GC5316 datasheet(27/75 Pages) TI

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GC5316

SLWS154A − JANUARY 2004 − REVISED MARCH 2004

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The diagram above shows the different signal processing blocks and general signal processing flow of an individual

transmit channel. Within a DUC block a single set of hardware performs these functions for one UMTS signal or two

CDMA signals. When processing two CDMA signals the gain, round, power meter, PFIR and CFIR blocks are time

shared to process both signals with one set of hardware. Each DUC can support one UMTS channel or two CDMA

channels.

Each DUC block accepts baseband serial data. At this point the gain can be adjusted and a pilot sequence can be

summed with the data. Power can be measured, and then the data is pulse-shape filtered and interpolated to a higher

rate. The programmable FIR filter (PFIR) is used to pulse shape the data and interpolates by a factor of two. The

compensating CIC filter (CFIR) compensates for the roll-off of the following CIC filter and also interpolates by a factor

of two. The CIC filter performs additional interpolation which is programmable. The delay adjust block permits the

channel’s delay to be adjusted relative to all other DUC channels.

The interpolated, filtered, and delayed data is then tuned to a user-programmed frequency with a digital mixer and

oscillator. The DUC’s output data then drives four independent sum chain paths, where output data from each DUC

can be summed into four composite streams.

Each function block is described in greater detail in subsequent sections.

Table 1. Programming

VARIABLE

DESCRIPTION

ddc_duc_ena

When set this turns on the DUC. When unset, the block is turned off.

cdma_mode

When set, the DUC block is in CDMA2000 mode.

3.1.1 Transmit Serial Input Interface

Frame Strobe

Clkdiv

Sync

Frame

Delay

Interleaved I,Q

2CDMA

CD MA DUC Channel A

DU C Block

CD MA DUC Channel B

Interleaved I,Q

1UMTS

CH A

CH B

Shared between two DUC blocks; ie 2k & 2k+1, k=0 to 5

1UMTS

Imsb

Imsb−1

Qmsb

Qmsb−1

Pins from adjacent DUC

txin_X_a

txin_X_b

Figure 22. Transmit Serial Input Interface

Each DUC block has two serial input data pins. These pins are used to transfer I/Q baseband data into the DUC

channel for interpolation, filtering, and tuning to a carrier frequency. How these pins are used depends on the channel

configuration of the DUC block.

When the block is configured for two CDMA channels, one pin (txin_X_a) accepts serial data for signal A, the other

pin (txin_X_b) for signal B. Input I and Q data, programmable up to 18 bits, is multiplexed over the serial input pin

starting with the most significant I bit. The maximum input bit rate is txclk. The interface can be programmed to accept

up to 32 bits, but only the upper 18 bits will be used as input signal data.

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