Method and apparatus for modulating/demodulating an FSK signal

An apparatus for modulating/demodulating a frequency deviation keying (FSK) signal, the apparatus comprising:

• a channel selection-modulator modulating an FSK signal by setting a frequency channel to be used;
• a phase locked loop generating a desired output frequency ‘fout’ compared to a reference frequency ‘fREF’ by adjusting a frequency division ratio (N+n) with respect to a frequency of the modulated FSK signal;
• and
• an output unit amplifying the FSK signal having the generated output frequency ‘fout’ and radiating the amplified FSK signal through an antenna,
• wherein each of the frequency channels is divided into two or more tones, and different frequency channels are allocated between the tones divided into two or more tones,
• when the FSK signal is a binary frequency shift keying (BFSK) signal, wherein the channel selection-modulator comprises:
• a summer summing up a channel selection signal (CHSEL<15:0>) set to bits corresponding to the center frequency ‘fc’ of the channel to be used according to the channel method and an offset signal (OFFSET<8:0>) set to bit that sets the frequency ‘f’ to 1 MHz;
• a subtractor subtracting the offset signal (OFFSET<8:0>) from the channel selection signal (CHSEL<15:00>);
• and
• a multiplexer outputting either bits corresponding to a sum frequency ‘fc+Δf’ of the center frequency ‘fc’ and a frequency deviation ‘Δf’ or bits corresponding to a difference frequency ‘fc−Δf’ between the center frequency and the frequency deviation ‘Δf’ according to a transmission data (TXDATA).