Interface joint for an electrosurgical apparatus

An interface joint for interconnecting an electrosurgical generator and an electrosurgical instrument, the interface joint comprising:

• a housing made of electrically insulating material, the housing having:
• an inlet for receiving radiofrequency (RF) electromagnetic (EM) energy or microwave frequency EM energy from the electrosurgical generator, and
• an outlet;
• and
• a coaxial cable assembly for connecting the outlet to the electrosurgical instrument, the coaxial cable assembly comprising a first cable section and a second cable section, wherein the first cable section has a lower loss per unit length than the second cable section;
• wherein the first cable section and the second cable section are coupled together by a transition portion, wherein the transition portion comprises a tapering section of coaxial cable in which at least one of applies:
• an inner conductor of the tapering section of coaxial cable tapers;
• an outer conductor of the tapering section of coaxial cable tapers;
• or
• a dielectric material of the tapering section of coaxial cable tapers;
• and
• wherein a ratio of an inner diameter of the outer conductor to an outer diameter of the inner conductor is constant through the tapering section.