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COTS Software Defined Radio for 5G Development
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Figure 2b
Each SDR board includes a precision timing system with a
multi-bit, fractional synthesizer for variable sampling rates
locked to an on-board OCXO, or a reference input signal (see
Figure 2b). These timing systems usually accept external
synchronization signals from a Network Time Protocol
(NTP) server or GPS receiver for the highly precise timing
requirements of a radar or cellular system. The precision is
also required for phase coherent sampling of the A/Ds, FPGA
DSP data synchronization, and D/A signal transmission.
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RF Coaxial
Connectors
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FMC
Connector
XMC Mezzanine Card
Functional Block Diagram
The XMC example A/D has a 200 MSPS maximum sampling
rate that can capture a 100 MHz Nyquist BW excluding
filtering. A common technique with digital radio is to acquire
channel information, or intermediate frequency (IF) BW by
under-sampling the signal. Figure 3 and text below explain
the "the Fan-fold" concept using multiple Nyquist zones.
