Radar Cross Section Research Paper

Radar cross section (RCS) or echo area or effective area is the measure of target’s ability to reflect radar signals in the direction of the radar receiver i.e. it is the measure of the ratio of the backscattered power per steradian in the direction of the radar to the power density that is intercepted by the target [1]. RCS is a measure of how detectable an object is with the radar. The IEEE dictionary of electrical and electronics terms[1]defines RCS as a measure of reflective strength of a target defined as 4π times the ratio of the power per unit solid angle scattered in a specified direction to the power per unit area in a plane wave incident on the scatterer from a specified direction. Radar cross section σ may be mathematically written

Radar cross section is a far field quantity and the illuminated and scattered waves can be taken as plane waves with complex amplitudes Einc and Escat . It is dependent on the direction of arrival of the incident wave and the direction of observation of the scattered wave and is known as bistatic cross section. When those two directions are coincident, it is known as the monostatic cross section. A schematic diagram of a typical far field arrangement for making RCS measurements is shown in the Fig.

However, this reflected power also dissipates and spreads out as it echoes back to the radar receiver. Since the power density has already been reduced by a factor of 1/R2 by the time it reaches the target and is again reduced by 1/R2 on the return trip, the final power density of the energy received by the radar is proportional to 1/R4. The ability of radar to detect the target depends on whether the amount of power returned is large enough to be differentiated from internal noise, ground clutter, background radiation and other sources of interference. The graph shown in Fig. 2.3 gives an idea about how little radar power is reflected back from the target and received by the radar. In this case, the target presents the same aspect to the radar at ranges from 1 to 50 miles. At a range of 50 miles, the relative power received by the radar is only 1.6 ×〖10〗^(-5)% of the strength at one mile. This diagram graphically illustrates how significant the effect of energy dissipation is with distance and how sensitive radars must be to detect targets at even short ranges