Voltage controlled variable tuning antenna

Abstract

A catheter shaft carries a coaxial cable, the terminal end of which contains a dipole antenna with opposing first and second helical elements. The first and second helical elements originate from a common connection to an outer conductor of the coaxial cable. The first and second helical elements are formed by winding flat wire around an outer insulator of the coaxial cable near a terminal end of the coaxial cable. A variable, controllable impedance is connected between an inner conductor of the coaxial cable and a point on the second helical element where the resistive component of the antenna's impedance matches the characteristic impedance of the coaxial cable. The impedance match minimizes reflective losses of the antenna, thereby maximizing power transferred to the antenna. The antenna has an effective electrical length which is equal to one-half the wavelength of the radiation emitted, independent of the physical length of the antenna. The antenna also has a radiation length which can be adjusted by varying the number in pitch and turns of the flat wire and the location of the impedance matching point.

Dependencies are inferred from the claim text.