Signal processing antennas - Part 1

In a complex system, such as a telecommunications network, radar or sonar, we often consider that each component (antenna, receiver, transmitter, etc.) performs its own specific system functions. Thus, directional properties are provided by the antenna, the spectrum and energy of the transmitted signal by the transmitter, detection and measurement of distance or speed by the receiver, and so on.

Yet there are common examples where this conception is contradicted. Historically, these were first found in the angular tracking systems of telecommunication satellites or radars. In monopulse technology, angular accuracy is achieved by combining the antenna with special receiver processing of the signals it receives. Other examples include imaging methods developed in particular for radio astronomy, and radar antenna anti-jamming techniques.

The field of signal-processing antennas is the result of the generalization of these examples. In a system designed along these lines, overall performance is the result of the symbiosis of the constituent parts in the processing of the signals they exchange. That's why a good understanding of this dossier presupposes sufficient general knowledge of Signal Processing (cf. ), particularly in its applications in telecommunications and radar (filtering, correlation, pulse compression, etc.).

However, wherever possible we have kept the mathematical apparatus to a minimum, so as not to obscure physical phenomena under the complexity of the calculations. Rather than approaching a problem in all its generality, we have often preferred to deal explicitly with a simple "canonical" aspect.

The range of methods and applications for signal-processing antennas is extremely broad: they are found not only in radiocommunications, radar and radio astronomy, but also in acoustics, geophysics, medical imaging and many other fields.

This dossier is divided into two parts.

This first part [E 3 320] will begin with a presentation and reminder of stationary linear systems. There is in fact a unifying concept which often allows the same language to be used for antennas as for the other constituent elements of a system: that of the linear spatial frequency filter, which is essentially based on the mathematical properties of the Fourier Transform. All the properties relating to signals with bounded-support spectra can therefore be transposed to antennas.

We will then consider two signal-processing antenna systems. We'll start with the study of space-time coded or synthetic antennas, in particular Synthetic Aperture Radar (SAR) antennas. Carried by aircraft or satellite, these antennas can provide a high-definition image...