dipole. Results are reported for the parasitic approach, which produces a broadband or multifrequency structure. The multifrequency antenna is controlled by an applied bias voltage. Simulations of the antenna showed the relationship between the diode junction capacitance and the isolation between the active and nonactive regions of the dipole.<>