| 摘要 |
PROBLEM TO BE SOLVED: To reduce harmonic noise of commercial frequency and random noise between harmonics entirely. SOLUTION: A two-cycle length of a communication frequency is used for a unit modulation block, and in the transmitter side, a carrier synchronously with the commercial frequency in a preceding half unit modulation block is subject to differential phase modulation at multipliers 4, 7 by using the phase of a signal at one preceding unit modulation block as a reference phase and the carrier signal is generated through direct spread processing by a data string for spread spectrum synchronously with the commercial frequency and the generation of the carrier is stopped by the multiplier 4 for a succeeding half unit modulation block. In the demodulator side, a differential filter 24 subtracts the reception signal at one preceding cycle of the commercial frequency from the reception signal and a multiplier 25 is used to multiply the subtracted signal in one preceding unit modulation block through a delay. Inverse spread processing and detection are conducted by the processing above. |
