The radio frequency receiver chip was designed in 18 months by students and researchers at IIT Bombay. It can receive in multiple frequency bands and handle weak signals. Besides, it can be converted into digital bits and processed by any standard digital signal processor (DSP) to determine one’s location precisely. “There were many design challenges to make the receiver work under all environmental conditions. We came up with patentable innovations, set up our internal review structure so that no bug passes through,” said Rajesh Zele, professor, Department of Electrical Engineering, IIT Bombay who led the efforts. India has had a fleet of navigational satellites for a few years, but there have been no commercial receivers so far that could receive its signals in multiple frequencies, IIT Bombay said in a statement. The nine satellites under NAVIC were built as an alternative to the GPS, as part of India’s space agency’s efforts to make the navigation system accessible for commercial applications.
“Sending out a chip is extremely expensive. So we had to make sure that it is designed perfectly. We incorporated many testing features for debugging – just in case something doesn’t work right. This is the first chip from our lab completely designed by students…We could not make mistakes. So, each team member checked other’s work and made sure all bugs were cleaned up before tape-out. I wanted everyone to go through the intense tape-out experience that each industry designer endures” he said. The Dhruva project was funded by the Ministry of Electronics and Information Technology (MeitY), with SAMEER (Society for Applied Microwave Electronics Engineering and Research) as the nodal agency. The research team also interfaced with the Space Applications Centre of the Indian Space Research Organisation.
“Getting a production-worthy RF chip designed in 18 months is an outstanding achievement for the students. Typically, in the industry setting, it takes about nine months to take a chip from conception to tape-out. We started from ground zero with no background,” said Zele. NAVIC (Navigation with Indian Constellation) is India’s geo-positioning system designed by ISRO to provide accurate positioning within the country. NAVIC satellites were sent to orbit a few years ago, but no commercial ‘receiver’ chip was available to receive signals from the satellites. Dhruva will help receive and clean up the signals received from NAVIC, which are 36,000 km above from the earth’s surface.
“Since the satellites are far away from the Earth, the received signals are extremely weak compared to the ambient noise floor. This chip can clean up all the interfering signals, sifting out the weak desired navigation signals,” according to IIT Bombay. The note added that these signals are further amplified by approximately 400,000 times before converting to digital bits using on-chip Analog-to-Digital Converters (ADCs).
Reflecting on the process behind the preparation of the chip ahead of the lockdown in the past few months, Zele said, “We have built a lab ground up for RFIC testing at IITB with a lot of high performance equipment. While the chip was in fab for about five months, we designed the PC Boards, software and hardware tools. The fielding was already setup for Dhruva chip arrival from foundry in December 2019. In the beginning, we all went through ‘butterflies in the stomach experience’ as the chip was powered up. Slowly, each and every block was brought to life. Amazingly, everything worked just as we expected. Finale happened just before lockdown when we successfully detected GPS satellite signals using our chip.”