Measurement of the capture effect of frequency modulation

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Author
Bevington, Dennis G.
Date
1989-12Advisor
Myers, Glen A.
Second Reader
Ha, T.T.
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Show full item recordAbstract
Capture Effect is a phenomenon associated with frequency modulation (EM). The capture effect relates the ability of the
receiver demodulator to recover the message of the dominant earner when two or more EM carriers of unequal power level
are present. In this research, an experimental system is constructed that generates the sum of two EM signals and demodulates
thai sum usmg a phase-locked loop (PEL). The effect on capture by several parameters is measured. These parameters are
the frequenc\ de\iation of the E.M signal, the frequency of the message, and the lowpass filter design of the PEL demodulator.
Capture ratios as small as 0.3S7 dB are observ ed. Results show that the frequency deviation of the stronger signal affects
capture. The frequency deviation of the weaker signal has no effect on capture. Frequencies of the messages ha\e small effects
on capture.
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