Pieces of equipment these days can let us know where they are. As a result of this, many new designs can take advantage of being trackable; not only can a query determine the route something has taken, but also other sensory data can be fused with this information to create a complete picture of the conditions that it has been exposed to (now common practice for verifying the freshness of produce).
People can be tracked like commercial assets, too, and we all have experienced smartphones and tablets connected with 3G and 4G services that feature location-awareness and location-sharing features. This is done with cellular algorithms that measure time, phase, and signal strength to arrive at an interpolated position which can be overlaid on a map or even an overhead satellite photo. Analysts predict the indoor location market to reach $4 billion in 2018.
While private and commercial Wi-Fi sources can be used as location beacons, Wi-Fi is not everywhere. Also, conditions can change, equipment can break or malfunction and, like maps, all of this data needs to be maintained to remain accurate.
GPS has fewer issues. Thanks to increasing demand and competition, newer generations of OEM GPS devices and modules use less power, are smaller, and have simpler user interfaces. Off-the-shelf modules are ready to place on your main board or in your box, and, you do not have to wait and pay for cellular services.
This article looks at some new GPS solutions for location-aware designs that use less power, are smaller in size, and are more highly accurate and dependable than previous parts. All parts, module, datasheets, development kits, and training material referenced here can be found online at Hotenda’s website.
Critically important components
The rapid development and use of drone aircraft is helping to create a booming market for precise, location-aware systems. This is no longer just a military technology, as news agencies, emergency disaster relief services, and same-day shipping companies are all vying to be a part of this trend.
Precise redundant location awareness is essential in these semi-autonomous machines as they will have to conform to mapped-out flight paths and no-fly zones. With liability at stake, a company could go belly up if one of its drones malfunctions and falls out of the sky, potentially causing damage or injury. So it is difficult to underestimate the importance of the GPS components used in these systems.
The ability to measure location may depend on the location of the GPS chips or modules. The main L1 1575.42 MHz RF signal from space satellites are weak signals and materials surrounding the GPS antenna may further weaken the signal. Also, the location of the GPS module can affect signal recovery, especially with a lot of high-speed digital switching taking place.
As a result, for critical applications, external antennas can be used like the Taoglas MA206.A.AB.004
adhesive-mounted 50 Ω GPS antenna disc (Figure 1). The Stingray, as it is called, is a GPS antenna and active (2.7 to 3.3 V) LNA that can be mounted remotely, such as on a mast of a ship. The relatively low noise (1.5 dB) and the high 32 dB gain are also sensitive at 2.4 GHz, allowing its dual use for G3/G4 use when close to land.
Figure 1: This active dual-band external antenna can extend the range and sensitivity of an embedded GPS chip or module that may not have a clear and unobstructed line-of-sight access to satellite data streams.
A ruggedized version of this approach is available out of the box with the Parallax 28508
combo GPS module and external coax antenna. Based on a BASIC Stamp module inside, it is usable as is or as a development and learning kit.
With GPS, the smaller the better, and since at the heart of every module is at least one chip, designers who wish to take matters into their own hands can take advantage of the chip-level solutions available. For very-high-volume applications, this can save money and result in the best design for the application.
Chip-level devices like the Skyworks SE4150L-R
provide a highly-integrated solution including dual-gain mode LNA (0 and 11 dB), dual-gain-mode mixer buffers (32 and 24 dB), and antenna switch with override. This part features two inputs that are selectable and is capable of detecting antenna currents to select the best input source.
Based on Silicon Germanium technology, the Skyworks part uses a highly linear on-chip LNA with one of the inputs allowing it to be used in a multifunction wireless system without external LNAs. A nice image reject, low-IF mixer is used with a linear AGC and on-chip IF filters as well.
Optimized for 3.3 V operation, the small (4 x 4 x 0.9 mm) fully-integrated receiver draws less than 10 µA in standby mode and features a nice flow-through layout to the GPS baseband devices. Note, an external antenna and/or matching networks are still needed, but in chip form designers can place parts to optimize mechanical constraints.
Maxim is another player in this arena and features its MAX2769BETI/V+
Universal GPS receiver chip, also with integrated high-performance LNA, antenna sensor and programmable gain amplifiers. The part sends ADC data to baseband or DSP processing as 4-bit signals representing sign and magnitude, unsigned binary, or two’s-complement formats with up to 3 bits per channel for I and Q data.
Also optimized for 3.3 V operation, the LNA and mixer inputs are 50 Ω. Operating from –40⁰ to +85⁰C, the parts draw a considerable 27 mA of current while in receive mode. Maxim also supplies PCB layout guides as a starting point.¹
Modules and canned solutions
For most engineers, the advantage of a module is that everything is small and self-contained (though it is still true that external antennas may be desirable to maximize sensitivity). Surface-mountable solutions are ideal since typically these modules will be carried on some sort of motherboard. What’s more, many of today’s modules are getting as small as the discrete chips we have to work with.
Take a look at the Telit Jupiter JF2-B3A3-DR
. This complete 48-channel GPS receiver module is larger than an individual 4 mm x 4 mm chip, but incorporates embedded Flash and supports international specifications including the GNSS Russian GPS counterpart (Figure 2). As a fully complete and characterized module, it specifies positioning accuracy down to less than 2.5 m, speed accuracies of 0.01 m/s, and heading accuracies less than 0.01⁰ resolution.
Figure 2: Fully-integrated modules include support for active and passive antennas. Serial access to data, control registers, RTC, and Flash can reduce overall system chip count.
It uses standard serial bus communications like I²C, SPI, and UART to save space, as do other members of the Jupiter F2 family of small-sized modules. It also features an impressive –163 dB sensitivity with features such as the ability to integrate with cellular services for semi-redundant operation (one or both signals may not be available at all times).
Telit also has the 3.3 V Jupiter N3 family with modules like the JN3-B3A3-LY
. While drawing a higher 32 mA of current, these modules feature fast time-to-location. This could be a critical feature in some circumstances. The module also includes a significant 16 Mbytes of Flash, enough for a fairly good map store of at least local destinations.
The JN3 builds on the SiRFstarIV architecture and uses instant fix and active jammer removal technologies that can help it navigate with –160 dBm sensitivity and track to –163 dBm sensitivity. It also supports satellite-based augmentation systems including WAAS, EGNOS, MSAS, and GAGAN services.
Many new and veteran players are actively supporting GPS and a lot of RF expertise is being used to create well-engineered modules for immediate use. Take a look at Taiyo Yuden’s GYSFFMAXX
technology, which also features an excellent –164 dBm sensitivity in its own little self-contained module (Figure 3).
Figure 3: The integration of true GPS into a peripheral-like functionality allows embedded host systems to be aware of location as part of its fused sensory inputs.
Like many new modular solutions, the self-contained systems also incorporate SBAS extended Ephemeris support (BEE and EPO), which improves horizontal position accuracy by correcting GPS signal errors caused by ionosphere disturbances, timing, and satellite orbit errors.
Another contestant is Inventek with its ISM480F1-C4.1
SiRFstar module with antenna. It also monitors and verifies 48 tracks at 1.8 V (with 3.3 V-tolerant I/O) with anti-jamming, incremental ephemeris collection (for fast first time fix), and serial interfaces (here UART, SPI, and I²C). Its –162 dBm sensitivity is pretty good, too.
Antenova is an antenna maker who is also supplying high-performance GPS modules like the M10382-A1
surface-mount module (Figure 4). Operating at 1.8 or 3.3 V (45 mA), this part is one of the company’s Radionova series receivers supported by the company’s Eval Kits. A smaller M10478-A1
module is also available, which draws a reduced 33 mA at 1.8 V supply.
Figure 4: Leveraging its antenna design experience, Antenova’s GPS modules integrate a high-performance antenna.
While an intimidating technology to some, the modern day implementations of GPS subsystems as a peripheral type of function has been sufficiently size- and cost-reduced to make it very attractive to designers. More companies entering this arena means new concepts as well as more aggressive pricing, making GPS location-aware technology economically feasible for additional (and perhaps not yet thought of) applications.
For more information about the parts discussed in this article, use the links provided to access product pages on the Hotenda website.
- Maxim Integrated “General Layout Guidelines for RF and Mixed-Signal PCBs”