An Analysis of the Response of Digital Demodulators to Frequency Shift Keyed Signals.
NAVAL POSTGRADUATE SCHOOL MONTEREY CALIF
Pagination or Media Count:
The theory and operational characteristics of a digital pulse counting frequency demodulator are presented. The demodulator, called the pulse width demodulator PWD in this report, is realized with solid state components and uses pulse circuitry to perform demodulation. The output of the demodulator may be applied to a low pass filter LPF to recover the modulating voltage. The PWD possesses the following properties 1 wideband operation, 2 no tuning requirement, 3 simple resistor adjustment for selecting the operating frequency range and 4 ability to operate at frequencies beyond the design range due to the circuits ability to automatically frequency divide. The demodulator performance for analog and digital FSK modulating voltages is obtained at both commercial intermediate frequencies of 455 kHz and 10.7 MHz. Its performance in the presence of noise is investigated and compared to theoretical results for non-coherent FSK systems.
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