Radar Cross Section is defined in a spherical coordinate system defined on the target’s body frame.
You can define two different coordinate frames:
- Rho from X-axis. The reference axis for the measurement of the RCS is the target's body frame X-axis. Rho and Theta angles along with the reference X-axis are defined as 0° respectively.
- Rho from Z-axis. The reference axis for the measurement of the RCS is the target's body frame Z-axis. The Rho and Theta angles are both defined as 0° along the Z-axis of the target's body frame.
Definitions and pictorial representations of Rho and Theta in each reference axis follow. Note that:
- Rho is measured from the reference axis to the incident vector.
- Theta is measured from the reference axis to the projection of the incident vector on the plane perpendicular to the reference axis.
Reference X-axis
The Rho angle is the angle off the reference X-axis, while the Theta angle is defined as the rotation around the reference axis starting from the Z-axis.
The range is 0° through 180° for the Rho angle, and -180° through +180° for the Theta angle.
The figure below shows the Rho and Theta angles defined in the target's body frame. The target body X-axis is used as the reference axis. The Rho angle is the angle between the reference X-axis and the incident wave (radar) direction.
Theta angle is measured from the body Z-axis to the projection of the incident vector onto the target body YZ plane; that is, the rotation angle around the reference X-axis.
Reference Z-axis
The Rho angle is the angle off the reference Z-axis, while the Theta angle is defined as the rotation around the reference axis starting from the X-axis.
The range is 0° through 180° for the Rho angle, and -180° through +180° for the Theta angle.
The figure below shows the Rho and Theta angles defined in the target's body frame. The target body Z-axis is used as the reference axis. The Rho angle is the angle between the reference Z-axis and the incident wave (radar) direction.
Theta angle is measured from the body X-axis to the projection of the incident vector onto the target body XY plane; that is, the rotation angle around the reference Z-axis.