In recent times, the use of Chemical Warfare (CW) agents against civilian and military by terrorists and rogue countries are recurrent. The examples of such attacks are available in open literature. They are highly dangerous due to their acute toxicity nature. They tend to stimulate and paralyze nerve system of the body and cause other toxic side effects. Once these toxic chemicals are released into the atmosphere, timely detection and identification of the same at standoff distances will help the defensive forces to take proper counter measures. Detection techniques such as ion mobility spectrometry, infrared spectrometry, Raman spectrometry, FTIR, LIDAR etc. have been used widely. Among all these techniques, Raman spectroscopy techniques and LIDAR (LIght Detection and Ranging) is the only active remote detection method that can detect and discriminate the chemical agents at standoff distances. Infrared DIAL (Differential Absorption Lidar) is a versatile technique for remote detection of various chemicals. DIAL technique can provide spatially resolved measurements of these agents with sufficient sensitivity (at few ppm levels) at ranges of several kilometers by exploiting the concept such as scattering and absorption from the atmosphere. The main objective of this review paper is to bring out the details of highly potential chemical warfare agents, their properties and laser based remote detection sensors. LIDAR technique is emphasized in more detail because of their long range detection capability, sensitivity and selectivity. An overview of existing R&D based and commercial systems is also discussed.

A compact dual-band out of phase difference power divider having microstrip transmission capability has been proposed in this paper. To realize the proposed power divider a dual-band quarter-wave transmission line (DBQWTL) with closed-form design equations have also been proposed. In order to validate the proposed approach, a power divider has been designed and implemented on a printed circuit board for 0.7GHz and 2.6GHz operating frequencies and tested. The S -parameters of the power divider have been measured at the operating frequencies with maximum ±0.26dB amplitude imbalance and ±2∘ phase deviation. The first time a dual-band out of phase power divider having microstrip compatibility is proposed. In addition, it has the smallest size, minimum phase deviation, design with fewer number of lumped components, and having output ports on the same plane.

In this article a temperature programmed desorption (TPD) on an uncoated surface acoustic wave (SAW) device has been explored for selectivity studies of chemical warfare agents (CWA). High sensitivity to mass change on SAW device surface was exploited to study desorption patterns in a novel way. CWA Simulants 2-chloroethyl ethyl sulfide (CEES), Methyl Salicylate (MS) and Dimethyl Methyl phosphonate (DMMP) were investigated at different concentrations. SAW device was cooled and exposed to simulant vapours resulting in physical adsorption of gas molecules on device surface and subsequently by ramp heating the device, vapours were desorbed. The change in SAW oscillation frequency, due to desorption, was monitored during the temperature ramping and desorption spectrum was obtained. Desorption spectra were statistically analyzed using Principal Component Analysis (PCA) and our results indicate that all the three compounds investigated produced distinct desorption patterns independent of concentrations. Through this work we aim to develop a reliable methodology for subsequent development of a hand held TDP-SAW detector for field applications.