1. CC11xx Range Improvements
Richard Wallace

2. Presentation Abstract
Abbreviations
General
NE1 Antenna
NE2 Antenna
SS2 Antenna
Out of the Box Experience
Existing range of CC11xx
Current Consumption
CC /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

3. Abbreviations - General
CC11xx CC1100, CC1101, CC1110, CC1111 and CC1150
TX Transmitter
RX Receiver
bps bits per second
PER Packet Error Rate
BOMa Existing reference design (CC1110)
BOMb Johanson Filter-balun design (CC1101)
BOMc Existing reference design (CC1101)
BOMc1 Extra filtering discrete balun design (CC1101)
BOMc_saw Existing reference design (CC1101)
np not performed

4. Abbreviations – NE1 Antenna

5. Abbreviations – NE2 Antenna

6. Abbreviations – SS2 Antenna (yellow)

7. 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 ?

8. 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

9. 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
Area of Improvement #2:
The design is sensitive due to antenna / load conditions. Large current consumption difference depending on the load.

10. CC1101 - 868/915 Reference Design Schematic
Balanced LPF for matching and reflecting harmonics.
50Ohm
Balun (LPF/HPF)
3 pole LPF
DC block
EM revisions: rev3.2 - latest with 3 pole LPF
rev 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)
Differential impedance as seen from the RF-port (RF_P and RF_N) towards the antenna is MHz.

11. 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.
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.
Square wave output from chip (TX).

12. 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.
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.
Square wave output from chip (TX).

13. 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.
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.
Distorted square wave output from chip (TX).
Impedance unknown at harmonic frequencies for most antenna vendors.

14. 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.

15. CC1101 Expected Range – 915MHz
Expected Range with perfect match: 915MHz: 360m

16. 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)

17. 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

18. 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

19. New RF Network Designs – SAW Filter Solution
High Insertion loss
Outstanding supression of spurious and harmonics
Small physical size (1x1.4mm)

20. New RF Network Designs – SAW Filter Solution
existing discrete balun
+ SAW filter (BOMc_saw)
Murata balun
+ SAW filter (BOM_board_2a)
22nH Shunt inductor
LDB21869M20C Standard Murata Balun
SAFEB915MAL0F00 SAW Filter
BOMc
SAFEB915MAL0F00 SAW Filter
LPF can be removed

21. New RF Network Designs – Johanson Filter-Balun Solution (BOMb)
Johanson Filter balun (BOMb)
Only 2 components required !

22. New RF Network Designs – Johanson Filter-Balun Solution (BOMb)
Simulations from Johanson Balun

23. Range Test Results

24. Best Results Obtained from Range Test Measurements
Setup
(CC1101, Tx + Rx; 250kbps, 0dBm)
Distance
(Line of Sight)
Maximum theoretical range
360m
Johanson Balun (BOMb, NE2)
290m
Original Discrete (BOMc, SS2)
250m
New Discrete (BOMc1, SS2)
Original Discrete + SAW (BOMc_saw, SS2)
240m
Original Discrete with kit antenna (BOMc, NE1)
160m

25. 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

26. Test Results - Current Consumption
– Effects of SAW filter can be compared with the figures highlighted in yellow

27. Test Result Matrix
Cost estimation include pick & place assembly cost, only RF network is included

28. Cost Calculations
All the prices are based upon information from the component vendors:
0.002 USD Murata Capacitor (COG, pF)
0.007 USD Multi-Layer 0402 Murata Inductor
0.049 USD Wire-Wound 0402 Murata Inductor
0.070 USD Murata Balun (500k/year)
0.160 USD Johanson Filter-Balun (500k / year)
0.190 USD Johanson Filter-Balun (50k / year)
0.250 USD Murata SAW Filter (500k/year)
0.300 USD Murata SAW Filter (500k/year)
0.030 USD Pick & Place Assembly Cost (per component)

29. 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.

30. Extra Slides - Current Consumption