HDM8515 데이터 시트보기 (PDF) - Hynix Semiconductor

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HDM8515

DVB/DSS Compliant Receiver

Hynix Semiconductor 

A4. Nyquist Criteria Considerations

The HDM8515 is clocked at 60MHz, yet processes signals with symbol rates as high as 45M

symbols-per-second. At first thought, this might appear to be violating the Nyquist criteria which

states that the sampling rate must be at least twice the highest frequency component. The total

bandwidth of the 45Msps signal, with 35% excess bandwidth, is about 60MHz.

The samples provided to the HDM8515 are complex samples, which is equivalent to 120M

samples-per-second, which does satisfy the Nyquist criteria. Another way of looking at this is to

examine the baseband signal. The signal bandwidth covers 60MHz, but the baseband spectrum

covers from -30MHz to +30MHz. There are no baseband frequency components greater than

30MHz, and the 60MHz clock is adequate as long as complex samples are taken.

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