SBASB20 September 2024 DDS39RF10 , DDS39RFS10
PRODUCTION DATA
Return-to-zero (RTZ) mode is similar to the standard zero-order hold mode used by DACs; however, the response adds a return-to-zero pulse for the second half of the sample period. The timing diagram for RTZ mode is given in Figure 7-5. This output waveform can be thought of as a rectangular filter in time domain that is half the length of that which is used in NRZ mode, resulting in a sinc response that is expanded by two times in the frequency domain. The result is a frequency response with less power loss in the 2nd Nyquist zone and a null at twice the sampling rate. It can be used for 1st and 2nd Nyquist zone applications. The return-to-zero pulse provides flatter response through the first Nyquist zone at a tradeoff of 6dB lower peak power. A plot of the frequency response of RTZ mode is shown in Figure 7-6.