Record and Playback Capabilities for Car Radio and GPS System Testing

December 1, 2012

With its international headquarters in Germany, IAV Automotive Engineering is one of the leading engineering and design providers for the automotive industry, working for automakers and component suppliers such as Audi, Bentley, BMW, Chrysler, Daimler, Ford, General Motors, Porsche, and Volkswagen. One of the company’s recent projects involved testing and validating in-vehicle radio and navigation systems for one of Germany’s leading car manufacturers.

IAV must perform thorough RF signal testing on these devices for all common analog and digital broadcast standards in Europe, including AM/FM, RDS, TMC, DAB/DMB, GPS, and HD Radio (IBOC). The company tests signals on various device models with a variety of functions and for diverse types of radio programming. In addition, these devices must be tested in various environmental and driving conditions throughout Europe, from a sunny day in London to a snowy night on winding roads in the French Alps.

Reproducible and Repeatable Methods

As part of this evaluation, IAV first performed static test and validation in the lab using a typical signal generator to measure metrics such as threshold, sensitivity, and signal-to-noise ratio. However, many problematic RF signal behaviors can only be experienced in a dynamic environment such as a moving vehicle. These impairments include multipath interference that occurs when a signal bounces off city skyscrapers, or weather-related fading and distortion due to fog and rain. Mathematical models and test file libraries fall short in emulating these degradations.

As a result, IAV sends dozens of “expert listeners” on the road every year to detect signal glitches for every possible test case. However, because this method offers no reproducibility — test engineers are required to travel for every radio model and every signal — this method becomes time-consuming and costly.

IAV needed to assemble a library of comparison points to help evaluate different devices under the same signal with different conditions, and under different signals with the same conditions, as well as other permutations. They needed repeatability to make their test and validation operations as efficient as possible.

Record and Playback Capability

To help address these challenges, IAV worked with engineers from Averna. IAV purchased the Averna RF Signal Record and Playback System — a turnkey solution for recording real-world signals and playing them back for laboratory analysis and part of the Universal Receiver Tester (URT) platform.

IAV built the record and playback system on the NI PXIe-1065 chassis, NI PXIe-8106 embedded controller, NI PXIe-5672 vector signal generator, and NI PXI-5661 vector signal analyzer, all from National Instruments (NI, Austin, TX). These key technologies offer up to 2 GB/s per-slot dedicated bandwidth for real-time data streaming from the RF module to the hard drive, as well as high-performance timing and synchronization capabilities. In addition, IAV created the software components using NI LabVIEW software.

The system was packaged for mobile use in an RF-shielded box that prevents noise and interference. The system ships with a DC/AC converter, a preamplifier system to optimize recordings with automatic gain control (AGC), and multimedia recording capabilities. Using off-the-shelf components from NI, IAV created a reliable turnkey system that the customer can use from the start of development, preassembled, and with no application software development required.

Custom RF Test Signal Library

Engineers at IAV can take the record and playback system on test drives in the trunk or back seat of a vehicle with the DC power supply connected to the vehicle’s battery. After connecting the antenna to the system, test engineers access the graphical user interface (GUI) through a laptop and LAN connection to control signal frequency, bandwidth, and amplification while recording a dynamic signal. IAV uses this method to record a variety of radio and navigation signals as they build a proprietary test file library for convenient playback at any time.

To further enhance this library, IAV records video and GPS data to capture the environmental context affecting the signal(s). For instance, IAV can record the exact location of the vehicle when the impairment occurred, and what the precise weather and road conditions were like. Because IAV engineers do not need to perform as much field testing, they invest more time into further improving device quality by subjecting the devices to more real-world signals and impairments in a condensed time period.

With the record and playback system, IAV can now instantly share recorded data with device manufacturers, component manufacturers, and automakers so that all parties can troubleshoot in-vehicle radio and navigation devices with identical signals, impairments, and environmental contexts to find the source of the problem. Thus, those responsible for product quality can remotely troubleshoot the devices.

This article was contributed by Etienne Frenette and Daniel Cox of Averna, and Hans-Joachim Tepper Tepper and Jeremy Goddard of IAV Automotive Engineering. For more information on the National Instruments products used in this application, visit http://info.hotims.com/40440-542 .

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