SAE International Development and Application of FM Multipath Distortion Rate Measurement System Using a Fading Emulator Based on Two-Stage Method 2016-01-0082

The suitability of FM radio receivers for automobiles has conventionally been rated by evaluating reception characteristics for broadcast waves in repeated driving tests in specific test environments. The evaluation of sound quality has relied on the auditory judgment due to difficulties to conduct quantitative evaluations by experiments. Thus the method had issues in terms of the reproducibility and objectivity of the evaluations. To address these issues, a two-stage method generating a virtual radio wave environment on a PC was developed. The research further defined the multipath distortion rate, M Dr , as an index for the sound quality evaluation of FM receivers, and the findings concerning the suitability of the evaluation of FM terminals for automobiles were reported at the 2015 SAE World Congress. However, extended periods of measurement were necessary because the upper limit for delay time, \u03c4 Max , cannot be determine in advance for the measurement of M Dr using the Two-Stage Method. This research clarified the characteristics of the multipath distortion rate, M Dr , in relation to the modulation frequency ( f m ) and the delay time ( \u03c4 ) of the FM broadcast wave, and preliminarily determined \u03c4 Max , the upper limit for delay time necessary for the Two-Stage Method. The research also indicated the possibility of applying the Two-Stage Method to Intelligent Transport Systems (ITS) to evaluate reception in the case of vehicle-to-vehicle communication on PC. By comparison with conventional proving trials, the Two-Stage Method makes it possible to generate radio wave environment characteristics as desired, and represents a useful evaluation tool displaying good reproducibility.