| 摘要 |
PURPOSE:To ensure the use of an FM wave detector of a narrow band and at the same time to simplify the constitution of an AFC circuit, by supplying one of a pair divided outputs to the FM wave detector and the other output to the AFC circuit, respectively. CONSTITUTION:The TV signal of a wide band to be FM-modulated which is received through an antenna 1 is supplied to a mixer 4 along with a local oscillating signal of 10.8GHz and supplied to an image eliminating BPF8 in the form of the 1st intermediate frequency signal. The output of a BPF8 is supplied to a mixer 10 along with the output of a local oscillator 11 and in the form of the 2nd intermediate frequency signal. Then an intermediate frequency signal of 130MHz is produced through a BPF13 and then supplied to an FM wave detector 24 through the first frequency divider 15. At the same time, the output of the divider 15 is supplied to an AFC circuit 17 via the 2nd frequency divider 16. The output of the circuit 17 is added with the channel selecting signal to be supplied to the oscillator 11 in the form of an oscillating frequency controlling signal. |
