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Dhruva: A Universal Navigation Receiver Front-end

Name: Vijay Kanchetla 

Department: Electrical Engineering

Name of supervisor: Prof. Rajesh Zele

 

Description of research work: 

Dhruva: A Universal Navigation Receiver Front-end

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 facilitates the delivery of food to your home from a restaurant. This technology finds its way in aerial, marine navigation too and it aids nations in surveying their territories, secure their borders, and manage disaster response. A navigation system includes constellations of Earth-orbiting satellites. Each of these satellites continuously transmits its position and time reference using radio waves. The navigation receivers capture these signals, amplify them and further process in the digital domain. Each receiver then 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 dependency on foreign navigation systems and to be self-reliant in this technology. 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 so far.

We 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. This chip can clean up all the interfering signals, sifting out the weak desired navigation signals. These are then 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 processed by any standard digital signal processor to determine one's location accurately. The IC is capable of tuning to the navigation signals transmitted at multiple frequencies viz. 1.175 GHz (NAVIC – L5 band), 1.227 GHz (GPS – L2 band), 1.575 GHz (GPS-L1 band), and 2.492 GHz (NAVIC – S-band). One of the challenges involved in the navigation receivers that work with multiple navigation systems is the tunability to different RF input frequencies and downconverting them to a low frequency using local oscillator. Typically the downconverted frequency will be in the order of a few MHz. In our IC, we integrated a Phase-Locked Loop (PLL) with a single Voltage Controlled Oscillator (VCO) to generate the all required frequencies to downconvert the incoming RF spectrum to a low frequency of 3 MHz. Along with GPS and NAVIC, the IC can be tuned to frequency bands occupied by other worldwide navigation systems, making it indeed a universal solution. This gives the software applications flexibility to switch to a navigation system with more visible satellites in a given location and, hence, help users with better accuracy. The chip fabricated in 65nm CMOS technology 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. Depending on the input signal strength, the IC can be programmed to meet the desired performance at reduced power consumption. The IC consumes a maximum of 60 mW from a 1.2 V power supply, which is comparable with the existing commercial navigation frontends.It took about eighteen months for our team to design the complete IC from the ground up incorporating various innovative ideas and to send it for fabrication. The chip came back from the foundry last December 2019. We designed the entire test and verification platform in the lab. Just before lockdown started, the IC’s functionality was successfully verified with GPS signals.

This project is funded by the Ministry of Electronics and Information Technology (MeitY), India. The team has been interacting with SAC-ISRO for specifications for 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 for mobile and commercial applications, Dhruva can be integrated into commercial implementations.

I would like to acknowledge all of my teammates contributed to Dhruva’s development: Santhosh Khyalia ( Ph.D. ), Ajinkya Kharalkar ( M.Tech ), Shubham Jain ( Ph.D. ), Swetha Jose ( M.Tech ), Jeffin Joy( M.Tech ), SyedHameed ( M.Tech ), Mukul Pancholi ( M.Tech ), Sumit Khalapure (Ph.D.)

Fig:  Clockwise from top left: 1) Die photo 2) QFN Packaged IC 3) PCB with Dhruva mounted

and 4) GPS satellites acquired