Chemical warfare agents (CWAs) are extremely lethal spices of mass destruction even at the low dosages which gives crucial importance to early detection and prevention. As a simulant of nerve agent sarin, Dimethyl methylphosphonate (DMMP) can be used because it has non-toxic properties and mimics the structural composition of sarin. In this paper, we summarize the CAW detection by designing a surface acoustic wave (SAW) and fabrication of polyhedral oligomeric silsesquioxane (POSS), thiourea (TU) and other hybrid composite materials for sensing materials. The sensing hybrid materials were fabricated by hydrosilylation reaction process and hydrothermal and thermal reduction process respectively. The synthesized materials were spin-coated or drop coated on the SAW and quartz crystal microbalance sensor as a thin layer deposition on the surface. Based on our experiments, several sensing polymers and hybrid oxides will be suggested for potential candidates of CWA sensing layers on portable SAW device.
If two signals, which have a same single frequency and different phases, impinge on an antenna array simultaneously at similar angles, a large error occurs in the angle estimation when the phase of two signals is different by 0 or 180 degrees. This phenomenon might occurs for low-flying target since direct signals and surface-reflected signals are on the same range bin because of relatively small bandwidth of shipborne radar. In this paper, we show the Cramer-Rao lower bound of the angle estimation lowered by using multiple frequencies. Also, using maximum likelihood estimation, we show that mean square error of the angle estimation lowered when we use multi-frequency radar.