The distribution of modulation frequencies has been determined for radiation chopped by passing chopper teeth, whose sides are radii of the chopper wheel, over a circular aperture. The calculation reported here establishes the relationship between the aperture radius-to-chopper wheel radius ratio and the number of notch-tooth pairs that will produce an amplitude of the fundamental frequency equal to the amplitude obtained for the ideal sinusoidal modulation of the radiation emanating from the same aperture. The rms value of the radiation modulated in the assumed manner is also discussed.
RICHMOND B. MCQUISTAN, "On Radiation Modulation," J. Opt. Soc. Am. 49, 70-73 (1959)