| 摘要 |
A frequency synthesizer, responsive to a reference signal having a frequency fr, for supplying an output signal at a frequency selectable from M times N signal frequencies (where M and N are preselected integers) is disclosed. In each disclosed arrangement, a set of M signals that are each harmonically related to fr is derived by a cascade connected harmonic generator and comb filter, and a set of M signals that are each harmonically related to fr/M is derived from the reference signal by a cascaded frequency divider, harmonic generator and comb filter. Each of these signal frequencies within the two sets of signals can be selectively coupled to the input ports of signal mixing apparatus and bandpass filtering is employed to couple either the mixer sum or difference frequency to the synthesizer output terminal. In some situations, a single mixer circuit and bandpass filter is employed. In other situations in which the desired frequency range and resolution cause undesired frequency components of the mixer signal to fall within the synthesized frequency range, mixing and filtering is effected in a number of subchannels, each of which include a mixer and filter. In such an arrangement, each mixer is commonly supplied with a signal selected from the set of M signals, the set of N signals is partitioned into a number of subsets that is identically equal to the number of subchannels employed, and the signal selection apparatus associated with the set of N signals supplies one signal of each signal subset to individual ones of the mixers.
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