Global Positioning System (GPS) receivers are being embedded into almost any bit of electronic gear that moves, from the electronic circuits in automobiles to cellular telephones and Personal Digital Assistants (PDAs). To support this "global" expansion, SiGe Semiconductor has developed its model SE4150L GPS radio receiver for next-generation embedded GPS applications. The tiny receiver targets the three main requirements of these emerging applications, with small size, low-power operation, and low bill of material (BOM) cost.
The SE4150L GPS radio receiver measures just 4 x 4 mm but provides the performance to support GPS service in a wide range of applications (see figure). The radio provides single conversion of L-band GPS signals at 1575.42 MHz, exhibiting a system noise figure of 1 dB and input third-order intercept of better than 0 dBm. The GPS receiver features a multi-bit (2-b SIGN and MAG digital IF) output, which improves sensitivity and interference resistance for GPS solutions.
The integrated-circuit (IC) receiver builds upon the success of the company's earlier silicon-germanium (SiGe) GPS receivers, models SE4120L and SE4110L. The SE4150L is optimized to run at +2.7 to +3.6 VDC, but incorporates current-controlled output buffers that support flexible interfacing over a wide supply voltage range of +1.7 to +3.6 VDC. To save battery power, the SE4150L draws less than 10 microamperes current in standby mode.
The SE4150L's small housing belies the level of integration within the receiver, which includes a fully integrated phase-lock-loop (PLL) frequency synthesizer, based on a voltage-controlled oscillator (VCO), that is compatible with the GPS 16.368-MHz reference frequency. The chip also contains a full downconversion receiver, with in-phase (I) and quadrature (Q) mixers, a buffer low-noise amplifier (LNA), input antenna LNA, linear automatic-gain-control (AGC) stage, intermediate-frequency (IF) filter, and analog-to-digital converter (ADC). The SE4150 has two gain/ intercept control inputs to optimize the front-end LNA and mixers.
The SE4150L GPS receiver simplifies dual-antenna system design since it integrates antenna sensing, switching, and includes a low-noise amplifier (LNA). This antenna-sensing capability eliminates the need for numerous discrete components to sense when an external antenna was connected.
The SE4150L automatically responds to connection of an external antenna and interfaces directly to the GPS baseband processor to form a complete GPS radio receiver system. As Stefan Fulga, director of Strategic Marketing, notes, "Because the LNA, switching functions, and the IF filter are on-chip, we have lowered the system noise figure and increased the input IP3 performance, which results in improved sensitivity and interference resistance when compared to existing products."
The SE4150L GPS receiver is supplied in a 24-pin QFN package and shipped in tape-and-reel format for use with automated assembly equipment. To help with design efforts, SiGe Semiconductor offers the SE4150LEK1 evaluation board and user guide and can provide on-site applications assistance to customers for the design and integration of a GPS system. P&A: less than $1.50 (10,000 qty.). SiGe Semiconductor, 1050 Morrison Dr., Suite 100, Ottawa, Ontario, Canada K2H 8K7; (613) 820-9244, FAX: (613) 820-4933, Internet: www.sige.com.