H/W Circuit Description; Rf Transceiver General Description; Receiver Part - LG MG180C Service Manual

3. H/W Circuit Description

3. H/W Circuit Description

3.1 RF Transceiver General Description

The RF parts consist of a transceiver part, a power amplifier part, a front-end module part, a voltage
supply part, and a VC-TCXO part.
The AeroII transceiver is composed of single RF chipset, Si4210-GM[U501] which is a quad-band
GSM/GPRS wireless communications. This device integrated a receiver based on a low IF (200KHz)
architecture and a transmitter based on modulation loop architecture. The transceiver employed a 3
wire serial interface to allow an external system controller to write the control registers for dividers,
receive path gain, power down setting, and other controls.

3.2 Receiver Part

The receiver part uses a low-IF receiver architecture that allows for the on-chip integration of the
channel selection filters, eliminating the external RF image reject filters and the IF SAW filter required
in conventional super-heterodyne architecture.
The Si4210-GM[U501] integrates four differential input LNAs that are matched to the 200 Ohm
balanced-output SAW filters through external LC matching networks. A quadrature image-rejection
mixer downconverts the RF signal to a 200kHz intermediate frequency (IF) with the RFLO from the
frequency synthesizer.
The mixer output is amplified with an analog programmable gain amplifier (PGA) and quadrature IF
signal is digitized with high resolution A/D converters (ADCs). The Si4210-GM[U501] downconverts
the ADC output to baseband with a digital 200kHz quadrature LO signal. Digital decimation and IIR
filters perform digital filtering , and remove blocking and reference interference signals. After filtering,
the digital output is scaled with digital PGA, which is controlled with the DGAIN[5:0] bits in register 20h.
The amplified digital output signal go through with DACs that drive a differential analog signal onto the
RXIP,RXIN,RXQP and RXQN pins to interface to standard analog ADC input baseband ICs.
Antenna Display
Antenna Bar Number
5 → 4
4 → 3
3 → 2
2 → 1
1 → 0
Table 3-1. Antenna Display
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Rx Power (dBm)
-85dBm±2dBm
-90dBm±2dBm
-95dBm±2dBm
-100dBm±2dBm
-105dBm±2dBm