| 摘要 |
PURPOSE:To improve the S/N of an FSK modulation receiver and to enhance the call sensitivity of a digital transmission receiver by providing a frequency conversion circuit, a band pass filter having a selectivity against an adjacent interference wave in an intermediate frequency and a band elimination filter blocking a narrow band in the vicinity of the intermediate frequency to the receiver. CONSTITUTION:The receiver is provided with band an elimination filter 12 with a narrow band in addition to a band pass filter securing the selectivity for an adjacent interference wave in an intermediate frequency. In this case, the S/N is improved to enhance the call sensitivity of the receiver by making the band for a noise component narrow without giving effect on the band width of the receiver. Thus, the S/N is improved without making the band width of the receiver narrow and an FSK modulation signal is demodulated to obtain an NRZ digital signal. |
