What a GPS chip has to do
A satellite positioning receiver has several jobs. It must pick up very weak radio signals from several satellites, identify each one, measure the arrival time of each signal to a tiny fraction of a second, decode the navigation message that gives satellite positions, and then calculate a location. Early receivers did this with separate components for the antenna, the radio-frequency section, the signal processing and the computing. Putting them into a few chips, and then into one, took roughly two decades of work.
Our article on early receiver hardware describes the first, bulky sets. The chip story starts where that one ends, in the late 1980s and 1990s.
Chipsets in stages
Engineers often describe the development as a series of steps rather than a single invention. The details vary by company, and exact dates in company histories are not always consistent, so the following is a general outline.
- Multi-chip sets: in the late 1980s and early 1990s, receivers were built around a few custom chips, one for the radio front end and others for correlating and processing the signals, plus a general-purpose microprocessor. This made handheld units possible, though power use and cost were still high.
- Highly integrated chipsets: through the 1990s, companies combined more functions, using the improving silicon chips of the time. Many of these suppliers sold chips to others, which let makers of navigation devices, rather than just the chip designers, build products.
- Single-chip receivers: in the 2000s, a receiver’s radio and digital processing could be placed on one piece of silicon, with the host device’s processor sometimes doing the final position calculation. This is the form found in most phones today.
The driver throughout was the advance in semiconductor manufacturing. Each new generation allowed more transistors on a chip, using less power per function, so that the heavy digital processing needed to search for signals could fit into a small, low-power package. The wider history of that process is covered in our article on integrated circuits.
Why phones changed the market
Early commercial demand came from surveyors, boaters, hikers and aircraft. In the United States, one important push for putting positioning into cellphones came from emergency calling. In 1996 the Federal Communications Commission issued rules requiring that wireless carriers be able to locate callers who dialed 911. Carriers could do this either with the network or by building positioning into the phones. The implementation took years and was done in phases, but the rules encouraged chip makers to develop receivers small and cheap enough for phones. The way these mobile devices developed is covered in our article on cellular networks.
Phones brought a particular problem: the receiver had to start quickly and work in poor conditions, such as indoors or between buildings. A standalone GPS receiver that is turned on after a long time can take a minute or more to acquire satellites, because it must download the satellite orbit data from a very slow broadcast. The solution was assisted positioning, where the phone gets orbit data and approximate time and position over the cellular network, allowing a much faster first fix. Some designs also used greater sensitivity, which allows tracking signals that are much weaker than those early receivers could handle.
Cars and consumer devices
Chips also made it possible to sell navigation devices at consumer prices. Some Japanese carmakers fitted satellite-based navigation as early as around 1990, and by the early 2000s such systems were common in expensive cars and then spread to cheaper models. Portable navigation units that stuck to a windshield became popular consumer products in the 2000s, until they were largely replaced by smartphones. The first handheld products of the period are covered in our account of handheld GPS.
Other uses followed as the cost of the chip fell:
- Cameras that record where a photo was taken.
- Fitness watches and trackers that map a run or ride.
- Fleet trackers for trucks and delivery vans.
- Pet and asset trackers, and devices that supply accurate time to equipment.
Increasingly, GPS functions were combined with chips for other wireless services, such as Wi-Fi and Bluetooth, so that one component handled several tasks.
Multi-constellation chips
Later chips are generally not GPS-only. They can use signals from other satellite navigation systems such as Russia’s GLONASS, Europe’s Galileo and China’s BeiDou. Using more satellites improves the chances of getting a fix in cities, where buildings block part of the sky. Some also use two frequencies to reduce errors caused by the atmosphere, a feature that was once limited to specialized equipment. Whether a particular phone does this depends on the model.
An unglamorous achievement
The GPS chip is rarely noticed, but the shrinking of the receiver is what turned a military navigation system into something that most people carry. A single chip in a smartphone does a job that once required equipment filling a rack. The chip also supports the technologies discussed in our article on smartphones, and many apps that depend on location, from maps to ride hailing, rely on it.