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Application note
BAL-NRF02D3 matched balun with integrated harmonics filter for
Nordic Semiconductor chips with ultralow power transceivers
Introduction
The nRF51422-CEAA, nRF51422-CDAB, nRF51422-CFAC and nRF51822-CEAA,
nRF51822-CDAB, nRF51822-CFAC from Nordic Semiconductor are 2.45 GHz combo chips
with an ultralow power transceiver.
The BAL-NRF02D3 from STMicroelectronics is an ultraminiature balun for which the
matching impedance has been customized for the nRF51422-CEAA, nRF51422-CDAB,
nRF51422-CFAC and nRF51822-CEAA, nRF51822-CDAB, nRF51822-CFAC Nordic
Semiconductor circuits.
The BAL-NRF02D3 integrates matching network and harmonics filters. It uses
STMicroelectronics’ IPD technology on non-conductive glass substrate which optimizes RF
performance.
The BAL-NRF02D3 has been tested and approved by Nordic Semiconductor on the
PCA10018 nRFgo module.The BAL-NRF02D3 demonstrates a higher system performance
compared to traditional solutions. This document presents the test and performance results.
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Test and performances
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Test and performances
Figure 1. BAL-NRF02D3 reference design from Nordic Semiconductor nRF51822 (WLCSP)
C1
12pF
C2
X1
16MHz
12pF
P0.29
P0.28
P0.27
P0.26
P0.25
P0.24
P0.23
P0.22
P0.21
C8
100nF
C7
B7
A8
A7
C5
A6
B6
B5
A5
A4
A3
A2
VCC_nRF
VCC_nRF
VDD
DCC
P0.30
P0.31
P0.00
P0.01
P0.02
P0.03
P0.04
P0.05
P0.06
P0.07
VDD
AVDD
VSS
VSS
VSS
ANT2
ANT1
VDD_PA
DEC2
P0.20
P0.19
P0.18
P0.17
nRF51822
P0.08
P0.09
P0.10
P0.11
P0.12
P0.13
P0.14
P0.15
P0.16
SWDIO
SWDCLK
B1
B4
J8
J7
H6
J6
J5
H5
H4
J4
J3
J2
H2
C8
H3
C11
100nF
B8
B9
D8
E8
C9
E9
D9
F9
F8
H9
G8
H7
H8
VSS
VSS
P0.08
P0.09
P0.10
P0.11
P0.12
P0.13
P0.14
P0.15
P0.16
SWDIO/nRESET
SWDCLK
VSS
VSS
C7
100nF
P0.30
P0.31
P0.00
P0.01
P0.02
P0.03
P0.04
P0.05
P0.06
P0.07
C9
1.0nF
P0.29
P0.28
P0.27
P0.26
P0.25
P0.24
P0.23
P0.22
P0.21
DEC1
XC2
XC1
VCC_nRF
A1
G6
G9
D7
C1
D1
E1
F1
G1
F2
H1
G2
B1
B3
A3
A2
ANT2
SE
ANT1
VDD_PA GND
A1 RF
B1
BAL-NRF02D3
P0.20
P0.19
P0.18
P0.17
C10
47nF
C3
2.2nF
U1
nRF51822-CEAA
R1
12k
Using BAL-NRF02D3 no external components are required for matching and for harmonic
filtering. Only a 2.2 nF external capacitor is required for VDD decoupling.
Figure 2. PCA10018 ST balun reference nRFgo module from Nordic Semiconductor
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Benefits of BAL-NRF02D3 reference design
Benefits of BAL-NRF02D3 reference design
The BAL-NRF02D3 provides two essential benefits:
•
Decrease in the BOM count by 80%, from 5 components to 1 component
•
More than 80% PCB area reduction compared to the original design with the
BAL-NRF01D3 and discrete components
Compared to discrete solutions, the BAL-NRF02D3 solution is much easier to implement.
Thanks to this smart implementation:
•
No RF measurement tools and RF skills are required to design and validate the
function.
•
Performance is less sensitive to component placement.
•
PCB design is symmetrical from differential output to antenna, providing much shorter
traces between transceiver outputs to the balun.
As a result, ST BAL-NRF02D3 reduces harmonics generation.
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Measured performances
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Measured performances
3.1
Nordic Semiconductor PCA10018 nRFgo module (nRF51822)
The results presented in this section are based on measurements performed with the
PCA10018 nRFgo module and the BAL-NRF02D3. The BAL-NRF02D3 balun offers high
suppression of 2nd to 4th harmonics and simplifies implementation of nRF51822 WLCSP as
regards FCC and ETSI compliance tests.
Table 1. Main parameter compensated measurements (2402 to 2480 MHz)
Parameter
Values
Parameter
PA_TX_FUND (0 dBm) (low)
0.56
PA_TX_2H (4 dBm)
-49.4
PA_TX_FUND (0 dBm) (mid)
0.85
PA_TX_3H (0 dBm)
-53.8
PA_TX_FUND (0 dBm) (high)
1.28
PA_TX_3H (4 dBm)
-41.7
PA_TX_FUND (4 dBm) (low)
4.18
PA_TX_4H (0 dBm)
-61.8
PA_TX_FUND (4 dBm) (mid)
4.2
PA_TX_4H (4 dBm)
-56.0
PA_TX_FUND (4 dBm) (high)
4.55
LO (0 dBm)
-60.3
PA_TX_2H (0 dBm)
-40.9
Receiver sensitivity [dBm]
-90.1
Figure 3. Output power carrier in 4dBm mode (not compensated)
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Measured performances
Figure 4. Second harmonic in 4dBm mode (not compensated)
Figure 5. Third harmonic in 4dBm mode (not compensated)
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Figure 6. Fourth harmonic in 4dBm mode (not compensated)
Figure 7. Receiver local oscillator leakage (RX_LO) in 4dBm mode (not compensated)
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Table 2. Compatibility matrix (nRF51422)
nRF51422 IC revision
Packet/variant
Build code
1
CEAA
A0A
2
CEAA
Bx0
CDAB
Ax0
CEAA
Cx0
CFAC
Ax0
3
Table 3. Compatibility matrix (nRF51822)
nRF51822 IC revision
Packet/variant
Build code
CEAA
BA
CEAA
B0
CEAA
CA0
CEAA
DA0
CEAA
Dx0
CDAB
Ax0
CEAA
Ex0
CFAC
Ax0
1
2
3
Layout recommendations for nRF51822 and nRF51422
Figure 8. BAL-NRF02D3 land pattern metrics
Top layer pad
Ø = 220 µm 650 µm
Soldermask opening
Ø = 320 µm
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Figure 9. PCB stack-up recommendation
35um
230um
35um
9 30um
35um
230um
35um
Figure 10. More layout information at Nordic Semiconductor’s web site
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Ordering information
Ordering information
Table 4. Ordering information
5
Part number
Marking
Weight
Base Qty
Delivery mode
BAL-NRF02D3
SC
1.82 mg
5000
Tape and reel
Revision history
Table 5. Document revision history
Date
Revision
Changes
05-Sep-2013
1
Initial release.
02-Sep-2015
2
Added Table 2 and Table 3. Updated Figure 10.
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