Abstract: Disclosed are methods, systems, and a device that includes an output for providing at least a first signal at a first frequency and a distinct second signal at a distinct second frequency, a first signal channel connected between a first waveguide port and the output, the first waveguide port providing a harmonic of the first signal, and, a distinct second signal channel connected between a second waveguide port and the output, the second waveguide port providing a harmonic of the second signal, where the first signal channel includes a notch filter centered substantially at the distinct second frequency, and the second signal channel includes a notch filter centered substantially at the first frequency.