103510-rf amplifier for nxp contactless reader ic's
TRANSCRIPT
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
1/21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
2/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
AN103510 NXP B.V. 2007. All rights reserved.Appl ication note Rev. 1.0 01 June 2007 2 of 21
Contact information
For additional information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Revision history
Rev Date Description
1.0 01.06.2007 Initial Version
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
3/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
AN103510 NXP B.V. 2007. All rights reserved.Appl ication note Rev. 1.0 01 June 2007 3 of 21
1. Introduction
The aim of this document is to provide a solution to increase the RF output power of NXP
contactless reader ICs. The RF amplifier system described in this application note
provides linearity and allows the use of different modulation indexes. Moreover, it
supports a wide bandwidth and its power added efficiency is greater than 30%.
The RF amplifier circuit is designed for following NXP contacless reader ICs: SLRC400
[1], MFRC500 [2], MFRC530 [3], MFRC531 [4] and CLRC632 [5].
1.1 How to use this document
Section 2 shows the necessary blocks of the RF amplification system. Each of these
blocks is briefly explained in section 3. Section 4 contains a schematic of the overall
amplification system and some hints of how to develop an appropriate PCB. Section 5
shows how an external amplification circuitry can improve reader characteristics.
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
4/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400RF Amplif ier for NXP Contactless Reader IC's
2. RF Amplification System
The block diagram in Fig 1 shows the complete RF amplifier system placed between theNXP contactless reader IC and the antenna. The system consists of a transmitting path
(blue) and a receiving path (red).
(1) This solution implements an active amplifier and filter for the receiver part
Fig 1. Block Diagram of RF Amplifier Solution
RF Power A/BAmplifier
MFRC500MFRC53xCLRC632SLRC400
TX1
TX2
RX
EMC-Filter
MatchingNetwork
Amplifier
OA 2
13.56 MHz
Band-Stop FilterBuffer
OA 1
EMC-Filter
RF Power A/B
Amplifier MatchingNetwork
ANTENNA
The main part of the RF amplifier stage in the transmitting path is built around a class
A/B RF amplifier working in a four-quadrant operation. It delivers the amplified current to
the antenna to generate a higher magnetic field.
A filter network before this RF amplifier stage acts as an EMC filter in order to attenuate
higher frequency components to form a sinusoidal waveform out of the square wave
signal coming from the contactless reader IC.
The receiver path is also accomplished by two parts, consisting on a 13.56 MHz
oscillator and a dual operational amplifier (OA). The oscillator acts as a band-stop filter
which decreases the 13.56 MHz carrier, such that the sideband levels can be better
amplified by the amplifier OA 2. OA 1 acts as a buffer amplifier which decouples the
signal from the antenna to the band-stop filter.
2.1 EMC Filter
The NXP contactless reader IC offers the output pins TX1 and TX2 which deliver square
wave signal shapes, where TX2 is phase delayed for 180 compared to TX1. These
signals are converted to sinusoidal waveforms by the EMC filters.
The EMC filter is directly connected to GND and TX1 and to GND and TX2 of the NXP
contactless reader IC. It consists of a series inductance and a parallel capacitance as
shown in Fig 2.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 4 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
5/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
NOTE: The amplitude of the signal will be increased because of the resonance effect of
the filter. This is desirable since it is the input signal for the A/B power amplifier. The
amplification of the voltage does not solely depend on the values for the coil and the
capacitor but also on the value of the input impedance of the A/B power amplifier. When
a 12V power supply is used, the peak-to-peak value for this signal must not exceed 10Vto prevent chipping.
1 2
L01
1 2
L02
C01
C02
TX1
TX2
GND
V1
V2
ZIN1
ZIN2GND
Fig 2. EMC Filt er
The filter is a low pass filter with a cut-off frequency of about 15MHz, which transforms
the rectangular signals coming from TX1 and TX2 into sinusoidal signals. The value of
the parallel capacitor is calculated with a predefined value for the cut-off frequency and
the coil.
Lf
C
g
=2
)2(
1
Assuming a value of 560nH for the inductor and 15.8MHz for the cut-off frequency the
required capacitance is determined to be 181pF.
( )pFC 181
10560108.152
1
92601 =
=
Table 1. Components of EMC Filter
Component Value
C01, C02 Typically 0402, 0603 or 0805 SMD parts with low tolerance (< 2%).NPO is required. The voltage limit has to be considered.
L01, L02 Typically a small inductance with high Q for general applications.The frequency range and the maximum allowed current have to be
considered. This inductance should be magnetically shielded.
NOTE: Please refer to the application note [6] for details.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 5 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
6/21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
7/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
AN103510 NXP B.V. 2007. All rights reserved.Appl ication note Rev. 1.0 01 June 2007 7 of 21
The collector currents of 2N3904 (NPN) and 2N3906 (PNP) transistors used in this
application are limited to 200mA. Thats why four of them are connected in parallel for
each stage, to increase the overall output current and withstand shorts and open loops.
Table 2. Components of A/B Power Ampli fier
Component Value
C1C4 DC blocker, 100nF; (Ceramic NP0, tolerance 2%)
RE1RE4 330(Small 0402, 0603 or 0805 SMD parts)
R1R16 47(e.g. MRS25, 0.6W)
D1D4 1N4007
Q1Q4,Q13Q16
2N3904 NPN Transistors or equivalent
Q5Q12 2N3906 PNP Transistors or equivalent
VCC 12V Power supply
2.3 Antenna Design & Matching
The sample antenna used in this application note is shown in Fig 4. The outline of therectangular antenna is approximately 10cm x 10cm. In order to match the antenna to
desired impedances some calculations for external passive components have to be
made.
The antenna must be connected to a network analyzer by using an appropriate test
fixture that does not influence the antenna parameters. The analyzer must be calibrated
(open, short and load calibration) and the test fixture compensated (electrical delay)
according to the instrument manual before each measurement.
Settings on the network analyzer:
S11, Chart: Smith Z
Start frequency: 1MHz
Stop frequency: above self-resonance frequency of the antenna
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
8/21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
9/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
At an operating frequency of 13.56MHz the skin effect has an impact on the system and
further calculations. The k-factor, which stands in relation to carrier frequency and self-
resonance frequency, is introduced to correct the results.
32.11056.13
1075.236
6
0
=
==
f
fk res
Thus, the parallel equivalent resistance is determined to be:
=== 5.9417101345.732.1' 3PP RkR
The Q-factor of the antenna is either calculated by the series equivalent resistance Rsorby the parallel equivalent resistance Rp.
A
P
S
A
L
R
R
LQ
=
=
'
( ) ( )=
=
=
178.15.9417
102364.11056.132
'
2662
P
A
SR
LR
The total series equivalent resistance is calculated by adding the DC resistance to the
series resistance RS:
=+=+= 367.1178.1189.0SDCA RRR
1
2
LA
RA
CA
A
B
Fig 6. Series equivalent circu it
89.77367.1
102364.11056.132 66=
=
=
A
A
R
LQ
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 9 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
10/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
A Q-factor of 78 for the sample antenna is too high for proximity reader applications. A
range of 8 to 15 is recommended in order to meet the ISO/IEC 14443-2 (2000) [7]
specification and to achieve best results for high data rate operations. Therefore, an
additional external damping resistor has to be added:
=
=
=
8.11367.18
102364.11056.132 66A
AExtern R
Q
LR
NOTE:For a symmetrical antenna the values of the capacitors will double and the values
of the resistors and inductors will be divided by two. Hence, the parallel equivalent
resistance for one half of the symmetrical antenna is determined as follows:
( )=
+
==
365.421
2
8.11367.1
2
1102364.11056.132
2
66
,
2
,
SUMS
totalPR
LR
Fig 7 shows the matching network for the antenna. It consists of one serial and one
parallel capacitor for each branch. The values to be tuned are CM1and CM2in order to get
defined matching impedances (25 for each branch). The values of these components
can be estimated according to following equations:
pFRR
C
totalPIN
M 357.114365.421251056.132
116
,
1
=
pF
CCL
C PA
M
64.37106.36210357.114
2
102364.1
)1056.132(
1
2
2
1
1212
626
12
2
=
NOTE: These calculated values for CM1 and CM2 are first order approximations since
the measurement of the antenna parameters cannot be done accurately. This is due to
the fact that the GND layer on the bottom side of the antenna builds an additional
parasitic capacitor which influences the measured values. However, it should help during
antenna tuning. The proper values have to be determined manually by testing and
measuring.
HINT: Start with the next lower value of the calculation of the conductance and then
increase until the desired impedance is achieved.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 10 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
11/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400RF Amplif ier for NXP Contactless Reader IC's
GND
Rextern/2
Rextern/2Vout1
1
2
Loop1
Vout2
1
2
Loop2
CM2
CM2
CM1
CM1
Fig 7. Matching network with C1 and C2
GND
Rextern/2
Rextern/2Vout1
Vout2
CM2
CM2
CM1
CM1
1
2
Loop1
1
2
Loop2
AntennaMatching Network
Since both amplifier branches are tuned to 25and the antenna is symmetrical, the
differential input impedance can be estimated to be 50.
More detailed information about antenna matching and design can be found in [6].
2.4 Receiving Circuit
The receiving path in Fig 8 shows that an oscillator is used to attenuate the 13.56MHzcarrier signal in order to decrease the carrier to side-band level ratio.
R17 and R18 build a voltage divider to handle the high voltage levels of around 15V( PP)
at the antenna (RX_Antenna Pin). Afterwards, a 1:1 buffer amplifier (OA 1) decouples the
signal from the band-stop filter by converting a high impedance at the input to low
impedance at the output. The series resistor R22 is used to limit the current and the
resistor RQdefines the attenuation factor of the band-stop filter. A starting value of
approximately 100 for RQis recommended. CQis a tuning capacitance on the
frequency axis. Due to the fact that the carrier level is decreased, a second amplifier
stage (OA 2) can be used to amplify the sideband levels which also have been slightly
damped by the band-stop filter.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 11 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
12/21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
13/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
AN103510 NXP B.V. 2007. All rights reserved.Appl ication note Rev. 1.0 01 June 2007 13 of 21
Component Value
R27 330, (Small 0402, 0603 or 0805 SMD parts)
R28 1.2k, depending on the desired amplification factor, (Small 0402,0603 or 0805 SMD parts)
RQ 100, depending on the desired attenuation factor, (Small 0402,0603 or 0805 SMD parts)
Q 13.56MHz oscillator
CQ Variable capacitor, 5-50pF
C6,C9Voltage stabilization, 1F, (Ceramic NP0, tolerance 2%)
C5,C7,C8 DC blocker, 100nF, (Ceramic NP0, tolerance 2%)
RX1 820, (Small 0402, 0603 or 0805 SMD parts)
RX2 560, (Small 0402, 0603 or 0805 SMD parts)
CX1 DC Blocker, 1nF, (Ceramic NP0, tolerance 2%)
CX2 Voltage stabilization, 100nF
VCC 12V Power supply
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
14/21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
15/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
3.2 Layout
Hintsfor the design:
The supply voltage should be EMC refined with suitable capacitors.
Spatial separation of the amplifier system and antenna is possible.
Keep tracks short.
Flood the prints with GND layers to avoid loops.
Do not connect the virtual GND of the antenna to the GND of the supply voltage toavoid common-mode currents.
The following plot Fig 10shows top layer and bottom layer of a sample print board of the
amplification system.
Fig 10. Top (red) and Bot tom (blue) layer for the RF Amplifi er System
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 15 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
16/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
4. Results
The following diagrams in Fig 11shows how the RF amplifier circuitry can improve
proximity reader characteristics.
The magnetic field strength shown in Fig 11has been increased by the amplificationsystem compared to the original system described in [6]. The reading distance for
1.5A/m, measured under maximum card loading conditions [8], was increased by 50%.
NOTE:In this case the Q-factor of the antenna in the original system is approximately
twice as high as for the sample antenna used in cooperation with the amplification
system.
H-Field Measurement at Room Temperature
Original vs Amplified
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
0 20 40 60 80 100 120 140
Distance in mm to Antenna surface
H
-FieldinA/m(
rms)
Original H-Field
Amplified H-Field
Fig 11. H-Field versus Reading Distance in mm to the Antenna Surface
Another important feature of the amplification system is that signal shapes according to
ISO/IEC 14443-2 (2000) [7] can be easily achieved as shown in Fig 12.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 16 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
17/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
Fig 12. Pulse shape for 106 kbit /s (left) and 848 kbit /s (right) both Type-A
The amplification system offers linearity allowing proper ISO/IEC 14443-2 (2000) [7]
Type-B data transmission with standard settings of the reader chip.
Fig 13. Type-B Communication
The sideband level sensitivity must not exceed the limit given in the standard ISO/IEC
CD 14443-2 (2007) [9] for a given value of the field strength. The next plot Fig 14proofs
that the requirement can be easily met.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 17 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
18/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
H-Field vs Sensitivity
0,0
2,0
4,0
6,0
8,0
10,0
12,0
14,0
16,0
18,0
20,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0
H-Feld in A/m
SensitivityinmVpp
Standard
Upper Sideband Level
Lower Sideband Level
Fig 14. Measured Sensiti vity versus H-Field
NOTE:The higher the H-field in the transmitting path, the higher the sensitivity of the
receiving path in order to achieve data transmission and reception in desired quality.
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 18 of 21
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
19/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
AN103510 NXP B.V. 2007. All rights reserved.
Appl ication note Rev. 1.0 01 June 2007 19 of 21
5. References
[1] Data Sheet; SL RC400 I Code Reader IC
[2] MIFARE MF RC500; Highly Integrated ISO 14443A Reader IC
[3] MIFARE MF RC 530 ISO14443A reader IC
[4] MIFARE MF RC531; ISO 14443 reader IC
[5] MIFARE and ICODE CL RC632 Multiple protocol contact less reader IC
[6] Directly Matched Antenna Design, Application Note
[7] ISO/IEC 14443-2 (2000)
[8] ISO10373-6 Identification cards Test methods part 6: Proximity cards
[9] ISO/IEC CD 14443-2 (2007)
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
20/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
AN103510 NXP B.V. 2007. All rights reserved.Appl ication note Rev. 1.0 01 June 2007 20 of 21
6. Legal information
6.1 DefinitionsDraft The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences
of use of such information.
6.2 DisclaimersGeneral Information in this document is believed to be accurate and
reliable. However, NXP Semiconductors does not give any representations
or warranties, expressed or implied, as to the accuracy or completeness of
such information and shall have no liability for the consequences of use of
such information.
Right to make changes NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
Suitability for use NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in medical, military, aircraft,
space or life support equipment, nor in applications where failure or
malfunction of a NXP Semiconductors product can reasonably be expectedto result in personal injury, death or severe property or environmental
damage. NXP Semiconductors accepts no liability for inclusion and/or use of
NXP Semiconductors products in such equipment or applications and
therefore such inclusion and/or use is for the customers own risk.
App licati ons Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
6.3 TrademarksNotice: All referenced brands, product names, service names and
trademarks are property of their respective owners.
MIFARE is a trademark of NXP B.V.
-
8/10/2019 103510-RF Amplifier for NXP Contactless Reader IC's
21/21
NXP Semiconductors MFRC500, MFRC53x, CLRC632, SLRC400 RF Ampl ifier for NXP Contactless Reader IC's
Please be aware that important notices concerning this document and the product(s)described herein, have been included in the section 'Legal information'.
NXP B.V. 2007. All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, email to: [email protected]
Date of release: 01 June 2007Document i dentifier: AN103510
7. Contents
1. Introduction .........................................................31.1 How to use this document..................................32. RF Ampl if icat ion System ....................................42.1 EMC Filter ....................................................... ...42.2 RF Power A/B Amplifier......................................62.3 Antenna Design & Matching............................... 72.4 Receiving Circuit .............................................. 113. Design of Overall System .................................143.1 Schematic ........................................................ 143.2 Layout ........................................................... ...154. Results ...............................................................165. References .........................................................196. Legal information ..............................................206.1 Definitions ........................................................ 206.2 Disclaimers.......................................................20 6.3 Trademarks...................................................... 207. Contents .............................................................21