LG GT540, Руководство по обслуживанию

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Only for training and service purposes
3. TECHNICAL BRIEF
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A generic, high-level functional block diagram of GT540 is shown in Figure 1-1. One antenna collects base station
forward link signals and radiates handset reverse link signals. The antenna connects with receive and transmit paths
through a ASM(Antenna-Switch-Module).
The UMTS receive paths each include an LNA, an RF band-pass filter, and a downconverter that translate the signal
directly from RF-to-baseband using radioOne ZIF techniques. The RFIC’s Rx analog baseband outputs, for the
receive chains, connect to the MSM IC. The UMTS and GSM Rx baseband outputs share the same inputs to the MSM
IC.
For the transmit chains, the RTR6285 IC directly translates the Tx baseband signals (from the MSM device) to an RF
signal using an internal LO generated by integrated onchip PLL and VCO. The RTR6285 IC outputs deliver fairly high-
level RF signals that are first filtered by Tx SAWs and then amplified by their respective UMTS PAs. In the GSM
receive path, the received RF signals are applied through their band-pass filters and down-converted directly to
baseband in the RTR6285 transceiver IC. These baseband outputs are shared with the UMTS receiver and routed to
the MSM IC for
further signal processing.
The GSM/EDGE transmit path employs one stage of up-conversion and, in order to improve efficiency, is divided
into phase and amplitude components to produce an open-loop Polar topology:
1. The on-chip quadrature up-converter translates the GMSK-modulated signal or 8-PSK modulated signal, to a
constant envelope phase signal at RF;
2. The amplitude-modulated (AM) component is applied to the ramping control pin of Polar power amplifier from a
DAC within the MSM GT540 power supply voltages are managed and regulated by the PM7540 Power Management
IC. This versatile device integrates all wireless handset power management, general housekeeping, and user
interface support functions into a single mixed signal IC.
It monitors and controls the external power source and coordinates battery recharging while maintaining the
handset supply voltages using low dropout, programmable regulators.
The device’s general housekeeping functions include an ADC and analog multiplexer circuit for monitoring on-chip
voltage sources, charging status, and current flow, as well as user-defined off-chip variables such as temperature, RF
output power, and battery ID.
Various oscillator, clock, and counter circuits support IC and higher-level handset functions. Key parameters such as
under-voltage lockout and crystal oscillator signal presence are monitored to protect against detrimental
conditions.