Series 2000 Reader System
High Performance RFM RI-RFM-007B
Reference Guide
11-06-21-042 April 1999
1
High Performance RFM RI-RFM-007B April 1999
Second Edition - April 1999
This manual describes the
hereafter referred to as the RFM.
TIRIS High Performance RFM RI-RFM-007B
,
Important Notice
Texas Instruments reserves the right to change its products or services or to
discontinue any product or serv ice at an y time witho ut n otice. T I pr ovides c ustom er
assistance in various technical areas, but does not have full access to data
concerning the use and applications of customer's products.
Therefore, TI assum es no liability and is not resp onsible for cus tomer applications
or product or software design or perform ance relating to systems or applications
incorporating TI products . In additio n, TI ass um es no liab ilit y and is not respons ible
for infringement of patents and/or any other int ellectual or industrial propert y rights
of third parties, which may result from assistance provided by TI.
TI products are not designed, intend ed, authorized or warranted to be suitable for
life support applications or any other life critical applications which could involve
potential risk of death, personal injury or severe property or environmental damage.
The
TIRIS
Instruments Incorporated.
Copyright 1998 Texas Instruments Incorporated. All rights reserved.
logo and the word
TIRIS
are registered trademarks of Texas
2
April 1999 Contents
Table of Contents
Preface.................................................................................................................5
Chapter 1: Product Description ........................................................................7
1.1 General.......................................................................................................8
1.2 Transmitter ...............................................................................................10
1.3 Receiver ...................................................................................................11
1.4 RFM Connectors and Jumpers ................................................................11
Chapter 2: Specifications ................................................................................17
2.1 Recommended Operating Conditions ......................................................18
2.2 Dimensions...............................................................................................22
Chapter 3: Installation......................................................................................23
3.1 Power Supply Requirements....................................................................24
3.2 Power Supply Connection........................................................................25
Chapter 4: Associated Antenna Systems......................................................27
4.1 Antenna Requirements.............................................................................28
4.2 Antenna Resonance Tuning.....................................................................29
4.3 Tuning Procedure.....................................................................................30
Appendices
Appendix 1: Expanding Antenna Tuning Inductance Range..........................33
Appendix 2: Field Strength Adjustment..........................................................37
Appendix 3: Adjustment of Oscillator Signal Pulse Width..............................39
Appendix 4: Threshold Level Adjustment.......................................................41
Appendix 5: Transmitter Carrier Phase Synchronization (CPS) ....................43
Appendix 6: Noise Considerations .................................................................47
Appendix 7: Over Voltage Protection .............................................................49
3
High Performance RFM RI-RFM-007B April 1999
Table Locations
Table 1: J1 Pin Functions ................................................................................................................................ 13
Table 2: J2 Pin Functions ................................................................................................................................ 14
Table 3: J4 Pin Functions ................................................................................................................................ 14
Table 4: J3 Pin Functions ................................................................................................................................ 15
Table 5: Antenna Connectors.......................................................................................................................... 15
Table 6: Operating Conditions......................................................................................................................... 18
Table 7: Electrical Characteristics ................................................................................................................... 20
Table 8: Timing Characteristics....................................................................................................................... 21
Table 9: Mechanical Parameters..................................................................................................................... 21
Table 10: Power Supply Ripple Specifications................................................................................................ 24
Table 11: Antenna Requirements.................................................................................................................... 28
Table 12: Capacitor Values for Expanding Antenna Tuning Range to Lower Values..................................... 34
Table 13: Capacitor Values Expanding Antenna Tuning Range to Higher Values ......................................... 35
Table 14: Oscillator Signal Pulse Width versus Resistor Value (estimated values)........................................ 40
Table 15: Maximum Distances between Antennas ......................................................................................... 44
Table 16: Characteristics of Radiated and Conducted Noise.......................................................................... 47
Figure Locations
Figure 1: RFM Block Schematic........................................................................................................................ 8
Figure 2: Pulse Width Examples ..................................................................................................................... 10
Figure 3: RFM Top View.................................................................................................................................. 12
Figure 4: RFM Bottom View............................................................................................................................. 13
Figure 5: Mechanical Dimensions ................................................................................................................... 22
Figure 6: External Ground Connection (GND to GNDP)................................................................................. 26
Figure 7: Tuning Example showing Increase of Total Tuning Capacity.......................................................... 31
Figure 8: Flow-chart for Tuning the Antenna to Resonance............................................................................ 32
Figure 9: Circuit for Expanding Antenna Tuning Range to Lower Values....................................................... 34
Figure 10: Circuit for Expanding Antenna Tuning Range to Higher Values.................................................... 35
Figure 11: Distance between Antennas (top view).......................................................................................... 44
Figure 12: Noise Testing Configuration........................................................................................................... 48
Figure 13: Circuit for Overvoltage Protection .................................................................................................. 50
4
FCC/PTT Regulations
The TIRIS RFM generates RF emissions at 134.2 kHz. The radiation of the
fundamental and harmonics will var y with the type of antenna and other devices or
functions connected to the RFM.
Prior to operating the RFM together with antenna(s), power supply and a control
module or other dev ices, the required FCC, PTT or relevant government agency
approvals must be obtained.
Preface
CE Conformity
Sale, lease or operation in some countries may be subject to prior approval by
governmental and other organizations or agencies.
A CE Declaration of Conformity is available for this module in a typical
configuration. An y device or s ystem incor porating th is m odule in a n y other tha n the
original CE configuration needs to be verified against the European EMC directive.
A separate Declarat ion of Conformity must be is sued by the system integrator or
user of such a system prior to marketing it and operating it in the European
Community.
5
High Performance RFM RI-RFM-007B April 1999
Conventions
Certain conventions are used in order to display important information in this
manual, these conventions are:
WARNING: A warning is used where care must be
taken, or a certain procedure must be followed, in
order to prevent injury or harm to your health.
CAUTION: This indicates information on conditions which
must be met, or a procedure which must be followed,
which if not heeded could cause permanent damage to the
RFM.
Note: Indicates conditions which must be met, or procedures which
must be followed, to ensure proper functioning of the RFM.
6
Chapter 1
Product Description
This chapter introduces the RFM component assemblies, s howing the transmitter
and receiver sections and placement of key user-accessible components.
Topic Page
1.1 General.......................................................................................................8
1.2 Transmitter ...............................................................................................10
1.3 Receiver ...................................................................................................11
1.4 RFM Connections and Jumpers...............................................................11
7
High Performance RFM RI-RFM-007B April 1999
1.1 General
WARNING: Care must be taken when handling the
RFM. High voltage across the antenna terminals, all
antenna components and some parts of the printed
circuit board (PCB) could be harmful to your health. If
the antenna insulation is damaged, the antenna
should not be connected to the RFM.
CAUTION: This product may be subject to damage by
electrostatic discharge (ESD). It should be handled by ESD
protected personnel at ESD secured workplaces only. The
transmitter power output stage can only operate with a
limited duty cycle. Please pay attention to this whilst
performing antenna tuning procedures. Ground pins GND
and GNDP must be connected externally to avoid damage
to the unit.
TXCT-
RXDT
RXCK
ATI
Interface
RXSS-
The RFM is an integra l part of the TIRIS system. Coupled with a Control Mod ule
and an antenna, it is use d for wir eles s identif icat ion of T IRIS transpo nder s. A block
schematic is shown in Figur e 1.
TX
Osc illator
RX
Demodulator
demodulator
6
ATI
Int
.
RXSS
Threshold
threshold
CPS
PWM Control Input
PW M
RX
Amplif ier
Overvoltage Protection
TX Powe r
Stage
Antenna
Circuit
TX/RX
Antenna
Figure 1: RFM Block Schematic
8
April 1999 Product Description
The RFM contains all the analogue functions of a TIRIS reading unit needed to
send an energizing signal via the antenna to initialize a TIRIS transponder, to
demodulate the received identification signal and to send the received data
together with clock signals to a Control Module.
The RFM also sends the necessary programming and addressing signals to
Read/Write and Multipage transponders.
The data input and output lines, which are connected to a data pr ocess ing u nit, are
low-power Schottky TTL and HCMOS logic compatible.
The functions of the RFM are described in the following section.
9
High Performance RFM RI-RFM-007B April 1999
1.2 Transmitter
The transmitter power s tage is supplied with power via two separate supply lines
VSP and GNDP. Because of the high current requirements for the transmitter
power stage, these supply lines are separated from the logic secti on supply lines
and have two pins per line.
The ground pins for the logic section and the transmitter are not connected
internally in order to a void possible problem s with a high resistivit y of GNDP pins
and in order to increase flexibility when using long supply lines. Pins GND and
GNDP must be connected to each other externally. For more details, refer to
Section 3.1, Power Supply Connection.
The regulated transm itter power stage supply may var y between +7V and +24V.
The supply lines VSP and VSL should be connected together when the supply
voltage is +7 V or more. For details refer to Section 2, Specifications.
Note: The RFM has an in-built temperature protection circuit which
sharply limits the transmitter power stage output if an over-current
situation or an over-tem perature environment c auses the tem perature
to exceed the allowed limits. After the devic e is switched off and has
time to recover (when the tem peratur e drops again or the o ver-c urrent
situation is otherwise rectified) the unit reverts to normal operation
when it is switched o n again. Such an occ urrence is an in dicatio n th at
the RFM is not being operated within specification.
The transmit frequency (134.2 kHz) from the oscillator is fed to the pulse width
modulator (PWM). By changing the value of a resistor, the PWM can s et the pulse
width ratio between 0% and 50%. For an example of two different oscill ator signal
pulse widths see Figur e 2. Decreasing the 134.2 k Hz frequency pulse width ratio
decreases the generated transmit (charge-up) field strength.
It is therefore possible to adjust th e generated field strength by selecting different
pulse width ratios. For more information about setting the field strength, refer to
Appendix 2, Field Strength Adjustment.
Pulse width of 50% Pulse width of 12.5%
Figure 2: Pulse Width Examples
10
April 1999 Product Description
CAUTION: The RFM must not be operated in continuous
transmit mode when operated at full power output. For
details please refer to Section 2, Specifications. When
using pulse widths smaller than 50%, the RFM transmitter
power stage works in a less efficient way. This leads to an
increased power dissipation and thus to higher
temperature increase of the transmitter power stage, so
ensure that more cooling is provided.
Note: If the RFM is going to be ph ysically located within the ante nna
field, it may be necessary to shield the module.
1.3 Receiver
The signal receive d from the transponder is a frequency s hift keying ( FSK) signal
with typical low and h igh bit frequenc ies of 134.2 k Hz and 123 .2 kHz r espectively.
The signal is received from the ante nna resonat or, whic h is capac itivel y coupled to
the receiver.
The signal RXCK is the ref erence clock signal to decode t he RXDT data stream.
The RXCK signal changes from low to high level during each data bit and the
RXDT signal is valid before and after this pos itive slope for a certain tim e window.
For more details refer to Table 8, Timing Characteristics.
The receiver also has a built-in RF receive signal strength detector. T he receive
signal strength is indicat ed b y the digit al out put RX SS- .
RXSS- becomes active ( logic low level) when the received RF signal strength
exceeds a defined l evel. This thr eshold level c an be adjus ted with a potentiom eter
(R409) on the RFM. The potentiometer is located near SW1 on the board. See
Figure 3, RFM Top View.
The RXSS- output is used for detect ion of other tr ansm itting re ading un its an d thus
can be used for wireless read cycle synchronization of several reading units.
1.4 RFM Connectors and Jumpers
There are a number of connectors, jumpers and other components on the RFM
available for use.
These are:
J1 Connector for supply voltages and interface signal lines to and from the
RFM
J2 Connector for the (optional) Anten na Tuning Indicator (ATI), which c an be
used for easy antenna tuning during installation.
11
High Performance RFM RI-RFM-007B April 1999
J3 Connector for antenna resonance tuning, used to connect the required
tuning capacitors.
J4 Connector for field strength adjustment resistor and also direct access to
receiver input.
JP3 Additional antenna damping connector.
JP4 Common-mode noise choke bypass.
R409 RXSS noise level adjustment potentiometer.
SW1 Default all on. (Pos. 1 CPS setting see Appendix 5.)
ANT1/ANT2 (two M3 screw connectors) connect the transmit/receive (TX/RX)
antenna to the RFM.
The RFM is normally mounted from the und er side utilizing ap propr i ate sp ac er s and
M3 mounting bolts.
The top view of the RF M ( witho ut th e n or mally fitted heatsink ) is shown in Figur e 3.
Connectors J2, J3, J4, J P3, JP4, R 409 , switch SW 1 and the antenn a ter m inals ar e
accessible from the top.
Figure 3: RFM Top View
12
April 1999 Product Description
The bottom view of the RFM is shown in F igure 4. The connector s J1, J2, J3 and
J4 are accessible from the underside. J1 is the 16-pin module connector, this
carries the supply voltage lines, the data, and the control lines.
J2
• •
• •
• •
J4
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
6
4
2
4
2
2
4
6
8
10
12
14
16
13
11
9
7
5
3
1
J3
• •
• •
• •
• •
• •
• •
• •
14
12
10
8
6
4
2
ANT 1
5
3
1
3
1
1
3
5
7
9
11
13
15
J1
ANT 2
Figure 4: RFM Bottom View
Table 1 lists the p in functi ons f or connec tor J1. T he conn ector t ype is 16 pin, 2 r ow
with 2.54 mm pin spacing.
Table 1: J1 Pin Functions
Pin# Signal Direction Description
1 GND IN Logic ground
2 TXCT- IN Tr ansmitter control input for activation of transmitter (active low, internal
pull-up resistor)
3 VSL IN Supply voltage for logic and receiver
4 RXDT OUT Logic level compatible receiver data signal output
5 RXSA IN/OUT Receiver signal strength adjust for RXSS- threshold level
6 RXCK OUT Logic level compatible receiver clock output
7 GNDP IN Transmitter power stage ground
8 No connection
9 GNDP IN Transmitter power stage ground
10 RSTP OUT Analog receiver signal strength test pin
11 VSP IN Supply voltage for transmitter power stage
12 CPS_OUT OUT Carrier Phase Synchronization os cil lat or signal output
13 VSP IN Supply voltage for transmitter power stage
14 RXSS- OUT Receiver signal strength output (active low)
15 No connection
16 CPS_IN IN Carrier Phase Synchronization os c illat or signal in put
13
High Performance RFM RI-RFM-007B April 1999
CAUTION: The transmitter ground pins GNDP and logic
ground pin GND must be connected together externally.
The RFM may be otherwise permanently damaged.
Table 2 lists the pin functions for the ATI connector J2: The connect or type is a
6 pin, 2 row connector with 2.54 mm pin spacing.
Table 2: J2 Pin Functions
Pin# Signal Direction Description
1 TXCT-R IN Transmitter control signal via resistor (active low)
2 GND OUT Logic ground
3 VD OUT Internal regulated logic supply voltage output
4 F_OSC-R IN/OUT Pulse width modulated transmitter oscillator signal via resistor
5 RXSS- OUT Receiver signal strength output (active low)
6 F_ANT OUT Antenna resonance frequency output signal (open collector)
Table 3 lists the pin functions for the J4 pulse width adjustment connector. The
connector type is 4 pin, 2 row with 2.54 mm pin spacing.
Table 3: J4 Pin Functions
Pin# Signal Description
1 RX Analog transponder signal
2 GNDA Ground antenna circuit
3 Pulse width adjusting resistor
connecting pin
4 GND Logic ground
14
April 1999 Product Description
Table 4 lists the functions f or connector J3. This is a 14 pin, 2 ro w connector with
2.54 mm pin spacing.
Table 4: J3 Pin Functions
Pin# Signal Description
1 ATC1 Antenna tuning capacitor 1 (weighted value 1)
2 GNDA Ground antenna circuit
3 ATC2 Antenna tuning capacitor 2 (weighted value 2)
4 GNDA Ground antenna circuit
5 ATC3 Antenna tuning capacitor 3 (weighted value 4)
6 GNDA Ground antenna circuit
7 ATC4 Antenna tuning capacitor 4 (weighted value 8)
8 GNDA Ground antenna circuit
9 ATC5 Antenna tuning capacitor 5 (weighted value 16)
10 GNDA Ground antenna circuit
11 ATC6 Antenna tuning capacitor 6 (weighted value 32)
12 GNDA Ground antenna circuit
13 AMTP Antenna circuit test point
14 No connection
Table 5 lists the pin f unctions for the antenna term inal connectors: Metric scre ws
size M3 are used for connection.
Table 5: Antenna Connectors
Signal Description
ANT1 Antenna resonator (capacitor side)
ANT2 Antenna resonator (transformer side)
Jumper JP4 allows enabling and disabling of common noise filtering for EMI
purposes. The default setting, with common noise filtering active, jum pers pins 2
and 3. A jumper between pins 1 and 2 bypasses common noise filtering.
15
Chapter 2
Specifications
This chapter lists the recommended operating conditions, electrical and mechanical
characteristics and dimensions.
Topic Page
2.1 Recommended Operating Conditions ......................................................18
2.2 Dimensions...............................................................................................22
17
High Performance RFM RI-RFM-007B April 1999
CAUTION: Exceeding recommended maximum ratings may
lead to permanent damage of the RFM. The RFM must not
be operated in continuous transmit mode when operated at
full power output. Install suitable heatsinks when operating
the RFM at pulse widths smaller than 50%.
2.1 Recommended Operating Conditions
Table 6 shows the recommended operating conditions.
Table 6: Operating Conditions
Symbol Parameter min. typ. max. Unit
V_VSP Supply voltage of transmitter power stage 7.0 12.0 24.0 V DC
I_VSP Curr ent consumption of transm itter power sta ge - refer to the formula
below
P_VSP Peak pulse power input to trans mitter po wer stage ( I_VSP * V _VSP *
Duty Cyc le)
V_ANT Antenna resonance voltage 250 380 Vpeak
V_ANT-25
V_ANT-D1Antenna resonance voltage for damping option using jumper JP3 50 60 Vpeak
Antenna resonance voltage (Pulse width setting ≤ 25%)
1.0 1.7 Apeak
20 W
200 Vpeak
V_ANTATI
V_VSL Supply voltage input for logic part 7.0 24.0 V DC
I_VD External current load on internal regulated logic supply voltage output 1.0 mA
T_oper Operating free-air temperature range -25 +70 ° C
T_store Storage temperature range -40 +85 ° C
Minimum antenna resonance voltage for correct operation of ATI 25 Vpeak
Note: Free-air temperature is the air temperature immediately
surrounding the RFM module. If the module is incorporated into a
housing, it must be guaranteed by proper design or cooling that the
internal temperature does not exceed the recommended operating
conditions.
18
April 1999 Specifications
In order to keep power consumption (P_ VSP) below 20 W it is advisab le to limit
I_VSP. The maximum allowed value, dependent on the configuration, can be
determined as follows (in the foll owing examples a supply voltage of 24 V_VSP is
used):
I_VSP =
where Duty Cycle =
Example 1:
I_VSP = = 1.66 A Duty Cycle = = 0.5
Example 2:
I_VSP = = 1.33 A Duty Cycle = = 0.625
The following methods can be used to measure the actual I_VSP value:
1. Use a battery powered oscilloscope to measure the voltage drop across a
P_VSP
V_VSP x Duty Cycle
Power on time
Total Read Cycle Time
Using Standard/Default Settings (≈10 read cycles/second):
20 W
24V x 0.5
Configured to No Sync (≈12 read cycles/second):
20 W
24V x 0.625
0.1 Ohm resistor placed in the DCIN+ line, and then calculate the actual
current using the formula I = V/R.
50 ms
100 ms
50 ms
80 ms
2. If a battery powered oscilloscope is not available, m easur e th e p oten tia l at b oth
sides of the 0.1 Ohm resistor (s ignal probe) with the GND probe at DCIN- and
determine the potential difference.
Ensure that the measured I_VSP value does not exceed the calculated value.
19
High Performance RFM RI-RFM-007B April 1999
Table 7: Electrical Characteristics
Symbol Parameter min. typ. max. Unit
I_VSL Supply current for logic and receiver part in transmit and receive
mode
ViL Low level input vo lt age of T X CT- 0 0.4 0.8 V
ViH High level input voltage of TXCT- 2.4 5.0 V
VoL Low level output voltage of RXDT and RXCK 0 0.4 0.8 V
VoH High level output voltage of RXDT and RXCK 4.0 5.25 V
VoL_R Low level output voltage of RXSS- 0.8 V
VoH_R High level output voltage of RXSS-
(see note below)
Fan-In
I_INTXCTFan-Out Low power Schottky compatible fan-out of signals RXDT and RXCK 3 FanOut_Rl Low power Schottky compatible fan-out of signal RXSS- (low level
FanOut_Rh Low power Schottky compatible fan-out of signal RXSS- (high level
l_J1 Cable length for connecting J1 of RFM to a Con trol Modul e using flat
l_CPS Cable length for c onnecting the Carrier Phase Synchronizati on signal
n_CPS Number of oscillator SLAVE RFMs, which can be driven from one
Com_Mode Common Mode Noise reduction ratio for noise coupled to both
R_GND Decoupling resistor between GND and GNDP (+/- 5%) 64.6 68 71.4 Ohm
Low power Schottky compatible fan-in of signals TXCT- (Iin = -400µA)
Input current for TXCT- signal, when the Accessor y Module RI-ACC-
ATI2 is connected
only)
only)
(see note below)
cable
between two RFMs
oscillator MASTER RFM
antenna terminals ANT1 and ANT2
14 18 22 mA
5.25 V
1-
2.0 2.5 3.0 mA
1-
00.52.0m
01.05.0m
15-
20 dB
Note: RXSS- has an internal pull-up resistor of 10 kOhm. The
parameter VoH_R ther efore depends on application specif ic external
components.
20
April 1999 Specifications
Table 8: Timing Characteristics
Symbol Parameter min. typ. max Unit
t_TX Transmit burst length for correct operation
(see note below)
t_dtck Delay time from beginni ng of data bit at RXDT being vali d to positive
slope of RXCK signal
t_dtvd Time for data bit of RXDT signal being valid after positive slope of
RXCK
t_ckhi Time for clock signal RXCK being high 55
t_ri
t_fi
t_ro
t_fo
t_ro_R Rise time of output signal RXSSt_fo Fall time of output signal RXSS- 1
tss_01Tl Propagation delay tim e from positive slope of TX CT- to positive slope
tss_10Tr Propagation delay time f rom negative slo pe of T XCT - to negati ve sl ope
t_short Maximum time of short circuit between antenna terminals ANT1 and
Necessary rise and fall times for input signal TXCT- and TXCT-R 1
Rise and fall time of output signals RXDT and RXCK 1
(no external connection)
of RXSS- signal (maximum sensitivity)
of RXSS- signal (minimum sensitivity)
ANT2 and short circuit of ANT1 or ANT2 to GNDA
15 50 100 ms
20
90
1
1
1
500 1000 1500
50 100 200
10 s
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
Note: Due to transponder parameters a minimum charge-up time of 15
ms is necessar y. Decreas ing c har ge-u p time decreases read r a nge by
sending less energy to the transponder.
CAUTION: The parameter t_short refers to a static short
circuit of the antenna terminals. Shorting the antenna
terminals during operation may cause permanent damage
to the RFM.
Table 9: Mechanical Parameters
Parameter Typical Unit
Height including mounting bolts 44.0 +/- 1.5 mm
Weight 260 g
Note: The heatsink is connected to the antenna resonator ground
GNDA. When connecting the heats ink to a h ousi ng, the heats ink m ust
be insulated from the housing.
21
High Performance RFM RI-RFM-007B April 1999
2.2 Dimensions
All measurements are in millimeters with a tolerance of +/- 0.5 mm unless
otherwise noted.
57.6 mm +/- 1.0 mm
4.83 mm
+/- 1.0 mm
93 mm +/- 1.0 mm
16.0 mm
+/- 1.0 mm
9.9 mm
+/- 1.0 mm
8.8 mm
+/- 1.0 mm
M3 Pressnuts
71.1mm
70.36 mm
83 mm +/- 1.0 mm
Figure 5: Mechanical Dimensions
22
Chapter 3
Installation
This chapter shows how to install the RFM and specifies power supply
requirements and connections.
Topic Page
3.1 Power Supply Requirements....................................................................24
3.2 Power Supply Connection........................................................................25
23
High Performance RFM RI-RFM-007B April 1999
3.1 Power Supply Requirements
The logic and recei ver sec tio ns of the RF M must be supplied v ia t he VSL a nd G ND
pins with unregulated voltag e.
The transmitter power stage is sep arate l y supplied via VS P and GN DP. As ther e is
no stabilization circuitr y on the RFM and as the transmitter power stage needs a
regulated suppl y voltage in or der to m eet FCC/PT T regulations, the suppl y volt age
for the transmitter power stage must be regulated externally.
For the voltage supply range please refer to Section 2, Specifications.
Note: The RFM should not be supplied by switched mode power
supplies (SMPS) as most SMPS operate at frequencies of ar ound 50
kHz. The harmonics of the generated field may interfere with the
TIRIS receiver and th er ef ore only linear power s up pl ies , or SMPS with
a fundamental operating frequency of 200 kHz or higher are
recommended.
Noise from power supplies or from interface lines may interfere with receiver
operation. It is rec ommended to add additional filter s in series to the supply and
interface lines if required by the app lication. For mor e details refer to App endix 6,
Noise Considerations and Appendix 7, Over Voltage Protectio n.
In order to guarantee full RF M performance, the power supplies s hould fulfill the
specifications for ripple voltage given in Table 10.
Table 10: Power Supply Ripple Specifications
Supply Type Maximum Ripple Voltage Allowable Ripple Frequency
Unregulated VSL supply 30 mVrms 0 to 100 kHz maximum
(sinusoidal)
Regulated VSP supply 50 mVrms 0 to 50 kHz maximum
(sinusoidal)
24
April 1999 Installation
3.2 Power Supply Connection
Ground pins for the logic/receiver part and the transmitter power stage are not
directly connected i nternally, the two different gr ounds having to be co nnected to
each other externally.
The only internal connection is via resistor R_GND, in order to avoid floating
grounds if these grounds are accidentally not connected to each other externally.
This is necessary for two reasons:
1. A high resistivity of the GND P pins could cause a voltage drop across these
pins, due to high transm itter power stage current (this does not apply to the
supply pins of the logic section). If the grounds wer e connected to each other
internally, this would also lift the internal logic ground and cause logic level
compatibility problems with the Control Module (see Figure 6).
2. In order to provide greater flexibility when using long supply lines.
Long VSP supply lines between the RFM and the Control Module cause a
voltage drop acros s this sup ply line ( again d ue to h igh trans mitter power stage
supply current). This voltage drop would also lift the logic ground and cause
logic level compatib ilit y problem s with the C ontro l Modul e. T his can be a voided
by connecting the grounds external ly in any of three different ways (see also
Figure 6) as described below:
• For cable lengths of up to 0.5 m between RFM a nd Control Mod ule, the RFM
ground pins GND and GNDP must be connected at the Control Module, as
shown in Figure 6. The grounds for the VSP, VSL and the Control Module
supply are connected together at a common ground. Alternatively, if the
voltage drop across the VSP su pply line is less than 0.5 V (lik ely in this cas e),
the ground pins GND and G ND P may be connected together at t he RF M.
If the
system has a TIRIS Control Module, the RFM ground pins GND and GNDP are
already connected together correctly on the Control Module. When using a
customer-specific controller, care must be taken to connect the RF M ground
pins GND and GNDP to an appropriate ground on the controller.
• For cable lengths of between 0.5 m and 2 m, the RFM groun d pins GND and
GNDP must be connected together at the Control Module in order to avoid
logic level com patibility problems c aused by the voltage drop ac ross the VSP
supply lines. Connecting the grou nd pins at the RF M is not p erm itted since t his
would lift the logic ground level.
25
High Performance RFM RI-RFM-007B April 1999
• Cable lengths longer than 2 m are not recommended. If the application
demands cabling longer than 2 m, the logic signal connections between the
RFM and the Control Module should be done via a differential interface (for
example RS422). Due to dif f erent gr oun d po tent ials at different loca tions it may
also be necessary to provide galvanic s ep ar ation of the interface sig na ls b y, f or
example, opto-couplers. In this case, to avoid problems with difference
voltages between GND and GNDP, these pins must always be connected
directly at the RFM. As shown in Figure 6, a shorting brid ge is necessary for
this purpose, situated as close as possible to the RFM.
CAUTION: The voltage between GND and GNDP must not
exceed ±0.5 V, otherwise the RFM will suffer damage.
+ VSL+ VSP
Common Ground
TIRIS RF Module
Bridge
VSP 13
Connector ST1
GND 1
GNDP 9
GNDP 7
to TX power stage
to Logic part
Ground Logic
R_GND
Ground TX power stage
Customer Specific Controller
+ Vsupply
Ground
Figure 6: External Ground Connection (GND to GNDP)
26
Chapter 4
Associated Antenna Systems
This chapter discusses antenna r equirements and a ntenna tuning proced ures and
flowcharts.
Topic
4.1 Antenna Requirements.............................................................................28
4.2 Antenna Resonance Tuning.....................................................................29
4.3 Tuning Procedure.....................................................................................30
Page
27
High Performance RFM RI-RFM-007B April 1999
4.1 Antenna Requirements
In order to achieve high voltages at the antenn a resonance circuit and t hus high
field strength at the antenna for the c harge-up (trans mit) function, the antenna coil
must be high Q. The recomm ended Q factor f or proper operation is listed in T able
11, Antenna requirements. The Q fac tor of the antenna may vary depending on the
type, the construction and the size of the antenna. Furthermore, this factor
depends on the wire type and wire cross-sectional area used for winding of the
antenna.
RF braided wire, consisting of a number of small single insulated wires is
recommended for winding of an antenna since it gives the highest Q factor and
thus the highest charge- up field strength, for example si ngle wire diameter of 0.1
mm (4 mil) and 120 single insulated wires.
Note: If a high Q is not required (for example for large in-ground
antennas), standard braided wire can be used.
In order to ensure that t he transmitter and rec eiver function correctly, the antenna
must be tuned to the resonanc e frequenc y of 134. 2 kHz. For a detai led descr iption
of the antenna resonance tuning procedure, refer to Chapter 4.2, Antenna
Resonance Tuning.
To ensure that the ant enna can be tun ed to resonanc e with the RFM, the antenna
inductance can only vary within the limits given in Table 11.
Table 11: Antenna Requirements
Parameter Conditions min. typ. max. Unit
L_ANT Antenna inductanc e range within whic h the anten na can
be tuned to resonance
Q_ANT Recommended Q factor of antenna coil for correct
operation
Note: Although a ferr ite core antenn a ma y have a high Q f actor und er
test conditions with low magnetic field strengths, the Q factor
decreases when a hi gh magnetic f ield str ength is app lied t o the ferrite
core.
26 27 27,9
40 450 -
µH
WARNING: Care must be taken when handling the
RFM. HIGH VOLTAGE across the antenna terminals
and all antenna resonator parts could be harmful to
your health. If the antenna insulation is damaged the
antenna should not be connected to the RFM.
28
April 1999 Associated Antenna Systems
When low field strength for larger antennas is necessary (Vpeak <60 V), the
antenna resonator can additiona lly be damped b y connectin g an on board damping
resistor, which m ay be done by closing jumper JP3 (see F igure 3). T his jumper is
open by default.
CAUTION: Only a certain maximum antenna resonance
voltage is allowed for this option. Please refer to Chapter
2.1, Recommended Operating Conditions, for details.
Note: The transform er of the transmitter power stage is operated at a
high magnetic flux. Due to the high level of m agnetic flux change, the
transformer may emit an audible tone. This may also occur with
antennas that have f errite cores (e.g. TIRIS Standar d Stick Antenna
RI-ANT-S02). This tone does not indicate a malfunction.
4.2 Antenna Resonance Tuning
In order to achieve a high charge-up field strength, the antenna resonator
frequency must be tu ned to t he tr a nsmitter frequency of 13 4.2 kHz. This is done by
changing the capacitance of the antenna resonator.
To compensate for the tolera nces of the antenn a coil an d the c apacit ors , six bi nary
weighted tuning capacitors (C_ATC1 to C_ATC6) have been included. Their values
are weighted in steps of 1, 2, 4, 8, 16 and 3 2, where C_ATC1 has the smallest
value correspond ing to the factor 1, C_ATC2 has double the capacity of C_ATC1,
so that C_ATC2 corresponds to the factor 2 and so o n. Each of the 6 tuning pi ns
has an adjacent ground pin for antenna tuning, using shorting bridges (jumpers).
Monitoring of the correct antenna resonance tuning can be performed using the
Antenna Tuning Indicator (ATI) tool RI-ACC-ATI2.
This device allows the transm itter to b e operate d in pulsed mode, in depend ently of
the Control Module. It indicates by LEDs whether the tuning capacity should be
increased or decreased (marked on the ATI as IN for increase and OUT for
decrease) and when the antenna is tune d to resonance, in which case the green
LED is on or flashing together with the IN or OU T LED. T he device is p lugged into
the RFM connector J2 during the tuni ng procedure, power be ing sup plied from this
module.
29
High Performance RFM RI-RFM-007B April 1999
The following notes refer to antenna resonance tuning in general:
Note: If an antenna has to be install ed in an e nvironm ent where m etal
is present, the tuning of the antenna must be done in this
environment, since the presenc e of metal changes the inducta nce of
the antenna. In addition, the Q factor of the antenna decreases,
thereby decreasing the field strength. The extent of the inductance
and quality factor red uc tio n depe nds on the kind of metal, the dis ta nc e
of the antenna from it and its size.
When the oscillator signal puls e width, or the supp ly volta ge VSP of a
RFM with a pre-tuned fer rite core antenna (f or exam ple: RI-ANT-S0 2)
is changed by a factor of more than 50% , the fer rite core ante nna has
to be re-tuned to the ne w conditions due to t he inductance ch anging
slightly at different field strengths.
Each antenna is tuned individually to the RFM and this results in a
unique tuning jumper arrangement for this combination of antenna
and RFM.
If a different antenna or RFM is connecte d, the ne w combinat ion mus t
be tuned to resonance again.
4.3 Tuning Procedure
1. Switch RFM power supply off.
2. Connect the antenna to the RFM by means of the two M3 screw connectors.
3. Install antenna tuning monitoring unit.
4. Switch RFM power supply on.
5. Tune antenna to resonance by changing the tuning capacity.
6. Switch RFM power supply off.
7. Disconnect monitoring unit.
8. Switch RFM power supply on again.
The antenna resonance tuning is now complete.
The tuning of a new antenna to the RFM is started with no jumpers (shorting
bridges) connected. While monitoring th e reson ance c ond ition as desc ribed abov e,
the jumpers are plugge d in or out, thus connecting and disc onnecting the tuning
capacitors in such a way that the total tu ning capacit y will increase in steps of the
smallest capacitance C_ATC1.
30
April 1999 Associated Antenna Systems
Counting-up of the binary weighted tuning capacitors is in principle done in the
following way:
1. No jumpers connected.
2. connect C_ATC1 (J3 pins 1 and 2).
3. disconnect C_ATC1 and connect C_ATC2.
4. Connect both C_ATC1 and C_ATC2 (and so on).
However, the tuning steps do not offer an absolutely continuously increasing
function, due to component toler ances. It is t heref ore poss ible that when the tun ing
value is increased by one binar y step the total tuning capacity actua lly decreases
(especially from tuning step 31 to 32), which can result in the generated field
strength not steadily increasi ng (as shown in Figure 7). This is not the c ase when
using the Antenna Tuning Indicator tool (ATI) since the indicated resonance
condition is always correct.
It is therefore recommended to perform resonance tuning according to the flowchart shown in Figure 8.
50
45
40
35
30
25
20
15
10
Tuning capacity
Field strength
5
0
1 4 7 101316192225283134374043464952555861
'false' resonance
point
Decimal value of tuning step
correc t resonance
point
Figure 7: Tuning Example showing Increase of Total Tuning Capacity
and Generated Field Strength (typical values)
31
High Performance RFM RI-RFM-007B April 1999
START
CONNECT ANTENNA TO THE RF MODULE
DISCONNECT ALL JUMPERS
CONTROL CURRENT INTO VSP PIN
INCREASE TUNING CAPACITY BY ONE BINARY STEP
CONTROL CURRENT INTO VSP PIN
MEASURED
No
VALUE HAS DECREASED IN
COMPARISON TO THE
PREVIOUS TUNING VALUE
Yes
INCREASE TUNING CAPACITY BY ONE BINARY STEP
CONTROL CURRENT INTO VSP PIN
MEASURED
No
DECREASE TUNING VALUE BY TWO BINARY STEPS
PLUG IN JUMPERS FOR TUNING THIS ANTENNA TO
VALUE HAS DECREASED IN
COMPARISON TO THE
PREVIOUS TUNING VALUE
Yes
THIS RF MODULE
STOP
Figure 8: Flow-chart for Tuning the Antenna to Resonance
32
Appendix 1
Expanding Antenna Tuning
Inductance Range
It is possible to expan d the tuning range of the ante nna inductance. T his may be
necessary when TIRIS stand ard antennas are used close to metal, when antenna
extension cables are used or when custom er s pecific ante nnas whic h might not be
within the necessary antenna tuning inductance range are used.
Note: Please remember that the c apacitors of external m odules have
to be able to withstand higher voltages when used together with a
RFM.
Expanding the ante nna tuning inductance range t o lower or higher valu es can be
done by connecting a dditional capacitors in parallel and in series to the antenna
resonator.
The capacitors have to be connecte d in paral lel and in seri es in order t o withstand
high voltages and currents occurring at the antenna resonance circuit.
WARNING: There is HIGH VOLTAGE present at all
antenna resonator components, which may be
harmful to health. The RFM must be switched OFF
while working on it. External components must be
mounted such that they cannot be accidentally
touched.
To ensure that the RFM functions correctly when the antenna tuning inductance
range is expanded, special capacitors, as listed below, must be used:
Capacitor type: - Polypropylene film capacitor
- Minimum 1250V DC operating voltage
- Capacitance tolerance: max. ±5%
- Type: SIEMENS "KP" or WIMA "FKP1"
33
High Performance RFM RI-RFM-007B April 1999
•
The antenna tuning in ductance range can be decreased to 13. 7 µH in six ranges,
as shown in Figure 9 and Table 12.
Figure 9: Circuit for Expanding Antenna Tuning Range to Lower Values
••
ANT 2
C1
C3
•
ANT 1
Table 12: Capacitor Values for Expanding Antenna Tuning Range to Lower
Values
Antenna inductance range Capacitor value
24.1 µH to 25.9 µH
22.3 µH to 24.0 µH
20.4 µH to 22.2 µH
18.4 µH to 20.3 µH
16.5 µH to 18.3 µH
13.7 µH to 16.4 µH
The antenna tuning inductanc e range can be increase d to 37.6 µH in 7 ranges, as
shown in Figure 10 and Table 13.
As shown, three capacitors (C1, C2, C 3) are connecte d in series with th e antenna
coil. The specification for these capacitors is listed below:
Capacitor type: - Polypropylene film capacitor
- Minimum 1250 VDC operating voltage
- Capacitance: 47 nF ±2.5%
- Type: SIEMENS "KP" or WIMA "FKP1"
C1, C2, C3, C4 = 3.3 nF
C1, C2, C3, C4 = 6.8 nF
C1, C2, C3, C4 = 11 nF
(10 nF and 1 nF in parallel)
C1, C2, C3, C4 = 16 nF
C1, C2, C3, C4 = 22 nF
C1, C2, C3, C4 = 32 nF
C2
C4
•
•
In addition to C1, C2 and C3, the capac itor C4 must be connected in para llel to th e
RFM antenna terminals. Different capacitor values are used for each range, the
values being given in Table 13.
34
April 1999 Appendix 1
•••••
ANT 2
C4
ANT 1
Figure 10: Circuit for Expanding Antenna Tuning Range to Higher Values
Table 13: Capacitor Values Expanding Antenna Tuning Range to Higher
Values
(C1, C2 & C3 = 47 nF)
Antenna inductance range Capacitor value
28.0 µH to 29.3 µH
29.4 µH to 31.0 µH
31.1 µH to 32.4 µH
32.5 µH to 33.8 µH
33.9 µH to 35.0 µH
35.1 µH to 36.2 µH
36.3 µH to 37.6 µH
Two serial connected TIRIS standard antennas C4 = 3.3 nF
•
C1
•
C4 = 18.3 nF
(parallel 6.8 nF, 6.8 nF, 4.7 nF)
C4 = 13.6 nF
(parallel 6.8 nF, 6.8 nF)
C4 = 10 nF
C4 = 6.8 nF
C4 = 3.98 nF
(parallel 3.3 nF, 0.68 nF)
C4 = 2.2 nF
C4 not needed
C2 and C3 not needed
C2
•
C3
•
•
Note: It is not recommended to use antennas with Q factors lower
than 50. Antennas with inductanc es lower than 13.7 µH or more than
37.8 µH should not be used except when co nnecting two ant ennas in
series since the additional capacitor values become very large.
Antennas with fewer turns (i.e. smaller inductance) generate less
charge-up field stre ngth under the same operating c onditions and in
addition also have less receive sensitivity. Using capacitors parallel to
the antenna resonator c hanges the coupling of the RFM 's transmitter
power stage thus reducing the generated field strength.
In order to avoid adaptation problem s, it is strongly recommended to
use standard TIRIS antennas.
35
Appendix 2
Field Strength Adjustment
The magnetic field strength generated determines the charge-up distance of the
transponder. The higher the magnetic field strength, the further the transponder
charge-up distance. T he charge-up distance does not, h owever, increase linearly
with the field strength.
The reading distance of a tr ans p ond er is d eter mined, amongst other f ac tors , by the
charge-up distance and the local noise level. Increasing the charge-up field
strength does not necessaril y increas e the read ing distan c e.
The field strength generated by the RFM depends on the four factors listed below:
1. Q factor of the antenna.
The Q factor is a m eas ure of the ef f iciency of the ant enna a nd t herefor e th e h igher
the Q factor of the antenna coil, the higher the field strength generated by the
RFM, assuming that all other parameters remain unchan ged. The Q factor of the
antenna itself depe nds on the cross-sectional area of the wire, the wire type, the
size of the antenna and the type of antenna (gate or ferrite). The lar ger the crosssectional area of th e RF braided wire, the higher the Q factor of the antenn a. RF
braided wire gives a higher Q factor than solid wire assuming that all other
parameters remain unchanged.
2. Size of the antenna.
The larger the antenna, the higher the field strength which is generated by the
RFM, since the antenna covers a larger area and thus generates a higher flux
assuming that all other parameters remain unc hanged. Large antennas have les s
immunity to noise for receive functions than small antennas.
37
High Performance RFM RI-RFM-007B April 1999
3. Supply voltage of the RFM power stage.
The higher the supp ly voltage of the RFM transmitter power stage (VSP v oltage),
the higher the field str ength which is gener ated by the R FM ass um ing that a ll other
parameters remain unchanged. However, the generated field strength does not
increase linearly with VSP supp ly voltage. In addition, ferrite c ore antennas show
saturation effects (saturation means here that the ferrite core cannot generate
more magnetic field strength, even with a higher input current).
4. The oscillator signal pulse width.
The bigger the selected transmitter oscillator signal pulse width, the higher the
magnetic field strength whic h is generated by the RFM, since m ore power is fed
into the antenna resonator b y the transmitter power stage as suming that all other
parameters remain unchanged.
The generated field strength can be measured in several ways. It may be
measured using a calibrated field strength meter or by measuring the antenna
resonance voltage using an oscilloscope and then calculating the field strength.
In summary: the generat ed field strength of an antenna c an be adjusted with the
supply voltage VSP of the RFM transmitter power stage and by selecting the
corresponding oscillator signal pulse width.
In cases where low field stren gths should be generated with large an tennas (RIANT-G01 and RI-ANT -G03), the ant enna res onator can be add itional ly dam ped b y
closing jumper JP3.
Using this optional dam ping f unc ti on a llows the field strength t o be ag ai n f ine- tu ned
to meet FCC/PTT regulations with select ion of the os cilla tor signa l pulse width in a
wide range of both larger and smaller values.
CAUTION: This damping option can only be used together
with the TIRIS standard antennas RI-ANT-G01 and RI-ANTG03. Only a certain maximum antenna resonance voltage is
allowed for this option. Please refer to Section 2.1,
Recommended Operating Conditions, for details.
Note: For correct adjustm ent of field strength according to FCC/PTT
values, especiall y for customized antenn as, a calibrated field strength
meter must be used. Field strength measurements must be taken on a
free field test site according to VDE 0871 or equivalent regulation.
38
Appendix 3
Adjustment of Oscillator Signal
Pulse Width
The RFM has an built-in feature to allow setting of the pulse width of the transmitter
signal coming from the oscillator . This enables the generated field s trength to be
reduced from 50% down to 0%.
For this purpose a p ulse width setting resistor may be ins erted between J4 pins 3
and 4 on the RFM. Inser ting a smaller resistance valu e decreases the pulse width
and thus also the field streng th. As d efault, no res istor is connecte d, thus s electing
the maximum pulse width of 50% and t he m axim um field strengt h. B y connec ting a
shorting bridge, the smallest pulse width of approximately 0% is selected.
Table 14 provides an overview of oscillator s ignal pulse width a nd corresponding
field strength reduction when dif fer ent oscilla tor si gnal p ulse widths are se lecte d b y
connecting different resistor val ues.
39
High Performance RFM RI-RFM-007B April 1999
Table 14: Oscillator Signal Pulse Width versus Resistor Value (estimated
values)
Resistor value
ΩΩΩΩ
[k
]
open 50 0
151 37 -3
59 25 -6
17 12 -12
10 6 -18
shorted 0
Oscillator signal
pulse width [%]
Field strength
reduction [dB]
∞
CAUTION: When using pulse widths smaller than 50%, the
RFM transmitter power stage works less efficiently. This
leads to an increased power dissipation and thus to a
higher temperature of the transmitter power stage. Ensure
that the antenna resonance voltage does not exceed 200
Vp when the selected oscillator signal pulse width setting
is smaller than 25%.
Note: The pulse width for an oscillator s ignal puls e width se tting of 5%
and smaller is extremely short. The pulse response of the RFM
transmitter power stage to this short puls e is differ ent for each uni t. In
order to have reproducible field strength values for different RFMs, it is
not recommended to use the smallest pulse width setting.
40
Appendix 4
Threshold Level Adjustment
The RFM has a built- in receive signa l field strength detector with the o utput signal
RXSS- and an on-boar d potentiom eter (R409) to ad just the thr eshold le vel of f ield
strength detection. The digital output RX SS- is used f or wir eless s ynchronizati on of
two or more reading units. This is necessary to ensure that if more than one
reading unit is in an area, they do not interfere with e ac h othe r. The Control Module
software monitors the RXSS- signal to detect whether other reading units are
transmitting. The Control Mo dule can op erate the transm itter of the RFM such that
the reading units either transm it simultaneousl y or alternatel y. In this way the rea d
cycles of each of the reading units occur at th e same time or at secure different
times. Depending on the antenna type used an d the local noise lev el, the RXSSthreshold level has to be adjusted. This needs to be done after the antenna has
been tuned to resonanc e. It is recommended t o use a small scr ewdriver to adjust
the RXSS- threshold l evel. The R409 potentiometer is located o n th e up per si de of
the RFM board near con nector switch SW 1. Turning the pot entiometer al l the way
clockwise (right-hand stop) , results in minim um thres hold sens itiv it y, i.e. the RX SSsignal will be activated at high receive field strength. This is the default position and
can be used for standard gate antennas. It may be necessary to increase the
sensitivity when using ferrite core antennas. If there is high no ise level in the area,
it is necessary to adjust the RXSS- threshold level.
Adjust the RXSS- threshold level as follows:
1. Turn the RXSS- thres ho ld le ve l p oten tiometer fully coun ter- cloc kwise (left-hand
stop).
2. Deactivate the transmitter by jumpering pin 1 to pin 3 of connector J2.
3. Ensure that no other reading units are tr ans mitting, by connecting p in 1 to pi n 3
of connector J2 (jumper) of all other RFMs in the area.
4. Monitor the voltage at RXSS- output pin with a voltmeter or an oscilloscope.
41
High Performance RFM RI-RFM-007B April 1999
5. Turn the RXSS- threshold level adjustment potentiometer on the RFM
clockwise, until the RXSS- o utput is just statically inactiv e. "Statically" means
no voltage spikes present on the RXSS- signal. 'Inactive' means that the
receive signal str ength is below the RXSS- t hreshold level and n ot triggering
RXSS- (the RXSS- output voltage remains > 4 V).
6. Remove all jumpers connected to J2
Note: Reducing the RXSS- threshold level sensitivity (turning the
potentiometer clock wise), reduc es the sens itivity of the built-in receive
signal strength detector. This has the effect that the distance for
wireless detection of other transmitting reading units is decreased,
leading to reduction of wire les s synchronization distanc e. The wireless
synchronization dis tance between two r eading units is norm ally about
15 meters for two aligne d stic k antennas (RI-ANT -S02) with m ax imum
receive field strength detection sensitivity.
When the RXSS- threshold level is adjusted such that it is too
sensitive, then the RX SS- output is constantl y active (i.e. low RXSSoutput level). Therefore a Control Module assumes that another
reading unit is trans mitting and continua lly tries to synchron ise to this
other reading unit. As a result, the r eading repetition rate decreases
from approximatel y 10 down to 5 readings per second. This read ing
unit can additionally no longer synchronise to other reading units,
causing interference with other reading units and reading at all
reading units becomes impossible.
The RXSS- threshold level must be adjusted individually for every
RFM and reading system antenna. In addition, the RXSS- threshold
level must be individually adjusted to the local noise level in the
application area where the antenna is used.
As high noise levels mean that the RXSS- threshold level must be
adjusted to a less sensitive value, it is recommended to reduce the
local noise level in or der to have high synchro ni zat io n s ens it i vity and a
long reading distance.
The RXSS- threshold level must be adjusted so that no spikes oc cur
on the RXSS- signal output since these lead to an incorrect
synchronization function. An oscilloscope should therefore be used
when adjusting the threshold level.
The Antenna Tuning Ind icator (RI-ACC-ATI2) acces sory can be used
to adjust the RXSS- threshold level, since this device automatically
switches the transm itter off and has an intern al spike extens i on c irc uit,
causing the RXSS- threshold leve l to be adjusted such that no spik es
occur on the RXSS- output.
42
Appendix 5
Transmitter Carrier Phase
Synchronization (CPS)
In some applications it is necessary to use several charge-up antennas close to
each other. Under thes e circumstances, the magnetic charge-up fields ge nerated
by different antennas superim pose on each other and m ay cause a beat ef fect on
the magnetic charge-up field, due to the slightly different transmit frequencies of
different RFMs.
The impact of this effect depends on three factors:
1. Antenna size:
The larger the size of the antennas, the further the distance between the
antennas must be, so that this effect does not occur.
2. Magnetic field strength:
The stronger the generated magnetic field strength, the further the distance
between the antennas must be such that the effect does not occur.
3. Orientation and distance between antennas:
Increasing the distance between antennas decreases the impact of this effect.
Note: Putting two antennas close together also changes antenna
inductance, so that the antennas may no longer be tuneable to
resonance.
43
High Performance RFM RI-RFM-007B April 1999
If several antennas are used close to each other, a check should be made to
determine if the char ge-up field strength ch anges regularly (i.e. bea t effect ). This
may be checked by verif ying the antenna reso nance voltage wit h an oscilloscope.
If the antenna reson ator voltage changes periodicall y by more than approxim ately
5% of the full amplitude it is appropriate to use wired transmitter carrier phase
synchronization.
In addition, the distances given in Table 15 can be used as a guideline to
determine when it is necessary to cross-check for beat effect. If these distances
are less than the va lue given in Table 15, a c heck f or beat ef fect s hould be m ade.
The values given refer to the distances shown in Figure 11 and are valid for
maximum charge-up field strength.
Distance D1
Antenna 1
Figure 11: Distance between Antennas (top view)
Table 15: Maximum Distances between Antennas
Antenna type Distance D1 [m] Distance D2 [m]
RI_ANT_S02 <=> RI_ANT_S02 0,8 1,0
RI_ANT_G01 <=> RI_ANT_G01 1.7 1.5
RI_ANT_G02 <=> RI_ANT_G02 1.3 1.0
RI_ANT_G04 <=> RI_ANT_G04 2.0 1.7
This effect will not occur if the tr ansm itter s of diff erent RF Ms are op erate d f rom the
same oscillator sig nal. T his is the re ason wh y the pu lse width m odulate d os cilla tor
signal is accessible at the connector J1.
Configuration
Antenna 2
Antenna 1 Antenna 2
Distance D2
Master or Slave sett ing of a RFM is deter mined by switch 1 p osition 1 (SW 1/1). If
this is in the ON position, the RFM is a MASTER, if in the OFF position, it is a
SLAVE. When a RFM has been configured as a m aster, then J 1 pin 12 of th is unit
should be connected t o J1 pin 16 of the slave units to allow the master oscillator
output (CPS_OUT) to drive the slave oscillator inputs (CPS_IN). The lo gic ground
(e.g. J1 pin 1) of both master and slave units should be connected together.
Caution: Use overvoltage protection components at the
CPS connector for CPS lines between 0.5m and 5m.
44
April 1999 Transmitter Carrier Phase Synchronization
Note: When using the transmitter Carrier Phase Synchronization
feature, it is absolutely nec essary that the read cycles of each of the
different Control Modules are synchronized. When the transmitter of
the oscillator MASTER RFM is not activated b y its Co ntrol Mo du le, t he
oscillator signal output of the oscillator MASTER RFM is disabled.
This means that all the oscillator SLAVE RFMs have no transmitter
oscillator input signa l an d thus no ne of the os c illa tor S LA V E RFMs ar e
able to transmit.
The read cycles of all RF Ms c on nec te d to this C P S i nterf ac e must be s ynchroni zed
and all read cycles must occur simultaneously. Refer to the Hardware and
Software Manuals for the TIRIS Control Modules for more information about the
necessary wiring and settings for synchronization of the RFM when using
transmitter Carrier Phase Sync hronization (CPS). If an application requires more
than one RFM to be used , or a longer Carrier Phase S ynchroni zatio n line th an t hat
specified in chapter 2, Specifications, must be used, it is necessary to drive the
pulse width modulated oscillator signal via a differential interface such as an
RS422 interface.
45
Appendix 6
Noise Considerations
Noise can have a negative effect on t he receive performance of the RFM. There
are two different k inds of noise: radiated and co nducted. Their character istics are
shown in Table 16.
Table 16: Characteristics of Radiated and Conducted Noise
Radiated Noise Conducted Noise
Source Inductive parts for example:
deflection coils, motor coils.
Path Via magnetic fields. Galvanically conducted via all cables (supply
Effect Disturbs receive function by
magnetic interference with signal
from transponder at the antenna.
Power units, for example: motors, switched
mode power supplies. Ca n be seen as voltage
spikes or ripple voltage.
and interface) connected to the RFM.
Leads to malfunc tion and reduced sensiti vity of
receiver circuitr y due to, for example, interfer ed
supply voltage.
Conducted noise can also cause radiated noise.
Method for detecting and distinguishing between noise types:
The principle of this pr ocedure is to el iminate a ny conduct ed noise from the supply
and all interface lines. In order to do t his test the RFM must be powered fr om a
battery (for example: 9 V, 20 m A) in order t o elim inate an y conducted n oise fr om a
power supply. Conducted nois e via the interfac e lines is eliminated f or this test b y
simply disconnecting all inter face lines to the RFM. The meas urement criteria for
low noise is the amplitude of the receive signal strength detector of the RFM.
The test pin RSTP at connector J1 pin 10 carries an analog output voltage
indicating the receive signal strength. This voltage should be measured in
combination with the antenna RI-ANT-G02. The necessary set-up for this test is
shown in Figure 12. This configuration operates the RFM from a battery and has no
interface line conn ected. As the transmitter is switched off in this configuration, a
normal battery may be used. A low noise level is indicated by an RSTP voltage of
less than 1.0 VDC when using antenna RI-ANT-G02.
47
High Performance RFM RI-RFM-007B April 1999
Note: Both noise types can be either differential or common mode
noise. Use common mode noise filters (for example: a BALUN
transformer) to reduce c ommon mode noise and use selecti ve filters
to reduce differential noise.
The following procedure for testing for noise impact should be im plemented when
the normal set-up for the RFM and antenna gives bad reading distances, even
though the antenna is correctly tuned for sufficient transponder charge-up.
Try the configuration shown in Figure 12. If this configuration shows bad noise
conditions (RST P voltage more than approxim ately 1.0 VDC) then the problem is
radiated noise.
Eliminate noise sources or try special antennas (e.g. noise-balanced antennas).
1. When the configuration of Figure 12 shows good noise conditions (RSTP
voltage less than 1.0 VDC) then the problem is conducted noise.
2. Change the conf igurat ion so that the interf ace lines are again c onnected to t he
RFM with the transm itter still switched off. If the RSTP voltage now in dicates
bad noise conditions, the conducted noise is coming via the interface lines.
3. T ry to el im inate the n oise on the interf ace lin es. See App endix 7, Over Voltag e
Protection.
4. When the configuration above (interface lines connected) shows good noise
conditions (RSTP voltage les s than 1.0 VDC), then the prob lem is conducted
noise via the supply lines.
5. Try to eliminate the noise on the supply lines. S ee Appendix 7, Over Volta ge
Protection.
RSTP
J1
VSP 13
•
VSP 11
•
GNDP 9
•
VSL 3
•
GND 1
10
7
ANT 2
ANT 1
TIRIS standard
antenna
RI-ANT-G02
Figure 12: Noise Testing Configuration
48
Appendix 7
Over Voltage Protection
For applications where there is a risk that volt age spik es and nois e are o n th e line s
to the RFM, additional protection circuitry and filters must be added.
A proposal on how this may be achieved is shown in Figure 13, and this circuit may
be used as a guideline for protection circuitry. This may not be sufficient for all
applications, however, and must be checked individually when necessary.
1. The supply input has to be protected against voltage spikes. R1 and D1 fulfil
this purpose. Zener diode D 1 clamps the voltage sp ikes to 18 volts so that the
maximum allowed transmitter power stage supply voltage is not appreciably
exceeded. For diode D1, type ZY18 is r ecommended, this type ha ving a 2 W
power dissipation. If a hig her c urr ent is n eed ed, dump type ZX18 ma y be used,
this diode having a 12.5 W power dissipation.
2. The Common Mode Choke Coil and the capacitors C1 and C2 are used to
reduce the conducted noise coming to the RFM via the supply lines.
3. All input and outpu t signals should be pr otected with 5.6 V zener diodes. The
specified type can dump 1.3 W.
4. The coils L1 to L6 are ferrite beads a nd should put in series to t he line when
conducted noise is observed ent er in g via the in terf ac e lines .
5. T he varistor V1 protec ts the a ntenna c ircu it aga inst high volt age in duced at the
antenna coil, for example by light ning. The type of varistor given is comm only
available but may not be sufficient for protection in all cases.
Note: The zener diodes types given in Figure 13 are com monly used
types, not special suppresser diodes for fast voltage spike
suppression. If the app lication requires it, special suppresser diodes
should be used.
49
High Performance RFM RI-RFM-007B April 1999
Figure 13: Circuit for Overvoltage Protection
All components must be mounted close to the RFM with the shortest possible
wiring
C1: 100 nF Ceramic R1: 1 Ohm / 2W V1: Varistor 420V
e.g Siemens S10V520K420
C2: 100 µF low ESR
CHOKE: Common
Mode Choke Coil
L1, L2, L3, L4, L5, L6:
Ferrite beads
R2, R3, R4, R5, R6, R7:
22 Ohm / 0.25W
D1: ZY18 resp. ZX18
D2,D3, D4, D5, D6, D7:
BZX85C5V6
50
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