Digital modulation circuit and method as well as digital...

Details Digital modulation circuit and method as well as digital... Digital modulation circuit and method as well as digital...

2011-03-08

2011-03-08

Fan, Chieh M (Department: 2611)

Pulse or digital communications

Receivers

C375S324000, C375S279000, C375S282000, C375S329000, C375S330000, C375S331000, C375S332000, C375S333000

Reexamination Certificate

active

07903760

ABSTRACT:
A mixer circuit accumulates I signal (digital signal of first channel) having its band limited by low-pass filter and first carrier signal to perform two-phase shift keying modulation thereon. An adder adds fundamental-wave component of bit clock signal BCK into Q signal (digital signal of second channel) having its band limited by the another low-pass filter to obtain a resultant added-up signal. Another mixer circuit accumulates the added-up signal and second carrier signal to perform two-phase shift keying modulation thereon. Output signals of the mixer circuits are input to another adder so that they may be added up to obtain a QPSK signal as a modulated quadrature signal. The QPSK signal contains frequency signals whose frequencies are a sum of bit clock frequency and carrier frequency and a difference between them. When demodulating, the carrier signal and the bit clock signal are reproduced using the frequency signals.

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