Page 2 GSM Technology Global System for Mobile Communications.
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Transcript of Page 2 GSM Technology Global System for Mobile Communications.
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Page 2
GSM Technology
Global System for Mobile Communications
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Analog and Digital
Speech Quality
Signal
Distance to the Transmitter
quality
Analog Signal
Digital Signal
SNR
r
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BTS transmits
MS transmits
0 1 2 3 4 5 6 7 0 1 2 3
5 6 7 0 1 2 3 4 5 6 7 0
from: An Introduction to GSM© Artech House, Inc.
TDD - Time Division Duplex
GSM Technology
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GSM Technology
TDMA frame and timeslot structure
0 1 2 3 4 5 6 7
4.615 ms
577 usec
3T
57Encrypted data
26Training Sequ.
1S
1S
57Encrypted data
3T
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Burst Structures
T
3
148 Bit = 546.12 µs
Coded Data
57
S
1
Training Sequence
26
Coded Data
57
S
1
T
3
GP
8.25TypeNumber of Bits
T
8
88 Bit = 324.72 µs
GP
68.25
Type
Number of Bits
T
3
Synchronization Seq.
41
Coded Data
36
T
3
148 Bit = 546.12 µs
T
3
GP
8.25
Type
Number of Bits
fixed bit sequence
142
T
3
148 Bit = 546.12 µs
Coded Data
39
Synchronization Sequence
64
Coded Data
39
T
3
GP
8.25
Type
Number of Bits
from: An Introduction to GSM© Artech House, Inc.
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FACCHFACCH
Logical Channels
SACCHSACCH
SCHSCH
TCHF/H
TCHF/H DCCHDCCH CCCHCCCH BCHBCH
RACHRACH
BCCHBCCH SCHSCH FCCHFCCH
AGCHAGCHPCHPCH
SDCCHSDCCH
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Frame structure
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Mapping of logical channels
F S CC -
D 0
D 0
D 1
D 1
D 2
D 2
D 3
D 3
D 4
D 4
D 5
D 5
D 6D 6
D 7
D 7
A 0
A 4
D 0
D 0
D 1
D 1
D 2
D 2
D 3
D 3
D 4
D 4
D 5
D 5
D 6
D 6
D 7
D 7
A 0
A 4
A 3A 1
A 5
A 2
A 6 A 7 --
- - -
-
--
- - -
-A 3A 1A 5
A 2
A 6 A 7
--
RD 3
D 3
D 0
D 0
D 1
D 1
D 2
D 2
A 0 A 1
A 3A 2F S
F SD 3D 2
D 3D 2F S
F S
D 1D 0
D 1D 0
A 2 A 3
A 1A 0
S:C:A:
F:B:D:R:
TDMA frame for frequency correction burstTDMA frame for BCCHTDMA frame for SDCCHTDMA frame for RACH
BCCH + CCCH(downlink)
BCCH + CCCH(uplink)
8 SDCCH/8(uplink)
8 SDCCH/8(downlink)
BCCH + CCCH4 SDCCH/4(downlink)
BCCH + CCCH4 SDCCH/4
(uplink)
TDMA frame for synchronization burstTDMA frame for CCCHTDMA frame for SACCH/C
51 fram es 235.38 m s»
R R R R R R R R R R R R R R R R R R R R R RR R R R R R R R R R R R R R R R R R R R R R R
RR R
RRR R
R
F S B C
F B CS
F S CC
F S CC
F S CCCCF SCCF SF S B C
R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R RR R R R R
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Frequency Hopping and Adjacent Channel Monitoring
3
downlink (Base Station transmits)
uplink (Mobile Station transmits)
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
0 1 2 5 01234567 0 1 2 3 45 6 7 7640 1 2 3 45 6 7
30 1 2 5 01234567 0 1 2 3 45 6 7 7640 1 2 3 45 6 7
30 1 2 5 01234567 0 1 2 3 45 6 7 7640 1 2 3 45 6 7
F1
F2
F3
F3
F1
F2
0
Mobile Station monitors different neighboring cells
1
0
0
5
5
5
1
1
6
6
6
from: An Introduction to GSM© Artech House, Inc.
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Burst Power-Time Template
from: An Introduction to GSM© Artech House, Inc.
dB
-1
-30
-70*
-6
+4+1
(147 bits)
10 µs
*or -36dBm, whatever value is higher
8 µs 542.8 µs 8 µs10 µs 10 µs10 µs
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Multipath Propagation
BTS
TSn TSn+1
from: An Introduction to GSM© Artech House, Inc.
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Timing Advance and RF Power Control
AB
AB
long signal delay
high signal attenuation
short signal delay
small signal attenuation
BTS
TSn TSn+1
from: An Introduction to GSM© Artech House, Inc.
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Handover from one BTS to another BTS
MSC BSC
BTS2
BTS1
MS
cell boundary
Handover of the MS fromBTS1 to BTS2 via the BSC
from: An Introduction to GSM© Artech House, Inc.
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RF Power Levels for the MS - International GSM
from: An Introduction to GSM© Artech House, Inc.
Power Class Max Power of MS Max Power of BS
1 20 W (43 dBm) 320 W (55 dBm)2 8 W (39 dBm) 160 W (52 dBm)3 5 W (37 dBm) 80 W (49 dBm)4 2 W (33 dBm) 40 W (46 dBm)5 0.8 W (29 dBm) 20 W (43 dBm)6 10 W (40 dBm)7 5 W (37 dBm)8 2.5 W (34 dBm)
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GSM Power Levels and Test Limits for the MS
Power Class Power Level Peak Power / Limits
1 0 43 dBm + - 2 dBm
1 1 41 dBm + - 3 dBm
1 2 2 39 dBm + - 3 dBm*)
1 2 3 3 37 dBm + - 3 dBm*)
1 2 3 4 35 dBm + - 3 dBm
1 2 3 4 533 dBm + - 3 dBm*)
1 2 3 4 6 31 dBm + - 3 dBm
1 2 3 4 5 7 29 dBm + - 3 dBm*)
1 2 3 4 5 8 27 dBm + - 3 dBm1 2 3 4 5 9 25 dBm + - 3 dBm1 2 3 4 5 10 23 dBm + - 3 dBm
1 2 3 4 5 11 21 dBm + - 3 dBm1 2 3 4 5 12 19 dBm + - 3 dBm
1 2 3 4 5 13 17 dBm + - 3 dBm
1 2 3 4 5 14 15 dBm + - 3 dBm1 2 3 4 5 15 13 dBm + - 3 dBm
*) +-2dBm if highestpower of a power class
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Speech Processing in GSM
D
A
SPEECH
ENCODER
SPEECH
DECODER
MICROPHONE
LOUD-
SPEAKER
DA
COMFORT
NOISE
FUNCTION
VAD
VAD
SPEECH
ENCODER
SPEECH
DECODER
COMFORT
NOISE
FUNCTION
EXTRA
POLATION
EXTRA-
POLATION
13 BIT
LINEAR/
8 BIT
A-LAW
MOBILE-STATION
FIXED
NETWORK
RADIO TRANSMISSION
RADIO
TRANSMISSION
from: An Introduction to GSM© Artech House, Inc.
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Full and Half Rate Speech Multiframes
T T T T T T T T T T T T T T T T T T T T T T T T S I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
T = TCH, S = SACCH, I = idle
26 Frames = 120 ms
T T T T T T T T T T T T S 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
T = TCH1, S = SACCH1, t = TCH2, s = SACCH2
t s t t t t t t t t t t t
from: An Introduction to GSM© Artech House, Inc.
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Authentication
A3
RAND RANDKi
SRESSRES
MS Network
= ?
yes/no?
(SRES)
Um Interface
from: An Introduction to GSM© Artech House, Inc.
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Authentication - Create ciphering key
A8
RANDKi
Kc
MS
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Start Ciphering
A5
Kc
MS Network
A5
Kc
DATA Ciphered
Ciphering
DATA
Command
DATA
Um Interface
from: An Introduction to GSM© Artech House, Inc.
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A/ D Speech Conversion
t
t
t
000001010011100101
110111
0
12
34567
Filtered Input
Signal
Sampling
Signal
Sampled Signal
Quantization
from: An Introduction to GSM© Artech House, Inc.
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Testing of Mobiles
Power Time Template, background informations
Noise floor
Cornerpoint (-x dBc @ y usec)
Time
Dynamic Range > 75 dBProgrammable CornerpointsZoom FunctionUser defined Power Time Template
Burstlength147 bits / 542 usec
next burst
Too fast rising edges create interference spectrumSlow edges overlap with neighbour burstsThe Power-Time- Template is the best compromise between both
PTT
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Testing of Mobiles
Phase, Peak and RMS measurements:
Analysis of Transmitter Modulation Quality:
- Symbol “distance” of 90 degree only for GSM- Any TX phase error reduces this symbol “distance”- In real systems there is the sum of system noise and TX phase errors- Peak errors of >45 degree will confuse demodulators
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Testing of Mobiles
10
00
01 11
area of confusion
Modulation principle Phase error + noise
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Testing of Mobiles
Frequency error:
The ability to adjust to the base station frequency
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Phase and Frequency Error
real phase trajectory from the received RF signal
90°
180°
-90°
-180°
calculated bit stream fromthe real phase trajectory(before differential encoding)
ideal, calculatedphase trajectory
90°
180°
-90°
calculated phase error and from this the resulting frequency errorphase error = deviation from the
correlation linefrequency error = inclination of the
correlation line
90°
180°
-90°
+1
-11 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 1816 19
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 181619
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 1816 19
-180°
-180°
1 2 3 4 5 6 7 9 10 11 12 13 14 15 17 1816 198
0°
0°
0°
from: An Introduction to GSM© Artech House, Inc.
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Testing of Mobiles
BER Measurements:
Switch mobile to “Loop back”Transmit random but coded data to mobileReceive bit patterns from mobileMatch in/out data of bitstream: “round trip delay”
Unprotected bits: BER class IIProtected bits with Viterbi coding: BER class I
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Testing a GSM Receiver with the 4400 (RX)
RX TX
DEC ENC
AUDIO
Combiner
LOOPBACK
Error
0010001001101
0010000001101
Bit Error Rate Test (BER)
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Testing of Mobiles
Spectrum Measurements:
Risk for interference of neighbouring channels
ETSI:- Spectrum due to transients- Spectrum due to modulation
High performance analyser needed
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Testing of Mobiles
Reports from the Mobile to the BS:
RXLEVEL: - (110 - Received Level in dBm) = RXLEV Report
RXQUAL:- Coded “BER” values ( = Viterbi activity)
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RX - LEV Measurements by the Mobile Station
RX Level Level at MS Receiver (dBm)
012...............6263
Less than - 110- 110 to - 109- 109 to - 108
...
...
...
...
...- 49 to - 48above - 48
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RX - QUAL Measurements by the Mobile Station
RX QualityRX-QUAL
Bit Error RateBER (%)
01234567
Below 0.20.2 to 0.40.4 to 0.80.8 to 1.61.6 to 3.23.2 to 6.46.4 to 12.8Above 12.8
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Alignments
Different designs requires different alignments
The following are just brief examples!
Divided into 4 sections:•Why and what to align•Transmitter and Fref alignments•Receiver and logic alignments•Innovative vs conventional alignments
Divided into 4 sections:•Why and what to align•Transmitter and Fref alignments•Receiver and logic alignments•Innovative vs conventional alignments
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Why and what to align
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Different receiver architectures
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Heterodyne Receiver - Basic theory
FrontEnd:
•Image rejection•LNA•Oscillator emmissions
1:st MF:
•Gain•Selectivity - adjacent channel suppression
2:nd MF:
•Improving selectivity•Reasonable sampling frequency
FrontEnd:
•Image rejection•LNA•Oscillator emmissions
1:st MF:
•Gain•Selectivity - adjacent channel suppression
2:nd MF:
•Improving selectivity•Reasonable sampling frequency
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Homodyne Receiver - Basic theory
• Homodyne- The 1:st (and only) LO has the same frequency as received signal
• Frequency conversion directly to baseband - direct conversion- Frequency selectivity is made on the baseband
• Moves much of the complexity from the radio to the logic parts
• Was uptil recently too complex to build
• Homodyne- The 1:st (and only) LO has the same frequency as received signal
• Frequency conversion directly to baseband - direct conversion- Frequency selectivity is made on the baseband
• Moves much of the complexity from the radio to the logic parts
• Was uptil recently too complex to build
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Homodyne Receiver - Basic theory
The problems…
• LO leakage- The LO:s frequency is same as the wanted
•DC offset- The LO-signal will be introcuced as a DC-level in the baseband signal
The problems…
• LO leakage- The LO:s frequency is same as the wanted
•DC offset- The LO-signal will be introcuced as a DC-level in the baseband signal
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Homodyne Receiver - Basic theory
The Problems…continued
• AM detection- DC offset that varies in amplitude - hard to exlude in an algorithm- AM detection comes from several different sources:
- Selfmixing- Bad IP2 in the baseband- Bad IP3 in LNA/mixer (crossmodulation)- Bad IP3 in the basband (crossmodulation)
The Problems…continued
• AM detection- DC offset that varies in amplitude - hard to exlude in an algorithm- AM detection comes from several different sources:
- Selfmixing- Bad IP2 in the baseband- Bad IP3 in LNA/mixer (crossmodulation)- Bad IP3 in the basband (crossmodulation)
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Homodyne Receiver - Basic theory
Interference from DC offset and AM detectioncan be many times higher than wanted signal
Conventional AGC can not be used => High dynamic ADC (24 bits or more)
Interference from DC offset and AM detectioncan be many times higher than wanted signal
Conventional AGC can not be used => High dynamic ADC (24 bits or more)
I
Q
DC/AM
Wanted signal
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Homodyne - Heterodyne Conclusion
Pro’s:•Choice of components•Well-known design
Con’s:•Requires large chip space
•(MF-filters, mixers, LO)•Expensive components•High current consumption
Pro’s:•Choice of components•Well-known design
Con’s:•Requires large chip space
•(MF-filters, mixers, LO)•Expensive components•High current consumption
Superheterodyne Homodyne
Pro’s:•Cheap•Small chip space•Low current consumption
Con’s:•Harder to protect from noise•LO leakage•DC offset•AM detection
Pro’s:•Cheap•Small chip space•Low current consumption
Con’s:•Harder to protect from noise•LO leakage•DC offset•AM detection
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Output power and PTT (1)
Spectrum due to switching derives from PTT
dB
-1
-30
-70*
-6
+4+1
(147 bits)
10 µs
*or -36dBm, whatever value is higher
8 µs 542.8 µs 8 µs10 µs 10 µs10 µs
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Output power and PTT (2)
Power Class Power Level Peak Power / Limits
1 0 43 dBm + - 2 dBm
1 1 41 dBm + - 3 dBm
1 2 2 39 dBm + - 3 dBm*)
1 2 3 3 37 dBm + - 3 dBm*)
1 2 3 4 35 dBm + - 3 dBm
1 2 3 4 5 33 dBm + - 3 dBm*)
1 2 3 4 6 31 dBm + - 3 dBm
1 2 3 4 5 7 29 dBm + - 3 dBm*)
1 2 3 4 5 8 27 dBm + - 3 dBm1 2 3 4 5 9 25 dBm + - 3 dBm1 2 3 4 5 10 23 dBm + - 3 dBm
1 2 3 4 5 11 21 dBm + - 3 dBm1 2 3 4 5 12 19 dBm + - 3 dBm
1 2 3 4 5 13 17 dBm + - 3 dBm
1 2 3 4 5 14 15 dBm + - 3 dBm1 2 3 4 5 15 13 dBm + - 3 dBm
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Output power and PTT (3)Output power and PTT (3)
Competitorsinaccuracy
Alignmentwindow
ExtendedAlignmentWindow
4400M
loweralignment
point+/- 2dB
35dB
31dB
0,5dB 0,15dB
1dB 1,7dB
Specification limit
Specification limit
Lower power consumptionExtended alignment window
Lower power consumptionExtended alignment window31,15dBm vs 31,5dBm
=> ~ 8,5% higher power consumption during burst
31,15dBm vs 33dBm => ~ 53,5% higher power consumption during burst
31,15dBm vs 31,5dBm => ~ 8,5% higher power consumption during burst
31,15dBm vs 33dBm => ~ 53,5% higher power consumption during burst
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Spectrum due to switching
dB
t100%90%Averaging
period
50%
midamble
Useful part of the burst
0%
Switching transients
Max-hold level = peak of switching transients
Video average level= spectrum due to
modulation
Power level Maximum level for various offsets from carrierfrequency
400 kHz 600 kHz 1200 kHz 1800 kHz39 dBm -13 dBm -21 dBm -21 dBm -24 dBm37 dBm -15 dBm -21 dBm -21 dBm -24 dBm35 dBm -17 dBm -21 dBm -21 dBm -24 dBm33 dBm -19 dBm -21 dBm -21 dBm -24 dBm31 dBm -21 dBm -23 dBm -23 dBm -26 dBm29 dBm -23 dBm -25 dBm -25 dBm -28 dBm27 dBm -23 dBm -26 dBm -27 dBm -30 dBm25 dBm -23 dBm -26 dBm -29 dBm -32 dBm23 dBm -23 dBm -26 dBm -31 dBm -34 dBm
<= +21 dBm -23 dBm -26 dBm -32 dBm -36 dBm
-24dBm-21dBm
-19dBm
+33dBm
-52dBc @ 400kHz
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Spectrum due to modulation
dB
t100%90%Averaging
period
50%
midamble
Useful part of the burst
0%
Switching transients
Max-hold level = peak of switching transients
Video average level= spectrum due to
modulation
-60dBc
-30dBc
+0,5dBc
power levels in dB relative to themeasurement at FT
Power level Frequency offset(kHz)
(dBm) 0-100 200 250 400 600 to <180039 +0,5 -30 -33 -60 -6637 +0,5 -30 -33 -60 -6435 +0,5 -30 -33 -60 -62
<= 33 +0,5 -30 -33 -60 -60The values above are subject to the minimum absolute levels (dBm)below.
-36 -36 -36 -36 -51
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Modulator alignment
Phase balanceAmplitude balance=> Low Fc feedthrough=> Desired Sideband suppression
Peak phase derives from oscillator noise
RES BW 10 kHz VBW 10 kHz SWP 30.0 msec
AT 30 dBREF 21.0 dBm
LOG
10dB/
CENTER 1.879800 GHz SPAN 1.000 MHz
-24.09 dBMKR -268 kHz
PG -6.8 dBPEAK
WA SB
SC FS
CORR
COPY DEV
PRNT PLT
Plot
Config
Config
Time
Date
Change
Prefix
More
1 of 3
-6 7 ,7 0 8 k H z
+ 6 7 ,7 0 8 k H z
-x x d B
F C + 6 7 ,7 0 8 k H z (m o d u la t io n fre q u e n c y )
F C
T X b a la n c e
3 :e M F
2 :a M F
4 :e M F
-1 3 5 ,4 2 k H z
-2 0 3 ,1 2 k H z
-2 7 0 ,8 3 k H z
~~
~~
+
I
Q
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Master Clock alignment
3 reasons:Absolute freqStep sizePulling range
3 reasons:Absolute freqStep sizePulling range
Ch freq.DAC
Freq.
Pulling range
Step size:Kp=*((y2-y1)/(x2-x1))
x1,y1
x2,y2
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Transmitter VCO alignment
Pushing marginPulling marginLocking time on all channelsCatch-and-hold ranges….in temperature
Pushing marginPulling marginLocking time on all channelsCatch-and-hold ranges….in temperature
VCOTo PA
Modulator
PHD
Fsynth
Vcc
DAC
PHD has a comparator output
PHD has a comparator output
Sweepgen.
VccHow to get into thecatch range of PHD?
How to get into thecatch range of PHD?Same locking timeon all channels?
Same locking timeon all channels?
PushingPulling
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Handover test
Different TX VCO’s for different bands
Often common up-converter
Different TX VCO’s for different bands
Often common up-converter
Different LO VCO’s for different bands
Often the same mixers
Different LO VCO’s for different bands
Often the same mixers
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Receiver and logic alignments
RSSIIQ Tuning RXCurrent/voltage alignmentTemperature sensorRTC
RSSIIQ Tuning RXCurrent/voltage alignmentTemperature sensorRTC
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RSSI alignment
Learn input power versus ADC response -> RXLev
Learn input power versus ADC response -> RXLev
Phone
Calibration equipment
Radiosignal (-50 dBm)Radiosignal (-50 dBm)
Measure signalMeasure signal The ADC respone points to
a specific EEPROM value
The ADC respone points to a specific EEPROM value
Send amplitude value of the injected signalSend amplitude value of the injected signal
Write amplitude value into EEPROMWrite amplitude value into EEPROM
EEPROM-address Value12 -50 dBm3456789
10
Compensation tableEEPROM-address Value
12 -50 dBm3456789
10
Compensation tableCompensation table
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IQ tuning RX alignment
Align the amplitude (and phase) relationship between the I&Q signals to achieve suppression of unwanted signals
Make sure that sufficient AM suppression is reached!
Homodyne receiversDouble-balanced quadrature mixers
Homodyne receiversDouble-balanced quadrature mixers
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BER testing
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Current/Voltage alignment
Current/voltage alignment
• Charging algorithm (Li-Ion)• Power off decision• ADC reference voltage
CHARGER IN
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RTC alignment/test
RTC - Real Time Clock• Can often be checked against the master clock• Separate oscillator to save power
RTC - Real Time Clock• Can often be checked against the master clock• Separate oscillator to save power
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