BENGALURU: Researchers at the Indian Institute of Science (IISc) here have developed a through-the-wall radar built on a chip smaller than a grain of rice.The team was led by Gaurab Banerjee , associate professor in the department of electrical communication engineering.The radar, developed using Complementary Metal Oxide Semiconductor (CMOS) technology, has a single transmitter, three receivers and an advanced frequency synthesiser capable of generating radar signals. The size enables mass production at low cost."Such radars can have wide-ranging applications in the defence sector, as well as areas such as healthcare, transportation and agriculture," an IISc statement said. "Only a handful of countries have the ability to put the entire electronics of a radar on a chip ," Banerjee said.Compared to conventional radars, TWR helps to not only sense the presence of individuals behind a wall but also classify their actions and postures. This makes it suitable for surveillance and detection of humans and objects in urban environments, and for search and rescue operations in military situations or natural disasters.The TWR imaging has always been a challenging radar design problem, Banerjee said, adding: "The signal can get significantly damped while passing through walls. To overcome this, radio waves consisting a large number of frequencies need to be used, which can complicate the design."He said: "These radars also use a more complex signal, known as a chirp, which requires customised electronics such as a microwave transmitter, a receiver and a frequency synthesiser."The IISc team has managed to squeeze all these components into a single chip. They used new architectural and circuit design techniques to overcome challenges specific to radars."The same techniques that have enabled smaller and cheaper smartphones can be used for a radar system," Banerjee said.Healthcare applicationAlthough the chip was originally developed for airport security applications, the scientists are exploring applications in healthcare too, to monitor the health of elderly people."A centrally-placed TWR system can scan the house, and construct a model when a person is standing or sitting down. If there is a sudden change in gait due to a fall, it can trigger an alarm," Banerjee said, adding that it can also monitor breathing and respiration rates and assess the severity of a fall.The research was funded by the IMPRINT programme of the government of India, with additional financial from the ministry of human resource development and the Defence Research and Development Organisation. Bharat Electronics Limited, a defence PSU, has been an active partner in this project.