GPS (Global Positioning System) satellite receivers are proliferating for myriad nomadic systems applications. If you’re not a microwave designer comfortable crafting RF circuits at 1.5-GHz, however, vendors are making it easier to embed critical high-performance GPS blocks.
Numerous off-the-shelf products range from receiver/active-antennas to LNAs (low-noise amplifiers) to single-chip and modular GPS receivers.
Look at the square-inch-sized Jupiter 30 GPS module from Navman Ltd. Slated for weak-signal applications that require geographic position information, the Jupiter 30 is a single-supply surface-mount receiver that integrates both baseband and RF sections.
The Jupiter 30 especially shines attaining GPS position fixes under low signal-strength conditions. It supports 20-channel operation, and can be integrated into products with active or passive GPS antennas.
In operation, the Jupiter 30 module can process nanovolt-level signals as low as -160-dBm. It uses more than 200,000 effective correlators, which makes it suitable for receiver designs that can track inside buildings, parking garages, shopping malls, and other low signal-strength environments.
Hot Acquisition Time
Nonetheless, the Jupiter 30 is fast. So-called hot acquisition time is less than one second to a first fix, with 32 seconds required for a warm start. Significantly, the module will acquire satellite signals in just 34 seconds from a complete cold start.
Navman makes this possible by use of shaped-filtering to reduce noise, and multi-path mitigation techniques. These features ensure track re-centering and elimination of jamming signals. A dynamic search feature also helps adapt the receiver in severe environments.
Internally, the Jupiter 30 marries a 0.5-ppm TCXO (temperature controlled crystal oscillator), an LNA, flash memory, and a SiRF Technology GSC3 chipset.
The Jupiter 30 also runs its own embedded ARM7 microcontroller (you’ll ultimately have an embedded design within your embedded design). The ARM (Advanced RISC Machines) micro has sufficient spare capacity for customizing your end-application.
Click to view block diagram
The 3-V Jupiter 30 is also power-managed and provides its own on-module voltage regulators. The device draws about 52-mA on average, dropping to 25-mA clocking at 1-Hz. A Hibernate mode drops current demand to a trifling 6.8-µA, which is just the ticket for battery-powered portable designs.
Click here for a previous eeProductCenter review, and additional information on the Navman device.
Or, search www.eeProductCenter.com for Article ID: 186500047.
NavSync Ltd. is another company making 3-V GPS receiver modules. NavSync is offering two new models in its CW25 Series. These surface-mount modules, measuring about the same size as Navman’s Jupiter 30 modules, can track at signal levels as low as -157-dBm, acquiring GPS lock at signals as low as -143-dBm. Even inside buildings.
The modules will give you a TTFF (time to first fix) of under 45 seconds outdoors during a cold start.
A Model CW25-ULS GPS receiver module, equipped with an embedded ARM 966E-S processor, is priced at $44. It has the same features as NavSync’s $40 CW25-NAV, but with the ability to use network assist data to quickly lock in on satellites under very low signal levels down to -155-dBm.
The network assist feature requires that ephemeris data be uploaded from a central base-station. As you’d expect, NavSync produces a Model CW55 GPS base-station designed to provide the network assist data via the GPRS network. The GPRS system can transmit to all CW25-ULS units located in a region.
Thanks to its high level of integration, this module gives you three ready-to-go serial I/O ports that are programmable to speeds of 38.4-kbits/s. Similarly, you get a 1-PPS (pulse-per-second) clock output and general purpose I/O, as well as NMEA (National Marine Electronics Association) connectivity and ASCII outputs.
Click to view block diagram
The CW25 modules are also power misers, typically drawing about 1-mA, but dropping to 1-µA in a power-down mode.
Click here for a previous eeProductCenter review, and additional information on the NavSync GPS module.
Or, search www.eeProductCenter.com for Article ID: 175400122.
Other companies also offer GPS receiver building blocks, and some of them are entirely monolithic. IC maker Atmel Corp. and Europe’s u-blox AG, for example, are jointly rolling out a single-chip dubbed the Antaris4 ATR0630.
The ATR0630 includes WAAS/EGNOS (Wide Area Augmentation System/European Geostationary Navigation Overlay Service) support, as well as A-GPS (Assisted GPS). This receiver provides a TTFF as low as four seconds.
Measuring 0.28 x 0.40-in. in size, the ATR0630 comprises a 16-channel GPS receiver. Like the Navman module, it packs an ARM7TDMI core, too, as well as RAM and ROM-based firmware. Unlike many Atmel ICs, no flash memory is used.
The ATR0630 provides on-chip USB (Universal Serial Bus) and SPI (Serial Peripheral Interconnect) connectivity, too. It requires just one external crystal for clocking; this need not be a TCXO.
The 96-pin BGA (ball grid array) package dissipates just 62-mW, which is just what’s needed in applications such as cellphones or consumer navigation products. The ATR0630 also includes a FixNOW power-savings feature, together with power management. These can bring current demand down to as low as 5-µA.
Click here for a previous eeProductCenter review, and additional information on the Atmel-ublox chip.
Or, search www.eeProductCenter.com for Article ID: 180203225.
Another board real-estate saving monolithic GPS receiver is soon to be available from SiRF Technology. The company’s pre-announced GSCi-5000 chip, intended for A-GPS operation, will be optimized to address the space and cost constraints of cellphone handsets.
Using a protocol based around 3GPP (Third Generation Partnership Project) A-GPS messages, SiRF says its GSCi-5000 will especially lend itself to cellphone software integration.
The ROM-programmed GSCi-5000 receiver, to be fabbed in CMOS and SiGe (silicon-germanium), will pack all of the functional blocks of a GPS receiver into a device measuring just 0.16 x 0.24-in., with a 40-mil Z-height.
LNA And Synthesizer
To be packaged in a 77-pin BGA, the diminutive GSCi-5000 looks like it will be a GPS powerhouse. It will include an on-chip LNA, as well as its own frequency synthesizer. Like the Navman module, SiRF’s chip will include circuitry to minimize RF jamming and compression.
Like the Navman module and Atmel IC, the GSCi-5000 will also be power-managed. It will offer a combination of self-managed periodic fix modes and a 5-µA Sleep mode.
Click here for a previous eeProductCenter review, and additional information on the SiRF chip.
Or, search www.eeProductCenter.com for Article ID: 180200705.
Transceiver With GPS
Qualcomm Inc. is also dishing up GPS silicon, but its device will be a single-chip CDMA2000 cellphone transceiver with simultaneous GPS.
Slated for delivery by year’s end, Qualcomm’s RTR6500 chip’s receive diversity function is designed to improve network capacity, and its integrated simultaneous-GPS provide a way to put location services into your handset design. The CMOS RTR6500 transceiver will support 800-MHz, 1.8-GHz, 1.9-GHz, and 2.1-GHz cellular applications.
The RTR6500 transceiver will also be power-managed, using Qualcomm’s IntelliCeiver dynamic power optimization designed to increase a cellphone’s talk and standby times. The IntelliCeiver will also monitor cellular RF signals and reduce current draw when higher power isn’t needed to transmit.
Click here for a previous eeProductCenter review, and additional information on Qualcomm’s devices.
Or, search www.eeProductCenter.com for Article ID: 184428902.
Speaking of LNAs, if you’re customizing your own GPS circuitry, you may want to check out the SMA661AS LNA devices from STMicroelectronics. The company is in the process of expanding its existing family of silicon MMICs (monolithic microwave ICs). A newly released MMIC amplifier is a single-chip designed expressly for GPS.
STMicroelectronics’s SMA661AS is billed as the first LNA MMIC with integrated matching networks and a power-down function. The 35-cent device, requiring only a single external input capacitor, is designed to reduce your BOM (bill of materials), and slash board real estate.
Implemented in 70-GHz SiGe BiCMOS, the temperature-compensated SMA661AS will give you a power gain of 17-dB at 1.575-GHz. Its NF (noise figure) is just 1.4-dB.
From the point of view of power, it draws 8.5-mA, but has a standby current demand of only 10-nanoamperes. SMA661AS devices are packaged in SOT-666 plastic packages measuring just 0.066 x 0.048-in., with a 22.8-mil profile.
Click here for a previous eeProductCenter review, and additional information on STM’s LNA.
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A competing company making LNAs is NEC California Eastern Laboratories. Its wares are optimized for in-vehicle GPS applications at 1.5-GHz.
The NEC UPG2311T5F LNA chip is a 2-stage affair, with provisions for a bandpass filter between the stages. You can see this partitioning in the block diagram (below).
Click to view block diagram
Housed in a 0.12 x 0.12-in. QFN surface-mount package, the UPG2311T5F is intended to replace two stages of discrete devices to simplify design, reduce parts-count, and lower the cost of assembly. Gain is 37-dB and the chip’s NF is 1.2-dB.
Click here for a previous eeProductCenter review, and additional information on NEC’s LNA.
Or, search www.eeProductCenter.com for Article ID: 183702523.
If you’re looking for a turnkey GPS receiver, check out Trimble Navigation Ltd.’s Acutime Gold GPS timing receiver. Slightly larger than a baseball and housed in an environmentally sealed enclosure, Trimble’s Acutime Gold provides a PPS output synchronized to Universal Coordinated Time within 15-ns.
It’s designed for adding GPS timing and synchronization into any application where ease of installation and long-term reliability is needed. Billed as a smart timing antenna, the unit is a pole-mounted GPS receiver and antenna.
The system can provide an independent timing source, within a firewall for example, for applications such as network fault detection or synchronization of wireless networks.
Once power is applied, the Acutime Gold receiver automatically tracks satellites and surveys its position to within meters. It then switches to over determined time mode and generates a PPS, outputting a time tag for each pulse. The system also outputs Trimble's TSIP ( standard interface protocol) or the industry-standard NMEA.
The Acutime Gold unit requires less than 70-mA at 12-V. It also meets the RoHS European Directive restrictions for hazardous substances.
Click here for a previous eeProductCenter review, and additional information on this Trimble receiver-in-an-antenna.
Or, search www.eeProductCenter.com for Article ID: 187000071.
For More Information
To learn more, contact these companies mentioned in this article, use these references:
Atmel Corp., 2325 Orchard Parkway, San Jose, Calif. 95131. Phone: 408-441-0311
Atmel, 408- 441-0311, www.atmel.com
Navman Ltd., New Zealand. Phone: +1-949-461-7150
Navman Ltd., +1-949-461-7150, www.navman.com
NavSync Ltd., Bay 143, Shannon Industrial Estate, Shannon, Co. Clare, Ireland. Phone: 00 353 61 475 666. Fax: 00 353 61 472 226. E-mail: email@example.com
NavSync (USA), 630-236-3026, www.navsync.com
NEC California Eastern Laboratories, 4590 Patrick Henry Dr. Santa Clara, Calf. 95054. Phone: 408-919-2247. Fax: 408-919-2213.
California Eastern Laboratories, 408-919-2247, www.cel.com
Qualcomm, Inc., 5775 Morehouse Dr., San Diego, Calif. 92121. Phone: 858- 587-1121. Fax: 858-658-2100
Qualcomm, 858-587-1121, www.qualcomm.com
SiRF Technology, Inc., 148 East Brokaw Rd., San Jose, Calif. 95112. Phone: 408-467-0410.
SiRF Technology Holdings, 408-467-0410, www.sirf.com
STMicroelectronics, 39, Chemin du Champ des Filles, C. P. 21, CH 1228 Plan-Les-Ouates, Geneva, Switzerland. Phone: +41 22 929 29 29. Fax: +41 22 929 29 00.
STMicroelectronics, +41 22 929 29 29, www.st.com
Trimble Navigation Limited, 935 Stewart Dr., Sunnyvale, Calif. 94085. Phone: 408-481-8000.
Trimble, 408-481-8000, www.trimble.com
u-blox AG, Zürcherstrasse 68, 8800 Thalwil Schweiz, Switzerland. Phone: +41 44 722 74 44
u-blox AG, 41 44 722 74 44, www.u-blox.com