| 摘要 |
A tuner includes a first mixer (14) which converts an input radio frequency (RF) signal to a first intermediate frequency (IF) signal at a a filter (22) using the output signal from a variable local oscillator (16) fed via a mixer (18) which is also supplied from a fixed frequency oscillator (20) and a second mixer (26) converts the first IF signal to a second IF signal at a filter (28) using the output signal from the oscillator (20), the second IF signal having a fixed frequency lower than the frequency of first IF signal. The frequency of oscillator (20) is lower than the lowest frequency of local oscillator (16). The oscillators 16 and 20 may each be a transistor (32, 70 Fig. 2) with a varactor diode (52) for tuning oscillator (16) and mixer (18) as a diode (64). <IMAGE> |
