In the era of smart devices and IoTs, navigation is one of the essential features that we use in various commercial and personal applications. It has changed the way we travel from one place to another, the way we explore an unknown neighborhood. This is the technology that drives your Ola/Uber to the desired destination and helps Swiggy deliver food to your home. This technology finds its way in aerial and marine navigation too. This Navigation technology aids nations survey their territories, secure their borders and manage disaster response.
A navigation system includes constellations of Earth-orbiting satellites. These satellites continuously transmit their position and time reference using radio waves. The navigation receivers capture these signals, amplify and then further process them in the digital domain. Each receiver determines its own position accurately based on the trilateration method using the signals received from multiple satellites.
Numerous nations have already deployed their own navigation satellite systems, like the United States’ Global Positioning System (GPS), Russian Federation’s Global Navigation Satellite System (GLONASS), Europe’s GALILEO, China’s Bei-Dou and Japan’s Quasi-Zenith Satellite System (QZSS). India indigenously developed its own navigation system, Indian Regional Navigation Satellite System (IRNSS) or Navigation with Indian Constellation (NAVIC), to reduce its reliance on foreign technology. During the Kargil War of 1999, the Indian troops could not access vital positioning information using the foreign GPS satellites. This experience underlined the compelling need to be self-reliant in this area. The IRNSS or NAVIC satellites have already been sent to orbit a few years ago by ISRO, however, no commercial receiver chip is available for all the NAVIC bands.
IIT Bombay researchers have designed Dhruva, a navigation receiver RF front-end integrated circuit (IC, chip) primarily targeted for Standard Positioning Service (SPS) in civilian applications provided by NAVIC and GPS. Since the satellites are far away from the Earth (Ex, NAVIC 36,000 km), 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. These are further amplified by approximately 400,000 times before converting to digital bits using on-chip Analog-to-Digital Converters (ADCs). The digital data from Dhruva can then be further processed by any standard digital signal processor to determine one’s location accurately.
The Dhruva IC is capable of tuning to the navigation signals transmitted at multiple frequencies viz. 1.176 GHz (NAVIC L5 band), 1.227 GHz (GPS L2 band), 1.575 GHz (GPS L1 band), and 2.492 GHz (NAVIC S band). In addition, the IC can be tuned to frequency bands occupied by other worldwide navigation systems, making it a truly universal solution. The chip with die-size 1.8 mm x 1.8 mm, is developed as a production-level IC with ESD protection, on-chip testing, and reference circuits operating from -40 to 100 °C. The chip can be programmed by an external controller through the SPI interface.
Dhruva chip is entirely designed by Ph.D. and M.Tech. students working with Prof. Rajesh Zele at IIT Bombay. After working in the IC design industry for a couple of decades, Prof. Zele joined IITB about three years ago. He teaches RF IC design and Analog IC design courses for Undergraduate and Postgraduate students. As part of the class project, he floated design topics that will make an impact for India. The goal was for students to gain insights into advanced RF/Analog IC design using the best industry practices. The students showed tremendous excitement following which the NAVIC RFIC design team was initiated (Vijay Kanchetla – Leader, Santhosh Khyalia, Ajinkya Kharalkar, Shubham Jain, Swetha Jose, Jeffin Joy, Syed Hameed, Mukul Pancholi, Sumit Khalapure, Amitesh Tripathi, Pawan Khanna and Sakshi Vastrad). It took about eighteen months to design the complete IC from the ground up incorporating various innovative ideas and to send it for fabrication in 65nm CMOS technology. The chip came back from the foundry last December. Students designed the entire test and verification platform in the lab. Just before lockdown started, the IITB team was able to successfully verify the IC functionality with GPS signals. This project is funded by the Ministry of Electronics and Information Technology (MeitY), India, with SAMEER as nodal agency. The team has been interacting with SAC-ISRO for specifications of the IC.
Going forward, the plan is to develop an advanced version of Dhruva with many additional features and a substantially smaller footprint. Once the Indian government mandates the use of NAVIC, Dhruva can be integrated into mobile and commercial applications.
“From the early days of studying the basics of IC design, to architecture planning, handling the design challenges, and to the day of witnessing working silicon on the bench, it has been an amazing journey with a great learning experience. There were several days when our team worked round the clock to come up with innovative solutions addressing the tough design challenges. As the team leader, I would say teamwork, critical analysis and constructive feedback are the key elements that made this project successful. Having a Guru who is available 247 to help students, technically and morally, is a privilege that we have. We are looking forward to designing the Dhruva 2.0, an advanced version with a whole lot more features. I believe that our work will help the nation!” -Vijay Kanchetla
“Getting a production worthy RF chip designed in eighteen 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 tapeout. We started from ground zero with no background. After an intense training cycle, the students set themselves up with micro-goals each week. 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. What I am most proud of is that I haven’t touched a single transistor during the design phase. Students took complete ownership. I believe this is a great step forward for us to become ‘AtmaNirbhar’ in developing essential technology for the nation” said Prof. Rajesh Zele.