ULTRASHORT MICROWAVE SIGNALS - A DIDACTIC DISCUSSION

As a consequence of the variation with frequency of the attenuation an d phase velocity of electromagnetic waves in tissue, the shape (variat ion of the electric field with time) of short electromagnetic pulses i ncident on tissue changes with depth of penetration. We show that a co njecture that such well-known and long understood changes in pulse sha pe may generate harmful biological effects is not credible. We also co nsider the suggestion that such pulses may be useful in medical imagin g and the mapping of the electrical properties of complex tissues and show that such use is impracticably difficult for fundamental reasons.