Spiral antenna with adaptive radiation pattern under electronic control

Variations are introduced in the current flow of the outer circumference of the spiral antenna by applying short circuits at different points on this section of the antenna. Both one-point and two-point short-circuits are considered. It is shown that the direction of the antenna beam is a function of the position of the short-circuit(s), with the gain staying uniform within /spl plusmn/1 dB and VSWR changing within acceptable limits. The antenna can be used in applications requiring adaptive beam direction. Limitations of the technique to control the beam direction are also addressed.