Beeinträchtigungen des Rundfunkempfangs im Kfz: Neue Bewertungsmethoden (English shop)

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This thesis presents a new method for assessing broadcast reception impairments caused by radio disturbances in motor vehicles. First, the broadcast reception system in the vehicle is described, which enables the reception of the wanted broadcast signals (radio and television), but also of the disturbance signals. The measurement and assessment of the disturbance signals generated by the vehicle itself is carried out in a shielded EMC test environment by means of a radio disturbance measuring receiver. It becomes apparent that, especially for digital radio services, the assessment with a radio disturbance measuring receiver according to established standards does not always correspond to the perceptible reception impairments.

In order to assess reception impairments, a wanted broadcast signal must be included in the considerations. The broadcast services and modulation types relevant to reception in the vehicle are therefore presented. For the assessment of reception impairments, a so-called AudioVideo test bench (AVP) was developed. The components of the AVP serve to generate the wanted broadcast signal, to add the wanted and the disturbance signal, and to receive these signals. The reception of the wanted signal with the superimposed disturbance signal is carried out by a broadcast receiver of the type actually used in vehicles. In the software-controlled test procedure, the demodulated, undisturbed received signal is in each case compared with the demodulated but disturbed received signal. For this comparison, the instrumental audio quality assessment methods PESQ and PEAQ are used to evaluate reception impairments in radio broadcasting services. With the AudioVideo test bench, in addition to the quality assessment, the attenuation of the existing disturbance signal can be determined at which a specified reception quality is achieved again.

The assessment of disturbance signals with the AVP is first evaluated using generic, mathematically describable disturbance signals. Subsequently, investigations of disturbance signals actually occurring in the vehicle were carried out. The comparison of the assessments obtained with the AVP and with the radio disturbance measuring receiver shows that the expected reception impairments cannot be reliably ruled out for all broadcast services by means of a detector-based assessment according to established standards. The reception impairments depend to a high degree on the disturbance signals, but also on the broadcast signals to be protected as well as on the reception conditions (reception level). By applying the AVP as a supplement to the assessment of disturbance signals with a radio disturbance measuring receiver, this problem can be solved. In order to increase efficiency and to avoid long test durations resulting from the additional use of the AVP, the possibilities of recording disturbance signals and reproducing them faithfully, as well as of simulating the reception impairments, were implemented.