Radar-invisibility on axis of rotationally symmetric reflectors

It has been observed that the monostatic radar cross section (RCS) of parabolic perfect electric conductor (PEC) reflectors vanishes at certain frequencies for broadside wave incidence. It has also been noticed that hyperbolic reflectors behave similarly, with very low RCS minima. This behavior is explained by using physical optics (PO) and verified via a numerical full-wave analysis. Relations between the physical dimensions of the reflector and the characteristic values of the RCS (notch frequencies, minimum and maximum value), as well as a comparison of different canonical reflectors, are given. The interest in the phenomenon described is at present essentially speculative, since, as pointed out in this letter, there are some significant limitations which restrict its practical utilization.