| 摘要 |
PURPOSE:To obtain a small sized FM wae-detection circuit requiring no adjustment, by connecting an AM wave-direction circuit to the poststage of a CCD filter and determining the center frequency of FM detection through the selection of a delay time by clock frequency of CCD and number of bits. CONSTITUTION:A part of an input signal 11 is given to a coefficient circuit 13, and a part of other parts is given to a coefficient circuit 15 via a CCD 12, other parts are given to a coefficient circuit 16 via a CCD 14 and the output of the coefficient circuits is summed 17. The coefficients K1, K3 of the circuits 13, 16 are both at ''x1'', and a coefficient K2 of the circuit 15 is at ''x2''. The CCD is driven with clocks having a specified number of bits N and frequency fk and has delay time T=N/ fk. With the constitution, an FM signal in angular velocity omega of carrier is inputted, and when the frequency changes by + or -DELTAomega to the center frequency, the transfer function of the circuit is about 2(1+ or -DELTAomega) to obtain an AM signal 18 proportional to the DELTAomega. When this output 18 is AM-detected 2, an FM detection signal to the FM input is obtained, no adjustment is required, no variance due to the change in the center frequency and the size can be made small. |
