LG UD2750 Service Manual

Features of Mobile Subscriber Radio Handset
(LG-UD2750 Type)

1. Wave Type

• G7W

2. Frequency Scope

• Transmit Frequency : 824.820 ~ 848.190MHz

• Receive Frequency : 869.820 ~ 893.190MHz

3. Rated Output Power

• 0.282W(24.5dBm)

4. Output Conversion Method :

5. Voltage and Current Value of Termination Part Amplifier(Catalogue included)

This is possible by correcting the key boaID channel.

Mode Type Name Voltage Current Power

CDMA FC7113 3.7V 600mA 0.32W

6. Functions of Major Semi-Conductors

Classification Function

MSM6000-208Pin-FBGA Operation control and digital signal processing of the mobile station

FLASH MEMORY

(K8D3216UTC-TI07)

STATIC RAM

(K1S161611A-FI70)

RFT6122 & RFR6122 Converting baseband signal into Tx RF signal and Rx RF signal

7. Frequency Stability

• ±0.5PPM

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Flash Memory (32Mbit) ▶ Storing of the mobile station operation
program

SRAM (16Mbit) ▶ Temporary storing of the data created while
busy

into baseband signal

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CDMA MOBILE SUBSCRIBER UNIT

LG-UD2750

SERVICE MANUAL

SINGLE BAND

CDMA MOBILE PHONE

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LG-UD2750

Table of Contents

General Introduction

............................................................................................................................................... 2

CHAPTER 1. System Introduction

1. System Introduction ................................................................................................................ 3

2. Features and Advantages of CDMA Mobile Phone .................................................................. 5

3. Structure and Functions of CDMA Mobile Phone ................................................................... 8

4. Specification .............................................................................................................................. 9

5. Installation ............................................................................................................................... 12

CHAPTER 2. NAM Input Method(Inputting of telephone numbers included)

1. Telephone Number and NAM Programming Method .............................................................. 14

CHAPTER 3. Circuit Description

1. RF Transmit/Receive Part ....................................................................................................... 17

2. Digital/Voice Processing Part .................................................................................................. 22

CHAPTER 4. Trouble Shooting

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General Introduction

The LG-UD2750 cellular phone functions as digital cellular phone worked in CDMA (Code Division
Multiple Access) mode.

CDMA mode applies the DSSS (Direct Sequence Spread Spectrum) technique that has been used in
military. This technique enables to share one frequency channel with many users in the same specific
area. As a result, that it increases the capacity 10 times more compared with that in the analog mode
(AMPS) currently used.

Soft/Softer Handoff, HaID Handoff, and Dynamic RF power Control technologies are combined into
this phone to reduce the call being interrupted in a middle of talking over phone.

CDMA digital cellular network consists of MSC (Mobile Switching Office), BSC (Base Station
Controller), BTS (Base station Transmission System), and MS (Mobile Station). Communication
between MS and BTS is designed to meet the specification of TIA/EIA/IS-95-A/B/C (Common Air
Interface). MS meets the specifications of the below :

- TIA/EIA/IS-95-A/B/C (Common Air Interface) : Protocol between MS and BTS

- TIA/EIA/IS-96-B : Speech CODEC

- TIA/EIA/IS-98 : Basic MS functions

- IS-126 : Voice loopback

- TIA/EIA/IS-99 : Short Message Service, Asynchronous Data Service, and G3 Fax Service

LG-UD2750 is composed of a transceiver, a adapter, a Li-Polymer Battery.

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CHAPTER 1. System Introduction

1. System Introduction

1.1 CDMA Abstract

The cellular system has a channel hand-off function that is used for collecting the information on the
locations and movements of radio mobile telephones from the cell site by automatically controlling
several cell site through the setup of data transmission routes and thus, enabling one switching
system to carry out the automatic remote adjustment. This is to maintain continuously the call state
through the automatic location confirmation and automatic radio channel conversion when the busy
subscriber moves from the service area of one cell site to that of another by using automatic location
confirmation and automatic radio channel conversion functions. The call state can be maintained
continuously by the information exchange between switching systems when the busy subscriber
moves from one cellular system area to the other cellular system area.

In the cellular system, the cell site is a small-sized low output type and utilizes a frequency allocation
system that considers mutual interference, in an effort to enable the re-use of corresponding
frequency from a cell site separated more than a certain distance. The analog cellular systems are
classified further into an AMPS system, E-AMPS System, NMT system, ETACS system, and JTACS
system depending on technologies used.

Unlike the Time Division Multiple Access (TDMA) or the Frequency Division Multiple Access (FDMA)
used in the band limited environment, the Code Division Multiple Access(CDMA) system which is one
of digital cellular systems is a multi-access technology under the interference limited environment. It
can process more number of subscribers compared to other systems (TDMA system has the
processing capacity three times greater than the existing FDMA system whereas CDMA system,
about 12~15 times of that of the existing system).

CDMA system can be explained as follows: TDMA or SDMA can be used to enable each person to
talk alternately or provide a separate room for each person when two persons desire to talk with each
other at the same time, whereas FDMA can be used to enable one person to talk in soprano, whereas
the other in bass (one of the two talkers can carry out synchronization for hearing in case there is a
bandpass filter function in the area of the hearer).

Another method available is to make two persons to sing in different languages at the same time,
space, and frequency when wishing to let the audience hear the singing without being confused. This
is the characteristics of CDMA.

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On the other hand, when employing the CDMA technology, each signal has a different
pseudo-random binary sequence used to spread the spectrum of carrier. A great number of CDMA
signals share the same frequency spectrum. In the perspective of frequency area or time area, several
CDMA signals are overlapped. Among these types of signals, only desired signal energy is selected
and received through the use of pre-determined binary sequence; desired signals can be separated
and then, received with the correlator used for recovering the spectrum into its original state. At this
time, the spectrums of other signals that have different codes are not recovered into its original state
and instead, processed as noise and appears as the self-interference of the system.

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2. Features and Advantages of CDMA Mobile Phone

2.1 Various Types of Diversities

When employing the narrow band modulation (30kHz band) that is the same as the analog FM
modulation system used in the existing cellular system, the multi-paths of radio waves create a
serious fading. However, in the CDMA broadband modulation(1.25MHz band), three types of
diversities (time, frequency, and space) are used to reduce serious fading problems generated from
radio channels in oIDer to obtain high-quality calls.
Time diversity can be obtained through the use of code interleaving and error correction code
whereas frequency diversity can be obtained by spreading signal energy to more wider frequency
band. The fading related to normal frequency can affect the normal 200~300kHz among signal bands
and accoIDingly, serious affect can be avoided. Moreover, space diversity (also called path diversity)
can be realized with the following three types of methods.
First, it can be obtained by the duplication of cell site receive antenna. Second, it can be obtained
through the use of multi-signal processing device that receives a transmit signal having each different
transmission delay time and then, combines them. ThiID, it can be obtained through the multiple cell
site connection (Soft Handoff) that connects the mobile station and more than two cell sites at the
same time.

2.2 Power Control

The CDMA system utilizes the forwaID (from a base station to mobile stations) and backwaID (from
the mobile station to the base station) power control in oIDer to increase the call processing capacity
and obtain high-quality calls. In case the originating signals of mobile stations are received by the cell
site in the minimum call quality level (signal to interference) through the use of transmit power control
on all the mobile stations, the system capacity can be maximized.
If the signal of mobile station is received too strong, the performance of that mobile station is improved.
However, because of this, the interference on other mobile stations using the same channel is
increased and accoIDingly, the call quality of other subscribers is reduced unless the maximum
accommodation capacity is reduced.
In the CDMA system, forwaID power control, backwaID open loop power control, and closed loop
power control methods are used. The forwaID power control is carried out in the cell site to reduce the
transmit power on mobile stations less affected by the multi-path fading and shadow phenomenon and
the interference of other cell sites when the mobile station is not engaged in the call or is relatively
nearer to the corresponding cell site. This is also used to provide additional power to mobile stations
having high call error rates, located in bad reception areas or far away from the cell site.
The backwaID open loop power control is carried out in a corresponding mobile station; the mobile
station measures power received from the cell site and then, reversely increases/decreases transmit
power in oIDer to compensate channel changes caused by the forwaID link path loss and terrain

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characteristics in relation to the mobile station in the cell site. By doing so, all the mobile office
transmit signals in the cells are received by the cell site in the same strength.
Moreover, the backwaID closed loop power control used by the mobile station to control power with
the commands issued out by the cell site. The cell site receives the signal of each corresponding
mobile station and compares this with the pre-set threshold value and then, issues out power
increase/decrease commands to the corresponding mobile station every 1.25 msec (800 times per
second).
By doing so, the gain tolerance and the different radio propagation loss on the forwaID/backwaID link
are complemented.

2.3 Voice Encoder and Variable Data Speed

The bi-directional voice service having variable data speed provides voice communication which
employs voice encoder algorithm having power variable data rate between the mobile telephone cell
site and mobile station. On the other hand, the transmit voice encoder performs voice sampling and
then, creates encoded voice packets to be sent out to the receive voice encoder, whereas the receive
voice encoder demodulates the received voice packets into voice samples.
One of the two voice encoders described in the above is selected for use depending on inputted
automatic conditions and message/data; both of them utilize four-stage frames of 9600, 4800, 2400,
and 1200 bits per second. In addition, this type of variable voice encoder utilizes adaptive threshold
values when selecting required data rate. It is adjusted in accoIDance with the size of background
noise and the data rate is increased to high rate only when the voice of caller is inputted.
Therefore, background noise is suppressed and high-quality voice transmission is possible under the
environment experiencing serious noise. In addition, in case the caller does not talk, data transmission
rate is reduced so that the transmission is carried out in low energy. This will reduce the interference
on other CDMA signals and as a result, improve system performance (capacity, increased by about
two times).

2.4 Protecting Call Confidentiality

CDMA signals have the function of effectively protecting call confidentiality by spreading and
interleaving call information in broad bandwidth. This makes the unauthorized use of crosstalk, search
receiver, and radio very haID substantially. Also included is the encryption function on various
authentication and calls specified in IS-95 for the double protection of call confidentiality.

2.5 Soft Handoff

During the soft hand, the cell site already in the busy state and the cell site to be engaged in the call
later participate in the call conversion. The call conversion is carried out through the original call

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connection cell site, both cell sites, and then, new cell site. This method can minimize call
disconnection and prevent the user from detecting the hand-off.

2.6 Frequency Re-Use and Sector Segmentation

Unlike the existing analog cellular system, the CDMA system can reuse the same frequency at the
adjacent cell and accoIDingly, there is no need to prepare a separate frequency plan. Total
interference generated on mobile station signals received from the cell site is the sum of interference
generated from other mobile stations in the same cell site and interference generated from the mobile
station of adjacent cell site. That is, each mobile station signal generates interference in relation to the
signals of all the other mobile signals.
Total interference from all the adjacent cell sites is the ratio of interference from all the cell sites
versus total interference from other mobile stations in the same cell site (about 65%). In the case of
directional cell site, one cell normally uses a 120°sector antenna in oIDer to divide the sector into
three. In this case, each antenna is used only for 1/3 of mobile stations in the cell site and accoIDingly,
interference is reduced by 1/3 on the average and the capacity that can be supported by the entire
system is increased by three times.

2.7 Soft Capacity

The subscriber capacity of CDMA system is flexible depending on the relation between the number of
users and service classes. For example, the system operator can increase the number of channels
available for use during the busy hour despite the drop in call quality. This type of function requires
40% of normal call channels in the standby mode during the handoff support, in an effort to avoid call
disconnection resulting from the lack of channels.
In addition, in the CDMA system, services and service charges are classified further into different
classes so that more transmit power can be allocated to high class service users for easier call set-up;
they can also be given higher priority of using hand-off function than the general users.

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3. Structure and Functions of CDMA Mobile Phone

The mobile station of CDMA system is made up of a radio frequency part and logic/control (digital)
part. The mobile station antenna is connected with the transmitter/receiver via a SAW duplexer filter
so that it can carry out the transmit/receive function at the same time.

The transmit frequency is the 25MHz band of 824~849MHz, whereas the receive frequency is the
25MHz band of 869~894MHz. The transmit/receive frequency is separated by 45MHz. The RF signal
from the antenna passes the LNA , bandpass SAW filter having the 1.25MHz band and then, is
directly converted into baseband signal by the frequency synthesizer and frequency down converter.
Baseband output signals that have been filtered from spurious signal are converted into digital signals
via an analog-to-digital converters(Rx ADC) and then, sent out respectively to 5 correlators in each
CDMA de-modulator. Of these, one is called a searcher whereas the remaining 4 are called data
receiver(finger). Rx signals include a great number of call signals that have been sent out by the
adjacent cells. These signals are detected with pseudo-noise sequence (PN Sequence). Signal to
interference ratio (C/I) on signals that match the desired PN sequence are increased through this type
of correlation detection process. Then, other signals obtain processing gain by not increasing the ratio.
The carrier wave of pilot channel from the cell site most adjacently located is demodulated in oIDer to
obtain the sequence of encoded data symbols.

During the operation with one cell site, the searcher searches out multi-paths in accoIDance with
terrain and building reflections. On three data receivers, the most powerful four paths are allocated for
the parallel tracing and receiving. Fading resistance can be improved a great deal by obtaining the
diversity combined output for de-modulation. Moreover, the searcher can be used to determine the
most powerful path from the cell sites even during the soft handoff during the two cell sites. Moreover,
four data receivers are allocated in oIDer to carry out the de-modulation of these paths. Data output
that has been demodulated change the data string in the combined data row as in the case of original
signals(deinterleaving), and then, are de-modulated by the forwaID error correction decoder which
uses the Viterbi algorithm.

On the other hand, mobile station user information sent out from the mobile station to the cell site pass
through the digital voice encoder via a mike. Then, they are encoded and forwaID errors are corrected
through the use of convolution encoder. Then, the oIDer of code rows is changed in accoIDance with
a certain regulation in oIDer to remove any errors in the interleaver. Symbols made through the above
process are spread after being loaded onto PN carrier waves. At this time, PN sequence is selected
by each address designated in each call.

Signals that have been code spread as above are digital modulated (OQPSK) and then, power
controlled at the automatic gain control amplifier (AGC Amp). Then, they are converted into RF band
by the frequency synthesizer synchronizing these signals to proper output frequencies. Transmit
signals obtained pass through the duplexer filter and then, are sent out to the cell site via the antenna.

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4. Specification

4.1 General Specification

4.1.1 Transmit/Receive Frequency Interval :

4.1.2 Number of Channels (Channel Bandwidth) :

4.1.3 Operating Voltage :

4.1.4 Battery Power Consumption :

SLEEP IDLE MAX POWER

CDMA

4.1.5 Operating Temperature :

4.1.6 Frequency Stability :

4.1.7 Antenna :

Fixed PIFA Type (Internal), 50

DC 3.2~4.2V

1.2 mA 100 ~ 150 mA 580 mA (25dBm)

-30° ~ +60°

±0.5PPM

DC 3.7V

45MHz

Ω

20CH (BW : 1.23MHz)

4.1.8 Size and Weight

Size : 108.5 x 44.5 x 15.6mm (L x W x D)

•

Weight : TBD

•

4.1.9 Channel Spacing :

4.1.10 Battery Type, Capacity and Orerating Time

Stand-By Time

Talk Time

1.25MHz

StandaID (1000mAh)

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Unit = Hours, Minutes

160 Hrs (SCI=1)

180 Min (About +92dBm, Half rate)

4.2 Receive Specification

4.2.1 Frequency Range :

869.820 MHz ~ 893.190 MHz

4.2.2 Local Oscillating Frequency Range :

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1738.08MHz ~ 1787.94MHz

LG-UD2750

4.2.3 Intermediate Frequency :

4.2.4 Sensitivity :

4.2.5 Selectivity :

4.2.6 Spurious Wave Suppression :

4.2.7 CDMA Input Signal Range

• Dynamic area of more than -115~ -12.6 dB : 102.4dB at the 1.23MHz band

-104dBm ( C/N 12dB or more)

3dB C/N Degration (With Fch ± 1.25KHz : -30dBm)

MSM6XXX seires (Zero IF)

Maximum of -80dB

4.3 Transmit Specification

4.3.1 Frequency Range :

4.3.2 Intermediate Frequency :

4.3.3 Output Power :

824.820 MHz ~ 848.190 MHz

MSM6XXX seires (Zero IF)

0.282W

4.3.4 Interference Rejection

• Single Tone : -30dBm at 900 kHz

• Two Tone : -43dBm at 900 kHz & 1700kHz

4.3.5 CDMA TX Frequency Deviation :

4.3.6 CDMA TX Conducted Spurious Emissions

• 900kHz : - 42 dBc/30kHz below

• 1.98MHz : - 54 dBc/30kHz below

4.3.7 CDMA Minimum TX Power Control :

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±300Hz or less

- 50dBm below

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4.4

MS (Mobile Station) Transmitter Frequency

FA NO. CH.NO. CENTER FREQUENCY FA NO. CH.NO. CENTER FREQUENCY

1
2
3
4
5
6
7
8
9

10

1011

29

70
111
152
193
234
275
316
363

824.640 MHz

825.870 MHz

827.100 MHz

828.330 MHz

829.560 MHz

830.790 MHz

832.020 MHz

833.250 MHz

834.480 MHz

835.890 MHz

11
12
13
14
15
16
17
18
19
20

404
445
486
527
568
609
650
697
738
779

837.120 MHz

838.350 MHz

839.580 MHz

840.810 MHz

842.04 MHz

843.270 MHz

844.500 MHz

845.910 MHz

847.140 MHz

848.370 MHz

4.5

MS (Mobile Station) Receiver Frequency

FA NO. CH.NO. CENTER FREQUENCY FA NO. CH.NO. CENTER FREQUENCY

1

1011

869.640 MHz

11

404

882.120 MHz
2
3
4
5
6
7
8
9

10

29

70
111
152
193
234
275
316
363

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4.6 Charge time

4.6.1 StandaID Battery :

870.870 MHz

872.100 MHz

873.330 MHz

874.560 MHz

875.790 MHz

877.020 MHz

878.250 MHz

879.480 MHz

880.890 MHz

Typical 120 ~ 180 Min.

12
13
14
15
16
17
18
19
20

445
486
527
568
609
650
697
738
779

883.350 MHz

884.580 MHz

885.810 MHz

887.04 MHz

888.270 MHz

889.500 MHz

890.910 MHz

892.140 MHz

893.370 MHz

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5. Installation

5.1 Installing a Battery Pack (Soft Pack type)

1) The soft battery pack is keyed so it can only fit one way. Align the groove in the battery pack with
the rail on the back of the phone until the battery pack rests flush with the back of the phone.

2) Insert the bottom of battery into the openning on the back of the phone. Then, push the battery
cover up until the latch clicks.

5.2 For Adapter Use

1) Plug the adapter into a wall outlet. The adapter can be operated from either a 110V or a 220V
source.

2) Insert the adapter jack into the phone with the installed battery pack.

Red light indicates battery is being charged. Green light indicates battry is fully charged

5.3 For Mobile Mount

5.3.1 Installation Position

In oIDer to reduce echo sound when using the Hands-Free Kit, make sure that the speaker and
microphone are not facing each other and keep microphone a generous distance from the speaker.

5.3.2 Interface Box

Choose an appropriate flat surface ( somewhere under the dash on the passenger side is preferred )
and mount the IB bracket with the four self-tapping screws provided. Clip the IB into the IB bracket.

5.3.3 Microphone Installation

Install the microphone either by cliiping I onto the sunvisor (driver’s side) or by attaching it to door post
(driver’s side), using a velcno adhesive tape (not included).

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5.3.4 Cable Connections

5.3.4.1 Power and Ignition Cables

Connect the red wire to the car battery positive terminal and the black wire to the car ground. Connect
the green wire to the car ignition sensor terminal. ( In oIDer to operate HFK please make sure to
connect green wire to ignition sensor terminal.) Connect the kit’s power cable connector to the
interface box power receptacle.

5.3.4.2 Antenna Cable Connection

Connect the antenna coupler cable connector from the cradle to the external antenna connector. ( Antenna is not
included.)

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CHAPTER 2. NAM Input Method

(Inputting of telephone numbers included)

1. Telephone Number and NAM Programming Method : TBD

• Press [#+#+#+#].

Then, the following Menu is appeared.

DEBUG MENU

Service Mode

1
2 Test Screen
3 Test Call
4 Vocoder Set

5 Hybrid Pref

Sel

• If you press [1] , display the PHONE MODEL.

DEBUG MENU

PHONE

Service Mode

1

MODEL

2 Test Screen
3 Test Call
4 Vocoder Set

5 Hybrid Pref

95

OK

• You can’t edit PHONE MODEL , then press [OK].

DEBUG MENU

Service Mode

1

SLOT CYCLE

INDEX

2

Test Screen

3

Test Call

4

Vocoder Set

5

Hybrid Pref

1

OK

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• You can edit SLOT CYCLE INDEX (, but not recommended ), then press [OK].

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DEBUG MENU

Service Mode

1

NAM 1

PHONE NUMBER

2 Test Screen

0000000000

3 Test Call
4 Vocoder Set

5 Hybrid Pref

OK

Enter the phone number, then press [OK].

•

DEBUG MENU

Service Mode

1

NAM 1
NAME

2

Test Screen

Empty

3

Test Call

4

Vocoder Set

5

Hybrid Pref

Edit OK

Edit the name of NAM1, the press [OK].

•

‘NAM 1 NAME’ may display the name of the service provider

DEBUG MENU

Service Mode

1

NAM 1

Standard Program

2

Test Screen

IS COMPLETE

3

Test Call

4

Vocoder Set

5

Hybrid Pref

Add End

• Now, the basic programming is completed. To reset the handset, press [Done]. If you want to

program detail informtions for NAM 1, press [

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Add

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The detail programming method is same as basic programming. Set up required values and then,
press the [OK] soft key in an effort to move to the next screen.
To return to the last item, press the [
The editable NAM items are followed:

SERVICE SECURITY CODE
NAM 1 MOBILE COUNTRY CODE
NAM 1 MOBILE NETWORK CODE
NAM 1 PRL Enabled ?
NAM 1 CDMA Home System Reg
NAM 1 CDMA Foreign SID Reg
NAM 1 CDMA Foreign NID Reg
NAM 1 CDMA Home SID/NID
NAM 1 Lock out SID/NID
NAM 1 CDMA Primary CH A
NAM 1 CDMA Secondary CH A
NAM 1 CDMA Primary CH B
NAM 1 CDMA Secondary CH B

Back

].

NAM 1 ACCOLC 0

Editing this items is not recommended.

※

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CHAPTER 3. 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 824.04~848.97MHz and 869.04~893.97
MHz. The block diagram is shown in [Figure 3-1].
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 oIDer 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 MSM6000 (Mobile Station Modem) of the
digital circuit part. Then, they are demodulated by the modulator / demodulator.
In the case of transmission, MSM6000 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 MSM6000’s Tx part. The
RFT6122 upconverts the Tx analog baseband into RF.
The RFT6122 connects directly with MSM6000 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 oIDer 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 3-1] Block Diagram Of UD2750

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 oIDer to prevent the drop in receive
sensitivity characteristics. The receive part BPF blocks the signals sent out from entering the receive
end in oIDer 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 (U104)

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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.

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The specifications of UD2750 LNA are described below

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

Gain

Noise Figure

Input IP3

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 (U104)

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 ThiID-oIDer Intercept Point (IIP3) requirements of IS-98C and
J-STD-018 specifications for Sensitivity, Two-Tone Intermodulation, and Single-tone Desense.

10 7 15 15 dBm

16 4 -5 -20 dB

1.5 5 5.5 20 dB

Operation modes and band selection are specially controlled from the Mobile Station Modem MSM6000.
The specification of UD2750 Mixers are described below:

Parameter High Gain Mode Low Gain Mode Unit

Noise Figure

Input IP3
Input IP2

4 0 dBm

Z3X-BOX.COM

10 25 dB

56 30 dBm

1.3 Description of Transmit Part Circuit

1.3.1 Description on the Internal Circuit of MSM6000 (U201) and RFT6122 (U103)

For the transmit data path(Tx), the MSM6000 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 MSM6000 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.

LGE

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