LG G8000 8 free download

File name LG G8000 8.pdf

3. TECHNICAL BRIEF 3. TECHNICAL BRIEF 3.1 Receiver The receiver part consists of a dual band (GSM & DCS) antenna switch, two RF SAW filters, an external dual RF VCO and a transceiver IC (TRF6150). All active circuits for a complete receiver chain with the exception of RF VCO are contained in the transceiver IC (TRF6150). The TRF6150 chip set has direct conversion structure, so the received RF signal is directly converted to base band I and Q signal by the transceiver IC (IF frequency is 0 Hz), which contains two LNAs and three direct conversion demodulators for E-GSM, DCS and PCS. The demodulated I and Q signals pass two base band AGC amplifiers and a channel filter, which are on both I and Q signal paths. The RF front-end circuit is shown Figure 3-1. Figure 3-1. RF front-end circuit - 12 - 3. TECHNICAL BRIEF 3.1.1 RF front end RF front end consists of an antenna, a dual band antenna switch, two RF SAWs and two LNAs for E- GSM, DCS band, which are contained in the transceiver IC (TRF6150). The RF received signals (GSM 925MHz ~ 960MHz, DCS 1805MHz ~ 1880MHz) are input via the antenna or coaxial connector. An antenna matching circuit is between the antenna and the connector. The antenna switch (FL103) is used to control the Rx and TX paths, which has two control signals VC1 and VC2 that are connected to 4-Input NOR Gate (U102) to switch either TX or RX path on. When the RX path is turned on, the received RF signal, which has passed through the dual band antenna switch, is filtered by an appropriate RF SAW filter for better stop band rejection. The filtered RF signal is amplified by an LNA integrated in the transceiver IC(TRF6150) and pass to a direct conversion demodulator. This process is the same both GSM and DCS. The logic and current is given below. Table 3-1. Table 3-1. The logic and current VC1 VC2 GSM TX 2.7 V 0V DCS TX 0V 2.7 V GSM/DCS RX 0V 0V 3.1.2 Demodulator and Baseband Processing IF stage is not necessary in this system because the receiver is based on direct conversion architecture. So the RX LO frequency is the same as input radio frequency. The amplified signal at LNA stage passes to a direct conversion demodulator and is mixed down to generate I&Q BB signals. The BB I&Q signals pass via two integrated baseband amplifiers with digitally programmable gain and two fully integrated baseband channel filters to the baseband A/D converters