Samsung SGH-E820 Service Manual

Also see for SGH-E820: User guide User manual

Contents

SAMSUNG Proprietary-Contents may change without notice1. SGH-E820 RF Circuit Description1) RX PART1. ASM(U100) Switching Tx, Rx path for GSM900, DCS1800 by logic controlling.2. ASM Control Logic (Q100, Q102) Truth TableVC1 VC2GSM Tx Mode H LDCS Tx Mode L HGSM Rx Mode L LDCS Rx Mode L L3. FILTERConverting electromagnetic field wave to acoustic wave and then pass the specific frequency band.- GSM FILTER (F101) For filtering the frequency band between 925 and 960 MHz- DCS FILTER (F102) For filtering the frequency band between 1805 and 1880 MHz.4. VC-TCXO (OSC101)This module generates the 26MHz reference clock to drive the logic and RF. After additional process, the reference clockapplies to the U102 Rx IQ demodulator and Tx IQ modulator. And then, the oscillator is controlled by serial data toselect channel and use fast lock mode for GPRS high class operation.5. Transceiver (U102)The receiver front-end which amplifies the GSM, DCS aerial signal, converts the chosen channel down to a low IF signalof 100 kHz. The first stage is composed of symmetrical low noise amplifiers (LNAs). They are matched to 50 ohm. TheLNAs are followed by an IQ down mixer. It consists of two mixers in parallel but driven by quadrature out of phase LOsignals. The In phase(I) and Quadrature phase(Q) IF signals are low pass filtered to provide protection from highfrequency offset interferes. The low IF I and Q signals are then fed into the channel filter. The front-end low IF I and Qoutputs enter the integrated bandpass channel filter with provision for five 8 dB gain steps in front of the filter.2) TX PARTBaseband IQ signal fed into offset PLL, this function is included inside of U102 chip. OSC100 chip generates modulatorsignal which power level is about 6.5dBm and fed into Power Amplifier(U101). The PA output power and power rampingare well controlled by Auto Power Control circuit. We use offset PLL below table.Modulation Spectrum200kHz offset30 kHz bandwidthGSM -36dBmDCS -36dBm400kHz offset30 kHz bandwidthGSM -36dBmDCS -36dBm600kHz ~ 1.8MHz offset30 kHz bandwidthGSM -51dBmDCS -56dBm