| 摘要 |
High-frequency wideband tuner for converting signals in an r.f. frequency band ranging from frequency f(1) to a frequency f(2) in an intermediate frequency signal having a fixed frequency f(if), comprising a tunable r.f. bandpass filter, an oscillator and a mixer stage which mixer stage has a first input for the output signal of the bandpass filter and a second input for a signal produced by the oscillator, in which the first bandpass filter has a passband from f(1)-f(x), a second bandpass filter is included having a passband from f(x)-f(2) and switching means are included for connecting, as selected, the output signal of the first or the second bandpass filter to the first input of the mixer stage. The oscillator being tuned over a frequency range from f(1)+f(if) to f(x)+f(if) if the mixer stage is connected to the first bandpass filter and over a frequency range from f(x)-f(if) to f(2)-f(if) if the mixer stage is connected to the second bandpass filter. By a combination of the double heterodyne and the single heterodyne principle, a tuner according to the invention particularly for satellite reception is realised in a simple manner, which tuner has a tuning range, for example, from 950-2750 MHz, which thus far has been impossible to cover with a single tuner. |
