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From BB

Interface

Block

To BB

Interface

Block

To Mux and

Sum Block

From

Distributor

Block

FIR

1 , 2

FIR

1 , 2

Farrow

1024

1–

Farrow

1024

1–

1–12 Channel DUC Block

1–12 Channel DDC Block

DUC Configuration

DDC Configuration

All 3 Blocks Interpolate

All 3 Blocks Decimate

CIC

1–3´

CIC

1–3´

NCO

B0448-01

Mixer

GC5330

GC5337

SLWS226 B

– DECEMBER 2010 – REVISED JANUARY 2011

www.ti.com

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 fS (sample rate), 83-dB rejection at ±0.375 output fS, and 56-dB rejection at ±0.4

output fS.

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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