Cisco Cisco Prisma II EDR Receiver Technical References
78-4016548-01 Rev C
9
Sampling and the bdr Product
Sampling and the bdr Product
The Cisco bdr product line uses high-speed A/D and D/A circuits to convert the
broadband reverse RF signals in an HFC reverse path into digital words for
transmission over a digital optical link.
Sampling and the 2.5 Gb/s 2:1 bdr Product
In the 2.5 Gb/s 2:1 bdr products, a pair of high-speed 12-bit A/D converters digitizes
the reverse RF signals on the transmit end. A 2.5 Gb/s digital optical link transports
the digital words to a pair of high-speed 12-bit D/A converters on the receive end,
which reconstructs the reverse RF signals.
Each A/D converter on the transmit end has its own RF input. This permits two
Each A/D converter on the transmit end has its own RF input. This permits two
separate reverse path spectra to be sampled. The A/D converters operate at a sample
frequency (F
S
) of 100 MHz. Consequently, each converter has a Nyquist frequency
(F
NYQUIST
) of 50 MHz. The Nyquist sampling criterion indicates that signals from DC to
50 MHz may be accurately sampled and reconstructed. In the case of the 2.5 Gb/s 2:1
bdr product, the band of signals of interest are limited to the 5 MHz to 42 MHz band.