Motorola A920 - Page 74

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A920: Harmony Lite (TX Section)

Description

The BBIF(BBIF_TX) is the transmit data path for transferring digitally sampled I / Q data from the POG. The demultiplexing unit performs the I/Q deinterleaving func-

tion to supply separate I and Q channel data into the transmit FIR filters. The FIR filter design is used to meet 3GPP spec requirements of simultaneous transmission of a

pilot channel and of multiple data channels each requiring a different spreading code and each requiring separate power control. The PN sequence generator provides I/Q

interleaved 8-bit PN data into the demultiplexing section. The DC correction(DCOC) block is able to correct for DC offsets due to the D/A‘s, anti-aliasing filters, and

transmit FIR filters in a feedback control loop. A mixed mode control loop located at the output of the transmit FIR filter is employed to correct DC offsets and I/Q gain

imbalances, i.e. DCOC and I/Q Phase and Gain equalizer. The outputs of the I/Q gain equalization unit is fed into 10-bit I and Q DAC‘s. The programmable gain anti-

aliasing filters, or TX smoothing filters, accepts differential I/Q signals of DC to 1.92MHz frequency components from the D/A Converters to attenuate the unwanted

clock signals of 15.36MHz and to smooth the signals for the TX modulator(MAX2363). The output of the TX smoothing filters are then fed into a multiplexed 6-bit A/D

with sample/hold scheme. This gives the information of the amplitude and the DC common mode voltage from the I / Q Tx filter outputs by a single Analog-to-Digital

Converter (ADC) as the part of digital correction loop.

The differential TX I and TX Q signal are finally fed into the TX modulator(MAX2363).

Motorola Confidential Proprietary

4-26

S/H

I/Q

Phase

and

Gain

Equal

10 bits

S/H