A new method of measuring standing wave distributions on electromagnetic waveguiding structures

A novel method of measuring standing-wave distributions, using a modulated scatterer and a microwave homodyne receiver, has been developed, analyzed, tested, and shown to yield accurate results. Because the modulated scatterer can take the form of a small photoconductive dipole on the end of an optical fiber, access to the field to be measured from a contiguous shielded region, as in slotted transmission line instruments, is not necessary. With the availability of relatively inexpensive computer-controlled micropositioners, the mechanical translation of such a scatterer along a microstrip transmission line designed for operation at millimeter wavelengths can be readily automated and combined with scatterer microwave signal measurements. Analysis shows that the modulated scattered microwave signal is proportional to the cube of the standing-wave pattern of microwave signal variation on the microwave guiding structure, assuming that a single mode of propagation is involved. This has been verified experimentally