Performance Monitoring During Fading
Users of the EV9000 Evaluation Kit will be able to compare the immunity to noise bursts of the FX919B
and FX929B devices operating in both ‘Track’ and ‘Slow Peak Detect’ modes.
Test 9 of version 4.0 Ev Kit software sends a stream of concentrated short messages (Frame Sync., Station
ID Block (FX929B specific) and a Header Block) without interleaving Symbol Sync. Patterns.
The receiving device is started with a single AQSC/AQLEV acquisition sequence, then reads the
messages using SFS, RSID and RHB tasks without any further AQSC/AQLEV unless the Data Quality
monitoring algorithm decides that re-acquisition is needed.
Noise bursts may be added to the signal to simulate a discriminator output during deep fading conditions,
i.e. the noise bursts may be generated by gating the output of a white noise generator set to 5kHz bandwidth
and with and RMS voltage set to 4 times the data signal rms voltage (this give noise peaks of about +V
DD
/2).
The length of each noise burst should be varied from 10µs to 5ms, for comparison with the graphs below.
The fading performance characterisation shown below was performed using the at 3.0V, 9600s/s,
PLLBW = Medium, FSTOL = 4, with and without the Data Quality monitoring algorithm enabled, and with
1250 messages transmitted for each test.
The following chart shows the marked improvements gained by use of the FX919B and FX929B ‘Track’
mode and the use of the Data Quality monitoring algorithm:
% of Tx messages that were
received
and had no crc errorin the Station ID block
100
90
80
70
60
FX929B Track
FX929B Track, DQ Algorithm
FX929B Slow PD
FX929B Slow PD, Q Algorithm
D
FX929A Rev C
FX929A Rev C DQ Algor
ithm
%
50
40
30
20
10
0
10
100
1000
10000
Noise burst lengt (µs)
h
The Data Quality monitoring algorithm used by TEST9 is as described in this application note and in section
1.6.6 of the FX919 and 929B Data Sheets.
A second measure of performance is the number of times that the Data Quality monitoring algorithm has to
force a re-acquisition, the following chart again shows the superiority of the FX919B and FX929B in ‘Track’
mode.
Re-acquisitions per second
60
50
40
FX929B Track
30
FX929B Slow PD
FX929A Rev C
20
10
0
10
100
1000
10000
Noise burst lengt (µs)
h
3
CMLMICRO [ CML MICROCIRCUITS ]
