Methods and apparatuses for direct multiplication Fourier transform millimeter wave spectroscopy are disclosed herein. A sample method includes generating at least one pulse of microwave electromagnetic energy. The sample method also includes frequency-multiplying the pulse(s) to generate at least one frequency-multiplied pulse and filtering at least one spurious harmonic of the frequency-multiplied pulse to generate at least one filtered pulse. The spurious harmonic is generated by frequency-multiplying the pulse. The method also includes exciting a sample using the filtered pulse. The method further includes detecting an emission from the sample. The emission is elicited at least in part by the filtered pulse.