March 1975 | NTIA Technical Memo OT TM 75 194

Measurement of interfer­ence effects between TDM-FM and FDM-FM microwave systems

Darren L. Smith

Abstract: Following the alignment and tuning of an analog FM microwave radio to handle a 12.6 Mb/s, 3-level partial response base­band, the effects of various types of interference on system performance were investigated. Since TDM-FM and FDM-FM microwave systems will be operating in the same frequency band, the mutual interference effects were investigated to determine the degree of degradation of system performance for each type of transmission. Bit-error-rate and orderwire signal-to-noise ratio were used as indices of TDM-FM system performance, and noise power ratio was used as the index for the FDM-FM system evaluation. These measurements indicate that the TDM-FM system can operate at higher interference levels than the Fm1:-FM system when subjected to TDM-FM interference.

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