| 摘要 |
A Pulsed Frequency Shift Keying (PFSK) modulation method and apparatus are described which uses narrow bipolar pulses (902) to shift the frequency of a carrier signal (904) generated by a phase locked loop (700) which results in a phase shift keying of the carrier signal (904). The first, positive-going narrow pulse (906) shifts the frequency of the carrier signal (904) from a first frequency to a second frequency, and returns the carrier to the first frequency thereby changing the phase of the carrier (904). Then, a second, negative-going narrow pulse (908) shifts the frequency of the carrier signal (904) from the first frequency to a third frequency, thus restoring the original phase of the carrier. A pair of positive-going and negative-going differential pulses (902) represents one symbol of transmitted information. The implementation of this pulsed frequency shift keying modulation may be in biphase shift keying, or in any number of multiple phase shift keying implementations where a single symbol represents more than one digital bit. |
