Location-based products using Global Positioning Satellite (GPS) signals are poised to revolutionize wireless service. Implementation of federally mandated mobile subscriber location requirements is fueling the rush to market. Meanwhile, manufacturers plan to capitalize on the presence of GPS-enabled mobiles by developing new consumer-oriented software applications and next-generation hardware that will make purchasing goods and services through wireless devices commonplace.
One of the most critical and essential elements of GPS receiver design is filtering at the RF stage. RF filters must be capable of providing ultra-low insertion loss to minimize signal recovery errors. Such errors can result in a loss of signal that could have dire consequences in E911 situations. Superior attenuation is also vital at key frequency ranges occupied by transmitters operating in all major voice and data protocols including AMPS, CDMA, TDMA, GSM and PCS. Size is another critical element for designers who look for a way to include the additional GPS receiver chain on already crowded PC boards.
A new GPS Rx surface acoustic wave (SAW) filter is designed to specifically address key performance specifications by providing typical insertion loss of just 1.3 dB and typical attenuation of 50 dB at the critical 824 to 869 and 1640 to 1926 frequency ranges. Figures 1 and 2 show the filter's typical insertion loss and attenuation vs. frequency, respectively. The model 855969 SAW filter is centered at 1575.42 MHz, with a bandwidth of 2.4 MHz for top performance. In addition, its 3.0 × 3.0 × 1.2 mm3 surface-mount package is 94 percent smaller than the current ceramic alternative, making it easy to incorporate into any PCB application. The product also features a simple 50 Ω single-ended source and load configuration, and requires no impedance matching for operation at 50 Ω .
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Additional information may be obtained from the company's Web site at www.sawtek.com on the "What's New" page, or phone for data sheets and full specifications. Purchase information may be obtained from Avnet Electronics Marketing at (800) 332-8638 or visit Avnet's Web site at www.em.avnet.com.
Sawtek Inc.,
Orlando, FL (407) 886-8860.
Circle No. 303