Serroydyne modulator based on circularly polarized wave reflection

In this paper, a technique is described whereby we can directly Serrodyne a signal reflected from a rotating metal disk. This is achieved by placing a spinning circular‐patch antenna (which has two short‐circuiting pins at its periphery) in the path of an incident circularly polarized (CP) field. When excited by a circularly polarized signal, the rotating disk produces a re‐reflected signal with a modulo 0° to 360° phase shift encoded onto it. The sense of the re‐radiated signal is the same as that of the incident signal. The developed technique can be used as a mechanical Serrodyne modulator providing a small frequency offset in the return signal that is directly related to direction and rate of rotation. A mathematical rationale for the principal of operation of the device is given and experimental validation of the method is provided. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 469–472, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20855