An Overview of NQR Signal Detection Algorithms

Abstract

Nuclear quadrupole resonance (NQR) is a solid-state radio frequency spectroscopic technique that can be used to detect the presence of quadrupolar nuclei, that are prevalent in many narcotics, drugs, and explosive materials. Similar to other modern spectroscopic techniques, such as nuclear magnetic resonance, and Raman spectroscopy, NQR also relies heavily on statistical signal processing systems for decision making and information extraction. This chapter provides an overview of the current state-of-the-art algorithms for detection, estimation, and classification of NQR signals. More specifically, the problem of NQR-based detection of illicit materials is considered in detail. Several single-and multi-sensor algorithms are reviewed that possess many features of practical importance, including (a) robustness to uncertainties in the assumed spectral amplitudes, (b) exploitation of the polymorphous nature of relevant compounds to improve detection, (c) ability to quantify mixtures, and (d) efficient estimation and cancellation of background noise and radio frequency interference.The authors are at

A novel wavelets method for cancelling time-varying interference in NQR signal detection

“…where Z (1) Nk 1 k 2 k 3 is created from Z (1) N following the rule of "Z Nk 1 k 2 k 3 from Z N ". Upon finding the component with smallest C (2) , marked as (k 1m 2 , k 2m 2 , k 3m 2 ), it is apparent that both (k 1m 2 , k 2m 2 , k 3m 2 ) and (k 1m 1 , k 2m 1 , k 3m 1 ) are important interference components. They can be removed as following:…”

“…Nuclear quadrupole resonance (NQR) signal detection is a useful approach for identifying the presence (or absence) of quadrupolar nuclei substances [1]. This approach has become popular, especially in pharmaceutical monitoring, landmine searching, and oil drilling, because medicine such as narcotics, explosives such as trinitrotoluen (TNT), and petroleum components have their unique NQR signal features/parameters including eigenfrequency and decay time [2][3][4].…”

An advanced beamforming approach based on two-channel echo-train system to cancel interference within an NQR signal resonance spectrum

“…The existence of materials or substances containing quadrupolar nuclei can be identified by detecting their featured NQR signals based on this principle. Applications of NQR signal detection include landmine detection, medicine authentication, security checking, oil drilling, etc, [2]. A typical quadrupolar nuclei that can be detected is 14 N, which is present in trinitrotoluen (TNT) in landmines and in the antimalarial medicine Metakelfin [3,4].…”

Detecting NQR signals severely polluted by interference

“…As a result, this technique has been applied to problems such as landmine and drug detection, medicine authentication, and oil drilling, etc. [2][3][4], in order to detect the quadrupolar nuclei which always exist in compounds of the objects of interest (such as the 14N of trinitrotoluen (TNT) in landmines). Several of the NQR signal parameters, such as frequency, signal damping time, and echo decay time depend on the source substance.…”

“…In recent years, algorithms based on least squares estimation or maximum likelihood theory [2,5,6] have shown good performance in NQR detection applications. Unfortunately, the NQR signal is usually weak relative to the total received signal.…”