GPS Receiver Attracts New Applications

Many third-generation or 3G applications are going to require cellular positioning—both for accuracy and to provide new services. In order for an individual to be directed to the gas station nearest to his or her vehicle, for example, the car's location must first be pinpointed. The same can be said of non-3G-related services. Think of the injured person rescued with help from the E-911 mandate, or the trucking company's fleet that can now be tracked. All of these examples represent the quintessential way in which most of the world expects the Global Positioning System (GPS) to serve the public.

With the release of the PointCharger SE4100 integrated-receiver IC, however, it may be time to start imagining new applications for GPS. Hailing from SiGe Semiconductor, this product is the first member of the company's PointCharger family of GPS devices (see figure). It delivers benchmark levels of power consumption and integration. As a result, it enables the operation of peripheral devices to be smaller and less expensive while offering longer battery-powered operation. Such devices are used for automotive-vehicle-location (AVL), covert-tracking, security, cellular, personal-digital-assistant (PDA), and personal-navigation systems.

Specifically, the SE4100 integrates the IF filter, voltage-controlled oscillator (VCO), tank circuitry, and low-noise amplifier (LNA) into a compact, 4-mm² package. The resulting device has a typical current draw of 10 mA from a 2.7-V supply. Beyond saving space and power, the act of integrating the complete receiver chain onto a single device substantially lowers the bill of materials (BOM) compared to most commercially available radios. Obviously, the SE4100's goal is to reduce cost and form factor while easing assembly, manufacture, and test.

So far, it seems to have succeeded. The silicon-germanium-based device exhibits the industry's lowest power consumption for a GPS radio with this level of integration. It has roughly a third of the current draw of competing bipolar solutions. Its low power consumption, high-performance LNA, and low external-component count allow the device to be very cost effectively implemented in the portable devices that house a GPS antenna within the same enclosure.

The SE4100 GPS receiver IC also flaunts features that enhance performance. The on-chip switchable gain LNA, for example, delivers a very low noise figure of 1.3 dB typical. It also enables quick recovery from either the power-saving mode or a radio-frequency overload from a local transmitter. The integrated circuit delivers a digital 4.092-MHz output, which is suitable for industry-standard GPS baseband solutions. When paired with many leading baseband circuits, the whole system consumes less than 120 mW in continuous operation. In addition, the SE4100 supports other intelligent power-saving modes that are offered by its companion baseband chips.

With this combination of features, the SE4100 is a good fit for the baseband chips that combine GPS positioning with a simple user application and control of a cellular modem. This union enables portable personal-tracking and navigation applications.

The PointCharger SE4100 was specifically designed to meet the requirements of covert and always-on applications. It serves those applications in which power has to be supplied or backed up from a source that's separate from the main battery. In aftermarket automotive devices, such as tracking systems or alarms, the already low power consumption of the GPS radio can be switched off completely. Or, it can be left with just its oscillator running to provide a clock for the baseband chip.

An antenna-detect function is included in the design as well. It can alert a user to a missing or shorted antenna. The SE4100 also is a fit for railway or other transport applications in which the only power source is a solar cell and rechargeable battery.

The SE4100 is sampling to customers now. It is supplied with extensive literature and supported by SiGe's team of applications design engineers. The device is priced at $3.50 in quantities of 10,000 (U.S. pricing). It comes in a 24-pin LPCC package.