LG LG-MC820 Bedienungsanleitung

CDMA MOBILE SUBSCRIBER UNIT

LG-MC820

SERVICE MANUAL

SINGLE BAND

CDMA MOBILE PHONE

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LG-MC820

Table of Contents

CHAPTER 1. Circuit Description

1. RF Transmit/Receive Part ......................................................................................................... 3

2. Digital/Voice Processing Part .................................................................................................... 8

CHAPTER 2. Trouble Shooting

CHAPTER 3. Safety

CHAPTER 4. Appendix

1) Assembly and Disassembly Diagram

2) RF Block Diagram

3) Circuit Diagram

4) Component Layout

5) Component List

5-1 Accessories

5-2 PCB

5-3 Mechanical Part

5-4 The Top of Board

5-5 The Bottom of Board

5-6 Key PCB.

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CHAPTER 1. Circuit Description

1. RF Transmit/Receive Part

1.1 Overview

The RF transmit/receive part employs the direct conversion architecture (ZIF, Zero Intermediate

Frequency). The transmit/receive frequency is respectively 824~849MHz and 869~894MHz.

The block diagram is shown in [Figure 1-1].

RF signals received through the antenna are fed into RFR6122 through the duplexer. And then, they

pass the low noise amplifier (LNA), combined with the signals of local oscillator (VCO) at the

frequency mixer in order to create baseband signal directly.

Baseband signals created are changed into digital signals by the analog / digital converter (ADC, A/D

Converter) and then, auto gain controlled and, sent to the MSM6025 (Mobile Station Modem) of the

digital circuit part. Then, they are demodulated by the modulator / demodulator.

In the case of transmission, MSM6025 modulates, interpolates, and converts the digital signal into an

analog baseband before sending it to the RFT6122.

RFT6122 receives OQPSK-modulated anlaog baseband signals from the MSM6025’s Tx part. The

RFT6122 upconverts the Tx analog baseband into RF.

The RFT6122 connects directly with MSM6025 using an analog baseband interface. In RFT6122, the

baseband quadrature signals are upconverted to the Cellular Tx frequency bands and amplified to

provide signal drive capability to the power amp.

After that, the RF signal is amplified by the Power Amp in order to have enough power for radiation.

Finally, the RF signal is sent out to the cell site via the antenna after going through the duplexer

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[Figure 1-1] Block Diagram Of MC820

1.2 Description of Receive Part Circuit

1.2.1 Duplexer (DP100)

The duplexer consists of the receive part bandpass filter (BPF) and the transmit part bandpass filter

(BPF) which have the function of separating transmit/receive signals in the full duplex system using

the transmit/receive common antenna. The transmit part BPF is used to suppress noises and spurious

waves entering the receive band among transmit signals in order to prevent the drop in receive

sensitivity characteristics. The receive part BPF blocks the signals sent out from entering the receive

end in order to improve sensitivity characteristics.

Insertion loss (IL) in the transmit band is 2.8dB (Max), whereas IL in the receive band is 2.1dB (Max).

The receive band attenuation amount of transmit filter is 51dB (Min) and the transmit band attenuation

amount of receive filter is 45dB or more (Min).

1.2.2 LNA (U107)

The RFR6122 has cellular LNA. The characteristics of Low Noise Amplifier (LNA) are low noise

figure, high gain, high intercept point and high reverse isolation. The frequency selectivity

characteristic of mobile phone is mostly determined by LNA.

The specifications of RD5330 LNA are described below.

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Parameter Gain Mode 0(G0) Gain Mode 1(G1) Gain Mode 2(G2) Gain Mode 3(G3) Unit

Gain 16 4 -5 -20 dB

Noise Figure 1.5 5 5.5 20 dB

Input IP3 10 7 15 15 dBm

1.2.3 Rx RF SAW FILTER (F101)

The main function of Rx RF SAW filter is to attenuate mobile phone spurious frequency, attenuate

noise amplified by the LNA and suppress second harmonic originating in the LNA.

1.2.4 Down-Converter Mixers (U107)

The RFR6122 device performs signal direct-down-conversion for Cellular applications. It contains all

the circuitry (with the exception of external filters) needed to support conversion of received RF

signals to baseband signals. The LO Buffer Amplifier buffers the RF VCO to the RF Transmit

Upconverter. RFR6122 offers the most advanced and integrated CDMA Rx solution designed to meet

cascaded Noise Figure (NF) and Third-order Intercept Point (IIP3) requirements of IS-98C and

J-STD-018 specifications for Sensitivity, Two-Tone Intermodulation, and Single-tone Desense.

Operation modes and band selection are specially controlled from the Mobile Station Modem MSM6025.

The specification of RD5330 Mixers are described below:

Parameter High Gain Mode Low Gain Mode Unit

Noise Figure 10 25 dB

Input IP3 4 0 dBm

Input IP2 56 30 dBm

1.3 Description of Transmit Part Circuit

1.3.1 Description on the Internal Circuit of MSM6025 (U201) and RFT6122 (U106)

For the transmit data path(Tx), the MSM6025 modulates, interpolates, and converts the digital signal

into an analog baseband before sending it to the RFT6122. The RFT6122 upconverts the Tx analog

baseband into RF. The MSM6025 communicates with the external RF and analog baseband to control

signal gain in the RF Rx and Tx signal paths, educe base band offset errors, and tune the system

frequency reference.

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The RFT6122 baseband-to-RF Transmit Processor performs all Tx signal-processing functions

required between digital baseband and the Power Amplifier Module (PAM). The baseband quadrature

signals are upconverted to the Cellular frequency bands and amplified to provide signal drive

capability to the PAM. The RFT6122 includes an mixer for up-converting analog baseband to RF, a

programmable PLL for generating Tx and Rx LO frequency, cellular driver amplifier and Tx power

control through an 85 dB VGA. As added benefit, the single sideband upconversion eliminates the

need for a band-pass filter normally required between the upconverter and driver amplifier.

I, I/, Q and Q/ signals proceed from the MSM6025 to RFT6122 are analog signal. In CDMA mode,

These signals are modulated by Offset Quadrature Phase Shift King (OQPSK). I and Q are 90 deg.

out of phase, and I and I/ are 180 deg. The mixer in RFT6122 converts baseband signals into RF

signals. After passing through the upconverters, RF signal is inputted into the Power Amplifier Module.

The RFT6122 Cellular CDMA RF specifications are described below:

Condition Min. Typ. Max. Unit

Rated Output Power Average CDMA Cellular 6 dBm

Min Output Power Average CDMA Cellular -75 dBm

Rx band noise power CDMA Cellular -132 dBm/Hz

ACPR Cellular: Fc±885kHz

Fc±1.98MHz

-52

-63

dBc

1.3.2 Power Amplifier (U104)

The power amplifier that can be used in the CDMA mode has linear amplification capability.

For higher efficiency, it is made up of one module (Monolithic Microwave Integrated Circuit) for which

RF input terminal and internal interface circuit are integrated onto one IC after going through the GaAs

HBT (heterojunction bipolar transistor) process.

The module of power amplifier is made up of an output end interface circuit including this module.

The maximum power that can be inputted through the input terminal is -1dBm and conversion gain is

about 28dB. RF transmit signals that have been amplified through the power amplifier are sent to the

duplexer.

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1.4 Description of Frequency Synthesizer Circuit

1.4.1 Voltage Controlled Temperature Compensation Crystal Oscillator (U101)

The temperature range that can be compensated by VC-TCXO which is the reference frequency

generator of a mobile station is -30~+80 °C.

VC-TCXO receives frequency tuning signals called TRK_LO_ADJ from MSM6025 as 0.5V~2.5V DC

via R and C filters in order to generate the reference frequency of 19.20MHz and input it into the

frequency synthesizer of UHF band. Frequency stability depending on temperature is ±2.0 ppm.

1.4.2 Voltage Controlled Oscillator (U107)

The internal VCO signal of RFR6122 is processed by the LO generation and distribution circuits in

RFR6122 to create Cellular quadrature downconverter’s LO signals. The LO signals applied at the

mixer ports are at the frequency different than the VCO frequency. This assures that the VCO

frequency is different than the RF frequency, an important consideration for Zero-IF processing. The

VCO frequency used are 1738.08~1787.94MHz for cellular and It is produced in single voltage

controlled oscillator of U107.

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2. Digital/Voice Processing Part

2.1 Overview

The digital/voice processing part processes the user's commands and processes all the digital and

voice signal processing in order to operate in the phone. The digital/voice processing part is made up

of a keypad/LCD, receptacle part, voice processing part, mobile station modem part, memory part,

and power supply part.

2.2 Configuration

2.2.1 Keypad/LCD and Receptacle Part

This is used to transmit keypad signals to MSM6025. It is made up of a keypad backlight part that

illuminates the keypad, LCD part that displays the operation status on to the screen, and a receptacle

that receives and sends out voice and data with external sources.

2.2.2 Voice Processing Part

The voice processing part is made up of an audio codec in MSM6025 used to convert MIC signals into

digital voice signals and other external MIDI Synthesizer used to convert digital voice signals into

analog voice signals, amplifying parts for amplifying the voice signals and MIC signals are on external

MIDI Synthesizer and Codec in MSM6025.

2.2.3 MSM6025 (Mobile Station Modem) Part

MSM6025 is the core elements of a CDMA mobile station and carries out the functions of CPU,

encoder, interleaver, deinterleaver, Viterbi decoder, Mod/Demod, codec, and vocoder.

2.2.4 Memory Part (MCP)

The memory part is made up of a flash memory 256(Mbit), PSRAM(64Mbit) for storing data.

2.2.5 Power Supply Part (U401, MAX1827)

The power supply part (MAX1827) is made up of devices for generating various types of power, used

for the digital/voice processing part and one DC/DC converter directly connetted to Batterry for LCD

display.

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2.3 Circuit Description

2.3.1 Keypad/LCD and Receptacle Part

Once the keypad is pressed, the key signals are sent out to MSM6025 for processing. In addition,

when the key is pressed, the keypad lights up through the use of 10 Blue LEDs and LCD backlights up

through the use of 2 white LEDs. The status and operation of a mobile station are displayed on the

screen for the user with the characters and icons on the LCD.

Receptacle(CON302) exchanges audio signals and data with external sources and external power.

Battery Connector receives power from the battery.

2.3.2 MSM Part

MSM6025 is the core element of a CDMA mobile station that includes ARM7TDMI microprocessor

core. The subsystems within the MSM6025 include a CDMA processor, a multi-standard Vocoder, an

integrated CODEC with earpiece and microphone amplifiers, general-purpose ADC for subsytem

monitoring, an ARM7TDMI microprocessor, and both Universal Serial Bus(USB) and an RS-232 serial

interfaces supporting forward and reverse link data communications of 307.2 Kbps simultaneously.

And it also contains complete digital modulation and demodulation systems for CDMA cellular

standards, as specified in IS-95-A/B/C.

The CPU controls total operations of the subscriber unit. Digital voice data, that have been inputted,

are encoded using the QCELP algorithm. Then, they are convolutionally encoded so that error

detection and correction are possible. Coded symbols are interleaved in order to avoid a burst error.

Each data channel is scrambled by the long code PN sequence of the user in order to ensure the

confidentiality of calls.

Moreover, binary quadrature codes are used based on Walsh functions in order to discern each

channel. Data created thus are 4-phase modulated by one pair of Pilot PN code and they are used to

create I and Q data.

When received, I and Q data are demodulated into symbols by the demodulator and then,

de-interleaved in reverse to the case of transmission. Then, the errors of data received from Viterbi

decoder are detected and corrected. They are voice decoded at the vocoder in order to output digital

voice data.

The MSM6025 also supports Enhanced Variable Rate Coder (EVRC) operation in addition to the

standard 8k and 13k vocoding rating.

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2.3.2.1 Audio Processing Part

MIC signals are inputted into the audio codec, and amplified with programmable gain, and converted

into digital signals(PCM). Then, they are inputted into MSM6025.

In addition, digital audio signals(PCM) outputted from MSM6025 are converted into analog signals

after going through the audio codec. These signals are amplified with programmable gain on codec’s

internal AMP and external MIDI Synthesizer, transferred to the ear-piece.

2.3.3 Memory Part

The memory part consists of a 256Mbits Flash Memory and a 64Mbits PSRAM(MCP). On the Flash

Memory, there are programs used for the operation of a mobile station and the non-volatile data of the

mobile station such as a ESN(Electronic Serial Number) are stored. The programs can be changed

through down loading after the assembling of mobile stations. On the PSRAM, data generated during

the operation of a mobile station are stored temporarily.

2.3.4 Power Supply Part

When the battery voltage (+4.2V) is fed and the PWR key of keypad is pressed, the power-up circuitry

in PM (power management) IC (U401) is activated by the PWR_ON_SW/ signal, and then the LDO

regulators embedded in PMIC for MSM are operated and +1.85V_MSMC, +2.85V_MSMP and

+2.6V_MSMA are generated.

The Rx part regulator (+2.6V_RX) is operated by the SBI(Seiral Bus Interface) control signal from

MSM6025. The Tx part regulator (+2.6V_TX) is operated by SBI(Seiral Bus Interface) control signal

from MSM6025.

The block diagram of power management IC is shown in [Figure 1-2].

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