Mitigation of am interference in digital transmission
The plain-old-telephone-system (POTS) is now increasingly used to carry high-speed data such as for Internet purpose. However, problem can occur if the telephone network is in close proximity to an AM radio transmitter, transmitting high power signal at a frequency which overlaps the bandwidth...
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| Format: | Thesis |
| Language: | English English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/7643/1/24p%20ERWAN%20SULAIMAN.pdf http://eprints.uthm.edu.my/7643/2/ERWAN%20SULAIMAN%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/7643/3/ERWAN%20SULAIMAN%20WATERMARK.pdf |
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| Summary: | The plain-old-telephone-system (POTS) is now increasingly used to carry
high-speed data such as for Internet purpose. However, problem can occur if the
telephone network is in close proximity to an AM radio transmitter, transmitting
high power signal at a frequency which overlaps the bandwidth of the Internet
transmission. The interfering electromagnetic field can induced enough current and
voltage in the telephone network and causing significant data errors. This report
presents a study on the effects of high-powered AM transmission at 576 kHz on a
digital transmission system. A GTEM Cell was used to generate the 576kHz clectric
field intensity varying from lV/m to 15 V/m with 80% amplitude modulation. The
electric field is imposed on a section of the cable and the Bit Error Rate (BER) is
noted using Data Tools 5000. Shielding technique was employed using four
conducted materials (soft steel, hard steel, aluminum and copper) in order to test the
attenuation of the electric field reaching the cable. Measured results showed that
copper (a= 5.87 x 107
S/m, fr =1) can reduce up to 70% of the BER. The
relationship between electric field E and BER for copper is expressed as
BER = 2 x 10~5
e0-3"^' +2.48x10"^ indicating that the BER increases exponentially
with the magnitude of the applied electric field. It is obvious from the work done in
this project that any network situated near a high-powered electromagnetic field
transmitter should employ a good shielded cabling system. It is recommended that
further study need to be carried out to find ways of mitigating the effects of the
interfering field such filtering and grounding. |
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