Page 1
Technical Description
Ericsson Mobile Phone EF738
Page 2
Technical Description
2
Page 3
Technical Description
Contents
Overview __________________________________________ 7
Basic Building Blocks ______________________________________ 8
Transceiver Block Diagram _________________________________ 9
PCB____________________________________________________ 10
Mechanical Design __________________________________11
Man Machine Interface (MMI)_______________________ 12
Keypad _________________________________________________ 12
Display _________________________________________________ 12
Acoustic Signals__________________________________________ 12
Top LED Indicator _______________________________________ 12
Radio Design______________________________________ 13
General Overview ________________________________________ 13
Antenna Connector________________________________________ ___ 13
Antenna Filters ______________________________________________ 13
Receiver Part________________________________________________ 14
Receiver Front End ________________________________________ 14
IF Part __________________________________________________ 14
Receiver Back-End ________________________________________ 15
Synthesizer _________________________________________________ 16
Programming_____________________________________________ 16
Power___________________________________________________ 16
Lock Detect ______________________________________________ 16
VCTCXO __________________________________________________ 17
Transmitter _________________________________________________ 18
TX Blocks ____________________________________________ ___ 18
MALIN____________________________________________________ 19
TX-IF VCO ______________________________________________ 19
TX Mixer_____________________________________________ ___ 19
TX Modulation ___________________________________________ 19
TX-IF Frequency Control ___________________________________ 19
Programmable Prescaler ____________________________________ 19
Power and Charging Design _________________________ 20
Regulators ______________________________________________ 20
Reset ___________________________________________________ 21
On/Off Control __________________________________________ 21
Charging Circuitry _______________________________________ 21
Transient/ESD Protection__________________________________ 22
Off Current Draw ________________________________________ 22
User Interface _____________________________________ 23
Illumination _____________________________________________ 23
Buzzer__________________________________________________ 23
LCD Display_____________________________________________ 23
Keypad _________________________________________________ 23
Continued on next page
3
Page 4
Technical Description
Logic Design _ ___ ___ ___ ____ ___ ___ ____ ___ ___ ____ ___ _ 24
GUSTAV ________________________________________________24
Circuit Description ___________________________________________ 24
6303 ____________________________________________________ 24
ROM ___________________________________________________ 24
RAM ___________________________________________________ 24
Bus Interface _____________________________________________ 24
Decoder _________________________________________________ 25
Serial Interface____________________________________________ 25
External Ports_____________________________________________ 25
WatchDog On/Off _________________________________________ 25
IFC_____________________________________________________ 25
BAR____________________________________________________ 25
Clock Generator___________________________________________ 25
Internal Ports _____________________________________________ 26
Modem__________________________________________________ 26
Baud Clock _____________________ _________________________ 26
I2C Controller ____________________________________________ 26
FLASH EPROM__________________________________________26
EEPROM________________________________________________26
Audio Design_________________ ___ ____ ___ ___ ____ ___ _ 27
Receive Audio Circuit Description ___________________________27
Receive Audio Interface _______________________________________ 27
De-Emphasis Network ________________________________________ 27
RXSENSE Programmable Gain Stage ____________________________ 27
Receive Bandpass Filter _______________________________________ 27
Expandor Gain ______________________________________________ 28
RX HF Attenuation___________________________________________ 28
RX Volume Control __________________________________________ 28
EARSENS Programmable Gain Stage ____________________________ 28
Externally Programmable Gain Stage______________________ _______ 28
Earpiece Driver______________________________________________ 29
AFMS _____________________________________________________ 29
Transmit Audio Circuit Description__________________________29
ATMS _____________________________________________________ 29
Microphone Input ____________________________________________ 29
Soft Limit __________________________________________________ 30
INPSENSE Programmable Gain Stage____________________________ 30
Transmit Bandpass Filter ______________________________________ 30
TX HF Attenuator____________________________________________ 30
Compressor_________________________________________________ 30
Pre-emphasis________________________________________________ 30
Hard Limit__________________________________________________ 31
Transmit Lowpass Filter_______________________________________ 31
AUDIODEV Programmable Gain Stage __________________________ 31
Summing Amplifier __________________________________________ 31
TXSENSE Programmable Gain Stage ____________________________ 31
Low Voltage Detect Circuit _________________________________31
Continued on next page
4
Page 5
Technical Description
RX and TX Sat Circuits ___________________________________ 32
RX SAT Filter ______________________________________________ 32
RX SAT Schmit Trigger_______________________________________ 32
TX SAT Filter_______________________________________________ 32
TX SATDEV Programmable Gain Stage__________________________ 32
8Kbit/s Manchester Data Circuit____________________________ 32
Data Filter__________________________________________________ 32
DATADEV Programmable Gain Stage ___________________________ 32
HandsFree Circuit________________________________________ 32
Software Design ___________________________________ 33
Power Down Control______________________________________ 33
Timing and Operation_____________________________________ 33
Main Modes of Operation______________________________________ 33
Power Saving Sleep Function___________________________________ 33
Software Assignments_____________________________________ 33
Technical Specifications_____________________________ 34
General ____________________________________________________ 34
Transmitter _________________________________________________ 34
Receiver ___________________________________________________ 34
5
Page 6
Technical Description
6
Page 7
Overview
Technical Description
The Ericsson
It is a class 4 cellular telephone that is fully compatible with the ETACS system
with extended frequencies.
EF738
The
telephone section
•
•
removable
•
removable
EF738
includes the following three exterior parts:
Mobile Phone is a small, lightweight phone operating at 3.8V.
(incl. keypad, chara cter di splay, earpiece, microphone and flip)
battery
antenna
Figure 1: The Ericsson Mobile Phone EF738
7
Page 8
Technical Description
Basic Building Blocks
The diagram below shows the basic building blocks:
ANTENNA
&
DUPLEXER
RX SYNTHESIZER TX
SYSTEM
BATTERY ACCESSORIES
Figure 2: Basic Building Blocks
LOGIC
USER
INTERFACE
AUDIO
8
Page 9
Technical Description
Transceiver Block Diagram
The transceiver (transmitter/receiver) consist of a digital part that controls and
supervises transmission/reception on the radio channel. It also handles keyboard,
display and protocol transmission to the MTX (Mobile Telephone eXchange). The
audio part controls audio signals for earphone, microphone and modem.
RADIO
TRANSMITTER
FREQ. GENERATOR
MOD. RECEIVER
mo d discr
AUDIO PROCESSING
MICRO/LOUDSPKR
Figure 3: Transceiver Block Diagram
control bus
LOGIC
CPU
MEMORIES
On/Off
KEYPAD
DISPLAY
ATMS/AFMS
MMI
E
X
T
E
R
N
A
L
C
O
N
N
E
C
T
O
R
9
Page 10
Technical Description
PCB
The printed circuit board is a 6-layer PCB where all comp onents are located in
layer 1 (primary side) and layer 6 (secondary side).
Layers 2 and 5 are ground planes and layers 3 and 4 are used for signal conducting.
ANT
RECEIVER
GUSTAV
Primary Side
IF PART
BERT-
DUPLEXER
VCO
INDY
MALIN
VCTCXO
BAT
CON
ANTON
Secondary Side
BUZZER
VOL
TRANSMITTER
VOL
MIA
KEYPAD
FLASH
SYSTEM CONNECTOR
EE-
PROM
Figure 4: PCB LayOut
SYSTEM CONNECTOR
10
Page 11
Mechanical Design
The phone is designed as a ‘brick’ with a mechanical assembly consisting mainly
of:
•
plastic front cover
•
plastic rear cover
•
plastic flip
•
keyboard
•
system connector
•
LCD light guide
•
metallic plastic for PCB shielding
It has been designed for easy assembly with 6 screws.
An optional clip can be mounted into the rear cover.
Technical Description
Figure 5: Mechanical Assembly
11
Page 12
Technical Description
Man Machine Interface (MMI)
Keypad
The keypad has back-lighting that makes it possible to operate the station in the
dark. The back lighting function (on 10sec/on 20sec/off) is selected by the user.
Note that the
connected to the 3.8V regulators enable inputs so that the power of GUSTAV is
forced On when this key is held down.
The volume keys are not located on the keypad. They are push button switches
mounted on the upper left hand side of the phone.
END/PWR/NO
key is not part of the keyboard scanning matrix. It is
Display
The segmented LCD contains one row of 10 alpha-numeric characters and one row
of icons.
The software for driving the display is contained in the Flash EPROM.
An elastomeric connector joins the PCB to the transparent conductive tracks on the
LCD module.
Acoustic Signals
The acoustic signa ls a re generated by a buzzer in the tr ansceiver . Th e acoustic level
as well as the frequency of the signal is variable in order to distinguish between different situations.
The different acoustic si gnals are:
•
Ring signals
•
Alarm signals
•
Low battery warning
•
Keypad tone or “click”
Top LED Indicator
A dual-colour LED (green & red) is positioned on the top front end.
Each LED is connected to a separate output port on GUSTAV.
Blinking rates and color of the Indicator LED are controlled by software.
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Page 13
Radio Design
General Overview
The radio operates on the ETACS frequency band. The transmitter operates at
872.0125 MHz to 905.9875 MHz and the receiver at 917.0125 MHz to 949.9875
MHz. The duplex spacing is 45MHz and the channel separation is 25KHz.
Together with the logic/audio part the radio fulfills the ETACS requ irements.
Technical Description
TX TX MIXER TX SYNTH
POWER
CONTROL
DUPLEX
FILTER
FRONT
END
Figure 6: Radio Block Diagram
Antenna Connector
962-995MHz
RX SYNTH
45MHz
IF
VCTCXO
14.85MHz
44.55MHz
450KHz
RADIO IF
BERTINDY
Audio In
Bus Control
Audio Out
The antenna connector con sists of a mechanical assembly that connects the antenna
to the radio. The impedance of the antenna connector is 50Ω.
Antenna Filters
The duplex filter consists of a 4-pole TX section of band pass characteristic with a
notch at the RX frequency and a 4-pole RX section filter with 50Ω impedance in
each direction.
The task for the TX filter is to suppre ss wide band noise evol ving from the VCO and
the power amplifier on RX frequencies.
The task for the RX branch is to suppress the transmitter signal to a level low
enough not to overdrive the receiver front end amplifier and attenuate external spurious signals.
The RX-section also suppresses leakage from the local oscillator.
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Page 14
Technical Description
Receiver Part
The front-end stage is the first link in the receiver chain. It’s purpose is to amplify
the RF and down-convert it to the 1st IF frequency and to set the RX system noise
figure. The desired input frequencies are within the range 917.0125 to 949.9875
MHz. The selected frequency is down-converted to 45 MHz and amplified. This
section includes a low-voltage RX front-end chip, “Low-voltage ANNIKA”, comprised of a low noise amplifier, a mixer, and the 1st image filter.
Receiver Front End
ANNIKA: RF-amplifier
The input of the integrated low-noise amplifier is matched for optimal performance
regarding minimum noise level and second order intermodulation performance.
It also provides a 50Ω load to the duplexer.
BP-filter
This bandpass fil te r i s a SAW filter needed for spurious response rejection (s uppr es sion of the first image frequency). The filter also suppresses the local oscillator
backwards to the antenna.
ANNIKA: Mixer
The integrated mixer in the same package as the LNA includes an internal buffer for
the Local Oscillator (LO) w hich allows low LO input power and immunity from
variations in LO input powe r . At the RF po rt, an i nductor r ejects th e nois e coming t o
the mixer directly at the IF band. The output of the mixer is converted to a higher
impedance to match the crystal filter in th e following IF circuitry.
IF Part
The IF/AF part is the second link in the receiver chain. It performs the major part of
the RF amplification and all the channel filtering. The 1st IF at 45 MHz is downconverted to 450 KHz and FM demodulated in Bertindy. The IF IC generates a DC
voltage (RSSI), whic h is logar ithmic al ly prop ortio nal to th e stre ngth of the r ece ived
signal.
To
Digit Discr
&
De-Emphasis
(BERTINDY)
From
ANNIKA
Mixer
IF/AF IC
2nd Mixer IF Amp Limiter
14
45MHz
Filter
2nd LO
from
BERTINDY
1st
450KHz
Filter
Figure 7: IF/AF Link
2nd
450KHz
Filter
Page 15
Technical Description
Receiver Back-End
The IF/AF circuit is an integrated bipolar circuit containing a mixer, IF amplifier,
limiter, RSSI circuits, and FM detection circuit. The rest of the required functions
are located in BERTINDY.
The 1st IF frequency of 45 MHz is f ed t o t he 2nd mixer where it is down-converte d
to 450 KHz (2nd IF) in the IC. The 2nd LO signal at 44.55 MHz for the mixer
comes from BERTINDY. Third harmonic of the reference oscillator frequency
(14.85 MHz) is used as the 2nd LO signal.
The 450 KHz signal is filter ed thr ough a ceramic 2n d IF filt er and fed to t he input of
the IF amplifier sta ge. The output signal from this s tage is filtered through a s econd
ceramic 2nd IF filter and is then applied to the limiter. The resulting 450 KHz
square-wave signal is fed to the digital discriminator in BERTINDY where it is
demodulated and de-emphasized before being passed to the ANTON IC for further
audio processing.
Band Pass 1st IF Filter (2nd Image Filter)
This crystal filter is needed for spurious response rejection (suppression of the 2nd
image frequ ency) and inter-modulation rejection. T he crystal filter is a band pass
filter with a center frequency of 45 MHz. Some channel filtering is also performed
in this filter.
Channel and Noise Reduction Filters
Two bandpass 2nd IF filters are needed for broadband noise reduction and desired
channel selection. Each filter is a ceramic 4-pole bandpass filter with a center frequency of 450 KHz.
450 KHz Output
From the limiter output, the 450 KHz square-wave signal is fed to the digital discriminator in BERTINDY for demodulation. This signal is also used by the AFC
algorithm in determin ing the f req uency er ror of t he 14.85 MHz refe re nce rel ative to
the received signal.
RSSI Output
A voltage which is logarithmically proportional to the RF input power of the
received signal is produced in the IF/AF IC.
RSSI Range
The lower end of the useable range is controlled primarily by the RF/IF gain of the
receiver while the uppe r end of th e RSSI vo ltage is contr olled by the supply vol tage
of the IF/AF chip.
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Page 16
Technical Description
Synthesizer
A 900 MHz RX synthesizer is used as first LO. The TX synthesizer is modulated
and working at a f ixed f re que ncy of 90 MHz. The TX freq uenc y i s obt ai ned by mixing the frequencies from the two synthesizers.
The main synthesizer uses fractional-N to achieve lower phase noise and faster
switching. In most applications the phase noise is proportional to the overall division ratio and since fractional-N uses a higher comparison frequency the phase
noise will be lower.
The auxiliary synthesizer is a conventional loop without fractional-N and the comparison frequency is 75 KHz.
The RX VCO is a module which operates between 914.0 40 MHz and 938.970 MHz.
The MALIN chip contains the TX VCO , TX buffer stage, TX mixer, RX buffer
stage and the RX prescaler.
The TX PLL, RX PLL and the lock detect logic are part of the BERTINDY chip.
Programming
The name of the PLL c ircuit is BERTINDY, which is a combination of the t wo chips
Bertram and Cindy. A three line bus is used to pro gram the syn thesizer with the hel p
of a clock frequency. The RX synthesizer is operat ing at 45 MHz above the required
RX frequency and a 14.85 MHz reference frequency is used.
Power
The synthesizer part in BERTINDY is put in power down mode by sending a command to the chip. The auxiliary and main synthesizer can be powered down separately and the RX-VCO is co ntrolle d by BERTINDY. The prescaler and the 90 MHz
VCO of MALIN is controlled by sending power up/down commands.
Lock Detect
A signal showing when the synthesizer is locked is implemented in BERTINDY.
The lock detect circ uit op erate s with both t he main a nd the auxili ary s ynthes izers . If
both synthesizers are enabled, the lock detect output becomes active when they are
both locked. If only one synthesizer is enabled, the lock detect output becomes
active when that one is locked.
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Page 17
Technical Description
VCTCXO
The task of the VCTCXO is to supply the synthesizer with a stable, accurate reference frequency. A 14.85 MHz crystal with DAC-controlled varactor diodes and a
transistor stage within BERTINDY constitues the TCXO circuit. A software algorithm is used for temperature compensation as well as an AFC function.
The operating frequency of the synthesizer reference oscillator is set by the crystal
element. The crysta l is specifi ed for a reso nant fre quency of 14.85 MHz a t a sp ecific
load capacitance. Tuning of the series resonance frequency is accomplished by
adjusting the total s eries capacita nce s een by t he crys tal. Varactor diodes provide the
method of varying the load capaci tan ce posed to the crystal. Both varactors ar e controlled by DAC’s within BERTINDY. DAC1 is the “fine tune” adjustment, and
DAC2 is the “coarse tune” adjustment.
Initial trimming for component tolerances is done by DAC2 in the factory. In the
field, the TCXO is adjusted mainly through DAC1 for temperature compensation
and AFC. DAC2 is only adjusted in the fie ld when ne cessary to maintain the full est
DAC1 range possible. This is where the integer ratio of tuning sensitivity is desirable.
The inherent frequen cy devia tions of the cr ystal when op erate d over t he fu ll te mperature range are corrected by a software controlled temperature compensation algorithm. A look-up table is stored in memory which is indexed by temperature
readings from a signal or iginating fr om a thermistor vo ltage divider network. This is
the only means for frequency compensation in the field when the down link signal
from the base station is weak and below the AFC threshold. When the base station
signal is above the threshold (roughly -110 dBm), and when the phone is in either
idle or conversation mode, the AFC algorithm is enabled. The temperature compensation table ensures that the TCXO frequency will be kept close enough to lock to
the base station signal and null out frequency error once the proper conditions are
met.
17
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Technical Description
Transmitter
The transmitter section amplifies the transmitter signal from approximately
0.25 mW to 1.25 W. This section is compound by a driver stage and a power amplifier.
Output power is regulated by a closed feedback loop incorporating a stripline coupler, Schottky rect ifie r diode, and a power ampli fier with hig h and variab le gain and
high efficiency.
F_TX
TX
Filter
Driver
Attenuator
Power
Amp
Power
Control
Duplexer Coupler
Rectifier
Power
Level
Antenna
Figure 8: Transmitter Block Diagram
TX Blocks
TX Driver Amplifier
The transistor used is a bipolar type in a common emitter configuration, which
offers unconditional stability and good dynamic range.
The output and inputs are matched to 50Ω, and there is an attenuation at the output
to avoid damage in PA.
Power Amplifier Module
The output power of the PA-module is varied by controlling the bias point. The saturated output power of the PA is dependent upon the load presented at its output.
For the required saturated output power and efficiency, a specified load must be
used.
18
Power Detector
The power sensing is done with a coupled stripline detector. This circuit senses forward power with some directional ity. A Schottky diode is used to rectify the RF and
this diode is forward biased to avoid having the diode snap off when detecting low
levels of RF. Direct temperature compensat ion is ac hieved by p roviding the detec tor
bias voltage via a matched diode
Power Control
The output power from the power ampl ifie r is re gulat ed by an act ive fe edback l oop.
The reference value is set via a D/A-converter in BERTINDY and is connected to
the positive input o f a n op-amp, where the detected output power level is connected
to the negative input of the same op-amp. The op-amp produces an error voltage
that controls the base c urrent of a transistor, which in turn varies th e output level of
the PA.
Page 19
Technical Description
TX Filtering
The reduction of TX spurious emissions and TX noise in the RX band is achieved
with two filters. The first is a bandpass SAW filter. The second filter is the TX
branch of the duplexer filter. The response is predominately band-pass with a notch
in the RX band to prote ct t he re cei ver fr om TX noise power . Hi gh frequency attenuation provides reduction in the level of TX harmonics.
Protection against E lec tro-Static Discharge (ESD) is also provided by t he hig h-pass
element of the duplexer TX branch.
MALIN
MALIN, is an integrated RF circuit for FDMA cellular telephones. The circuit is
designed for a radio architecture using one synthesizer for both RX and TX parts.
The transmitter portion consists of a TX-IF VCO and a TX-mixer. The base-band
signal modulates the TX-IF via an external tank circuit which is then up-converted
to the TX frequency by t he TX-mixer. A programmable prescaler is i ncluded f or use
in the main synthesiz er l oop, and power d own c ontrol is p rovide d for current savin g.
TX-IF VCO
The TX-IF is generated by an internal oscillat or of MALIN. T uni ng is performed by
an external tank circuit where the center frequency is controlled by the auxiliary
synthesizer using a va racto r diode. The TX-I F signal is also buf f ered and sent to the
auxiliary synthesizer to maintain a constant 90 MHz TX-IF frequency.
TX Mixer
The TX mixer multiplies the TX-IF signal with the first LO signal from th e main
VCO to create the desired output signal. The mixer is designed to have a low noise
floor in order not to affect the receiver performance. The output is differential and
an LC network is used to align the signals to make them combine constructively.
TX Modulation
The modulation of the transmitter occurs in the TX-IF VCO tank circuit. The baseband signal coming from the audio IC ANTON is filtered and used to shift the resonant frequency of the ext ernal t ank circ uit b y the var ying capa citance of th e varact or
diode.
TX-IF Frequency Control
The center frequency of the TX-IF VCO is controlled by the auxiliary synthesizer
located in BERTINDY. A portion of the TX-IF sig nal is bu f fered and sent t o the TX
oscillator outputs. This signal is used to lock the TX-IF in the Auxiliary PLL.
Programmable Prescaler
MALIN also includes a prescaler for use in the main synthesizer loop. The divider
has separate Vcc and ground connections to provide good isolation from the TXPA
outputs.
19
Page 20
Technical Description
Power and Charging Design
3.8V Regulator
Battery Voltage
(MIA)
Flash
GUSTAV 3.3V
GUSTAV 3.8V
EEPROM
Battery
Connector
System
Connector
VCO
TX Buffer
Red/Green LED
Backlight LEDs
Buzzer
3.8V Regulator
Buzzer Driver
LED Driver
Buzzer &
Indicator Light
Regulator
LCD
ANTON
MIA
Accessories
BERTINDY
DOUT1
BERTINDY
VCO
BERTINDY
DOUT0
MALIN RX Parts
Power Amp
Low Level
TX Power
Coupler
LNA/Mixer
IF Chip
20
BERTINDY 2nd
Figure 9: Power Distribution
Regulators
The phone is powered by three regulators as follows:
•
VDIG powers the digital/audio/user interface circuitry
•
VMALIN powers MALIN TX and buffer
•
VRAD powers the remaining radio circuitry
LO
Page 21
Technical Description
The regulators have got an enable input, which is used to power the phone on/off.
The minimum voltage for turning the regulators on is 2.0V, and the maximum for
turning them off is 0.18V.
Reset
The digital voltage VDIG is monito red by a low vol tage detec tor i n ANT ON. While
the phone is operating, and if VDIG drops below 3.35V (typical), ANTON’s LVN
open-drain output will se t GUSTAV’s reset input (MRN) low, causing the processor
to reset. Upon power-up, an RC filter holds GUSTAV’s reset input low for the
required 20 ms delay.
On/Off Control
The phone may be powered on by either pressing the ON/OFF/END key, or by
applying 7.0V-10.0V at DCIO.
When the ON/OFF/END key is pressed for at least 200 ms, this key powers on the
phone by connecting the battery voltage to the enable inputs of the regulators
through a diode. The processor then comes out of re set and la tches the ena ble inputs
of the regulators.
Chargers and accessories power on the phone by applying 7.0V-10.0V at DCIO.
The voltage difference between DCIO and the battery voltage turns on a transistor
connected to the enable input s of the reg ulato rs. As with the ON/OFF/END key, the
DCIO voltage must be present for at least 200 ms in order to power on the phone.
If no charger is connected, the phone is powered-off by pressing and then releasing
the ON/OFF/END key. Pressing the ON/OFF/END key generates an interrupt to
GUST AV via a transistor . GUSTAV then tries to disable the regulat ors but thes e will
stay on until the ON/O FF/ END k ey i s re leased. If a charger is connected, the phone
will stay on until the processor detects that the charger has been removed (no current from charger to phone). The phone cannot turn itself off as long as a charger is
connected.
Charging Circuitry
The phone software controls charging by turning a FET switch on/off, based on battery voltage and charging current through a 0.1Ω resistor. Chargers are designed to
have an open-circ uit vo lt age l ess t han 10V, and supply an avera ge c urren t of approximately 700mA when connected to a battery through the FET switch. A resistor
allows a dead battery to become trickle charged high enough for the phone to turn
on. MIA provides charge switch control and analog outputs corresponding to
charger current and battery voltage. These outputs are connected to BERTINDY’s
A/D inputs. GUSTAV turns on the charge switch using a current cont rol output port,
which is connected to an input of MIA. If the battery voltage is less than 8.0V, the
current control port control s the on/o ff sta te of the FET switch. I f the batter y voltage
is greater than 8.0V, MIA keeps the charge switch off regardless of the state of the
current co ntrol port.
21
Page 22
Technical Description
Transient/ESD Protection
Diodes are used for ESD protection on the System Connector outputs. The inputs
have got resistors between the System Connector and the ASIC input ports. Capacitors on DCIO prevent spikes caused by charger cable inductance when the charge
switch is turned off. They also protect MIA and the FET-switch from ESD and provide de-coupling for voltage ripple. A capacitor and a varistor provide de-coupling
and high-voltage / ESD protection on the battery voltage.
Off Current Draw
The current draw when the phone is of f shoul d be as lo w as poss ible in order to prevent low batteries fr om being t oo heavi ly dis char ged . The only c omponent s direc tly
connected to the battery which may draw current when the phone is off are MIA, a
low voltage detector, and the regulators.
22
Page 23
User Interface
Illumination
The phone is illuminated with 14 SMD LED’s, 4 for the display and 10 for the keyboard. The LED’s are switched on and off from GUSTAV. A voltage regulating circuit is included which prevents changes in the battery voltage from affecting the
backlighting intensity.
Buzzer
The buzzer, which emits the Beep-, Ring- and Alarm signals, is an electromagnetic
resonance buzzer with a resonance frequency of about 3 KHz.
The sounds are generated in GUSTAV by software control and then fed to the
buzzer.
Technical Description
LCD Display
The display is a 1- row segmented LCD which uti li zes chi p on gla ss t echnology for
mounting of the driver chip on the LCD module. No negative voltage supply is
required for this LCD and no contrast control is needed since the display in
utilizes a technology which provides a wide viewing cone.
EF738
Keypad
There is a 5 x 4 keyboard scanning connected to GUSTAV.
A detection signa l is se t high when the
at a feed-back signal GUSTAV is informed and turns the phone on.
END/PWR/NO
key is pressed and b y looking
23
Page 24
Technical Description
Logic Design
GUSTAV
GUSTAV is a uP ASIC that consists of 15 blocks:
•
6303
•
ROM
•
RAM
•
Bus Interf ace
•
Decoder
•
Serial Interface
•
External Ports
•
Watchdog On/Off
•
IFC
•
BAR
•
Clock Generator
•
Internal Ports
•
Modem
•
Baud Clock
•
I2C Controller
Circuit Description
6303
The processor is an 8 bit processor with an asynchronous full duplex serial communication interface, DTMS/DFMS, for external connections.
ROM
There is an internal 512 byte ROM in GUSTAV which holds a Primitive Interface
Program, used for code loading into the RAM. After a reset, the CPU will begin
executing the code in IROM. If the SERV line is high, the ROM code continues to
execute, otherwise the program code in the external EPROM is started.
RAM
There are 6016 bytes of RAM available in GUSTAV. The processor uses this memory as working space whe n the ph one i s tur ned on. Wh en t urned off, data that has to
be saved will be stored in the EEPROM before turn off.
Bus Interface
The bus interface will provide the data and address lines to the external Flash
EPROM and will also handle the internal busses in GUSTAV.
24
Page 25
Technical Description
Decoder
The decoder in GUSTAV is an address decoder which has outputs for both internal
functions and logic control signals such as chip selects (CS), write (W) and output
enable (OE ).
Serial Interface
The serial interface in GUSTAV has a transmitter block and a receiver block.
The transmitter block consists of four write registers, a clock divider, and other
logic for genera ting int errupts and la tch sign als. Data is tr ansmitte d and r eceived v ia
a serial interface data line.
The receiver block consists of three read registers in which the received data may be
read one byte at a time by the processor.
External Ports
This block manages the keyboard along with the handling of binary input/output
ports where some inputs are connected to the interrupt control block.
WatchDog On/Off
The Watchdog On/Off block in GUSTAV contains the watchdog block and the
Autonomous Time Out (ATO) block. This block consists of a four second counter,
which when overflown, activates a reset circuit and generates a 100ms reset.
The ATO is a supervising block that monitors the status of the received carrier
detect and the transmitter power. If the transmitte d power is detected without the
received carrier detect for 30 seconds, the ATO initiates a hardware turn off of the
phone.
IFC
The IFC counter is used to count a predetermined number of periods of the IF from
the radio interface LSI.
BAR
The output from the bar generator is a continuous pulse train with program controlled ON and OFF time. This makes it possible to vary signal parameters such as:
•
tone frequency
•
signal period
•
signal on time
•
volume
Clock Generator
The processor clock is generated from an external signal or crystal.
An 8.064 MHz clock gives a system clock frequency of 1.008 MHz (or 2.016 MHz
in Turbo mode). The serial interface clock will always be 1.008 MHz. The clock
generator block has many divider steps to generate all clock frequencies that are
required inside GUSTAV and on the logic PCB.
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Technical Description
Internal Ports
There are three 8 bit rea d and thre e 8 bi t write p orts in t his bloc k that ar e used within
GUST AV.
Modem
The modem part supports two different cellular systems, AMPS and TACS, which
consists o f data receiver, data transmitter, SAT detector, and SAT tra nsmitter.
The data receiver consists of three parts: digital discriminator, data decoder, and
wordsync detector.
The data transmitter sends data bytewise where the most significant bit is transmitted first.
The SAT-detection consists of continuous measurements of 10-12 ms and the three
frequencies being used are 5970, 6000 and 6030 Hz.
SAT-generation of the three frequencies is also done in GUSTAV.
Baud Clock
This block generates the baud rate for the serial interface of GUSTAV and is selectable among the following baud rates.
600 (Power on default)
1200
2400
4800
9600
I2C Controller
This part controls the communication between the EEPROM and the display.
FLASH EPROM
The system program is store d in a l ow voltag e Flash EPROM with 12 8k x 8 bit area.
EEPROM
The ‘customer’ PROM is a CMOS EEPROM with 4k x 8 bit area. Data that has to
be saved when the station is turned off is stored in this memory, which contains the
telephone number, short numbers, talk time, area ID and other radio/audio information.
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Page 27
Audio Design
The baseband audio is processed by ANTON which is a mixed signal ASIC with a
compander, filters, limiters and programmable gain blocks.
Receive Audio Circuit Description
Receive Audio Interface
The receive audio is demodulated by a digital discrimina tor in BER TI NDY and then
passed through a first order active bandpass filter which is comprised of an op-amp
located in BERTINDY. External resistors and capacitors set the gain and bandpass
of the filter and the outp ut of thi s filt er is the n AC coupl ed throug h a capaci tor to an
external de-emphasis network. The interface between the radio and the baseband
audio is between the discriminator’s bandpass filter and the external de-emphasis
network.
Technical Description
De-Emphasis Network
The de-emphasis network is composed of two series resistors and a shunt capacitor.
The audio is routed through a resistor pair into the receive input port on ANTON.
The received SAT is tapped off between the resistor pair and routed to a port on
ANTON. The shunt capacitor provides the necessary de-emphasis slope to restore
the low frequency components of the audio that were attenuated by the pre-emphasis in the base station transmit path.
RXSENSE Programmable Gain Stage
The receive audio enters ANTON at the receive input port. The signal first passes
through an anti-aliasing filter and is then routed to the RXSENSE programmable
gain stage. This gain stage is provided to trim out the tolerances between the discriminator output and the expander input. The RXSENSE gain stage has a nominal
gain of 8 dB and can be adjusted +6.4/-6.0 dB in steps of +0.4 dB.
Test mode 10 ‘RX Sensitivity’ can be used to update this gain stage.
This stage is used to adjust the AFMS level to 25 mVrms with a 1 kHz tone at 2.3
kHz deviation and nominal volume.
Receive Bandpass Filter
The output of the RXSENSE stage is fed into a 300 Hz to 3 kHz switch-capacitor
bandpass filter.
27
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Technical Description
Expandor Gain
The gain in the expandor is a function of the input signal level with the following
relationship for the expandor:
2(X0 - X1 ) = Y0 - Y1
where: X0 = reference input (unaffected level)
The relationship states that a change in the input from X0 to X1 will produce a
change in the output from Y0 to Y1 that equals 1:2.
The gain, A, is then:
A = Y1 - X1 = Y0 - 2X0 +X1
RX HF Attenuation
Y0 = reference output
X1 = input
Y1 = output
Following the expander is a 0 to -49 dB attenuator for full duplex handsfree operation. This stage is programmabl e in st eps of 7 dB. When the e xtern al audio signal o n
the system connector is low, the software implements a handsfree algorithm that
attenuates the unused audio path to prevent feedback from external speakers to the
microphone.
Under normal modes of o per at ion this stage is se t to 0 dB. However, dur ing the generation of DTMF tones to the earpiece, this stage is used to attenuate the signal to
prevent clipping.
RX Volume Control
The RX audio level is controlled by a 0 to -24 dB gain stage in steps of 3 dB.
EARSENS Programmable Gain Stage
A programmable gain stage is provided to trim the level to the Earpiece to provide
84 dBspl with a 1 kHz tone at 2.3 kHz deviation and max. volume setting (0 dB).
This stage is programmable in 0.4 dB steps from -2.8 to 3.2 dBs.
Test Mode 28 ‘Earpiece’ is used to trim this stage.
Externally Programmable Gain Stage
28
An inverting amplifier follows the EARSENSE stage. The input and feedback elements are external to allow for e xternal programming of gain and filtering.
This stage is bypassed when the earpiece drivers are put in external mode .
Page 29
Technical Description
Earpiece Driver
The earpiece driv er is composed of a differential pair, a non-inverting amplifier and
an inverting amplifier.
The drivers can be software configured in four modes:
•
single-ended
•
differential
•
external
•
muted
A resistor is added in series with the earpiece as a pad to limit the maximum acoustic level to 103 dBspl. The ga ins in t he ASIC ar e set t o force t he signa l in to cli pping
at maximum deviation and maximum volume and the excess amplitude is divided
down between the resistor and the earpiece.
AFMS
The inverting earpiece amp is used to generate the AFMS signal. The signal is AC
coupled to reduce popping when connecting a portable handsfree unit.
Transmit Audio Circuit Description
ATMS
The ATMS signal is AC coupled to the transmit audio path via a capacitor and is
then reduced by 2 dB and biased to a voltage. A switch to this voltage is also connected to the output of the ATMS port to provide a bias for the portable handsfree
microphone. This switch is controlled by the microprocessor, but can be controlled
directly by the PORTHF port of the system connector.
Microphone Input
The ASIC has a switchable +22/+32 dB gain stage for amplifying low level microphone signals. The ASIC also provides a low noise bias voltage for microphone
biasing.
ANTON is designed to provide gain to the portable handsfree microphone by the
use of software controlled switches which are located before and after the Mic gain
stage, to allow routin g of the signal from the ATMS port through the Mic amplifier.
The switches can be c onfigure d to ro ute the mi c audio th rough t he mic amp, to route
ATMS through the mic amp or to bypass ATMS around the mic amp. In all three
cases, the output of this block is routed to the soft limiter.
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Page 30
Technical Description
Soft Limit
A 0 to -30 dB attenuator follows the audio input block where this soft limit is enabled through software and is used to limit clipping before the compressor. The soft
limit is controlled by two threshold comparators. When the signal exceeds the
threshold, a clock will step a tap on a resistor ladder to increase the attenuation.
When the level drops below the threshold, a slower clock steps the tap back up the
resistor ladder to reduce the attenuation.
INPSENSE Programmable Gain Stage
The soft limit output is AC coupled into the INPSENSE programmable stage and
this stage is used to adjust the audio level into the compressor. The gain is programmed through software i n a range from +2 to +14.4 d B in steps of 0.8 dB where
the nominal setting is +8 dB .
This stage has calibration settings for three modes of operation:
•
•
•
external audio
internal audio
DTMF tones
The three calibration values are stored in the EEPROM.
Transmit Bandpass Filter
The next block in the transmit audio chain is a switched capacitor bandpass filter
which is designed to allow frequencies from 300 to 3000 Hz to pass through.
TX HF Attenuator
Following the bandpass filter is a 0 to -49 dB attenuator for full duplex handsfree
operation, which is programmable in steps of 7 dB. When the external audio signal
on the system connector is low, t h e sof twar e impl ements a handsfree algorith m that
attenuates the unused audio path to prevent feedback from external speakers to
microphone.
Compressor
The audio is AC coupled from the transmit handsfree attenuator block into a 2:1
switch capacitor compressor. This stage is enabled during the conversation modes
of the phone and can be bypassed for testing.
Test mode 29 has two options for control of the compressor.
30
An integrator using an amplifier in the ASIC is configured to provi de feedback from
the output to the input of the compressor.
Pre-emphasis
A 3 dB/Octave high pass filter follows the compressor. This filter is used to equalize
the audio spectrum by attenuating the low frequency components of the signal.
Page 31
Technical Description
Hard Limit
A +13.5 dB gain hard limit follows the pre-emphasis block in the transmit audio
path in order to limit the max imum audio level out of the ASIC a nd int o the modul ator block.
Transmit Lowpass Filter
A 3 kHz lowpa ss filter follo ws the hard limit to filter out the harmonic components
caused by clipping in the hard limit.
AUDIODEV Programmable Gain Stage
The AUDIODEV programmable gain stage follows the TX lowpass filter to allow
adjustment of the maximum transmit deviation. This stage is provided to trim out
tolerances in the following summing stage.
The nominal gain in the AUDIODEV stage is 0 dB with an adjustment range from
+3.2 to -2.8 dB in steps of 0.4 dB.
Test mode 14 can be used to adjust the AUDIODEV stage for TX audio.
The transmitted DTMF tone has a sepa rate set ti ng f or AUDIODEV in EEPROM. It
needs to be adjusted to provide enough gain after the compressor so that the signal
does not clip in the compressor.
Summing Amplifier
The summing amplifier is provided to combine the TX audio / DTMF tone, SAT
tone and Manchester data into the modulat or. The input resistors and feedback resistor for this circuit are external to the AS IC to allow for gain adjustments.
TXSENSE Programmable Gain Stage
The TXSENSE programmable gain stage is an amplifier which is provided to trim
out tolerances in the modulator but is currently not used, however set to a default
value of 0 dB. This stag e has an adju stme nt r ange f ro m +3. 2 to -2.8 d B wi th st ep s of
0.4 dB.
Low Voltage Detect Circuit
A comparator is included in ANT ON to provi de a reset si gnal to GUSTAV when the
regulated voltage drops below appr oximat ely 3.3 V. This circuit is enabled at power
up and can be disabled by software to save a small portion of current in standby
mode.
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Page 32
Technical Description
RX and TX Sat Circuits
RX SAT Filter
A 6 kHz bandpass filter is included to capture the received SAT tone from the composite received audio signal
RX SAT Schmit Trigger
The filtered SAT signal is then amplified and routed to a schmit trigger circuit in
ANTON where it is squared up and driven to GUSTAV as a digital signal.
TX SAT Filter
The TX SAT signal originates in GUSTAV as a digital signal. The TX SAT filter is a
6 kHz bandpass filter for removal of high order harmonics from the signal.
TX SATDEV Programmable Gain Stage
A programmable gain stage SATDEV is provided to adjust tolerances in the summing circuit to maintain the proper signal level to transmit a 6 kHz SAT tone at 1.7
kHz FM deviation. This gain stage is nominally 0 dB with an adjustment range of
+4.8 to -4.5 dB in steps of 0.3 dB.
Test mode 22 can be used to adjust SATDEV.
8Kbit/s Manchester Data Circuit
Data Filter
A 20 kHz lowpass filter is provided to limit the frequency components of the digitally generated Manchester data.
Data is transmitted as an 8 kHz signal at 6.2 kHz FM deviation.
DATADEV Programmable Gain Stage
The filtered data signal is routed to a programmable gain stage, DATADEV, for
trimming out tolerances in the summing amplifier. The DATADEV gain stage is
nominally 0 dB with an adjustment range of +3.2 to -2.8 dB with steps of 0.4 dB.
32
HandsFree Circuit
ANTON includes rectifier circuits for audio detec tion in the RX and TX paths.
A single port is provided for the monitoring of the rectified signal.
A switch is software controlled to select the RX or TX path for samplin g.
An external capacitor is provided to set the time constant for each path.
Page 33
Software Design
Power Down Control
All voltage regulators ar e on all the time when in SLEEP, STAND BY and TRANSMIT mode. The operation modes of ANTON and BERTINDY are software controlled directly from GUSTAV through the serial interface.
Timing and Operation
In the ETACS system it is most important that a well working sleep function can be
implemented as this will increase the standby time by several hours.
Main Modes of Operation
The transceiver hardwar e operation c an be split into four main modes: OFF, SLEEP,
STAND BY and TRANSMIT.
Technical Description
•
OFF is when all regulated power are switched off by the on/off logic. The hardware is powered up when the voltage regulators are enabled. At power-up the
8 MHz clock frequency synthesizer has to be loaded with the correct division
ratios and the RAM has to loaded as well. All software controlled circuits have
to be initiated and loaded with thei r default settings, and then powered down by
software until needed again.
•
SLEEP mode is the lowest operation mode the transceiver can be put in (excl.
OFF mode). All receiver, transmitter and audio circuits are put in power down
mode or switched off.
•
STAND BY mode is the normal data receive mode, where the transceiver can
listen to the data signalling from the base station.
•
TRANSMIT mode is the normal conversation/data mode.
Power Saving Sleep Function
When in STAND BY mode the transceiver doesn’t have to be awake listening all
the time as there are time slots where the transceiver can be put into SLEEP mode.
Software Assignments
Software is loaded via the serial channel through GUSTAV into the Flash EPROM
and the main assignments are:
•
controller of the hardware circuitry
•
communicator with the cellular system via the RF link
•
provider and handler of the operating interface to the user
•
provider of test and tune commands for factory and field service
•
co-ordinator of the overall system (e.g. operating system)
•
controller of the battery charging
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Page 34
Technical Description
Technical Specifications
General
Phone Model: EF738
Type Number: 1030601-BV
System: ETACS
Frequency Range: TX: 872 - 905 MHz
Channel Spacing: 25kHz
Number of Channels: 1320
Modulation: FM
Frequency Stability: ±2.5ppm
Duplex Spacing: 45MHz
LCD: One 10 chrs. alphanumeric line
Keypad: 17 front keys, 2 side keys
Antenna: quarter-wave
External Antenna Jack: No
Voltage Operation: 4.8V
Power Consumption: <590mA at level 2 (full power)
Standard Battery Durability:
Dimensions: 106 x 50 x 24 mm; 4.17 x 1.97 x 0.94 in
Weight: 70g; 2.5oz (excl. battery)
Te mperature Range: -10° to +55°C; +14° to +131°F (operating)
Humidity: 0 - 95% relative humidity
RX: 917 - 950 MHz
One status indicator line (icons)
<45
mA (standby)
<30mA (standby with DRX)
≈
80 min. conversation
≈
22 hours standby
137g; 4.8oz (incl. standard battery)
-40° to +70°C; -40° to +185°F (storage)
34
Transmitter
RF Power Output: 26.5dBm (level 2)
Output Impedance 50
Spurious Emission (TX): <-26dBm below 1GHz; <-30dBm above 1GHz
Ω
Receiver
RF Level:
≥
-113dBm (20dB SINAB)
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