CC11xx Range Improvements
Richard Wallace
Presentation Abstract
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Presentation Abstract
Abbreviations
– General
– NE1 Antenna
– NE2 Antenna
– SS2 Antenna
Out of the Box Experience
– Existing range of CC11xx
– Current Consumption
CC1101 868/915 Reference Design Schematic
Abstracts from DN017 - CC11xx 868/915 MHz RF Matching
Effects of non-50ohm wideband load - Antenna Impedance
Improvement Goals
Calculated Expected Range for 915MHz, CC1101
New RF Network Designs
– Discrete Solutions
– SAW Filter Solution
– Johanson Filter-Balun Solution
Range Test Results
Best Results Obtained
Results from initial Conclusion from Range Measurements
Test Results - Current Consumption
Test Result Matrix
Conclusions
Extra Slides
Abbreviations - General
CC11xx
TX
RX
bps
PER
BOMa
BOMb
BOMc
BOMc1
BOMc_saw
np
CC1100, CC1101, CC1110, CC1111 and CC1150
Transmitter
Receiver
bits per second
Packet Error Rate
Existing reference design
(CC1110)
Johanson Filter-balun design
(CC1101)
Existing reference design
(CC1101)
Extra filtering discrete balun design (CC1101)
Existing reference design
(CC1101)
not performed
Abbreviations – NE1 Antenna
Abbreviations – NE2 Antenna
Abbreviations – SS2 Antenna
(yellow)
Existing range of CC11xx – Out of the Box Experience
Setup
(250kbps, 1.3m above
ground, 0dBm, Tx + Rx)
Distance
(Line of Sight)
CC2510 (KA)
120m
CC1110 (NE1)
??
CC1101 (NE1)
??
What range do we have today ?
Existing range of CC11xx – Out of the Box Experience
Setup
(250kbps, 1.3m above
ground, 0dBm, Tx + Rx)
Distance
(Line of Sight)
CC2510 (KA)
120m
CC1110 (NE1)
130m
CC1101 (NE1)
160m
Area of Improvement #1:
Range between 2 units implementing CC11xx is not good
enough and the performance can be improved
Variation of Current Consumption - Out of the Box Experience
CC1101; 915MHz, simple unmodulated TX carrier; 10dBm, all values are in mA
“close” measurements are close proximity to the antenna
BOM
default (BOMc) #1
default (BOMc) #2
50ohm
31,94
31,12
Open
25,18
24,87
difference
6,76
6,25
NE1
31,19
30,60
NE1 close difference
29,46
1,73
29,48
1,12
NE2
36,70
36,25
Area of Improvement #2:
The design is sensitive due to antenna / load conditions. Large
current consumption difference depending on the load.
NE2 close difference
33,35
3,35
32,52
3,73
CC1101 - 868/915 Reference Design Schematic
Balanced LPF
for matching
and reflecting
harmonics.
Balun
(LPF/HPF)
50Ohm
3 pole LPF
DC block
EM revisions:
rev3.2 - latest with 3 pole LPF
Differential impedance as seen from the
RF-port (RF_P and RF_N) towards the
antenna is 86.5 + j43 @ 868 MHz.
rev3.1 - 2 pole LPF (L123,
C123) low supression of 2nd
harm for 3- 7dBm output
power.
rev2.2 - Obsolete - radiation
emission problems (does not
have any balanced LPF)
CC1101 - 868/915 Reference Design Schematic – Abstracts from DN017
An ideal output signal from the CC11xx
products in TX mode is a square wave signal
at the RF_P and RF_N pins and a sine wave
at the antenna port.
To achieve this, the filterbalun must reflect
the harmonics back towards the RF_P and
RF_N ports.
The shape of the square wave pulse depends
on the impedance at the different harmonics.
Square wave output
from chip (TX).
The current consumption in TX depends on
the shape of the signal at RF_P and RF_N.
Lowest possible current consumption is
achieved by having the odd harmonics (3rd
and 5th) reflected back.
CC1101 - 868/915 Reference Design Schematic – Abstracts from DN017
Unexpected high current consumption in a
design may be caused by incorrect or
missing reflection of harmonics. The simplest
way of reflecting the harmonics towards the
chip is to have a differential low pass filter
between the CC11xx and the balun.
Ideally the series inductors, L121 and L131,
will reflect harmonics towards the chips with
high real part of the impedance.
Square wave output
from chip (TX).
The low pass filter will also lower the
harmonics level into the balun and reducing
the risk of having unwanted radiated power
through the balun and the single ended filter.
Effects of non-50ohm wideband load - Antenna Impedance
All RF equipment have a wideband
impedance of 50 ohms so good
measurements results are obtained since the
design can be optimised for the wideband
load of 50ohms.
However, antennas are normally adapted to
50ohms at their operating frequency but the
impedance at the harmonics is not 50ohms.
Distorted square wave
output from chip (TX).
Impedance unknown
at harmonic
frequencies for most
antenna vendors.
Depending on the antenna impedance at the
harmonic frequencies; different results can
be obtained from vendor to vendor since the
reflected signal to the chip is distorting the
square wave output due to phase change.
Ideally, the load should be capable of a
mismatch and the output from the chip
should not be effected.
Improvement Goals
Area of Improvement #1:
•
Out of box experience is poor since the range between 2
units implementing CC11xx is not good enough.
Area of Improvement #2:
• Improve the reference design so that the design is not so
sensitive on the load conditions.
CC1101 Expected Range – 915MHz
Friis_equation_with_Ground_model
Transmitted power (suplied from transmitter)
Gain in Transmitting antenna
Gain in Receiving antenna
Dielectric constant for ground (typical 18)
Index
CC1101, 915MHz, 250kbaud sensitivity = -94dBm
Free Space and Ground model
1.3
1.3
360
915
V
[m]
[m]
[m]
[MHz]
-40
0
18
6
20
40
60
80
100 120 140 160 180 200 220 240 260 280 300 320 340 360 380
-50
0 [dBm]
0 [dB]
0 [dB]
Received power [dBm]
Transmitting antenna location, height over ground
Receiving antenna location, height over ground
Distance between antennas
Frequency
Signal polarity Horisontal=H, Vertical=V
-60
-70
-80
-90
-100
Friis
Distance [m]
Ground model Vertical polarisation
CC1101, 915MHz, 250kbaud sensitivity = -94dBm
Expected Range with perfect match:
915MHz: 360m
New RF Network Designs
The following RF network concepts will be tested to see if the range can
be further improved and the load variation sensitivity can be reduced:
• Discrete Solution
– Existing discrete solution (BOMc)
– Extra filtering Discrete Balun Solution (BOMc1)
• SAW Filter Solution
– existing discrete balun + SAW filter (BOMc_saw)
– Murata balun + SAW filter (BOM_board_2a)
• Chip Filter Balun (Johanson) Solution (BOMb)
New RF Network Designs - Discrete Solutions
Existing discrete solution
(BOMc)
Extra Filtering Discrete Balun
Solution (BOMc1)
Two extra series inductors
LPF can be reduced for cost reductions
New RF Network Designs - Discrete Solutions
• Original BOM attenuates the second harmonic by 28dB (BOMc)
• BOMc1 with extra filtering components uses two additonal
inductors to give additional filtering to achieve a larger attenuation
of the second harmonic; expected attenuation is 50dB
New RF Network Designs – SAW Filter Solution
• High Insertion loss
• Outstanding supression of
spurious and harmonics
• Small physical size (1x1.4mm)
New RF Network Designs – SAW Filter Solution
existing discrete balun
+ SAW filter (BOMc_saw)
– BOMc
– SAFEB915MAL0F00 SAW Filter
– LPF can be removed
Murata balun
+ SAW filter (BOM_board_2a)
– 22nH Shunt inductor
– LDB21869M20C Standard Murata Balun
– SAFEB915MAL0F00 SAW Filter
New RF Network Designs – Johanson Filter-Balun Solution (BOMb)
Johanson Filter balun (BOMb)
• Only 2 components required !
New RF Network Designs – Johanson Filter-Balun Solution (BOMb)
Simulations from Johanson Balun
Range Test Results
0dBm, 915MHz, sens optimized, 1% PER. 1.3m above ground
500kbps
250kbps
CC1110 NE1
NE2
SS2
130m
NE1
190m
NE2
SS2
195m
BOMb
915MHz
PER 1e-2
0dBm
CC1101 NE1 NE2 SS2
NE1
160m
NE2
165m
SS2
-
CC1101 NE1
NE2
SS2
NE1
210m
NE2
290m
SS2
250m
BOMc
915MHz
PER 1e-2
0dBm
CC1101 NE1 NE2 SS2
NE1
115m
NE2
120m
SS2
-
CC1101 NE1
NE2
SS2
NE1
160m
NE2
230m
SS2
250m
BOMa
PER -xdBm
0dBm
BOMc_saw
915MHz
PER 1e-2
0dBm
CC1101 NE1
NE2
SS2
NE1
110m
NE2
230m
SS2
240m
BOMc1
915MHz
PER 1e-2
0dBm
CC1101 NE1
NE2
SS2
NE1
160m
NE2
240m
SS2
250m
Best Results Obtained from Range Test Measurements
Setup
Distance
(CC1101, Tx + Rx; 250kbps, 0dBm)
(Line of Sight)
Maximum theoretical range
360m
Johanson Balun (BOMb, NE2)
290m
Original Discrete (BOMc, SS2)
250m
New Discrete (BOMc1, SS2)
250m
Original Discrete + SAW
(BOMc_saw, SS2)
240m
Original Discrete with kit antenna
(BOMc, NE1)
160m
Conclusions from Range Measurements
•
CC1101 compared to CC1110 has a greater range of 21% to 23% depending on
antenna.
•
Both CC1110 & CC1101 showed a range improvement of 41% when the antenna was
changed from the standard NE1 antenna to the dipole NE2 antenna.
•
SS2 antenna is best suited for the discrete solution. Better performance than NE2.
•
Caluclated range of approx 360m should be expected with 0dBm, 915MHz & 250kbps.
•
CC1101 has as good range as CC1000 for the same sensitivity.
•
NE1 antenna must be changed asap in the kit to NE2 or SS2.
•
With a Johansson balun the distance was increased by 32% to 35% depending on
antenna used on the CC1101 setup.
•
Best results are with the NE2 antenna and Johnson balun solution so far.
•
NE2 antenna is best suited for the Johanson balun solution
Test Results - Current Consumption
CC1101; 915MHz, simple unmodulated TX carrier; 10dBm
BOM
default (BOMc) #1
default (BOMc) #2
new discrete (BOMc1) #1
new discrete (BOMc1) #2
Johanson (BOMb) #7
Johanson (BOMb) #11
default (BOMc + SAW) #1
default (BOMc + SAW) #2
50ohm
31,94
31,12
30,73
31,16
33,75
32,37
33,10
32,36
Open
25,18
24,87
25,67
26,97
30,31
28,45
30,70
31,71
all values are in mA
difference
6,76
6,25
5,06
4,19
3,44
3,92
2,40
0,65
NE1
31,19
30,60
31,50
32,32
32,25
31,00
37,65
36,11
NE1 close difference
29,46
1,73
29,48
1,12
32,40
0,90
34,04
1,72
29,90
2,35
28,55
2,45
36,99
0,66
35,68
0,43
– Effects of SAW filter can be compared with the figures highlighted in yellow
NE2
36,70
36,25
36,28
35,18
30,72
29,75
35,17
33,67
NE2 close difference
33,35
3,35
32,52
3,73
31,57
4,71
31,58
3,60
32,55
1,83
32,25
2,50
33,45
1,72
31,98
1,69
Test Result Matrix
CC1101, 0dBm, 915MHz, 250kbps, sens optimized, 1% PER
Current deviation (mA, 10dB, static unmodulated TX)
Cost ($)
NE2 close delta
NE2
NE1 close delta
NE1
500k/y 50ohm Open delta
NE1
Range (m)
SS2
NE2
Discrete Solution
Standard Discrete
BOMc
160m
230m
250m
0.45
31.94
25.18
6.76
31.19
29.46
1.73
36.70
33.35
3.35
Extra Filtering Discrete
BOMc1
160m
240m
250m
0.53
30.73
25.67
5.06
31.50
32.40
0.90
36.28
31.57
4.71
SAW Filter Solution
Discrete Balun + SAW
BOMc_saw
110m
230m
240m
0.61
33.10
30.70
2.40
37.65
36.99
0.66
35.17
33.45
1.72
Murata Balun + SAW
BOM_Board_2_a
np
np
np
0.45
31.25
32.78
1.53
28.56
29.40
0.84
29.16
30.10
0.94
210m
290m
250m
0.23
33.75
30.31
3.44
32.25
29.90
2.35
30.72
32.55
1.83
DUT Description
Johanson Filter Balun
BOMb
• Cost estimation include pick & place assembly cost, only RF network is included
Cost Calculations
All the prices are based upon information from the component vendors:
• 0.002 USD
• 0.007 USD
• 0.049 USD
• 0.070 USD
• 0.160 USD
• 0.190 USD
• 0.250 USD
• 0.300 USD
0402 Murata Capacitor (COG, pF)
Multi-Layer 0402 Murata Inductor
Wire-Wound 0402 Murata Inductor
Murata Balun (500k/year)
Johanson Filter-Balun (500k / year)
Johanson Filter-Balun (50k / year)
Murata SAW Filter (500k/year)
Murata SAW Filter (500k/year)
• 0.030 USD
•
Pick & Place Assembly Cost (per component)
Conclusions
New application in-designs:
Discrete Solution:
• Lowest component cost, good range, but susceptible to load changes
• Extra filtering solution only improved load susceptibility slightly, no range
improvement compared to standard discrete solution (at the moment).
SAW filter Solution:
• with discrete balun: highest cost, good range, not susceptible to load
variations
• with Murata balun: low total cost, good range, not susceptible to load
variations and compact solution
Johanson Filter-Balun Solution:
• Lowest total cost, best range, not least susceptible to load variations, best
all-round solution.
• Only two components, minor risk for in-design errors
Out of box Experience - Evaluation Kit:
• New Antenna (NE2 or SS2) will be replacing old antenna (NE1); range
improvement of >41% with new antenna.
Extra Slides - Current Consumption