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Nonlinear Radar Systems

#2636


Development of Systems for Diagnostics, Monitoring, and Observation Based on Nonlinear-Radar Principles

Tech Area / Field

  • PHY-RAW/Radiofrequency Waves/Physics
  • INF-SIG/Sensors and Signal Processing/Information and Communications

Status
3 Approved without Funding

Registration date
10.11.2002

Leading Institute
Institute of Measuring Systems, Russia, N. Novgorod reg., N. Novgorod

Supporting institutes

  • Nizhni Novgorod State University name after N.I. Lobachevsky, Russia, N. Novgorod reg., N. Novgorod\nScientific Research Radiophysical Institute, Russia, N. Novgorod reg., N. Novgorod\nRussian Academy of Sciences / Institute of Radioengineering and Electronics, Russia, Moscow

Collaborators

  • University of Warwick / Space & Astrophysics Group, UK, Coventry\nCRAG Group Limited, UK, London

Project summary

Project Objectives.

This project is aimed at developing new nonlinear-radar methods and techniques allowing one to solve efficiently the problems on remote detection, identification, and monitoring of objects of both artificial and natural origin in the presence of high-level background noise and multilobe back scattering, especially in the cases where conventional radar methods and other known methods of object detection (optical monitoring, acoustic sounding, etc.) do not work efficiently.

Introduction.

In the past decade, a trend towards development of nonlinear-radar principles has appeared. Nonlinear radar is based on the reception and analysis of sounding signals reemitted by nonlinear scatterers (NSs). Nonlinear scatterers are passive reemitting objects of artificial or natural origin containing electronic units, imperfect electric contacts, or other elements with nonlinear conductance, capacitance, or inductance. First of all, the nonlinear-radar effect is determined by the unique property of NSs to reemit a signal separated against background of signals reflected from the usual scatterers due to the appearance of a spectral part which comprises components absent in the sounding signal.

The property of NSs to enrich the scattered-signal spectrum makes it possible to separate the reemitted signal against background of signals reflected from the ground, trees, buildings, wavy sea surface, etc., which are not NSs. In this respect, the NS can be considered as a low-cost, small-size, self-contained source of “labelled” electromagnetic radiation. The signal from this source (its spectral content, level, etc.) is determined by the nonlinear-element parameters and the characteristics of nonlinear loads included in the scatterer. The possibility to control the scattered-signal characteristics allows one to use the artificial (or, in some cases, natural) NS as an unconventional “transponder” transmitting information from the point at which it is located to the data-gathering point. This information can be entered into the reemitted signal by modulation of the parameters of sensors included in the NS and capable of responding to the state of the environment or studied objects.

It should be emphasized that the nonlinear scatterer can be located in places with a hindered access, inside a bulk of matter, and in aggressive media in the presence of appropriate insulation. In this case, the reading and analysis of information can be performed via a radio channel only remotely.

Of significant interest is the fact that the field reflected from nonlinear scatterers comprises signals both at the sounding frequency and the nonlinearly produced frequencies. Thus, the resulting spectrum contains a greater amount of information on both the scatterers themselves and the surrounding space as compared to the field received in linear radar, when only a single frequency (sounding-signal frequency) is used. The above property of the nonlinear scatterer allows one to solve the identification problem as well as to remotely obtain information on a change in the structure of space in the vicinity of the NS.

Among the evident advantages of nonlinear scatterers, one should mention their small sizes and masses, high reliability, absence of permanent necessary servicing, permanent operation readiness, standby operation regime (the scatterer response appears only in the presence of the sounding signal), and low cost.

Main directions of research within the project framework.

During project implementation, the following devices and technologies are anticipated to be developed:

1. Small-size, self-contained, feederless transducers of physical quantities in the form of nonlinear scatterers of various design with inclusions of sensors.

(a) Small passive transducers of the local values of electromagnetic-field parameters, enabling one to perform measurements with minimum distortions in the studied field.

Fields of Application:

– antenna measurements;


– analysis of electromagnetic compatibility of devices;
– measurements performed during scientific research;
– the use of nonlinear transducers as elements of radar systems.

(b) Sensors of different gases in the atmosphere, enabling one to determine remotely the presence and density of poisonous substances and explosives.

Fields of Application:

– search for gas leakage in gas pipe-lines and facilities of the chemical and nuclear industry under the conditions of a hindered access to the places of a possible leakage, etc.;


– remote monitoring of the chemical content of the atmosphere;
– scientific research.

(c) Object markers as long-range Radio Frequency IDentification (RFID) systems.

Fields of Application:

– monitoring of freight transportation;


– search for people missing in crashes and natural calamities;
– search for crashed aircrafts;
– monitoring of taking the goods from supermarkets.

2. Nonlinear-radar-based systems of remote search for explosive means.

Fields of Application:

– humanitarian mine clearing;


– fight against terrorism (search for charges with electronic fuzes, radio-controlled fougasses, and bugs).

3. Observation systems using nonlinear-scatterer arrays.

Short-range radar based on the concept of detection of either distortions caused by a detected object in the structure of a quasistatic electric field or distortions in the interference pattern formed in closed volumes.

Fields of Application:

– systems for orientation under the conditions of a limited visual range (smoke, dust, and fog);


– undersurface sounding of the Earth (search for objects in the upper layers of the ground);
– introscopy;
– alarm and security systems;
– systems of an active spatial interface allowing one to realize a non-contact human-computer interaction in the specified spatial region.

4. Systems for detection of a man and remote monitoring of man’s basic physiological parameters (motion, breathing, and pulse).

Fields of Application:

– detection of people in building ruins after earthquakes and other natural calamities;


– remote monitoring of the physiological parameters of biological objects (people and animals) in the absence of a possibility to perform their visual observation.

To carry out successfully the project tasks, it is planned to perform comprehensive theoretical and experimental studies of the electrodynamics of nonlinear scatterers, including:

(a) development of theoretical models and a thorough analysis of operation regimes of nonlinear scatterers in the form of thin metal antennas containing lumped and distributed nonlinear elements of various types;


(b) development of theoretical models of antenna arrays made of nonlinear scatterers and a study of their operation regimes;
(c) development of solid-state nonlinear structures with the specified current-voltage and capacitor-voltage characteristics of nonlinearity;
(d) search for and investigation of nonlinear phenomena allowing one to remotely control the electrodynamic parameters of nonlinear scatterers;
(e) development of methods for processing of nonlinear-radar data and synthesis of an optimum spatio-temporal structure of radar signals.


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