Effective use of RF test tools speed the design of in-vehicle radio systems - Embedded.com

Effective use of RF test tools speed the design of in-vehicle radio systems

This “Product How-To” article focuses how to use a certain product in an embedded system and is written by a company representative.

The percentage of in-vehicle modules equipped with radio interfaces hasgrown rapidly in recent years. Common applications include remotekeyless entry for car doors with theft protection, and transmitters foropening garage doors or for controlling auxiliary heating systems.

As a general rule, these components operate in the ISM band where nolicense is required. GPS-based navigation systems are also in greatdemand. More GSM modules are also being factory-installed in cars. Oneobjective is to improve the quality of mobile radio applications.

Another is to improve wireless audio communications where necessary,using Bluetooth interfaces for making phone calls and for audioreception among passengers. Some newer applications include tirepressure monitoring systems for bolstering the safety of cars andtrucks, and DVB-T receivers for dependable TV reception.

In some cases, diagnostic systems with radio interfaces have alreadybeen installed for use by car repair centers and emergency helpers.Other applications include radio sensors for monitoring temperature,pressure and speed parameters in the engine compartment.

In the near future, we can expect to see radio interfaces based onWiMAX and other standards for mobile reception of high data rates.Radio communications systems that will help prevent vehicle collisionsare also being developed.In all of these examples, a radio interface isneeded.

Depending on the particular requirements, these interfaces operatein different frequency bands and need to be optimized for differentdata rates and safety standards.These new technologies are highlydependent on reliable functioning of the radio interface.

In case of safety-related systems, proper operation can mean thedifference between life and death.During production, modules musttypically be checked and adjusted to ensure compliance with theapplicable radio standard (Table 1below ).

Table1: Modules must be checked and adjusted to ensure compliance with radiostandard.

The safety aspect, in conjunction with extreme requirements posed bycan also be fitted with absorbers to attenuate reflections ofhigh-frequency electromagnetic waves and ensure stable, reproduciblemeasurements. Absorbers are also effective in audio applications,reducing internal reflections and ambient sound.

New RF test chambers of the R&S TS712x series (Figure 1, below )are geared towardfulfilling the requirements of automatic production lines.Characteristics include long service life, rugged design and automaticopening and closing of the RF chamber.

With a frequency range of 300MHz to 6GHz, the chambers are suitablefor tests on modules with radio interfaces based on standards such asISM, GSM, CDMA, UMTS, Wi-Fi, Bluetooth and WiMAX.The product family hastwo base models that differ primarily in terms of width.

Figure1: With a frequency range of 300MHz to 6GHz, the test chambers aresuitable for tests on modules with radio interfaces based on a widevariety of standards.

Each of these models also comes in automatic and manual versions tomeet different needs. The narrow TS7121 model has a width of 155mm andis intended for testing smaller devices such as RFID modules, radiosensors and receivers, remote keyless entry and smaller Bluetoothmodules.

With a width of 330mm, the TS7123 model handles tests on deviceswith up to double-height DIN slots and is suitable for testingautomotive applications such as car radios, navigation systems andinfotainment systems.

The wider RF chamber also provides room for integrating subsystemsfor generating special ambient conditions. A good example is a pressurechamber for testing sensors used in tire pressure monitoring systems.

By combining the two chambers, you can perform tests on the radiointerfaces and check whether the tire pressure sensors are workingproperly under a wide range of pressure conditions. The automotiveindustry requires suppliers to perform extensive tests, includingdocumentation of test results.

The TS7810 RF test system comprises an RF test chamber and softwarefor final testing of tire pressure sensors.The pressure chambersimulates tire pressure inside the RF test chamber.

Figure2: A waveform generator stimulates the tire pressure sensor with a125kHz LF data telegram to transmit its data, including ID number,pressure and temperature.

A waveform generator (Figure 2 above )stimulates the tire pressure sensor with a 125KHz LF data telegram totransmit data such as ID number, pressure and temperature. The RF datatelegram is picked up by an ISM antenna in the test chamber anddemodulated in the spectrum analyzer.

The system software evaluates the information and gives Go/NoGoinformation.Automatic RF test chambers are used primarily in productionapplications. The manual version is designed especially for use inservice work, quality assurance, and research and development.

Table2: When combined with suitable antennas, RF test chambers can be usedto rapidly implement a wide variety of applications.

Since automatic and manual versions of the RF test chambers have thesame basic design, identical measurement conditions are ensured indevelopment, production and service work. When combined with suitableantennas, the RF test chambers can be used to rapidly implement a widevariety of applications.

They provide an optimum solution in cases where fast retooling ofproduction processes is essential (Table2 above ). Finished products are released to the market withoutstanding quality, which can represent a critical competitiveadvantage in the future.

Gert Heuer is Product Manager atRohde & Schwarz

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