Analog Devices ADRV9001 User Manual page 197

Reference Manual
RECEIVER DEMODULATOR
Carrier Frequency Corrector (CFC)
The carrier frequency corrector (CFC) in rxnbdem removes the carrier frequency offset. This module can be bypassed.
In a communication system, the desired signal is transmitted by the transmitter at RF over the air. As the clock reference at the transmitter and
receiver are independent, this can result in the RF carrier frequency offset between the transmitter and the receiver. This frequency difference
is called the carrier frequency offset (CFO). The CFC in rxnbdem enables the BBIC to remove the CFO before the channel selection filtering
(receiver PFIR) at the receiver side. The BBIC must estimate and input the correction value applied to the CFC. The correction value change
can occur immediately or relative to the receiver frame boundary.
The CFC is implemented as a digital down converter (DDC), which consists of an NCO and a complex multiplier in the datapath. As the
correction value, ensure the NCO frequency word is in the range of minute (±20 k, 20% of sample rate).
Figure 173 shows the spectrum of the desired tone and generated NCO spurs levels relative to the desired tone for the CFC NCO at 61.44 MHz
sampling frequency. The outlined plots show a typical case {-20 MHz Continuous Wave (CW)} and some worst cases.
the NCO output spurs are −100 dBc below the desired tone across the range of [−f
−20 MHz CW
►
fs/16 CW
►
fs/8 CW
►
fs/4 CW
►
Note: These four tones' frequencies are not within the defined NCO range, but are just for the NCO spurs level demonstration.
Receiver Programmable FIR Filter
The receiver programmable FIR filter in rxnbdem is multifunctional and customizable. However, this module can be bypassed.
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Figure 173. Output Spectrum of the CFC/NCO as f = 61.44 MHz
S
/2, f /2]:
S S
ADRV9001
Figure 173 shows that
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