Antenna Diversity

AN14463

Antenna, Wi-Fi, Bluetooth, Bluetooth LE, 802.15.4, diversity, single antenna, dual antenna, front-end, radio performance

NXP B.V.

Antenna Diversity

24 gen 2025 — Antenna diversity feature is used to improve and optimize the signal quality. The front-end design includes two or more antennas to reduce the effects of ...

AN14463: Antenna Diversity - Application note

IW612: 2.4/5 GHz Dual-Band 1x1 Wi-Fi 6 (802.11ax) Bluetooth 5.4 802.15.4 Tri-Radio Solution | NXP Semiconductors

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Document DEVICE REPORTAN14463

AN14463
Antenna Diversity
Rev. 1.0 -- 24 January 2025

Application note

Document information

Information

Content

Keywords

Antenna, Wi-Fi, Bluetooth, Bluetooth LE, 802.15.4, diversity, single antenna, dual antenna, frontend, radio performance

Abstract

Explains antenna diversity feature, single antenna design, and dual antenna design.

NXP Semiconductors

AN14463
Antenna Diversity

1 About this document
Antenna diversity feature is used to improve and optimize the signal quality. The front-end design includes two or more antennas to reduce the effects of interference. This document explains the different types of RF frontend antenna configurations with and without antenna diversity. Each design has specific benefits related to cost, radio priority, and more. Contact your NXP representative for more information and guidance on which design is best suited to your application.
1.1 Supported devices
This document applies to the following wireless SoCs:
· IW416 · IW610 · AW611 · IW611 · IW612 · 88W8987 · RW610 · RW612 · 88W8801

AN14463
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Rev. 1.0 -- 24 January 2025

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AN14463
Antenna Diversity

2 Wi-Fi antenna diversity algorithm
Antenna diversity is used to determine the best suited antenna for real time performance. The feature can be enabled by firmware when the NXP wireless SoC is in client mode. The firmware must evaluate and compare each antenna at a set evaluation interval to determine which antenna best fits the environmental condition. At every evaluation interval, the firmware checks the performance of each antenna for the following parameters:
· TX frame error rate (FER) · RX signal to noise ratio (SNR) · Number of missed beacons
The evaluation interval is user configurable and dynamic. By default, the evaluation interval is set to trigger every 6 seconds but the interval may scale with the SNR measured on the current antenna.
· 10 < SNR < 40: user configured time (the default is 6 seconds) · SNR 10: 0.5x of user configured time (the default is 3 seconds) · SNR 5: 0.25x of user configured time (the default is 1.5 seconds) · SNR 40: 2x of user configured time (the default is 12 seconds)
The firmware compares the measurement of each antenna parameters (FER, SNR, and number of missed beacons), and selects the best antenna based on the following:
· If the difference between the two antenna FER values is greater than 5% over 100 TX attempts, the antenna with the lowest FER is selected.
· If the difference between the two antenna SNR is greater than 3 dB, the antenna with the highest SNR is selected.
· If the difference between the number of missed beacons between the two antennas is greater than five beacons, the antenna with the lowest number of missed beacons is selected.
The selected antenna is used until the next evaluation interval, when the evaluation and comparison cycle is repeated.
Figure 1 illustrates the antenna diversity algorithm.

Occurs every 6 seconds (configurable)

Antenna selection

Selects the best antenna

Evaluation period on antenna 1

Comparison period

Evaluation period on antenna 2
Figure 1.Illustration of antenna diversity algorithm

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Rev. 1.0 -- 24 January 2025

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AN14463
Antenna Diversity

3 Front-end configurations
The antenna diversity setup depends on the front-end design. This document covers the following front-end designs: · Single-antenna design · Dual-antenna design
3.1 Single-antenna design
In a single-antenna design, the Wi-Fi and Bluetooth/802.15.4 radios share the same antenna. · A single pole double throw (SPDT) switch is used between the 2.4 GHz Wi-Fi and Bluetooth/802.15.4 radios. · A diplexer is used between the 5 GHz Wi-Fi radio and SPDT switch.
Figure 2 illustrates a single-antenna design without diversity.

Main (Ant 1)

Wireless SoC

Wi-Fi 5 GHz

Wi-Fi 2.4 GHz Bluetooth/802.15.4

SPDT Switch

Diplexer

Figure 2.Single-antenna design without diversity
To enable antenna diversity on a single antenna design, an additional SPDT diversity switch and auxiliary antenna are required. The additional SPDT switch is used to select the best antenna based on the firmware algorithm (Section 2). Figure 3 illustrates a single-antenna design with diversity.
Main (Ant 1) Aux (Ant 2)

Wireless SoC

Wi-Fi 5 GHz

Wi-Fi 2.4 GHz Bluetooth/802.15.4

SPDT Switch

Diplexer

SPDT diversity switch

Figure 3.Single antenna design with diversity

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Rev. 1.0 -- 24 January 2025

NXP Semiconductors

AN14463
Antenna Diversity

3.2 Dual-antenna design
In a dual-antenna design, the Wi-Fi and Bluetooth/802.15.4 radios use separate antennas. The operation of the Wi-Fi and Bluetooth/802.15.4 radios is simultaneous given the appropriate antenna isolation.
· The diplexer between the Wi-Fi radio and the antenna is used for the 2.4 GHz and 5 GHz RF paths. · The Bluetooth/802.15.4 radio uses a separate antenna. Figure 4 illustrates a dual-antenna design without diversity.

Wi-Fi (Ant 1)

Bluetooth/802.15.4 (Ant 2)

Wireless SoC

Wi-Fi 5 GHz Wi-Fi 2.4 GHz

Diplexer

Bluetooth/802.15.4

Figure 4.Dual-antenna design without diversity
To enable antenna diversity on a dual-antenna design, an additional double pole double throw (DPDT) switch is added after the diplexer. The DPDT switch is used to select the best antenna based on the antenna diversity algorithm. When the Wi-Fi and Bluetooth/802.15.4 radios operate simultaneously, the firmware allocates the best antenna to the Wi-Fi radio. The DPDT switch allocates the other antenna to the Bluetooth/802.15.4 radio. Figure 5 illustrates a dual-antenna design with diversity.
Aux (Ant 2) Main (Ant 1)

Wireless SoC

Wi-Fi 5 GHz Wi-Fi 2.4 GHz
Bluetooth/802.15.4

Diplexer

Figure 5.Dual-antenna design with diversity

DPDT diversity switch

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Rev. 1.0 -- 24 January 2025

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AN14463
Antenna Diversity

The dual-antenna design can also include an auxiliary Wi-Fi antenna that supports diversity, and a separate antenna for Bluetooth/802.15.4 radio without antenna diversity. In this configuration, the Wi-Fi and Bluetooth/802.15.4 radios can operate simultaneously given the appropriate antenna isolation.
· An SPDT diversity switch is used to select the best antenna for Wi-Fi. · The Bluetooth/802.15.4 radio operates on a separate antenna.
Figure 6 illustrates the dual-antenna design with the auxiliary Wi-Fi antenna thaht supports diversity.

Wi-Fi antenna 1

Wi-Fi antenna 2

Bluetooth/802.15.4 antenna

Wireless SoC

Wi-Fi 5 GHz Wi-Fi 2.4 GHz

Diplexer

SPDT diversity switch Bluetooth/802.15.4

Figure 6.Dual-antenna design with auxiliary Wi-Fi antenna and diversity

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Rev. 1.0 -- 24 January 2025

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AN14463
Antenna Diversity

4 RF Front-end (FE) switch setting configuration
The Wi-Fi and Bluetooth/802.15.4 front-end parameters are configurable using the calibration data. The frontend parameters are used:
· To enable antenna diversity. · To configure the RF controls of the SPDT or DPDT switch.
Use additional parameters in the calibration data to optimize the radio transmit power and reduce TX frame error rate (FER), RX signal to noise ratio (SNR), and the number of missed beacons. Refer to [1], [2], [3], [4], [5], or [6].

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Rev. 1.0 -- 24 January 2025

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AN14463
Antenna Diversity

5 Enabling antenna diversity
Antenna diversity is enabled by software during runtime. The procedure depends on the operating system of the host device.

5.1 Linux and Android
To enable antenna diversity on an NXP wireless SoC with a Linux/Android host platform: · Wait for the firmware download to complete. · Go to the directory with the configuration file of the wireless SoC. The path is /proc/mwlan/adapter0/config. · Issue the command to set the antenna configuration.
echo "antcfg=<Antenna mode> <Evaluation interval (ms)>" > /proc/mwlan/adapter0/config

Table 1.Command parameters

Parameter

Description

Antenna mode

Antenna mode for TX/RX 0x1 = RF path set to Antenna 1 (disable antenna diversity) 0x2 = RF path set to Antenna 2 (disable antenna diversity) 0xffff = Enable antenna diversity

Evaluation interval

Evaluation interval in milliseconds (ms) Enter interval as a hexadecimal number The default value is 0x1770 (6000 ms) Note: This parameter is only needed when Antenna mode is set to 0xffff.

Example of command to enable antenna diversity with a 6 second evaluation interval:

echo "antcfg=0xffff" > /proc/mwlan/adapter0/config

Example of command to disable antenna diversity and set TX/RX path to Antenna 1:

echo "antcfg=1" > /proc/mwlan/adapter0/config

Command to readback the antenna diversity configuration:

cat /proc/mwlan/adapter0/config

Example of command readback:

hardware_status=0 netlink_num=31 drv_mode=7 hssetpara=7,0xff,200,400 sdcmd52rw=0 0x0 0x00 rf_test_mode=0 antcfg=0xffff 6000 1

The values in bold show that antenna diversity is enabled with a 6000ms evaluation time and the current antenna is set to 1.

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Rev. 1.0 -- 24 January 2025

NXP Semiconductors

AN14463
Antenna Diversity

5.2 FreeRTOS
To enable antenna diversity on the wireless SoC with a FreeRTOS host platform: · Wait for the firmware download to complete. · Issue the command to set the antenna configuration.
wlan-set-antcfg <Antenna mode> <Evaluation interval>

Table 2.Command parameters

Parameter

Description

Antenna mode

Antenna mode for TX/RX 0x1 = RF path set to Antenna 1 (disable antenna diversity) 0x2 = RF path set to Antenna 2 (disable antenna diversity) 0xffff = enable antenna diversity

Evaluation interval

Evaluation interval in milliseconds (ms) Enter interval as a decimal number The default value is 6000 Note: This parameter is only needed when Antenna mode is set to 0xffff.

Example of command to enable antenna diversity with a 6 second evaluation interval:

wlan-set-antcfg 0xffff

Example of command to disable antenna diversity and set TX/RX path to Antenna 1:

wlan-set-antcfg 1

Command to readback the antenna diversity configuration:

wlan-get-antcfg

Example of command readback:

Mode of Tx/Rx path is : ffff Evaluate time : 6000 Default diversity mode. Current antenna is Ant1

The return values in bold show that antenna diversity is enabled with a 6000 ms evaluation time and current antenna set to 1.

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Rev. 1.0 -- 24 January 2025

NXP Semiconductors

AN14463
Antenna Diversity

6 Abbreviations

Table 3.Abbreviations

Abbreviation

Definition

Ant

antenna

DPDT

double dipole pole throw

front-end

FEM

front-end module

FER

frame error rate

low energy

SDPT

single dipole pole throw

SNR

signal to noise ratio

7 References
[1] Application note 88W8801 Calibration Structure (link) [2] Application note 88W8987 Calibration Structure (link) [3] Application note AN12794: IW416 Calibration Structure (link) [4] Application note AN13983: Calibration Structure for AW611, IW611, and IW612 (link) [5] Application note AN13639: Calibration Structure for RW61x [6] Application note AN14308: Calibration Structure for IW610 (link)

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Rev. 1.0 -- 24 January 2025

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AN14463
Antenna Diversity

8 Note about the source code in the document
The example code shown in this document has the following copyright and BSD-3-Clause license:
Copyright 2025 NXP Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials must be provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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9 Revision history

Table 4.Revision history Document ID
AN14463 v.1.0

Release date 24 January 2025

Description · Initial version

AN14463
Antenna Diversity

AN14463
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 1.0 -- 24 January 2025

NXP Semiconductors

AN14463
Antenna Diversity

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AN14463
Antenna Diversity

Tables

Tab. 1. Command parameters .......................................8 Tab. 2. Command parameters .......................................9

Tab. 3. Abbreviations ...................................................10 Tab. 4. Revision history ...............................................12

Figures

Fig. 1. Fig. 2. Fig. 3. Fig. 4.

Illustration of antenna diversity algorithm .......... 3 Single-antenna design without diversity ............ 4 Single antenna design with diversity ................. 4 Dual-antenna design without diversity ...............5

Fig. 5. Fig. 6.

Dual-antenna design with diversity ....................5 Dual-antenna design with auxiliary Wi-Fi antenna and diversity ........................................ 6

AN14463
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Rev. 1.0 -- 24 January 2025

NXP Semiconductors

Contents

About this document .......................................2

1.1

Supported devices ............................................. 2

Wi-Fi antenna diversity algorithm .................. 3

Front-end configurations ................................ 4

3.1

Single-antenna design ....................................... 4

3.2

Dual-antenna design ..........................................5

RF Front-end (FE) switch setting

configuration .................................................... 7

Enabling antenna diversity ............................. 8

5.1

Linux and Android ............................................. 8

5.2

FreeRTOS ..........................................................9

Abbreviations ................................................. 10

References ......................................................10

Note about the source code in the

document ........................................................11

Revision history .............................................12

Legal information ...........................................13

AN14463
Antenna Diversity

Please be aware that important notices concerning this document and the product(s) described herein, have been included in section 'Legal information'.

For more information, please visit: https://www.nxp.com

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Date of release: 24 January 2025 Document identifier: AN14463

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