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This article describes a method for generating a binary frequency shift keyed signal without using a voltage controlled oscillator.
English (United States)
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A Method for Generating Binary Frequency Shift Keyed Signal
This article describes a method for generating a binary frequency shift keyed
signal without using a voltage controlled oscillator.
Referring to the figure, the precoder generates two digital signals a(t) and
b(t). These signals are filtered by two identical lowpass filters (LPF) whose pulse
response is a half cycle of a sinusoidal signal with the period equal to twice the
bit time. The waveforms a(t) and b(t) and their lowpass filtered versions for an
arbitrary input data sequence ...0,0,1,1,1,... are shown in the figure.
The two quadrature carrier signals are modulated by the outputs from the
lowpass filters and the resulting signals are summed to generate the binary
frequency shift keyed signal. The frequency of the output signal is increased or
decreased by an amount equal to 1/(2 bit time) when the data is 1 or 0,