Study On Radio Frequency Interference In Sound System

Abstract

The growth in the number of wireless devices and applications underscores the need for characterizing and mitigating interference induced problems such as distortion and blocking. A typical interference scenario involves the detection of a small amplitude signal of interest (SOI) in the presence of a large amplitude interfering signal; it is desirable to attenuate the interfering signal while preserving the integrity of SOI and an appropriate dynamic range. Internal or external sources of electromagnetic interference can degrade the performance of sensitive analog/digital circuits inside the audio equipment. Sources of RFI can be classified in numerous ways. Based on the method in which RFI is introduced in the systems, sources are classified as either Radiated or Conductive. Conductive RFI is caused by the physical contact of conductors as opposed to radiated RFI that is picked up by the radio. Radiated RFI is the dominant source that limits the performance of typical commercial wireless communication systems. This thesis investigates the sources and strength of interference inside Television studio; mainly the radiated interferences and its effect on the audio quality of television production studio. Specifically, the means of RFI from the nearby AM transmitter entering television sound system, types and length of audio cables which can be used to reduce this interference will be studied. Different microphone from various manufacturer used to identify and test interfering signal strength. Since those RFI from AM transmitters picked from ground, test will be made by operating these microphones at different height from the ground. The variation in strength of interfering signal at different distance from the source will be made and compared will the audio level standard. Online prediction and analysis software are used to perform the task of AM propagation prediction in 24 hour of broadcast which will identify types of propagation during day and night time. This RF propagation also depend on soil resistance in addition to time of broadcast. Different ways of mitigating or reducing interference from AM transmitters will be tested. The best solutions will be identified from the designing point view, while studio and transmitter location selection and construction.