A system for delivering energy, comprising: a housing (112, 114) having an antenna attached at the distal end thereof, the antenna configured to receive a microwave signal and radiate energy at at least two wavelengths, wherein the antenna is a di-pole antenna comprising proximal and distal radiating portions (216a, 216b); and a microwave generator operable to provide the microwave signal to the antenna, wherein the microwave generator is operable to generate a combined microwave signal containing microwave energy having at least a first and a second wavelength; the microwave generator operable to deliver the combined microwave signal to the microwave antenna, wherein the first and second wavelengths are capable of creating resonance in the antenna, and wherein the microwave generator further includes: a first microwave signal generator operable to generate a first microwave signal at the first wavelength; a second microwave signal generator operable to generate a second microwave signal at the second wavelength; at least one phase shifter (154a, 154b) configured to shift the phase of one of the first and second microwave signals relative to each other; a signal mixer that is operable to combine the first and second microwave signals to generate the combined microwave signal; a mixed signal amplifier circuit comprising a signal measurement device for measuring forward and/or reflective power; and a processor; wherein the processor includes an algorithm configured to calculate or adjust the wavelength generated by the first and/or the second signal generator, wherein the mixed signal amplifier circuit is configured to provide forward and/or reflected power feedback to the processor and the processor is configured to calculate or adjust one or more properties of the generated signals, wherein the processor is configured to determine a first resonant frequency by varying the first wavelength generated by the first microwave signal generator and the processor is configured so that the second wavelength of the second microwave signal generator is determined by a similar algorithm or is calculated as a harmonic of the first wavelength. a housing (112, 114) having an antenna attached at the distal end thereof, the antenna configured to receive a microwave signal and radiate energy at at least two wavelengths, wherein the antenna is a di-pole antenna comprising proximal and distal radiating portions (216a, 216b); and a microwave generator operable to provide the microwave signal to the antenna, wherein the microwave generator is operable to generate a combined microwave signal containing microwave energy having at least a first and a second wavelength; the microwave generator operable to deliver the combined microwave signal to the microwave antenna, wherein the first and second wavelengths are capable of creating resonance in the antenna, and a first microwave signal generator operable to generate a first microwave signal at the first wavelength; a second microwave signal generator operable to generate a second microwave signal at the second wavelength; at least one phase shifter (154a, 154b) configured to shift the phase of one of the first and second microwave signals relative to each other; a signal mixer that is operable to combine the first and second microwave signals to generate the combined microwave signal; a mixed signal amplifier circuit comprising a signal measurement device for measuring forward and/or reflective power; and a processor; wherein the processor includes an algorithm configured to calculate or adjust the wavelength generated by the first and/or the second signal generator, wherein the mixed signal amplifier circuit is configured to provide forward and/or reflected power feedback to the processor and the processor is configured to calculate or adjust one or more properties of the generated signals, wherein the processor is configured to determine a first resonant frequency by varying the first wavelength generated by the first microwave signal generator and the processor is configured so that the second wavelength of the second microwave signal generator is determined by a similar algorithm or is calculated as a harmonic of the first wavelength.