A Wide-Bandwidth-Output Direct Digital Synthesizer with Multiple Delay Generators
Hideyuki Nosaka, Yo Yamaguchi, Masahiro Muraguchi · Japanese Journal of Applied Physics · 2000
A new type of phase interpolation direct digital synthesizer (DDS) that can generate signals up to the clock frequency is proposed. The maximum output frequencies of conventional DDSs are limited to half the clock frequencies. To eliminate this frequency limit, we designed a new ROM-less DDS with multiple delay generators that are mutually triggered by a pulse distributor. Pulse distribution plays an important role in reducing the effective resetting time of the delay generators. We derived a theoretical expression which gives the maximum output frequency of the new DDS. According to the expression, the maximum output frequency can be determined by the number of delay generators and maximum leaking time. We also show that the new DDS can produce output signals up to the clock frequency with three or four delay generators. Experimental results confirm frequency synthesizer operation in which the spurious level is reduced by the delay generators. The results also confirm that the maximum output frequency is not limited to half the clock frequency when using two delay generators. This is consistent with the theoretical expression.