| 摘要 |
PURPOSE:To reproduce a reference carrier wave of a base band having high performance and high stability with a simple circuit constitution, by drawing cos2theta and sin2theta out of an n-phase PSK input signal. CONSTITUTION:A reference carrier wave is reproduced by using phase wave detectors 21 and 22 and a VCO23 which give an orthogonal wave detection to an n-phase PSK input signal (n=2<m>, m>=integer of 2). Then costheta is applied to an input (a) of an EX-OR25 from the detector 22, and at the same time sintheta is applied to an input (b) from the detector 21. Thus the OR25 delivers a waveform of sintheta when the input of one side is positive with the other input set at zero or negative. An absolute value circuit 26 receives costheta delivered from the detector 22 and delivers cos2theta. Then sin2theta and cos2theta are applied to an EX-OR27, and sin4theta is obtained at the output of the OR27. The VCO23 is controlled via a loop filter 28. Thus a reference carrier wave which is synchronous with the carrier wave of a received 4-phase PSK modulate wave can be obtained. |
