# HF Radar Signatures and Their Use for Target Classification, Recognition and Identification

## TL;DR

This paper explores how HF radar can classify and identify vehicles beyond just detecting them, using a framework based on radar signatures and physical principles.

## Contribution

The paper introduces a semantic framework and taxonomy for target characterization in HF radar systems.

## Key findings

- A semantic framework for discussing target characterization is established.
- A taxonomy of target signature domains and characterization methods is presented.
- The physics underlying each characterization method is examined with real data examples.

## Abstract

HF radar provides efficient, wide-area surveillance of air and surface vehicles at over-the-horizon ranges, but it is often the case that knowing the mere presence of a ship or aircraft has limited value. In order to assess any situation and take appropriate action, the radar operator needs information on the types of vehicles involved, whether they belong to known classes, and, ideally, their unique identities. The extent to which a radar can deliver such information depends not only on radar design but also on the depth of understanding of the physics responsible for the vehicle radar signatures, together with radar operating procedures and signal processing architectures that retrieve the target information.

Main findings
a semantic framework for discussing target characterizationa taxonomy of target signature domains and characterization methodsan examination of the physics underlying each method, with illustrative examples

a semantic framework for discussing target characterization

a taxonomy of target signature domains and characterization methods

an examination of the physics underlying each method, with illustrative examples

Implications

The results of this paper will support HF radar operational effectiveness in many domains, including:the recognized air picture (RAP) and recognized surface picture (RSP)early warning and threat assessmentover-the-horizon targetingradar resource allocation

the recognized air picture (RAP) and recognized surface picture (RSP)

early warning and threat assessment

over-the-horizon targeting

radar resource allocation

The challenging goal of equipping HF radars with a target classification ability has been pursued for many years, yet no satisfactory system-level methodology has been reported. This shortcoming severely limits the utility of radar information as, without knowing the nature of detected objects, there is little prospect of understanding the situation and tailoring a suitable response. In this paper, we present a framework within which a comprehensive approach to target characterization can be formulated. We proceed to explore a wide range of physical mechanisms whereby target information is impressed on HF radar echoes, illustrated with real data. This paper concludes with a commentary on the difficulty of integrating target classification, recognition, and identification procedures with other radar tasks and resource management.