Velocity modulation microwave amplifier with multiple band interaction structures

A microwave amplifier, comprising:

• electron gun means for generating an electron beam which propagates along a predetermined axis;
• collector means disposed along the predetermined axis for capturing the electron beam;
• first interaction structure means having a first input for receiving a first microwave input signal in a first frequency band and a first output for transmitting a first output signal, wherein the first interaction structure means is positioned between the electron gun means and the collector means and disposed along the predetermined axis for receiving the electron beam and for velocity modulating the electron beam with the first microwave input signal and extracting the first output signal resulting from amplification of the first input signal in the first interaction structure means from the electron beam at the first output;
• second interaction structure means having a second input for receiving a second microwave input signal in a second frequency band and a second output for transmitting a second output signal, wherein the second interaction structure means is positioned between the first interaction structure means and the collector means and disposed along the predetermined axis for receiving the electron beam and for velocity modulating the electron beam with the second microwave input signal and extracting the second output signal resulting from amplification of the second input signal in the second interaction structure means from the electron beam at the second output;
• first means for generating the first input signal;
• second means for generating the second input signal;
• and
• selecting means operatively coupled between the first means and the second means and between the first and second inputs for selectively coupling the first means to the first input of the first interactive structure means or the second means to second input of the second interactive structure means, but not both;
• wherein the second interaction structure means is configured so as to be nonresponsive to the modulation of the electron beam resulting from the first interaction structure means.