engleski

Walsh function synthesis of the combined multiple shift-keyed modulated signals

A detection probability of the shift-keyed signals can be increased by the introduction of redundant phase, frequency and/or amplitude information elements. For the evaluation of the resultatnt influence on the receiving side detection probability and spectral occupancy penalty, it is necessary to build a modulator by which can be easily synthesized all combinations of the shift-keyed signals. The paper introduces the Walsh function based generator for synthesis of the combined multiple shift-keyed signals: MP-PSK/MF-FSK, MP-PSK/MA-ASK, MF-FSK/MA-ASK, and MP-PSK/MF-FSK/MA-ASK. The proposed generation technique is chosen because the generator can be realized digitally in the small ROM-less PLD with a small number of components outside of the chip. The basis of the generator is the synthesis of the sine-wave carrier by Walsh functions. This synthesized carrier is modulated by a digital signal, producing single or combined shift-keyed modulated signals. Frequency modulation is achieved by the change of input clock frequency, discrete phase shifts are synthesized within the generator by special shift-functions set, and discrete amplitude elements are get from the attached gain control amplifier. The generator is realized digitally in low complexity PLD, with D/A conversion weighted resistor network and gain control amplifier outside of the chip. The paper presents oscillograms and power spectrum for the two combined multiple shift-keyed modulated signals.

Walsh function; shift-keying modulator; PSK; ASK; FSK

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