Dhruva, an indigenous guide chip

Location services have become an essential part of everyone’s life, especially for navigation using mobile phones. The popular location service is the Global Positioning System (GPS), a satellite navigation system owned by the United States of America. However, access to GPS is controlled by the United States government and is not always guaranteed. For example, the United States did not allow the Indian Armed Forces to use GPS during the Kargil War. This prompted the Indian government to develop its own indigenous satellite navigation system, NAVIC.

Working towards Atma Nirbhar Bharat, NAVIC (NAVigation with Indian Constellation) is an Indian locally developed satellite navigation system that provides reliable access across the Indian subcontinent. This constellation provides accurate position information service to users in India as well as the region extending up to 1,500 km from its border, which is its main service area. It also provides limited service beyond this region. The system can be used for land, air and sea navigation; disaster management; vehicle tracking and fleet management; visual and voice navigation for drivers; integration with mobile phones; mapping and geodetic data capture; visual and voice navigation for drivers; integration with mobile phones; mapping and geodetic data capture; location-based services; search and rescue services; visual and voice navigation for drivers.

However, none of the mobile manufacturers has yet integrated NAVIC as a common choice of positioning system. Currently, there is no single unified solution capable of receiving all NAVIC bands as well as various other global navigation satellite systems. This motivated Professor Rajesh Harishchandra Zele and his team at IIT Bombay to develop a NAVIC compatible RF receiver called DHRUVA.

Dhruva sows the seeds of high performance RF IC development in India, for India. Dhruva is the first locally designed navigation receiver chip to work for all NAVIC (L5 & S) and GPS (L1 & L2) navigation frequency bands. This is a starting point for becoming independent in this high-end technological field. Several PhD and MTech students are extensively trained to take circuit ideas from concept design to chip manufacturing and testing. This is one of the most important missions of the Indian government’s Fableless Chip Design initiative.

Developing such an integrated circuit involved several challenges. The signals received are very weak compared to the ambient noise. Thus, the receiver must eliminate all interfering signals, filter out the weak navigation signals desired, then amplify them almost 400,000 times, then digitize the analog signals using integrated analog-to-digital converters. The digital signal processor on DHRUVA processes digital signals to determine the user’s location.

Various circuit design innovations at Dhruva have resulted in the development of a production-ready receiver chip with robust performance under extreme temperature conditions.

The invention relates to a new compact and reconfigurable on-chip frequency synthesizer for navigation receivers. The synthesizer is based on a voltage controlled oscillator (VCO) with an on-chip frequency multiplier. A new control scheme is proposed which allows the use of a single VCO to synthesize multiple RF frequencies. A low phase noise high performance VCO with improved temperature characteristics is designed. The VCO operates over a wide temperature range of -40 to +125 degrees Celsius. The VCO operates at a 1.8 V supply voltage and draws only 1.5 mW from a 3 V supply. The synthesizer can be used in navigation receivers to synthesize multiple RF frequencies for signals navigation from the same chip.

In addition, a unique, compact and fully integrated Variable Gain Amplifier (VGA) for navigation receivers is designed in 65 nm CMOS technology occupying an active chip area of ​​1.96 mm². A new wideband input matched to a differential LNA with the on-chip harmonic matching network is offered to avoid external balun and matching networks in the front end of the receiver. A novel DC offset correction circuit is also provided which cancels the DC offset in the LNA output using an on-chip voltage controlled current source (VCIS).

Thus, the receiver is fully integrated with no external components, making it suitable for easy integration into system-on-chip for large-scale deployment in commercial applications such as vehicle tracking, vessel tracking, ship monitoring, etc. rail/road/water transport, and other navigation applications and consumer electronics such as mobile phones and tablets. With the specifications obtained, the VGA is suitable for navigation using IRNSS, GPS, Galileo and Beidou signals.

The development of this chip is a boost for indigenous technology development activities that could potentially guide a host of applications, particularly navigation.

Editor’s Note: This is part of the special Lab Stories feature we are bringing to you.

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