Radars: basic principles - Detection parameters

This article covers all the phenomena involved in "radar detection," that is, the radar's ability to detect the presence of target echoes in an environment contaminated by noise, and to locate those targets.

First, he discusses the basic concepts required for quantifying noise and the useful signal.

With regard to noise, the following concepts are discussed:

• gain and bandwidth of a receiver;

• additional noise temperature;

• noise temperature and noise figure of a receiving chain;

• frequency characteristics and filtering.

With regard to the useful signal, the following concepts are discussed:

• mathematical expression of the signal;

• temporal representation of power and energy;

• vector and complex representation of the signal;

• the concept of an equivalent complex signal;

• spectrum and filtering, based on a physical interpretation of the Fourier transform;

• analysis of typical signal spectra with and without a carrier;

• Spectral analysis of signal power and energy.

These simple concepts form the theoretical foundation essential for studying radar receiver performance, as will be discussed in the articles “Detection of Moving Targets in Clutter” and “Advanced Radar Signal Processing,” which follow this article.

Here, they are directly applied to the study of optimal filtering for a radar receiver, which addresses the following topics in turn:

• the issue of radar reception in the presence of noise;

• the search for a filter that solves this problem and its performance in terms of signal-to-noise ratio after filtering.

This will lead to the derivation of the "radar equation" in successive steps:

• deriving the signal propagation equation between the radar and the target;

• application of the concept of adaptive filtering to detection in the presence of noise;

• the radar equation for a silent and jamming target;

• Radar equation in a jammed environment.

Next, the probabilistic aspect of radar detection is addressed, which will lead to the establishment of relationships between the signal-to-noise ratio...