PHASE CONTINUOUS FSK MODULATION SYSTEM

摘要

PURPOSE:To decrease the occupied band width as well as to improve the error rate property by securing the continuous phase at the exchange point of the modulation element with the correlation ensured and then giving the redundancy to the signal between the adjacent elements. CONSTITUTION:The transmission data is supplied through input terminal 100 in the form of ''1'' and ''0''. For the supplied data, the continuous three bits (ak, ak-1 and ak-2) are stored in shift register 1 to be stored to deliver the modulation exponents (2ak-ak-1-ak-2) to output 102 via the code converter of 2. The product of output 102 and 103 is obtained through multiplier M, and thus the shift component is obtained at output 104 from the carrier frequency which varies for 1/fs(fs=clock frequency) seconds. The sum of output 104 and 105 is secured by adder A, and the cumulative addition is given by accumulator 3 with every 1/fs seconds. The output of accumulator 3 is converted to the amplitude value of the cosine wave through the phase value and via conversion table 4 and then turned to a continuous waveform through D/A converter 5.