| 摘要 |
A signal generator apparatus (100) comprises a controller (102) coupled to a VCO oscillator circuit (122). The oscillator circuit (122) covers a range of output frequencies. In order to maintain low gain and hence minimize noise over the range of output frequencies, the frequency range is divided into a number of frequency windows or sub-ranges. Adjacent sub-ranges overlap at a crossover frequency. The system is arranged to scan at least part of the range of output frequencies and calculate a crossover frequency. The boundaries of the frequency windows are detected by monitoring a lock condition of frequency synthesizer (112). Thus, in contrast to prior art where crossover frequencies are identified and stored during manufacture, boundaries between frequency sub-ranges are found in use by a calibration routine (fig.2). |
