Nokia 9500 Service Manual 07 ra2 RF.book

Nokia Customer Care

7 - RF Description and

Troubleshooting

Issue 1 09/04 COMPANY CONFIDENTIAL

RA-2/3

Nokia Customer Care

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RA-2/3 7 - RF Description and Troubleshooting Nokia Customer Care

Table of Contents

Page No

CMT RF................................................................................................................. 5

Top-level description.......................................................................................... 5

RA-2 test point locations................................................................................... 6

Test points ......................................................................................................... 8

RF implementation in RA-2/3........................................................................... 11

Frequency plan ..............................................................................................11

RF block diagram ...........................................................................................12

Antenna switch module (ASM) .......................................................................12

DC characteristics ..........................................................................................13

Regulators................................................................................................. 13

DC supply currents.................................................................................... 13

Typical current consumption...................................................................... 14

Power distribution diagram........................................................................ 15

RF characteristics ............................................................................................ 16

Channel numbers and frequencies ................................................................ 16

RF Troubleshooting..........................................................................................17

Receiver description and troubleshooting........................................................ 17

Rx front end ...................................................................................................17

Antenna .........................................................................................................17

Receiver characteristics .................................................................................18

General instructions for Rx troubleshooting ...................................................19

Troubleshooting diagram for GSM850 receiver......................................... 23

Troubleshooting diagram for GSM900 receiver......................................... 24

Troubleshooting diagram for GSM1800 receiver....................................... 25

Troubleshooting diagram for GSM1900 receiver....................................... 26

Transmitter description and troubleshooting.................................................... 27

Power amplifier ..............................................................................................27

RF ASIC Helgo ..............................................................................................27

AFC function ..................................................................................................28

Transmitter characteristics .............................................................................28

General instructions for Tx troubleshooting ................................................... 28

Transmitter troubleshooting diagram......................................................... 30

HELGO IC troubleshooting diagram.......................................................... 31

PA and antenna switch troubleshooting diagram...................................... 32

Pictures of transmitter signals ................................................................... 33

Additional information for EDGE troubleshooting ............................................ 35

Transmitter EDGE troubleshooting diagram.............................................. 36

HELGO EDGE troubleshooting diagram................................................... 37

PA and antenna switch EDGE troubleshooting diagram........................... 38

Pictures of EDGE transmitter signals .............................................................39

Synthesizer description and troubleshooting................................................... 43

Frequency synthesizers .................................................................................43

General instructions for synthesizer troubleshooting .....................................43

Troubleshooting diagram for synthesizer .................................................. 44

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Table of Contents

Page No

Pictures of synthesizer signals.................................................................. 45

Frequency Lists ..............................................................................................48

GSM850 .................................................................................................... 48

GSM900 (including EGSM900)................................................................. 49

GSM1800 .................................................................................................. 50

GSM1900 .................................................................................................. 51

RF tunings after repairs ................................................................................... 52

WLAN RF Description....................................................................................... 53

RF operating modes ........................................................................................ 54

Transmitter .....................................................................................................54

Receiver .........................................................................................................55

Synthesizer .................................................................................................... 55

Antenna ..........................................................................................................55

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RA-2/3 7 - RF Description and Troubleshooting Nokia Customer Care

CMT RF

■ Top-level description

The RF module performs the necessary high frequency operations of the GSM850/EGSM900/ 1800/1900 tripleband (EDGE) engine. Both the transmitter and receiver have been implemented by using direct conversion architecture which means that the modulator and demodulator operate at the channel frequency.

The core of the RF is an application-specific integrated circuit, Helgo. Another core component is a power amplifier module which includes two amplifier chains, one for GSM850/EGSM900 and the other for GSM1800/GSM1900.

Other key components include

• 26 MHz VCTCXO for frequency reference

• 3296-3980 MHz SHF VCO (super high frequency voltage controlled oscillator)

• Antenna switch module (ASM)

• Four SAW filters

The control information for the RF is coming from the baseband section of the engine through a serial bus, referred later on as RFBus.

The whole RF circuitry is located on one side of the 8-layer PWB. EMC leakage is prevented by using a metal cans. The RF circuits are separated into two

blocks.

• PA, ASM, LNA, baluns for Rx/Tx and Rx/Tx SAWs.

• Helgo RF IC, VCO + balun, VCTCXO, baluns and EGSM Rx filter

The RF transmission lines constitute of striplines and microstriplines after PA.

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■ RA-2 test point locations

Figure 1: Top view

N6400 pins 39-42

C2104

C2105

R2106

C4104

R2125

L7830

Z7808

R6304

N6301 pin3

C4105

J2809

J8120

C2210

C6404

R6402

R6405

C5001

R5001

R4100

R2000

L2335

C6428

C6433

C6455 C6456

C2108

C2107

J2 280

R2126

R2004

G6400 pin3

N6300 pin3

N6405 pin2

C6407

L4201

C4203

C5000

J4100

J4803

R4101

C2881

C2204

R2902

J2803

J28 00

L2330 L2333

C2202L2206

L7702

L2331

V7802 pins1,6,4

C7714

R7711

Z7800

C7713

RefClk

R6411

R6428

C6446

C6445

R6404

J4805

C4800

C4801

R6043

J7503

J7510

R7522

R7525

L7823

L7822

C2006

C5083

C5089

R4808

R4801

J4802

J7 450

C4819

J7511

L7810

L2332

C2005

C6302

D6310 pins 5&6

C6310

PURX

R4800

R4418

G7500

C7506

C2232

L2334

L7805

VCTRL

L7709

L7710

R7715

L7700

N4490 pin3&4

C6401

R6305

L4202

N6303 pin4

N6303 pin3

C4211

R4802

R4415

R7500

C 5837

C7553

C7536

C7535

L7809

Z7809

C7510

Power 2.8

Power 1.8

C6307

C6314

N6300 pin5

C4204

J7509

J7502

J7501

C7551

C7520

N6302 pin3

J4815

G7501

R7725

C7707

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Figure 2: Bottom view

N4400 B-Cover switch

GND

R4202

L2020

X2021 pins

Charge

11-14

R2001

SIM

C4202

J4413

J5107

J5106

C2037

R4422

J4414

Trace

5108J

102J5

J5104

Production

testpoints

X2021 pins 6&7

N6402 pins 1&3

J1053

C2038

Bluetooth

Mic

MMC

C5200

R5202

J1150

J31 80

50J15

J51 00

30J17

J3104

J3109

J3 610

J3103

J2122 J2120 J2121

8J31 2

J3102

J3101

J3180

J3181

J3100

N7100

Battery

J0222

J2021

20J20

IHF

J2032

Zocus

J2031

J2033

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■ Test points

Table 1: Rx test points

Signal name: Ref:

LNA_VCC V7802 LNA_IN V7802 LNA_P V7802 RXI J7510 RXQ J7511

Table 2: Antenna switch test points

Signal name: Ref:

VANT_1 Z7800 VANT_2 Z7800 VANT_3 Z7800 GSM_Rx Z7800 DCS_Rx Z7800 PCS_Rx Z7800 TX_IN_EGSM/850 Z7800

Table 3: Helgo serial interface test points

Signal name: Ref:

RFBusClk J7501 RFBusEna1 J7502 RFBusData J7509 Reset J7503

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Table 4: Synthesizer test points

Signal name: Ref:

VCO_out G7500 VCTCXO_out G7501

Table 5: GSM900/850 Rx helgo input test points

Ref:

RX filter Z7809 Inductor L7809 Inductor L7810

Table 6: GSM1800 Rx helgo input test points

Filter Z7808 Inductor L7823 Inductor L7822 Inductor L7830

Table 7: GSM1900 Rx helgo input test points

Inductor L7805

Table 8: Tx PA input test points

Signal name: Ref:

Rfin_900/850 C7707

Ref:

Rfin_1800/190 L7702

Table 9: Tx filter/balun input test points

Signal name: Ref:

RfinP_900 L7700 RfinM_900 L7700

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RfinP_1800_1900 C7709 RfinM_1800_1900 C7710

Table 10: PA control signal test points

Signal name: Ref:

VPCTRL_900 R7715 VPCTRL_1800_1900 R7711 TXIM C7535 TXIP C7535 TXQM C7536 TXQP C7536 TXC R7522 TXP J7504 (test pad)

Table 11: Rx test points

Signal name: Ref:

VR1 C7551 VR2 C7520 VR3 C7583 VR4 C7510 VR5 C7553 VR6 C7506 VR7 R7500 VrefRF01 R7525 VBAT C7725 VTXB_900 C7713 VTXB_1800_1900 C7714

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■ RF implementation in RA-2/3

Frequency plan

The RF frequency plan is shown below. The VCO operates at the channel fre quency multiplied by two or four depending on the frequency band of operation. This means that the baseband modulated signals are directly converted up to the transmission frequency and the received RF signals directly down to the baseband frequency.

Figure 3: RF frequency plan

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Nokia Customer Care 7 - RF Description and Troubleshooting

RF block diagram

Antenna switch module (ASM)

Helgo

Figure 4: ASM

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DC characteristics

Regulators

The transceiver baseband section has a multi function analog ASIC, UEM, which contains among other functions six pieces of 2.78 V linear regulators and a 4.8 V switch ing regulator. All the regulators can be controlled individually by the 2.78 V logic directly or through a control register. Normally, direct control is needed because of switching speed requirement: the regulators are used to enable the RF-functions which means that the controls must be fast enough.

The use of the regulators can be seen in the power distribution diagram which is p resented in Figure 6, “Power distribution diagram,” on page 15.

The seven regulators are named VR1 to VR7. VrefRF01 is used as a reference voltage for Helgo.

The regulators (except for VR7) are connected to the Helgo. Different modes of operation can be selected inside the Helgo according to the control information coming through the RFBus.

DC supply currents

Figure 5: DC power supplies

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Typical current consumption

The table shows the typical current consumption in different operation modes.

Operation mode

Power OFF < 10 uA Leakage current (triple band

Rx, EGSM900/GSM850 75 mA, peak Rx, GSM1800/GSM1900 70 mA, peak Tx, power level 5, EGSM900/

GSM850 Tx, power level 0, GSM1800/

GSM1900

1700 mA, peak

1000 mA, peak

Current

consumption

Notes

PA)

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Power distribution diagram

Figure 6: Power distribution diagram

HELGO

LNA GSM1800/ 1900

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■ RF characteristics

Channel numbers and frequencies

System Channel number Tx frequency Rx frequency Unit

GSM850 128< =n <=251 F= 824.2+0.2* (n -

128)

GSM900 0 < =n <=124 F = 890 + 0.2 * n F = 935 + 0.2 * n MHz

975<= n <= 1023 F= 890+0.2* (n -1024) F= 935+0.2* (n -1024) MHz GSM1800 512 <= n <= 885 F=1710.2+0.2*(n-512) F=1805.2+0.2*(n-512) MHz GSM1900 512 <= n <=810 F=1850.2+0.2*(n-512) F=1930.2+0.2*(n-512) MHz

F= 869,2+0.2* (n -128) MHz

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RF Troubleshooting

All measurements should be done using a spectrum analyzer with a high-frequency high-impedance passive probe (LO-/reference frequencies and RF power levels) and an oscilloscope with a 10:1 probe (DC-voltages and low frequency signals).

The RF section is build around one RF ASIC (HELGO N7500). For easier troubleshootin g, this RF troubleshooting document is divided into sections.

Before changing HELGO, please check that both supply voltages and serial communication coming from baseband to HELGO are OK. Please note that the grounding of the PA module is directly below the PA module, so it is difficult to check or change.

Most RF semiconductors are static discharge sensitive! Therefore ESD protection must be taken care of during repair (ground straps and ESD soldering irons). HELGO and PA are moisture sensitive so parts must be pre-baked prior to soldering.

Apart from key components described in this document there are a lot of discrete components (resistors, inductors and capacitors) of which troubleshooting is done by checking if the sold ering of the component is done properly (for factory repairs checking if it is missing from the PWB). You can check capacitors for shortening and resistors for value by means of an ohmmeter, but be aware in-circuit measurements should be evaluated carefully.

Please be aware that all measured voltages or RF levels in this document are rough figures. Especially RF levels vary due to different measuring equipment or different grounding of the probe used. When using an RF probe use a pair of metallic tweezers to connect the probe ground to the PWB ground as close to the measurement point as possible.

■ Receiver description and troubleshooting

Each receiver path is a direct conversion linear receiver. From the antenna, the received RFsignal is fed to a front end module where a diplexer first divides the signal into two separate paths according to the band of operation: either lower, GSM850/EGSM900 or upper, GSM1800/GSM1900 path.

Most of the receiver circuitry is included in Helgo.

Rx front end

The front end features include:

• Antenna 50 ohm input

• RXs single outputs

• TXs single 50 ohm inputs

• 3 control lines from Helgo

Antenna

The RA-2/3 GSM850/EGSM900/GSM1800/GSM1900 transceiver features an internal antenna. There are two triple-band antennas: one for RA-2 and one for RA-3.

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