Motorola V975 Service Manual

Motorola Confidential Proprietary
V975/V980Theory of Operation
3-10
Draft 1.0
RF WCDMA Transmitter
Harmony WCDMA TX (U100)
The Harmony provides pulse shaping and modulation
of the 8-bit interleaved TX data coming from the POG.
RF carrier suppression and baseband DC offset, I/Q
gain and phase equilization will be then be performed.
Finally, the I/Q signal is passed through a DAC and fed
into the Rattler IC.
An 8-bit parallel interleaved data interface (BBIF_TX)
is used to load the I and Q chip data from POG into the
WCDMA signal path. Alternately, a PN calibration sig-
nal may also be loaded into this signal path for correc-
tion of baseband DC offsets and I/Q imbalances during
transmitter warmup sequences. The parallel I and Q
data from POG is first pulse shaped at a 7.68 MHz
sampling rate using 31-tap SRRC FIR filters for the I
and Q channels. These filters’ outputs are then interpo-
lated to a 30.72 MHz sampling rate using two stages of
halfband interpolation filters.
The 12-bit outputs from the baseband pulse shaping
and modulation system are fed into this DC and I/Q
correction system. The specified 12 bit inputs first pass
through the DC offset, I/Q phase and gain equalization
blocks. The output samples from the gain equalizer are
then fed into the sigma delta DACs at a higher sampling
rate to minimize anti-aliasing filtering requirements. Fol-
lowing the DACs, there is an analog gain stage with 5
attenuation settings available for the baseband gain con-
trol system. Following this stage, a 2-pole passive filter
and a 4th order Butterworth filter is employed in the
quadrature signal path to eliminate the shaped noise from
the sigma delta D/A’s. The outputs of these reconstruc-
tion filters feed into the RF modulator IC (Rattler).
B
B_QX
BB_Q
BB_IX
BB_I
HARMONY
(U100)
LP F
DC Offset
Correction &
Inp ut
Baseband
Attenuator
WCDMA
FIR Filter
WCDMA
Inte rpolation
I/Q Ga in
& Phase
Equilize r
BBIF_TX(7:0)
WCDMA
Xm it D ata
Inp u t W o rd
PN Cal
Source
Figure 3-13. Harmony WCDMA TX (U100)
RF WCDMA Transmitter

Motorola V975 Specifications

General

Brand	Motorola
Model	V975
Category	Cell Phone
Language	English