Methods and devices for generating and delivering shaped microwave fields

A medical device for treating tissue by applying a microwave energy from a transmission line coupled to a power supply, the medical device comprising:

• an antenna comprising a radiating element, a shaping element and a dielectric piece;
• the shaping element being electrically grounded using the power supply;
• the dielectric piece having a distal end portion extending along a center of the antenna on a longitudinal axis of the antenna;
• and
• the radiating element having a first portion and a second portion, and a middle portion therebetween which collectively form a working profile, the radiating element configured to be constrained within a delivery device and to assume the working profile when unconstrained, where the radiating element is coupled to the dielectric piece, wherein the first portion and the second portion are coupled to the dielectric piece where the first portion and the second portion are spaced apart and extend in opposite directions longitudinally along the longitudinal axis, and where the distal end portion of the dielectric piece is directly coupled to the middle portion;
• and
• wherein application of microwave energy from the power supply to the antenna generates a microwave field.