array. Two different approaches are used to process the results. Depending on the type of
system, one or both of the following may be used:
Wavefront analysis (WFA).
Wavefront testing (WFT).
Figure 2-13. Interferometric system.
Wavefront analysis accepts all signals but attempts to recover the major ones. it attempts
this by analyzing the complex voltages measured on the elements of the antenna array under
Wavefront testing accepts only signals arriving from one direction or quasi uni-modal
propagation (QUMP). QUMP is achieved by detecting a linear phase shift across the array
with near equal amplitudes on all the elements. (This process is also called coincidence
The requirements for an efficient coupling system for DF are simple, and there are several
types in use, some more complex than others, but all categorized into two groups;