ZHCS065G March 2011 – January 2024 DAC3482
PRODUCTION DATA
Nyquist theory states that the data rate must be at least two times the highest signal frequency. The data will be sent to the DAC as complex baseband data. Due to the quadrature nature of the signal, each in-phase (I component) and quadrature (Q component) need to have 250MHz of bandwidth to construct 500MHz of complex bandwidth. Since the interpolation filter design is not the ideal half-band filter design with infinite roll-off at FDATA/2 (refer to Section 6.3.6 for more detail), the filter limits the useable input bandwidth to about 44 percent of FDATA with less than 0.1dB of FIR filter roll-off. Therefore, the minimum data input rate is 568MSPS. Since the standard telecom data rate is typically multiples of 30.72 MSPS, the DAC input data rate is chosen to be 20 times of 30.72MSPS, which is 614.4 MSPS.