What are the basic radar measurements that can be achieved from a Distributed target

When dealing with distributed targets, radar systems can extract several key measurements to provide detailed information about the target. Distributed targets are those that occupy a larger spatial extent and may consist of multiple scattering centers, as opposed to point targets which are small and localized. The basic radar measurements for distributed targets include:

1. Range:

• Definition: The distance from the radar to various parts of the distributed target.
• Measurement: Determined by the time delay between the transmission of the radar pulse and the reception of the reflected signals.
• Application: Provides information about the spatial extent and shape of the target.

2. Range Profile:

• Definition: A representation of the radar cross section (RCS) as a function of range.
• Measurement: Obtained by analyzing the returned signal strength at different time delays, giving a profile of reflectivity along the line of sight.
• Application: Helps in identifying the structure and features of the target.

3. Doppler Velocity:

• Definition: The relative velocity of the target (or parts of the target) with respect to the radar, measured along the line of sight.
• Measurement: Derived from the frequency shift of the returned signal due to the Doppler effect.
• Application: Provides information about the motion of the target, such as speed and direction.

4. Doppler Spectrum:

• Definition: A distribution of the target's velocities across different parts of the distributed target.
• Measurement: Analyzed by performing a Fourier transform on the time-domain signal to separate different velocity components.
• Application: Useful for understanding the movement and dynamics of various parts of the target, such as rotation or vibration.

5. Angle of Arrival (Azimuth and Elevation):

• Definition: The direction from which the radar signal is reflected back, measured in terms of azimuth (horizontal angle) and elevation (vertical angle).
• Measurement: Achieved using beamforming techniques or monopulse radar methods to determine the direction of the incoming signals.
• Application: Determines the spatial orientation and position of different parts of the distributed target.

6. Cross-Range Resolution:

• Definition: The resolution of the radar in the direction perpendicular to the line of sight.
• Measurement: Enhanced using synthetic aperture radar (SAR) or inverse synthetic aperture radar (ISAR) techniques.
• Application: Provides detailed imaging of the target's structure and can distinguish between closely spaced features.

7. Polarization:

• Definition: The orientation of the electromagnetic wave's electric field.
• Measurement: By transmitting and receiving signals with different polarizations (e.g., horizontal, vertical, circular), the radar can analyze how the target affects the polarization state.
• Application: Helps in identifying material properties and surface characteristics of the target.

8. Radar Cross Section (RCS):

• Definition: A measure of how much energy a target reflects back to the radar.
• Measurement: Determined by the strength of the returned signal.
• Application: Provides information about the size, shape, and material properties of the target.

Summary:

Distributed targets provide a rich set of data for radar systems to analyze. By measuring range, range profile, Doppler velocity, Doppler spectrum, angle of arrival, cross-range resolution, polarization, and radar cross-section, radar systems can gain comprehensive information about the target's size, shape, motion, orientation, and material properties. These measurements are crucial for applications in surveillance, reconnaissance, navigation, and object identification.