Surgical cutting apparatus (100, 200, 300, 700, 800) having: a microwave radiation source (102, 202, 302, 360, 702, 802) arranged to generate a first microwave radiation signal having a first frequency and a second microwave radiation signal having a second frequency; a surgical instrument (104, 304, 400, 500, 600, 704, 804) having a cutting element comprising: a blade with an edge (402, 404, 502, 504, 602, 604) for cutting biological tissue, and a first antenna (410, 510, 610) connectable to the source to receive the first microwave radiation signal and arranged to emit a substantially uniform microwave radiation field at the first frequency along the edge of the blade of the cutting element, and a second antenna (416, 508, 611) connectable to the source to receive the second microwave radiation signal and arranged to emit from the surgical instrument a microwave radiation field at the second frequency, wherein the second frequency is lower than the first frequency, and wherein the edge (402, 404, 502, 504, 602, 604) of the blade of the cutting element comprises a radiating portion for the first antenna (410, 510, 610) and the second antenna (416, 508, 611) is mounted adjacent the edge of the blade of the cutting element, whereby both antennas emit a substantially uniform microwave radiation field along the edge of the blade of the cutting element. a microwave radiation source (102, 202, 302, 360, 702, 802) arranged to generate a first microwave radiation signal having a first frequency and a second microwave radiation signal having a second frequency; a surgical instrument (104, 304, 400, 500, 600, 704, 804) having a cutting element comprising: a blade with an edge (402, 404, 502, 504, 602, 604) for cutting biological tissue, and a first antenna (410, 510, 610) connectable to the source to receive the first microwave radiation signal and arranged to emit a substantially uniform microwave radiation field at the first frequency along the edge of the blade of the cutting element, and a second antenna (416, 508, 611) connectable to the source to receive the second microwave radiation signal and arranged to emit from the surgical instrument a microwave radiation field at the second frequency, a blade with an edge (402, 404, 502, 504, 602, 604) for cutting biological tissue, and a first antenna (410, 510, 610) connectable to the source to receive the first microwave radiation signal and arranged to emit a substantially uniform microwave radiation field at the first frequency along the edge of the blade of the cutting element, and a second antenna (416, 508, 611) connectable to the source to receive the second microwave radiation signal and arranged to emit from the surgical instrument a microwave radiation field at the second frequency, wherein the second frequency is lower than the first frequency, and wherein the edge (402, 404, 502, 504, 602, 604) of the blade of the cutting element comprises a radiating portion for the first antenna (410, 510, 610) and the second antenna (416, 508, 611) is mounted adjacent the edge of the blade of the cutting element, whereby both antennas emit a substantially uniform microwave radiation field along the edge of the blade of the cutting element.