The basic idea is that the DDS provides only a part of the output signal band, and up-conversion into the higher frequencies is carried out by analog techniques because the spurious performance and the power consumption are not good in the wide output bandwidth DDS (Figure 2.8, Figure 2.9). The critical path of the signal could be accomplished by the DDS, which has the advantages of a fast switching time, a fine frequency resolution, and a coherent frequency hopping. Three up-conversion possibilities are introduced in this chapter: a DDS/PLL hybrid, a DDS/mixer hybrid and a DDS quadrature modulator.
KeywordsPhase Noise Local Oscillator Reference Frequency Output Frequency Loop Filter
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