AN_TDA5225_Sensitivity

S m a r t L E W I S TM R X +
TDA522 5
Enhanced Sensitivity Multi-Configuration Receiver
Han dling of Sensi t i vi t y
App lication No te
v1.0, 2010-03-24
Wireless Control
Edition 2010-03-24
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2010 Infineon Technologies AG
All Rights Reserved.
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TDA5225
Handling of Sensitivity
TDA5225 Enhanced Sensitivity Multi-Configuration Receiver
Revision History: 2010-03-24, v1.0
Previous Revision: --Page
Subjects (major changes since last revision)
Trademarks of Infineon Technologies AG
BlueMoon™, COMNEON™, C166™, CROSSAVE™, CanPAK™, CIPOS™, CoolMOS™, CoolSET™,
CORECONTROL™, DAVE™, EasyPIM™, EconoBRIDGE™, EconoDUAL™, EconoPACK™, EconoPIM™,
EiceDRIVER™, EUPEC™, FCOS™, HITFET™, HybridPACK™, ISOFACE™, I²RF™, IsoPACK™, MIPAQ™,
ModSTACK™, my-d™, NovalithIC™, OmniTune™, OptiMOS™, ORIGA™, PROFET™, PRO-SIL™,
PRIMARION™, PrimePACK™, RASIC™, ReverSave™, SatRIC™, SensoNor™, SIEGET™, SINDRION™,
SMARTi™, SmartLEWIS™, TEMPFET™, thinQ!™, TriCore™, TRENCHSTOP™, X-GOLD™, XMM™, X-PMU™,
XPOSYS™.
Other Trademarks
Advance Design System™ (ADS) of Agilent Technologies, AMBA™, ARM™, MULTI-ICE™, PRIMECELL™,
REALVIEW™, THUMB™ of ARM Limited, UK. AUTOSAR™ is licensed by AUTOSAR development partnership.
Bluetooth™ of Bluetooth SIG Inc. CAT-iq™ of DECT Forum. COLOSSUS™, FirstGPS™ of Trimble Navigation
Ltd. EMV™ of EMVCo, LLC (Visa Holdings Inc.). EPCOS™ of Epcos AG. FLEXGO™ of Microsoft Corporation.
FlexRay™ is licensed by FlexRay Consortium. HYPERTERMINAL™ of Hilgraeve Incorporated. IEC™ of
Commission Electrotechnique Internationale. IrDA™ of Infrared Data Association Corporation. ISO™ of
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. MATLAB™ of MathWorks, Inc. MAXIM™ of
Maxim Integrated Products, Inc. MICROTEC™, NUCLEUS™ of Mentor Graphics Corporation. Mifare™ of NXP.
MIPI™ of MIPI Alliance, Inc. MIPS™ of MIPS Technologies, Inc., USA. muRata™ of MURATA
MANUFACTURING CO., MICROWAVE OFFICE™ (MWO) of Applied Wave Research Inc., OmniVision™ of
OmniVision Technologies, Inc. Openwave™ Openwave Systems Inc. RED HAT™ Red Hat, Inc. RFMD™ RF
Micro Devices, Inc. SIRIUS™ of Sirius Sattelite Radio Inc. SOLARIS™ of Sun Microsystems, Inc. SPANSION™
of Spansion LLC Ltd. Symbian™ of Symbian Software Limited. TAIYO YUDEN™ of Taiyo Yuden Co.
TEAKLITE™ of CEVA, Inc. TEKTRONIX™ of Tektronix Inc. TOKO™ of TOKO KABUSHIKI KAISHA TA. UNIX™
of X/Open Company Limited. VERILOG™, PALLADIUM™ of Cadence Design Systems, Inc. VLYNQ™ of Texas
Instruments Incorporated. VXWORKS™, WIND RIVER™ of WIND RIVER SYSTEMS, INC. ZETEX™ of Diodes
Zetex Limited.
Last Trademarks Update 2010-03-22
Application Note
3
v1.0, 2010-03-24
TDA5225
Handling of Sensitivity
Table of Contents
Table of Contents
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1
Overview and General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
2.1
2.2
TDA5225 Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Output Signal DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Output Signal DATA_MATCHFIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3
Final Conclusion - Data Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Application Note
4
v1.0, 2010-03-24
TDA5225
Handling of Sensitivity
List of Figures
List of Figures
Figure 1
Figure 2
Matched Filter Output Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Matched Filter Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Application Note
5
v1.0, 2010-03-24
TDA5225
Handling of Sensitivity
Overview and General Information
1
Overview and General Information
This document gives a simple overview on how to use the TDA5225 for best achievable sensitivity results.
For the TDA5225, the output signals DATA or DATA_MATCHFIL can be used (transparent mode).
BER sensitivity measurements, as noted in the data sheet, use the transparent receive mode TMMF
(DATA_MATCHFIL output signal), where the received data is sampled with ideal data clock.
The DATA_MATCHFIL output signal will provide higher systematic jitter than the DATA output signal.
Please keep in mind, that the achievable sensitivity in both transparent modes is significantly depending on the
implemented clock and data recovery algorithm of the user software in the application controller.
For the sensitivity values given in the data sheet, also the filter settings in the signal chain (on-chip BPF and FSK
PDF filter) are noted. In case these filter setting need to be adapted for the application, the achievable sensitivity
will change accordingly.
2
TDA5225 Output Signals
There are two output sources of the matched filter shown in Figure 1:
•
•
DATA: DC cancellation (Raw DATA Slicer) is applied to the 1-chip MF output
DATA_MATCHFIL: The signum is taken from the 2-chip MF output, no DC cancellation necessary
DATA_MATCHFIL has about 3 dB better performance than DATA output, but DATA_MATCHFIL output signal will
provide higher systematic jitter than the DATA output signal (see different slopes of MF signal in Figure 2).
8 to 16 smps
per chip
Matched Filter
1-chip
2- chip
from ASK/
FSK demodulator
RAW data slicer for
external processing
SIGN
DATA
DATA_ MATCHFIL
(Sliced RAW Data for
external processing)
(Matched Filtered Data
for external processing)
~ 3dB better BER
Figure 1
Matched Filter Output Sources
Application Note
6
v1.0, 2010-03-24
TDA5225
Handling of Sensitivity
TDA5225 Output Signals
DATA (1-chip)
DATA_MATCHFIL (2-chip)
Biphase-S
Biphase-S
Data
[ RAW]
1
0
1
0
0
1
Data
[ RAW]
1
1
0
1
0
0
1
1
Data
[ Biphase-S ]
Data
[ Biphase-S]
t
t
2 Chip MF
1 Chip MF
t
t
TDA5225
Strobes
Strobes
t
t
RAW
Dataslicer
MF SGN
t
t
Sampled Data
Sampled Data
n
Binary Data
x[n]
1
1
0
1
0
0
1
0
1
0
1
1
0
n
Binary Data
0
0
0
1
1
1
0
n
Decoded Data
1
0
1
0
0
1
n
1
Decoded Data
0
1
0
0
1
m
Sampling and decoding by application controller
Figure 2
Matched Filter Output Signals
2.1
Output Signal DATA
A DC offset of the 1-chip MF signal must be compensated to be able to slice the data correctly.
This DC cancellation is based on a BW-adjustable digital lowpass filter. The bandwidth of the DC removal filter
used for the Raw Data slicer (external slicer, register x_EXTSLC) can be increased to achieve a faster settling
time. Faster settling time comes at the cost of higher ripple which causes more jitter at the output.
NOTE: The ripple introduced by fast DC cancellation will also cause a decrease of performance.
The settling time does not only depend on the selected DC removal filter bandwidth but also on the frequency
offset.
•
•
In FSK a frequency offset introduces a DC offset at the output of the Matched Filter
In ASK there is also a DC offset introduced due to the antilog function needed for linearization of the input
signal
The preamble of the transmitted signal must be long enough for the filter to settle.
Application Note
7
v1.0, 2010-03-24
TDA5225
Handling of Sensitivity
Final Conclusion - Data Jitter
2.2
Output Signal DATA_MATCHFIL
On usage of the 2-chip Matched Filter output, the DC cancellation is achieved within one symbol.
There is no ripple because of the DC cancellation, therefore the sensitivity is increased, but DATA_MATCHFIL
output signal will provide higher systematic jitter, due to different slopes of MF signal shown in Figure 2.
The „systematic jitter“ is data-dependent and can therefore be compensated by the application controller.
3
Final Conclusion - Data Jitter
Three types of jitter are superimposed at the output and contribute differently at different input power levels:
•
•
•
Systematic Jitter can be reduced by oversampling (TDA5225 Explorer software tool is generating the optimal
chip-internal oversampling). This jitter can also be observed at good RF input power levels.
Smaller DC canceller bandwidth (RAW Data Slicer) can be used to reduce ripple and therefore reduce the jitter
slightly, but this increases the slicer settling time. For the final application a trade-off between settling time and
ripple must be made.
Jitter due to Noise can not be reduced (except for a BPF BW reduction) and limits therefore the achievable
performance.
IMPORTANT NOTE: When the software clock-data recovery in the application controller requires an additional
criterion of a certain allowed jitter at the output signal of the radio, the noted high sensitivity can NOT (not even
under best case conditions) be achieved at the Raw Data Slicer output (DATA).
Usage of the 2-chip matched filter output (DATA_MATCHFIL) and compensation for systematic pulse width
“modulation” needs to be done in the external “high performance” software clock recovery, which may require a
strong application controller.
Note: The TDA5235/40 can deliver high sensitivity due to internal available multi-bit signals (TDA5225 only
delivers a 1-bit output signal) and a real hardware clock-recovery unit.
Application Note
8
v1.0, 2010-03-24
w w w . i n f i n e o n . c o m
Published by Infineon Technologies AG
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