A helical scan in radar is a scanning technique primarily used in search mode where the radar continuously sweeps 360° in azimuth while simultaneously and smoothly varying its elevation angle. This creates a pattern resembling a helix, allowing for comprehensive volume coverage.
Understanding Helical Scan
Helical scan is a sophisticated radar scanning method designed for efficient target detection over a large area. It shares some similarities with a raster scan but extends its capabilities to achieve full azimuthal coverage.
Key characteristics and operational aspects of a helical scan include:
- Primary Application: Helical scans are generally used in search mode. This means they are ideal for initial detection of targets within a specified volume, rather than for precise tracking of known targets.
- Azimuth Coverage: Unlike some limited-sector scans, a helical scan ensures the radar covers 360° in azimuth. This comprehensive rotational sweep allows the radar to scan all directions around its location.
- Elevation Dynamics: The defining feature of a helical scan is how it handles elevation. While the azimuth sweep is carried out, the elevation angle is continuously increased or decreased. This synchronized movement allows the radar beam to smoothly sweep the covered elevation range, creating a three-dimensional scanning pattern.
- Scan Pattern: The combination of continuous 360° azimuth rotation and simultaneous, progressive elevation change results in a path that resembles a helix or a spiral, hence the name "helical scan." This unique pattern ensures that the entire volume within the radar's operational limits is systematically examined.
Comparison with Raster Scan:
| Feature | Helical Scan | Raster Scan |
|---|---|---|
| Azimuth | Covers full 360° | Typically covers a limited azimuth sector |
| Elevation | Continuously increased or decreased during azimuth | Stepped or incrementally changed after each azimuth sweep |
| Volume Scan | Optimized for full 3D volume search | Often used for sector-based search or specific height bands |
| Movement | Smooth, continuous spiral-like path | Zig-zag pattern across a defined area |
This method is highly effective for surveillance and early warning systems, providing a complete situational awareness by detecting objects across a broad range of altitudes and directions.
