Analog Devices ADRV9001 User Manual page 151

Preliminary Technical Data
profile onto the Rx Programmable FIR to perform common filtering. However, after the CFO is corrected via Carrier Frequency
Corrector block, a tight filter profile can be loaded to perform the deep channel selection filtering. The change in the filter profile can be
initiated by the BBIC on demand in the RF_Enabled State.
BEFORE CFOIS CORRECTED.
Frequency Discriminator
Frequency Discriminator in rxnbdem is to translate the IQ signal into Frequency Deviation (FD) signal, performing the frequency
demodulation in the digital domain. This module can be bypassed.
Illustrated by Figure 129, the Frequency Discriminator outputs the transient frequency deviation (FD) and the transient squared
magnitude (Mag2) sample by sample. The output FD and the output Mag2 are defined as followed:
where atan2 is same as the function in Octave, and D is the programmable delay. Typically, D is chosen as '1', which means 1
sampling clock delay.
Assuming the input IQ signal is the complex single tone, given by
where A is the signal magnitude, f
D × 2f /f while the output Mag2 is A
t S
NB Programmable FIR
NB Programmable FIR in rxnbdem is to perform the pulse shaping filtering or the low pass filtering at the output of the Frequency
Discriminator. This module can be bypassed.
The NB Programmable FIR supports up to 128 taps. Each tap is 24 bits width including the sign-bit, and only 1 set of customized FIR
profiles can be loaded.
Resampler
Resampler in rxnbdem adjusts the sampling phase of the IQ signal or that of the FD signal. This module can be bypassed.
LOOSE FILTER PROFILE
CFO
THE WANTED CHANNEL
DC
Figure 128. Loose Filter Profile vs. Tight Filter Profile
I
D
Q D
Figure 129. Functional Diagram of Frequency Discriminator
is the tone frequency, f
t
2 .
TIGHT FILTER PROFILE
DC
X
ATAN2
Y
–
is the sampling frequency. The output of the frequency discriminator (FD) is
S
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THE WANTED CHANNEL
AFTER CFO IS CORRECTED.
FREQUENCY
DEVIATION
(FD)
SQUARED
MAGNITUDE
(Mag2)
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