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Linley Newsletter

Imagination Cuts GNSS Power

November 20, 2018

Author: Tom R. Halfhill

It’s midnight curfew. Your teenagers are safely home, but do you know where your cows are? Tracking farm animals is only one application for a low-power location device that employs a global navigation satellite system (GNSS). Others include cargo logistics, smart-city infrastructure, remote patient monitors, and any mobile IoT client. But conventional GNSS positioning may use too much energy for a small battery-powered tracking device. So Imagination Technologies is offering a new synthesizable hardware/software package that can integrate a low-power GNSS receiver in almost any chip.

Imagination announced the Ensigma Series 4 GNSS package at the recent Linley Fall Processor Conference. It’s licensable intellectual property (IP) for chip designers that’s based on previous Ensigma designs for Wi-Fi and Bluetooth (see MPR 6/22/15, “Imagination Whispers to Wearables”). It includes a GNSS tuner, a MIPS M6250 core, internal mem­ory, accelerators for vector processing and fast Fourier trans­forms (FFTs), interfaces for a host CPU and host mem­ory, and GNSS software. The MIPS core, assisted by the accelerators, performs the GNSS baseband tasks.

The Series 4 supports the GPS, Glonass, Beidou, and Galileo constella­tions (or any subset). The package omits the analog front end (AFE), which isn’t synthesizable and which the custom­er licenses separately. Excluding the AFE, the full set of En­sigma compo­nents occupy about 2.5mm2 of silicon in 40nm CMOS.

To save power, Ensigma Series 4 quickly acquires a satellite fix and shuts down until the next location update. It’s designed for devices that need fewer updates than a fast-moving vehicle. Because farm animals, shipping containers, and home-care patients usually move more slowly than cars, periodic fixes are sufficient. Even an autonomous tractor plowing a field may need to fix its position less often than a vehicle traveling on a public street. By supporting the major constellations and offering configurable IP that’s stingy with every milliwatt, Ensigma Series 4 can bring location awareness to a wider array of low-power devices. 

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