Pam (Sky77328, U500) - LG KG245 Service Manual

3. TECHNICAL BRIEF
B. OPLL
The OPLL consists of a feedback mixer, a phase detector, a loop filter, and a fully integrated TXVCO. The
TXVCO is centered between the DCS 1800 and PCS 1900 bands, and its output is divided by 2 for the
GSM 850 and E-GSM 900 bands. The RFLO frequency is generated between 1272 and 1483 MHz. To
allow a single VCO to be used for the RFLO, high-side injection is used for the GSM 850 and E-GSM 900
bands, and low-side injection is used for the DCS 1800 and PCS 1900 bands. The I and Q signals are
automatically swapped when switching bands. Additionally, the SWAP bit in register 03h can be used to
manually exchange the I and Q signals.
Low-pass filters before the OPLL phase detector reduce the harmonic content of the quadrature modulator
and feedback mixer outputs. The cutoff frequency of the filters is programmable with the FIF[3:0] bits in
register 04h (Figure 3-3), and should be set to the recommended settings detailed in the register
description.

3.2 PAM (SKY77328, U500)

The SKY77328 Power Amplifier Module (PAM) is designed in a low profile (1.2 mm), compact form factor
for quad-band cellular handsets comprising GSM850/900, DCS1800, and PCS1900 operation. The PAM
also supports Class 12 General Packet Radio Service (GPRS) multi-slot operation.
The module consists of separate GSM850/900 PA and DCS1800/PCS1900 PA blocks, impedance-
matching circuitry for 50 Ω input and output impedances, and a Power Amplifier Control (PAC) block with an
internal current-sense resistor.
Figure. 3-4 SKY77328
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