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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 and nRF51822-CEAA 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, and nRF51822-CEAA
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.
September 2013
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Test and performances
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1
Test and performances
Figure 1. BAL-NRF02D3 reference design from Nordic Semiconductor nRF51822-CEAA (WLCSP)
C1
12pF
C2
12pF
X1
16MHz
C8
100nF
P0.29
P0.28
P0.27
P0.26
P0.25
P0.24
P0.23
P0.22
P0.21
VCC_nRF
C9
1.0nF
A1
G6
G9
D7
C1
D1
E1
F1
G1
F2
H1
G2
VCC_nRF
P0.30
P0.31
P0.00
P0.01
P0.02
P0.03
P0.04
P0.05
P0.06
P0.07
B8
B9
D8
E8
C9
E9
D9
F9
F8
H9
G8
H7
H8
VDD
DCC
P0.30
P0.31
P0.00
P0.01
P0.02
P0.03
P0.04
P0.05
P0.06
P0.07
VDD
C7
100nF
P0.29
P0.28
P0.27
P0.26
P0.25
P0.24
P0.23
P0.22
P0.21
DEC1
XC2
XC1
AVDD
VSS
VSS
VSS
ANT2
ANT1
VDD_PA
DEC2
P0.20
P0.19
P0.18
P0.17
C7
B7
A8
A7
C5
A6
B6
B5
A5
A4
A3
A2
B1
B3
A3
A2
P0.20
P0.19
P0.18
P0.17
C10
47nF
C3
2.2nF
ANT2
SE
ANT1
VDD_PA GND
BAL-NRF02D3
A1
RF
B1
VCC_nRF
C11
100nF
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
nRF51822
Using BAL-NRF02D3
no external components
are required for matching and for harmonic
filtering. Only a 2.2 nF external capacitor is required for V
DD
decoupling.
Figure 2. PCA10018 ST balun reference nRFgo module from Nordic Semiconductor
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B1
B4
J8
P0.08
J7
P0.09
P0.10
H6
P0.11
J6
J5
P0.12
H5
P0.13
H4
P0.14
P0.15
J4
J3
P0.16
J2
SWDIO
SWDCLK
H2
C8
H3
U1
nRF51822-CEAA
R1
12k
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Benefits of BAL-NRF02D3 reference design
2
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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3.1
Measured performances
Nordic Semiconductor PCA10018 nRFgo module
(nRF51822-CEAA)
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 2
nd
to 4
th
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
PA_TX_FUND (0 dBm) (low)
PA_TX_FUND (0 dBm) (mid)
PA_TX_FUND (0 dBm) (high)
PA_TX_FUND (4 dBm) (low)
PA_TX_FUND (4 dBm) (mid)
PA_TX_FUND (4 dBm) (high)
PA_TX_2H (0 dBm)
Values
0.56
0.85
1.28
4.18
4.2
4.55
-40.9
Parameter
PA_TX_2H (4 dBm)
PA_TX_3H (0 dBm)
PA_TX_3H (4 dBm)
PA_TX_4H (0 dBm)
PA_TX_4H (4 dBm)
LO (0 dBm)
Receiver sensitivity [dBm]
Values
-49.4
-53.8
-41.7
-61.8
-56.0
-60.3
-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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