New RF test solution ensures quality of automotive wireless modules

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New RF test solution ensures quality of automotive wireless modules [Copy link]

The use of modules and devices with a wide variety of RF interfaces is growing in all kinds of vehicles. Because these modules must meet stringent reliability requirements, reproducible measurement results must be obtained during adjustment and final testing. With highly effective shielding and rigorous design, the new RF test chamber equipment from Rohde & Schwarz ensures that automotive modules with RF interfaces are tested without interference. It supports a wide range of standards, including ISM, GSM, CDMA, WLAN and Bluetooth.

Today, car buyers expect to buy well-made, reliable and, most importantly, safe communication and infotainment systems. The challenge facing current and future car manufacturers is to create reliable test methods to ensure the quality of these systems. As product life cycles become shorter and the in-vehicle electronics become more complex, designers need faster and more flexible solutions to meet the challenges of fast time to market. Rohde & Schwarz equipment and systems provide excellent measurement accuracy and speed to meet these requirements.

Figure 1: Rohde & Schwarz RF test system for tire pressure sensors

Wireless modules in cars

In recent years, the number of in-vehicle modules equipped with RF interfaces has grown rapidly. Common applications include: remote keyless entry (RKE) systems with anti-theft protection, transmitters for opening the trunk or controlling the auxiliary heating system. Generally speaking, these modules operate in the unlicensed ISM band. There is also a huge demand for GPS navigation systems. More and more GSM modules are also entering the automotive original equipment market. One goal is to improve the quality of mobile radio applications; another goal is to improve the quality of wireless audio communication, where Bluetooth interfaces are used to make calls and receive audio signals among passengers.

Some newer applications include tire pressure monitoring systems for ensuring the safety of cars and trucks, and DVB-T receivers for reliable TV reception. In some cases, diagnostic systems with RF interfaces have been installed in car repair centers and emergency support centers. Other applications include: sensors for monitoring engine compartment temperature, pressure and speed parameters.

In the near future, we can expect to see RF interfaces based on WiMAX and other standards used for high data rate mobile reception. Radio communication systems that help prevent collisions between vehicles are also under development. In all these examples, RF interfaces are needed. Depending on the specific requirements, these interfaces operate in different frequency bands and need to be optimized to support different data rates and security standards.

Figure 2: Block diagram of the RF test system of Figure 1

These technologies are highly dependent on the reliable functioning of the RF interface. In safety-related systems, correct operation can be a matter of life and death.

At the beginning of production, these modules must generally be checked and adjusted to ensure compliance with the applicable wireless standards. Safety aspects must be able to cope with extreme environmental conditions, and the interfaces must be thoroughly tested after final installation. Here, it is necessary to test the effects of large temperature changes and vibration resistance.

In order to obtain reproducible results for RF interface tests, it is crucial to ensure that external interference does not affect the test. In addition, it is necessary to ensure that other nearby devices and test systems are not affected by the test. The only way to meet these requirements is to use an RF chamber with appropriate shielding (Figure 2). The chamber can also be filled with absorbent materials to attenuate the reflection of high-frequency electromagnetic waves and ensure stable and reproducible measurements. Absorbent materials are also effective in audio applications, namely to reduce internal reflections and ambient noise.

Rohde & Schwarz has a deep foundation in RF technology and is currently expanding the company's tested product line of manual RF test fixtures to a new product series of RF test chambers.

RF Test Chamber Product Line R&S TS712x

The new RF test chambers of the R&S TS712x series are designed for the needs of automated production lines. Features include long service life, rugged design and automatic opening and closing of the RF chamber. With high shielding effectiveness in the range from 300MHz to 6GHz, the test chamber is suitable for testing modules with RF interfaces that comply with various standards, including ISM, GSM, CDMA, UMTS, WLAN, Bluetooth and WiMAX.

The product family has two basic models, which differ in width. To meet different needs, each model has an automatic and manual version. The narrow model is the R&S TS7121, which is only 155mm wide and is mainly used to test smaller devices such as RFID modules, wireless sensors and receivers, RKE and smaller Bluetooth modules.

The R&S TS7123 instrument has a 330mm wide handle for testing electronic devices in double DIN slots, making it ideal for automotive testing. This model is suitable for testing car radios, navigation systems and infotainment systems. The wider RF chamber provides more space to integrate subsystems that generate special environmental conditions, and the pressure chamber used for TPMS pressure sensor testing is a good example. By combining the two chambers, the RF interface can be tested and the tire pressure sensor can be checked for proper operation under a wide range of typical pressure conditions.

Table 1: Application of various wireless standards in the automotive industry

The automation industry requires its suppliers to perform extensive tests, including the documentation of the test results. Only an automated test system like the R&S TS7180 equipped with an RF test chamber can meet this requirement.

The pressure chamber simulates the tire pressure inside the RF test chamber. A waveform generator stimulates the tire pressure sensor with a 125kHz LF data telegram to send data (ID number, pressure and temperature). This RF data telegram is picked up by the ISM antenna in the test chamber and demodulated in the spectrum analyzer. Its system software evaluates this information and gives a GO/NoGo message.