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A Key Component for Intelligent Transportation Systems

Tue, 04/14/2009 - 9:02am

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Proper timing components will not only produce optimal performance of your end design, but also deliver the most cost effective solution.

By NDK America, Inc.

Figure 1. Intelligent transportation systems could be use in accident avoidance between cars as signals would detect encroaching danger and automatic braking would be applied.
With General Motor’s OnStar services and Ford’s Sync system already positioned in their market and Europe’s C2C (car-to-car) and C2I (car-to-infrastructure) communication consortium striving to set a standard, wireless in and out of car communication is going to be on the rise. Features of these systems include hazard alerts, road conditions warnings, traffic jam diversions, optimal speed advisories, detection of emergency vehicles, remote diagnostics, internet access, pre-crash warnings, messaging to other vehicles, music, and information downloads. To take full advantage of these features a communication standard shared by all will need to be set, much like Bluetooth technology allows various devices from different manufacturers to work in harmony. Infrastructure technologies like LTE, WiMAX, 3G, and 4G are being considered as a potential backbone. Installed in the car would be a multifunctional femto cell feeding the intelligent transportation and entertainment system. It is important to work closely with your frequency control device supplier early in the design process. By sharing your electrical and environmental requirements, they will be able to suggest the proper timing components that will not only produce optimal performance of your end design, but also deliver the most cost-effective solution.

A Stable Frequency Source is Critical

Figure 2. The smallest available GPS specification TCXOs are the NT2016. It measures just W=2.0xD=1.6mm.
Safety applications where wireless technology is required demand an extremely reliable and stable frequency source. An application example of this might be an accident avoidance system versus a multi-media function. These safety applications require frequency control components that are manufactured to a higher level of performance standards. Whether a crystal unit or complete oscillator, manufacturers use specifically engineered materials and assembly processes to assure these timing devices can handle the various rigorous environmental challenges presented in real automotive conditions. These conditions include operation in the extreme temperature ranges of -40°C to +150°C and being capable of handling high shock and vibration (see Chart 1.) After assembly, these components are put through additional functional testing than non-safety applications.

Chart 1. Specifications for a crystal designed for safety applications.
Multi-function access points could possibly be the gateway inside of the intelligent automobile. Working with LTE and/or WiMAX infrastructure, they will deliver in-car communication access. Their main functions will be to deliver vehicle-to-vehicle and vehicle-to-infrastructure communication. A stable timing source for this application is an SMD VCTCXO, measuring 3.2 × 2.5 mm with a height of only 0.9 mm maximum. It allows the user to adjust the frequency by raising or lowering the voltage—thus locking or synchronizing it to a higher-level source. These devices are suited for GPS disciplined applications, giving the system a cost effective yet extremely stable & reliable frequency control solution in the event that the source is intermittently lost. They are available in a frequency range of 19.2 to 40 MHz and exhibit frequency stability over -10°C to +70°C at VCONT of 1.5 VDC is ۫.5 ppm max. The frequency slope is ۪.050 ppm/°C max. from -10° to +55°C and ۪.100 ppm/°C max. from +55 to +70°C (see Chart 2. for additional data).

Specifying the Correct Frequency Device


click to enlarge

Chart 2. Specifications for a VCTCXO for GPS disciplined applications delivers great cost verses performance benefits.
Additional functions could be added to these access points creating feature rich devices. They might provide functions such as internet access, GPS navigation, wireless phone service, WiFi wireless networks, and mobile PDA interface. They could also act as a distribution hub for multi-media and entertainment. Highly integrated circuits capable of processing the data received from the host are available to perform many of the functions for these end appliances. But, they too require a highly stable frequency source. Many integrated circuit manufacturers have recognized the importance of specifying the correct frequency devices for optimal performance. When IC manufacturers work closely with a timing device supplier, specifying the optimal crystals and or oscillators for the device before final tape-out, the end user’s design can enjoy a much faster time-to-market and volume. Since these access points are in a controlled environment, the frequency control components do not have to meet the same demanding requirements of a safety application, thus delivering reliable frequency sources at the most cost effective rate.

It sure sounds exciting and we are starting to see results from all the hard work happening in today’s market. There is a long way to go though in terms of setting an all vehicle standard to enable the full capabilities of intelligent transportation systems. As new applications arise, remember the importance of working early and closely with your frequency control supplier to achieve optimal performance and cost with your component selection.

About the Company
NDK America, Inc. is a leading manufacturer of quartz crystal electronic components, including Crystals, Crystal clock oscillators, XOs, TCXOs, VCXOs, OCXOs, MCFs, and SAW filters.  The company’s high quality products are found in an array of electronic devices in a broad range of industries. Contact NDK at 800-635-9825, www.ndk.com

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