This document provides recommendations for matching a 2.4 GHz RF transceiver to achieve optimal performance. It describes measuring the transceiver output without a direct connection, then matching to 50 ohms for receive mode before tuning transmit mode. Procedures are outlined for measuring and adjusting filter and diplexer matching values to achieve low insertion loss and return loss. The document also recommends steps for combining and fine-tuning the filter and transceiver matching.

1. 1

2. WLAN RF Transceivers
 Qualcomm WCN 3660 [15]
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3. 2.4 GHz Matching Procedures and Recommendations
 2.4 GHz RF Path [15]
Transceiver
2.4 GHz BPF
2.4 GHz / 5 GHz
Diplexer
PDET5 GHz
Coupler
3

4. 2.4 GHz Matching Procedures and Recommendations
 Step1. Measure chip output performance. Do not
measure at the RF I/O directly, as it is not matched [7]
 Start with Rx and match to 50 Ω impedance.
 Performance goal at RF launch:
 Once Rx match is close to 50 Ω impedance, change to Tx
mode and fine tune for Tx performance to acceptable level
Transceiver
Z1
Z2
RF launch
port here for
measurement
4

5. 2.4 GHz Matching Procedures and Recommendations
 RF launch example [7]
 It is very important to use a short RF launch with
sufficient ground.
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6. 2.4 GHz Matching Procedures and Recommendations
 General S-parameters measurement needs two ports,
one port is source, and the other is load.
 Nevertheless, for the situation, RX S-parameters
measurement needs only one port. Because the only
port is source, and transceiver(must be powered on) is
just the load.
Transceiver
Z1
Z2
RF launch
port here for
measurement
SourceLoad
6

7. 2.4 GHz Matching Procedures and Recommendations
 Indeed, to check Tx S-Parameters needs to remove
transceiver(due to reference plane). But this requires a
lot of hard work.
Transceiver
Z1
Z2
Port 1 Port 2
S11
Chip 2.4 GHz
I/O Pin
 Hence, for Tx Mode, just start with initial LC value and
fine tune for Tx performance such as EVM and power.
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8. 2.4 GHz Matching Procedures and Recommendations
 Rx S-Parameters for 2.4 GHz [7]
8

9. 2.4 GHz Matching Procedures and Recommendations
 Step2. Tune filter matching values for 50Ω matching [7]
 Start with the recommended matching values from the
manufacturer’s filter data sheet.
 Measure return loss and insertion loss for filter and
diplexer with their matching values:
 Place two RF launches (pigtails) at ports 1 and 2.
2.4 GHz BPF 2.4 GHz / 5 GHz
Diplexer
5 GHz
Port 1 Port 2
Matching
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10. 2.4 GHz Matching Procedures and Recommendations
 The input / output impedance of filter and diplexer should be
broadband and close to 50 Ω. Otherwise, the frequency
response of filter and diplexer will be unexpected, and the
loss and outband rejection will become poor.
 Measure return loss and insertion loss for filter and
diplexer with their matching values (cont.) :
 The insertion loss (S21) from port1 to port 2 should be as
expected from filter and diplexer specifications. The example
below shows ~ 2.3 dB of loss [7].
 Make sure insertion loss (S21) is as low as possible because
the final achievable performance will vary based on
the path loss of the front-end components.
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11. 2.4 GHz Matching Procedures and Recommendations
 Measure return loss and insertion loss for filter and
diplexer with their matching values (cont.) :
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12. 2.4 GHz Matching Procedures and Recommendations
 Step3. Combine filter matching and RF I/O matching,
and then perform fine-tuning.
 Please keep in mind that PDET (Power Detrctor) is RF
path as well, which affects EVM and TSSI. Hence,
reserve match networks in PDET trace in advance.
PDET
Coupler
Matching
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13. 2.4 GHz Matching Procedures and Recommendations
 Because filter matching is well controlled in step 2 by
S-parameters check. Thus, start with tweaking
transceiver and PDET matching values by measuring
TX performance at first.
 If TX performance is still not acceptable by tweaking
transceiver and PDET matching values, return to step2
until TX performance and Rx S-Parameters are both
acceptable.
Transceiver
2.4 GHz BPF
2.4 GHz / 5 GHz
Diplexer
PDET
5 GHz
Coupler
Matching Matching
Matching
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14. 5GHz Matching Procedures and Recommendations for
FEM
 5 GHz RF Path [7]
Transceiver
2.4 GHz / 5 GHz
Diplexer
2.4 GHz
FEM
Rx
PDET
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15. 5GHz Matching Procedures and Recommendations for
FEM
 5 GHz RF Path (cont.)
Transceiver
2.4 GHz / 5 GHz
Diplexer
2.4 GHz
FEM
Rx
PDET
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16. 5GHz Matching Procedures and Recommendations for
FEM
Transceiver
Z2
Z3
RF launch
port here for
measurement
Z1
 Step1. Measure DA output performance. Verify the RF
performance coming out of the chip is in line with the
transceiver specification. Adjust matching components
if necessary to achieve acceptable performance.
 Because WIFI 5 GHz has wider RF bandwidth from 5170
to 5835 MHz (~15% fractional BW), it's better to reserve
at least three components(T-type or pi-type) for match
networks to achieve broadband matching.
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17. 5GHz Matching Procedures and Recommendations for
FEM
 Step2. Measure and adjust the FEM match networks.
 In order to accurately measure S11 of the FEM, the FEM
must be powered on.
 Setting the output power of the network analyzer too
high can damage the FEM. Set the network analyzer to 0
dBm or lower.
MatchingFEM
Port 1 Port 2
Rx
S11
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18. 5GHz Matching Procedures and Recommendations for
FEM
 Step3. Measure S11 and path loss after FEM
2.4 GHz / 5 GHz
Diplexer
2.4 GHz PDET
Port 1
Matching
Port 2
S11
 Using a 2nd RF launch or an RF switch connector, load
port 2 and measure S-parameters [7].
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19. 5GHz Matching Procedures and Recommendations for
FEM
 Step4. Measure system performance:
 If the results are worse than expected, return to steps 2
and 3 for further tuning. 19

20. 5GHz Matching Procedures and Recommendations for
FEM
 Step5. Measure 5G Rx input impedance.
Matching 2FEM
Port 1
Rx
S11
Transceiver
Matching 1
 Because matching 2 is well controlled in step 2. Thus,
start with tweaking matching 1 to achieve 50Ω.
 If necessary, to adjust matching2 further to to achieve
50Ω. But need to return to step 4 to check system
performance is still acceptable or not [7].
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21. 5GHz Matching Procedures and Recommendations for
FEM
 Step6. Test 5G sensitivity.
 See the transceiver device specification for the
expected sensitivity results.
 If the results are worse than expected, return to step 5
and adjust the Rx matching components.
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22. Reference
[1] CHALLENGES IN DESIGNING 5 GHZ 802.11AC WIFI POWER AMPLIFIERS, RFMD
[2] WCN3660 EVM Degradation Issue Technical Note, Qualcomm
[3] SE5516A: Dual-Band 802.11a/b/g/n/ac WLAN Front-End Module, SKYWORKS
[4] 802.11ac Technology Introduction White Paper, RHODE & SCHWARZ
[5] WLAN IEEE 802.11ac Wide bandwidth high speed 802.11ac technology and testing,
RHODE & SCHWARZ
[6] ACPF-7024 ISM Bandpass Filter (2401 – 2482 MHz), AVAGO
[7] WCN36x0(A) RF Matching Guidelines, Qualcomm
[8] MCS Index for 802.11n and 802.11ac Chart
[9] Sources of Error in IQ Based RF Signal Generation
[10] Integration Aids 802.11ac Mobile Wi-Fi Front Ends
[11] Mini filters for multiband devices, TDK
[12] QCA61x4-1 RF Matching Guidelines, Qualcomm
[13] QCA61x4, QCA937x, QCA65x4 Design Guidelines/Training Slides, Qualcomm
[14] QCA6164-1 with External 2.4G and 5G RFFM Reference Design Example, Qualcomm
[15] WLAN/BT/FM Training Using WCN3660, WCN3660A, or WCN3680, Qualcomm
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