A millimeter wave integrated lithium niobate modulator, consisting of a titanium diffused optical waveguide Mach-Zender interferometer and a traveling wave coplanar waveguide electrode with periodic series stubs, is analyzed through the application of Floquet's theorem. First, a design equation for the modulator is derived by expanding the RF signal along the optical waveguide into space harmonics and then matching the velocity of the dominant space harmonic to the velocity of the optical signal. Then, the frequency response of the modulator is found by integrating, over the modulator's length, the local optical phase shifts that are electro-optically induced by all of the RF space harmonics. Finally, it is shown how the concepts developed here for an ideal (no reflections) periodic structure can be applied to the experimental determination of the modulator response by characterizing isolated unit sections of a real electrode. This approach has the added advantage of facilitating RF inmpedance matching to the modulator.