A review of CAD techniques for the radio and radar performance of aircraft

External radiofrequency electromagnetic fields induce currents in conducting parts of the exterior surface of an aircraft. These currents cause new re-radiated fields and this process is fundamental to the detection of the aircraft by distant radar. The surface currents also interact with receiving antennas on the aircraft in various ways, depending on the frequency band. A further issue that is of increasing concern is that of the interaction between external radio waves and internal electronic systems inside the aircraft skin. The scattering properties of the aircraft when illuminated by an external radar are mainly of concern in military applications, where a small radar cross-section (RCS) is always desirable: this imposes a strong constraint on the exterior design of the aircraft, probably the dominant constraint if `stealth´ is desired. The detailed analysis of all of the affects discussed above requires techniques for modelling the interaction of the exterior structure of the aircraft with electromagnetic waves, which are normally considered to emanate either from a source point on the aircraft, or from a distant source. Except for the very simplest of shapes (spheroids), this cannot be done analytically and a discrete numerical model is instead required. Techniques currently used to achieve this may be divided into three broad categories, as follows: (i) differential-equation methods, (ii) integral equation methods, and (iii) ray-tracing methods