| 摘要 |
PURPOSE:To secure the quick frequency follow-up properties with a fine frequency step space for the radio communication unit featuring such type in that the local oscillation frequency is varied in steps of a fixed space to set the operation frequency, by securing the interpolation via the VXO (variable frequency crystal oscillator). CONSTITUTION:Input signal F is mixed with 1st local oscillation frequency f1 through mixer 1 to be changed into 1st intermediate frequency F1, and then mixed with 2nd local oscillation frequency f2 at mixer 2 to be changed into 2nd intermediate frequency F2 for amplification and detection. Then frequency f1 supplied from VCO3 is divided at programable divider 4 and then undergoes the phase comparison with the frequency of reference oscillator 6 through phase comparator 5. And the control DC voltage caused by the phase difference of both frequencies is fed back to VCO3 to stabilize the oscillation frequency. In this case, the frequency of VCO3 varies with the frequency step equal to the frequency of oscillator 6 with every increment and decrement of the division ratio of divider 4 in one unit. Frequency f2 is supplied from VXO7 to give the interpolation to the step space of frequency f1. |
