Picosecond dual-source interferometer extending Fourier-transform spectrometer to microwave regime

We report a dual-source interferometer based on nonlinear transmission lines and integrated antennas which interfaces directly with a Fourier-transform infrared (FTIR) spectrometer to enable longer-wavelength measurements than normally possible with a black-body source. As a demonstration, we show preliminary transmission measurements through a plate of high-resistivity silicon.