| 摘要 |
PROBLEM TO BE SOLVED: To recover a carrier and to correct a phase error with high stability and high precision by receiving a transmission signal with a pilot carrier inserted thereto not via a high pass filter, using an AFC circuit to obtain a frequency difference, and thereby controlling a transmitter. SOLUTION: Data at an input terminal 1 are given to a mapping section 2, in which mapping signals I, Q are obtained, and subject to band limit and waveform shaping b roll-off filters 3i, q and the result is given to a frequency conversion section 4. The results are fed to a prime filter 5 and a D/A converter, a DC component is added to the signal I by an adder 8 and the result is subject to quadrature modulation by a quadrature modulator consisting of a phase shifter 11 and an adder 12 or the like. Thus, a signal to which a pilot carrier is inserted is obtained not via a high pass filter. The signal is received at a reception terminal 14 and an AFC circuit 21 obtains a frequency difference by the pilot carrier at a transmission side to control a transmitter 19. Since the pilot carrier is inserted to detect a frequency error and a phase error, carrier recovery and correction of a phase error are attained with high stability and high precision. |
