| 摘要 |
A burst mode digital communications system which is unique in that it modulates a sinusoidal carrier with discrete cosine segments. The discrete cosine segments may contain different time and amplitude values. The discrete cosine segments may be combined with each other or with zero slope level segments in order to effectively modulate the sinusoidal carrier. Rather than employing the use of filters for controlling instantaneous voltage changes, the present communications system forces the bit edges of the discrete cosine segments to occur at the zero slope points of a cosine wave, where no voltage changes occur. The communications system utilizes direct digital synthesis in order to create a carrier signal which closely represents sinusoidal carrier signal. The present communication system may be used in conjunction with various conventional methods such as phase-shift keying and amplitude-shift keying. A device is also disclosed for demodulating the carrier signal in order to recover the original base band signal. The burst mode digital communications system may also demodulate data by employing adaptive templates for more accurately determining received digital symbols. |
