TX IQ tuning .........................................................................................................................................34
TX power level tuning ........................................................................................................................39
This document describes troubleshooting and RF tuning of RH-51/52, RH-67/68. In general, two types of measurements have to be done during troubleshooting and repair of
phones:
•RF measurements shall be done with a spectrum analyzer, either connected directly
to the RF connector of the RF adapter board SA-29, or used together with a highfrequency probe to measure RF signals at points along the TX or RX chain.
•LF (Low-Frequency) and DC measurements shall be done either with a multimeter, or
with an oscilloscope together with a 10:1 probe.
All tuning must be done with Phoenix Service Software 2004.32.2.58 or later.
Always make sure that the measurement set-up has been calibrated when measuring RF
parameters at the RF connector. Remember to include the correct losses in the module
repair jig and the connecting cable when realigning the phone.
Most RF semiconductors are static discharge sensitive. ESD protection must be taken
into account during repair (ground straps and ESD soldering irons).
Helgo RF ASIC is moisture sensitive. Therefore, Helgo RF ASIC must be pre-baked prior
to soldering unless it is stored in a sealed moisture barrier bag.
RF calibration done via Phoenix software is temperature sensitive because of calibration of 26MHz reference oscillator (VCXO). According to the Helgo specification,
the ambient temperature has to be in the range of 22 to 36°C.
General troubleshooting
Note: In this text the following terms are used interchangeably:
GSM900 = EGSM900 = EGSM
GSM1800 = DCS band = PCN band
GSM1900 = PCS band
The first step of fault-finding should always be a visual inspection. Carefully inspect the
RF area using a microscope and look for solder bridges, missing components, short circuits, components that have partially come off and other anomalies. Capacitors can be
checked to see that they are not short-circuited, and inductors that they are not open
circuits. Also check that power supply lines are not short-circuited, i.e. not 0Ω to ground.
Instruments needed for troubleshooting (minimum requirement):
•oscilloscope
•multimeter
•spectrum analyzer (SA)
Note:
Always use an attenuator at the spectrum analyzer input to ensure that the SA will not become damaged by
excessive input power from the phone. Check the spectrum analyzer for maximum allowable input power.
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For example, when transmitting in the EGSM band at max power level, the output power will be around
+33dBm. By using a 10dB attenuator the actual input to the SA will then be +23dBm. Also adjust the internal attenuator so that the transmitted signal is reduced to less than around -10dBm in order to avoid saturation of SA input stage.
Each receiver path is a direct conversion linear receiver. From the antenna, the received
RF signal is fed to a front end module where a diplexer first divides the signal to two
separate paths according to the band of operation: either lower, GSM850/EGSM900 or
upper, GSM1800/1900 path. At each of the paths follows a pin-diode switch, which is
used to select either a receive- or transmit mode. At the upper band in the receive mode
either GSM1800 or 1900 path is further selected by another pin-diode switch. The selections are controlled by Helgo, which obtains the mode/band and timing information
through the RFBus. After the switches an external bandpass filter follows each receiver
paths. Thereafter, the signal is fed to the LNA's. GSM850/EGSM900 and GSM1800 LNA's
are integrated in Helgo, while the GSM1900 LNA is a discrete component placed
between SAW filter and balun. In GSM1900, the amplified signal is fed to a pre-gain
stage of the mixer. GSM850/EGSM900 and GSM1800 LNA's are connected directly to the
pregain stages. The pregain stages as well as all the following receiver blocks are integrated in Helgo. The LNA's have three gain levels. The first one is the maximum gain, the
second one is about 30 dB below the maximum, and the last one is the off state.
After the pregain stages there are demodulator mixers at each signal path to convert the
RF signal directly down to baseband I and Q signals. Local oscillator signals for the mixers are generated by an external VCO. The frequency is divided by two in GSM1800 and
GSM1900 and by four in GSM850/EGSM900. Those frequency dividers are integrated in
Helgo and in addition to the division they also provide accurate phase shifting by 90
degrees which is needed for the demodulator mixers.
The demodulator output signals are all differential. After the demodulators there are
amplifiers called DtoS (differential to single ended) which convert the differential signals
to single ended. Before that, they combine the signals from the three demodulators to a
single path which means that from the output of the demodulators to the baseband
interface are just two signal paths (I and Q), which are common to all the frequency
bands of operation. In addition, the DtoS amplifiers perform the first part of the channel
filtering and AGC (automatic gain control). They have two gain stages, the first one with
a constant gain of 12 dB and -3 dB bandwidth of 85 kHz and the second one with a
switchable gain of ±6 dB. The filters in the DtoS blocks are active RC filters. The rest of
the analog channel filtering is provided by blocks called BIQUAD which include modified
Sallen-Key biquad filters.
After the DtoS and BIQUAD blocks, there is another AGC-amplifier which provides a gain
control range of 42 dB in 6 dB steps. The correlation between the gain steps and the
absolute received power levels is found by a calibration routine in the production for
each assembled phone.
In addition to the AGC steps, the last AGC stage also performs the real time DC offset
compensation, which is needed in a direct conversion receiver to cancel out the effect of
the local oscillator leakage. DC offset compensation is performed during an operation
called DCN1. DCN1 is carried out by charging capacitors at the input of the last AGC
stages to a voltage, which causes a zero DC offset. To improve the accuracy a DC level
alignment possibility has been added to Helgo.
After the last AGC stages the single ended and filtered I- and Q-signals are fed to the RX
Measuring the RX module manually using oscilloscope and spectrum analyzer
Spectrum analyzer level values depend on the probe type and should be validated using a
known good sample. The levels that are given here are measured using a high frequency
probe.
Measuring with oscilloscope at test point RXI (J827) or RXQ (J828) ) and RXID (J261) or
RXQD (J262) is recommended only if RSSI reading does not provide enough information.
GSM 900/850
Start Phoenix Service Software and establish connection to the phone
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Input freq/level of signal generator is 942.4677MHz, -60dBm
(881.6677MHz for GSM850)
Note: Because DC compensation doesn’t work during continuous mode, DC offset level at RXI and RXQ will
gradually shift from the optimized level. To have most reliable result, it is highly advisable to set operation
mode from burst to continuous just before measuring values and complete measurement within no longer
than 30 seconds.
Figure 4: Troubleshooting chart for EGSM900 (GSM850)
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Input freq/level of signal generator is 1842.8677MHz, -60dBm
Note: Because DC compensation doesn’t work during continuous mode, DC offset level at RXI and RXQ will
gradually shift from the optimized level. To have most reliable result, it is highly advisable to set operation
mode from burst to continuous just before measuring values and complete measurement within no longer
than 30 seconds.
Start Phoenix Service Software and establish connection to the phone.
SelectFile Open Product
RH-51, -52, -67 or -68
SelectTestingRF controls
Select BandGSM1900
Active unitRX
Operation mode Continuous *
RX/TX channel 661
AGC12
Input freq/level of signal generator is 1960.0677MHz, -60dBm
Note: Because DC compensation doesn’t work during continuous mode, DC offset level at RXI and RXQ will
gradually shift from the optimized level. To have most reliable result, it is highly advisable to set operation
mode from burst to continuous just before measuring values and complete measurement within no longer
than 30 seconds.
This calibration calibrates the baseband filter inside Helgo ASIC. It is done by internally
measuring a prototype filter, for this reason the calibration is done once, not separately 3
bands.
This tuning doesn’t require RF input from an external signal generator.
Select TuningRX Channel Select Filter Calibration
Check “Save to Phone”
PressTune
Press Stop to store the data to the phone.
RX channel select filter calibration is finished.
RX calibration
The "RX calibration" is used to determine gain at different gain settings for front-end
and the Helgo ASIC and needs to be done in all three bands.
RX calibration requires an external signal generator.
A simple block diagram of the TX part of the phone is shown in the following figure. The
voice or data signals to be transmitted come from the UEME IC in the BB (baseband)
area, and go to the Helgo IC, where they are up-converted to RF. The TX signals going
from UEME to Helgo are called the IQ-signals, and consist of two balanced signals {
TXIN, TXIP } and { TXQN, TXQP }, i.e. a total of four signal lines. In addition to the IQ signals, there are also control signals going between BB and RF.
Figure 12: TX RF block diagram
BB-RF
Interface
Signals:
From UEME:
TXIQ
Helgo
4
V_BAT
1800 / 1900MHz
PA
Ant-Switch
1/2
900MHz
RFBusClk
RFBusEna1
RFBus Data
Reset
4
1/4
2
LO
Synthesizer
(LO=Local Oscillator)
VPCTRL_900
VPCTRL_1800_1900
SAW
2
Power Loop Filter
DET
The following picture shows the two shielding cans where the TX circuitry is located (the
lids have been removed). The upper shielding can contains BB-RF interface circuitry, the
Helgo RF system IC, a SAW filter for the GSM/EGSM band, and a balun for the DCS/PCS
band. The lower shielding can contains the power amplifier (PA) and the antenna switch
module (ASM).
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(E)GSM
SAW filter
Helgo
DCS/PCS
Balun
Preparation for troubleshooting
•Place the phone (mechanics removed) on module jig.
•Connect the module jig to the PC via a DAU-9P cable.
•Connect the module jig to a power supply (4.2V).
•Connect the RF output to a spectrum analyzer or another measurement instrument.
Use a 10dB attenuator at the input to spectrum analyzer to avoid damaging it.
•Make sure the dongle is connected and start Phoenix.
•In Phoenix: File → Open Product → RH-51, -52, -67 or -68 Product Menu.
•Select Testing → RF Controls.
•From the toolbar: set Operating Mode to Local.
•Select band ‘GSM850’ ‘GSM900’, ‘GSM1800’ or ‘GSM1900’.
•Set Operation Mode to Burst.
ASM
hh
Power
Amplifier
•Set Active Unit to Tx.
•Set Tx Data Type to All 1.
•Set Rx/Tx Channel to 190 for GSM850, 37 for GSM900, 700 for GSM1800 or 661 for
GSM1900.
•Set Tx PA Mode to Free.
•Set Tx Power Level to 5 in GSM850/GSM900, otherwise to 0.
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Transmitter tuning
In the transmitter there are two kinds of tunings that can be done; IQ tuning and power
level tuning. In general, different repairs require different tunings. In order to decide
which tuning is necessary after a repair, it is important to understand well the functionality of the repaired circuit. In general, it is recommended that if any TX component is
changed, both these tunings be done. All tunings are done in local mode, and using Phoe-nix to control the phone.
In addition to that, note that the product has two different variants; RH-51, -67
(GSM900/GSM1800/GSM1900) and RH-52, -68 (GSM850/GSM1800/GSM1900), and
please proceed the tuning with corresponding bands for those variants. In this document,
some examples are described using GSM900 case, however please replace its description
as GSM850 if you handle the RH-52, -68 variant.
Also, as the RH-51/52, RH-67/68 doesn’t support EDGE feature, you don’t need to consider operating / tuning the phones in EDGE mode although Phoenix sometimes has a
control selectional box to enable EDGE.
TX IQ tuning
The tuning must be carried out in all three bands. In addition to Phoenix, a spectrum
analyzer (SA) is needed. Connect the SA to the RF connector of the module jig. The settings of the spectrum analyzer will depend on the band to be tuned. The following table
summarizes the settings for each of the three bands.
Figure 19: Spectrum analyzer screen shot when performing IQ tuning, part 1
Ref Lvl
Ref Lvl
35 dBm
35 dBm
3
27.5 dB Offset
30
20
10
Marker 1 [T1]
33.35 dBm
897.33229000 MHz
1
RBW 3 kHz
VBW 3 kHz
SWT 3 s
1 [T1] 33.35 dBm
897.33229000 MHz
2 [T1] -6.76 dBm
897.40000000 MHz
3 [T1] -10.74 dBm
897.46771000 MHz
RF Att 30 dB
UnitdBm
A
0
-10
-20
-30
-40
-50
-60
-6
Date: 14.JAN.2002 13:11:55
The purpose of this tuning is to reduce the frequency components at marker 2 (carrier
leakage) and marker 3 (+67kHz / upper sideband) as much as possible. Adjust the ‘TXI DC
Offset’ and the ‘TXQ DC Offset’ buttons in the TX IQ Tuning window so that the carrier
level (marker 2) reaches a minimum. After this adjustment is done, the carrier (marker 2)
should be at least 40dB below the lower side band (marker 1).
1M
2
3
30 kHz/Center 897.4 MHzSpan 300 kHz
Next, use the ‘Amplitude difference’ and the ‘Phase difference’ buttons in the TX IQ Tuning window to adjust the upper side band (marker 3) to a minimum. Now, marker 3
should also be at least 40dB below marker 1.
At this point, the spectrum analyzer screen should look similar to that of the figure
below.
Figure 20: Spectrum analyzer screen shot when performing IQ tuning, part 2
Ref Lvl
Ref Lvl
35dBm
35dBm
Ref Lvl
Ref Lvl
35
35dBm
35 dBm
27.5dB Offset
30
35
27.5 dB Offset
30
20
20
10
10
0
0
10
-10
20
-20
30
-30
40
-40
50
-50
60
65
-60
-65
e:14.JAN.200213:23:02
Date: 14.JAN.2002 13:23:02
33.40 dBm
Marker 1 [T1]
897.33229000 MHz
33.40 dBm
1
897.33229000 MHz
1
VBW 3 kHz
RBW 3 kHz
SWT 3 s
VBW 3 kHz
SWT 3 s
897.33229000 MHz
897.40000000 MHz
897.46771000 MHz
>40dB
>40dB
suppression
1 [T1]33.40 dBm
2 [T1] -20.35dBm
897.33229000 MHz
3 [T1] -27.60dBm
897.40000000 MHz
897.46771000 MHz
RF Att 30 dB
UnitdBm
UnitdBm
1 [T1] 33.40 dBm
2 [T1] -20.35 dBm
3 [T1] -27.60 dBm
suppression
2
2
30 kHz/Center897.4 MHzSpan300 kHz
30 kHz/Center 897.4 MHzSpan 300 kHz
3
3
A
A
1M
1M
After reducing the amplitude of the frequency components at marker 2 and 3 to a minimum, press ‘Save & Continue’. The EGSM tuning has now been completed.
Now, using the spectrum analyzer settings listed in Table “Spectrum analyzer settings”
and the RF control settings listed in Table “RF Control window settings”, follow exactly
the same procedure to perform IQ tuning in the GSM1800 and GSM1900 bands.
This tuning is done separately in all three bands, and requires a spectrum analyzer to
measure the burst power of the GSM RF signal. When measuring the RF output (burst)
power on a spectrum analyzer, use the settings found in the following table:
Table 3: Spectrum analyzer settings for Tx power level tuning
GSM850GSM900GSM1800GSM1900
Center frequency836.6MHz897.4MHz1747.8MHz1880MHz
Frequency spanZero-spanZero-spanZero-spanZero-span
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Phoenix should now look similar to the figure below.
Figure 22: Phoenix Power Level Tuning menu
Connect the module jig RF output to the measurement instrument. The power must be
tuned in only high TX PA mode in all bands of GSM850, GSM900, GSM1800 and
GSM1900.
For each band, tune the power by adjusting the coefficient in the ‘Tx Power Level Tuning’
window in Phoenix until the target level is reached (measured on the spectrum analyzer).
Remember to take into account the external power loss, i.e. the loss of the cable and the
external attenuator at the spectrum analyzer input.
The coefficient must be tuned for the base level and other levels marked with bold letters
in Phoenix (GSM850/GSM900: PL19 / 15 / 5, GSM1800/1900: PL15, 11, 0). The target
power levels are specified as listed in the following table:
Table 4: Spectrum analyzer settings for Tx level tuning
GSM850GSM900GSM1800GSM1900
LV532.5dBmLV532.5dBmLV030.0dBmLV030.0dBm
LV1513.0dBmLV1513.0dBmLV118.0dBmLV118.0dBm
LV195.0dBmLV195.0dBmLV150.0dBmLV150.0dBm
Base-27.0dBmBase-27.0dBmBase-27.0dBmBase-27.0dBm
When the tuning for the levels marked with bold letters has been completed, press ‘Cal-
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The PLL is capable of tuning frequency range for GSM band 850/900/1800/1900. Hence
PLL is common in all variants.
The VCO frequency is locked by a PLL (phase locked loop) into a stable frequency source
given by a VCTCXO, which is running at 26 MHz. The frequency of the VCTCXO is in turn
locked into the frequency of the base station with the help of an AFC (automatic frequency control) voltage, which is generated in UEME by an 11-bit D/A (digital-to-analog)
converter.
The PLL is integrated in Helgo and it is controlled through the RFBus. The PLL consists of
a 64/65 (P/P+1) prescaler, N- and A-divider, reference divider, phase detector and a
charge pump for the external loop filter. The 4 GHz oscillator signal, generated by the
VCO, is fed through a 180 degrees balanced phase shifter to the prescaler and the output
of the prescaler is fed to the N- and A-divider, which produces the input to the phase
detector. The phase detector compares this signal to the reference signal, which is
divided by the reference divider from the VCTCXO frequency. The frequency of the reference signal is 400 kHz. The output of the phase detector is connected to the charge
pump, which charges or discharges the integrator capacitor in the loop filter depending
on the phase of the measured frequency compared to the reference frequency. The integrator output voltage is finally connected to the control input of the VCO. The VCO operates at the channel frequency multiplied by two in DCS1800/PCS1900 and by four in
GSM850/EGSM900. The required frequency dividers for modulator and demodulator mixers are integrated in Helgo.
Loop filter filters out the comparison pulses of the phase detector and generates a DC
control voltage to the VCO. The loop filter determines the step response of the PLL (settling time) and contributes to the stability of the loop. Other filter components are for
sideband rejection. The dividers are controlled via the RFBus. RFBusData is for the data,
RFBusClk is a serial clock for the bus and RFBusEna1X is a latch enable, which stores the
new data into the dividers.
Figure 27: Synthesizer key components without shielding frame
No failure i.e. soldering or component failure for simple SMD components such as resistors, inductors and capacitors.
Failure in one particular operating GSM channel whether Tx or Rx in which the synthesizer is the cause of the failure, all other GSM channel in Tx/Rx should fail.
Measuring the synthesizer manually using spectrum analyzer
Spectrum analyzer level values depend on the probe type and should be validated using a
known good sample. The levels that are given here are measured using a high frequency
probe. Spectrum analyzer should be at least capable of measuring signal upto 4.5 GHz.
This document describes BC02 bluetooth solution troubleshooting for Care. Applicable
parts can be copied to phone products’ service document. It is assumed that the main
service manual includes part “How to connect Phoenix to phone”.
Bluetooth component placement
Figure 32: RH-51/52, RH-67/68 Bluetooth component placement