GC5330IZEV Datasheet, PDF (16/49 Pages) Texas Instruments – Wideband Transmit-Receive Digital Signal Processors

GC5330
GC5337
SLWS226 B – DECEMBER 2010 – REVISED JANUARY 2011
From BB
Interface
Block
1–12 Channel DUC Block
NCO
FIR
1´, 2´
Farrow
1–1024´
CIC
1–3´
All 3 Blocks Interpolate
X
Mixer
DUC Configuration
To Mux and
Sum Block
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To BB
Interface
Block
1–12 Channel DDC Block
NCO
FIR
1´, 2´
Farrow
1–1024´
CIC
1–3´
All 3 Blocks Decimate
X
Mixer
From
Distributor
Block
DDC Configuration
B0448-01
Figure 12. DUC and DDC Functional Block Diagram
In combination with the follow-on mux and sum block, the DUC block interpolates, filters, mixes each carrier, and
combines multiple channels into one to four wideband, composite TX signal streams. Any input channel can be
mapped to any TX stream in the mux and sum block.
The DDC configuration accepts an RX stream from the distributor block and provides mixing, decimation filtering,
fractional resampling, and filtering to RX channels. The RX block outputs are mapped to the mixer CIC stream
via the distributor block.
Each DDUC block contains a finite impulse response (FIR) filter, a fractional resampler (Farrow filter), a
cascaded integrator-comb (CIC) filter, a complex mixer and NCO for channel placement in the composite stream,
and a programmable frequency hopper (see Figure 12).
The number of taps available in the FIR filter depends on various parameters such as the BBclk rate (derived
from DPDCLK) , input sample rate, interpolate and decimate settings, and number of channels. Different tap
values may be used for each channel (however, that reduces the number of filter taps available).
Note that the input sample rate is the input from the TX BB input formatter for the DUC configuration and the
input from the distributor block for DDC configuration. The number of taps for various wireless standards and
configurations is shown in Table 4.
The Farrow filter supports one real channel or 1–12 complex channels and can be configured for any resampling
ratio from 1 to 1024 with 32-bit resolution. A different delay value for each channel is supported. The Farrow filter
is used to resample different TX BB input sample rates to a common CFR and DPD sample rate, and it provides
95-dB rejection at ±0.25 output f_S (sample rate), 83-dB rejection at ±0.375 output f_S, and 56-dB rejection at ±0.4
output f_S.
The CIC interpolates or decimates by a factor of 1, 2, or 3. If each DDUC must support more than eight carriers,
the CIC must interpolate/decimate by 3. If each DDUC must support between four and eight carriers, the CIC can
interpolate/decimate by 2 or 3. If each DDUC must support fewer than four carriers, the CIC can interpolate by 1,
2, or 3.
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