Radar Cross Section

Radar Cross Section Overview

The size and ability of a target to reflect radar energy is defined by a single term, \sigma , known as the radar cross-section, which has units of m^2 . This unit shows that the radar cross section is an area. The target radar cross sectional area depends on:

• The target’s physical geometry and exterior features:
  • Smooth edges or surface would scatter the waves in all directions, hence lower RCS. Whereas, sharp corners will focus the return signal back in the direction of the source leading to higher RCS. (Image below for different target geometries)
• The direction of the illuminating radar,
• The radar transmitter’s frequency,
• The material used in the cars, trucks, bicycles, and even in some cases, the clothing material for pedestrians.

If absolutely all of the incident radar energy on the target were reflected equally in all directions, then the radar cross section would be equal to the target's cross-sectional area as seen by the transmitter. In practice, some energy is absorbed and the reflected energy is not distributed equally in all directions. Therefore, the radar cross-section is quite difficult to estimate and is normally determined by measurement.

RCS Units

This RCS can also be defined using a logarithmic value (dB), since it increases the return signal strength. The formula for converting from RCS to dB is given by:

The following table shows RCS values for different targets in both m^2 and dB. You can use the formula above to see how the two columns of the table are related. For example, from the table below we can see that for an automobile:

RCS Quiz