NXP Semiconductors AN13887 Installation and operating instructions

AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer
Coexistence
Rev. 1 — 27 October 2023 Application note
Document information
Information Content
Keywords AN13887, K32W148, IEEE 802.15.4, noise interference, sinewave interference, Bluetooth
audio interference, Wi-Fi interference, carrier-to-noise ratio, packet error rate, adjacent-channel
interference
Abstract This document provides the RF system evaluation test results of NXP K32W148 MCU for IEEE
802.15.4 applications with coexistence of these interferers: noise, sinewave, Bluetooth audio, and
Wi-Fi.

NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
1 Introduction
This document provides the RF system evaluation test results of NXP K32W148 MCU for IEEE 802.15.4
applications with coexistence of these interferers: noise, sinewave, Bluetooth audio, and Wi-Fi. The tests are
based on offset quadrature phase-shift keying (OQPSK) modulation.
The document also describes test setup and provides steps to perform the tests.
Note: To get the K32W148 radio parameters, see the K32W14x Product Family Data Sheet (K32W1480).
1.1 K32W148 evaluation kit
For evaluating K32W148 performance, NXP K32W148 evaluation kit (K32W148-EVK board) is used (shown in
Figure 1).
J7 (SMA)
J6
(Ranger 4)
ANT1
SW3
(WUU)
SW2
(NMI)
SW1
(reset)
SW4
(target MCU boot)
J5
(Ranger 4)
J14
(USB)
J1 (Arduino DL)
J13 (mikroBUS)
J12 (mikroBUS)
J4 (Arduino AN)
J16
(SWD)
D7
LED1
LED3
LED2
D12
D16
D17
D11
D14
D15
D13
J3 (Arduino PWR)
J2 (Arduino DH)
SW5
(wake-up)
K32W148 MCU
Figure 1. K32W148-EVK board
For more information on the K32W148-EVK board, see K32W148-EVK Board User Manual (K32W148-
EVKUM).
1.2 System requirements
The following equipments are used to perform RX and TX measurements:
•R&S SFU as the interferer source for noise, sinewave, Bluetooth audio, and Wi-Fi interference tests. Any
generator with ARB can be used as interference source.
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
•R&S SMBV100A for generating the desired IEEE 802.15.4 signal. Any generator with ARB can be used as
IEEE 802.15.4 signal generator.
•PC equipped with a general-purpose interface bus (GPIB) card
To communicate with the K32W148 MCU, the PC should have Tera Term installed.
Before performing any measurement, a binary code must be loaded into the flash memory of the board
using the In-System Programming (ISP) utility. For details, see the KW45B41Z and K32W148 In-System
Programming Utility application note (AN13859).
Figure 2 shows an example binary code from Connectivity Test Tool that used by NXP for tests described in this
document.
Figure 2. Binary code loaded
1.3 List of tests
Following are the tests conducted on the K32W148 MCU:
•Noise interference:
–Carrier-to-noise ratio (C/N) vs frequency
Note: Carrier-to-noise ratio (C/N) is also known as signal-to-noise ratio (SNR).
–Packet error rate (PER) vs C/N
•Sinewave (continuous wave) interference
•Bluetooth audio interference
•Wi-Fi interference:
–Adjacent-channel interference (ACI)
–Co-channel
2 Noise interference
This section is divided into the following subsections:
•Noise interference test setup
•Noise interference tests
2.1 Noise interference test setup
Setup diagram
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
Figure 3 shows the setup diagram of the noise interference test.
SMBV100A: IEEE 802.15.4
signal generator
SFU: White noise generator
Spectrum analyzer
+
I2C / UART
Trigger
RF cable
RF combiner
Figure 3. Noise interference test setup
Signal definition
Carrier-to-noise (C/N) measurement highlights the demodulator (baseband) section performance.
White noise is added into the desired channel. The noise power is increased until the criteria PER = 1% is met.
The C/N is calculated on 2.3 MHz bandwidth.
Figure 4 shows the settings required for the noise interference test.
Frequency
Power
5 MHz (spacing)
Noise source
96 MHz
C/N within
bandwidth
= 2.3 MHz
IEEE 802.15.4
Figure 4. White noise interference test settings
2.2 Noise interference tests
This section is divided into the following subsections:
•C/N vs frequency test
•PER vs C/N test
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
2.2.1 C/N vs frequency test
Test method
Follow these steps to perform the C/N vs frequency test:
1. Configure the K32W148 radio as follows:
•RX mode
•Modulated
•Continuous mode
•Frequency: From channel 11 (2405 MHz) to channel 26 (2480 MHz)
2. Configure the desired signal on the signal generator as follows:
•IEEE 802.15.4 modulated signal (typically 1000 packets of 20 bytes)
•Continuous mode
•Frequency: From channel 11 (2405 MHz) to channel 26 (2480 MHz)
•RF output power level (fixed): -78.5 dBm
3. Configure the noise generator (SFU) as follows:
•Center frequency: Channel 18 (2440 MHz)
•Bandwidth: 2 MHz
4. Check the power levels of the desired IEEE 802.15.4 signal and noise signal on the spectrum analyzer,
which performs power calibration on these signals:
•Span is 10 MHz.
•C/N function is enabled with a channel bandwidth at 2 MHz.
5. For each channel of the desired signal, start from a C/N where PER is at 0%, then decrease it until the
criteria PER = 1% is met, and then, record and plot the C/N value, as shown in Figure 5.
Test results
Figure 5 shows the results of the C/N vs frequency test.
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
2405 2410 2415 2420 2425 2430 2435 2440 2445 2450 2455 2460 2465 2470 2475 2480
Channel frequency (MHz)
C/N (dB)
Figure 5. C/N vs frequency test results
Conclusion
C/N performance is independent from the channel (purely baseband performance). Typically, the measured C/N
is 8 dB.
2.2.2 PER vs C/N test
Test method
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
Follow these steps to perform the PER vs C/N test:
1. Configure the K32W148 radio as follows:
•RX mode
•Modulated
•Continuous mode
•Frequency: From channel 11 (2405 MHz) to channel 26 (2480 MHz)
2. Configure the desired signal on the signal generator as follows:
•IEEE 802.15.4 modulated signal (typically 1000 packets of 20 bytes)
•Continuous mode
•Frequency: From channel 11 (2405 MHz) to channel 26 (2480 MHz)
•RF output power level (fixed): -78.5 dBm
•Configure the noise generator (SFU) as follows:
–Center frequency: 2440 MHz
–Bandwidth: 2 MHz
•Check the power levels of the desired IEEE 802.15.4 signal and noise signal on the spectrum analyzer, which
performs power calibration on these signals:
–Span is 10 MHz.
–C/N function is enabled with a channel bandwidth at 2 MHz.
•For each channel of the desired signal, start from a C/N where PER is at 0%, then decrease it and plot the C/
N and PER values, as shown in Figure 6.
Test results
Figure 6 shows the results of the PER vs C/N test where center frequency is at 2440 MHz.
0
10
20
30
40
50
60
70
80
90
100
5 6 7 8 9 10
C/N (dB)
PER (%)
Figure 6. PER vs C/N test results
Conclusion
When the noise increases, PER degrades smoothly – no abrupt degradation.
3 Sinewave interference
This section is divided into the following subsections:
•Sinewave interference test setup
•Sinewave interference test
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
3.1 Sinewave interference test setup
Setup diagram
Figure 7 shows the setup diagram of the sinewave interference test.
SMBV100A: IEEE 802.15.4
signal generator
SFU: Sinewave generator
Spectrum analyzer
+
I2C / UART
Trigger
RF cable
RF combiner
Figure 7. Sinewave interference test setup
Signal definition
In this test case, a pure sinewave is used to measure the adjacent-channel interference (ACI) (N±8) and co-
channel immunity.
The sinewave power is increased until the criteria PER = 1% is met.
Figure 8 shows the settings required for the sinewave interference test.
Frequency
Power Pure sinewave
IEEE 802.15.4
Figure 8. Pure sinewave interference – test settings
3.2 Sinewave interference test
Test method
Follow these steps to perform the sinewave interference test:
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
1. Configure the K32W148 radio as follows:
•RX mode
•Modulated
•Continuous mode
•Frequency: Channel 18 (2440 MHz)
2. Configure the desired signal on the signal generator as follows:
•IEEE 802.15.4 modulated signal (typically 1000 packets of 20 bytes)
•Continuous mode
•Frequency: On one channel, channel 18 (2440 MHz)
3. Check the power levels of the desired signal and the sinewave (-20 dBm) on the spectrum analyzer.
4. For a pure sinewave interferer swept from channel 11 (2405 MHz) to channel 18 (2440 MHz) with a constant
power level set at -20 dBm, decrease the power level until the criteria PER = 1% is met. Then, note the
required power level and the frequency of the sinewave.
Test results
Figure 9 shows the results of the sinewave interference test where sinewave interferer is at 2440 MHz / 20 dBm
and PER (sensitivity) is at 1%.
-120
-100
-80
-60
-40
-20
0
2405 2410 2415 2420 2425 2430 2435 2440 2445 2450 2455 2460 2465 2470 2475 2480
Channel frequency (MHz)
Power level (dBm)
Figure 9. RF input power level vs continuous wave interferer test results
Conclusion
A sinewave signal at a slightly higher power level (-20 dBm) acts as a blocker; therefore, the K32W148 receiver
regulates its receiver gain.
4 Bluetooth audio interference
This section is divided into the following subsections:
•Bluetooth audio interference test setup
•Bluetooth audio interference test
4.1 Bluetooth audio interference test setup
Setup diagram
Figure 10 shows the setup diagram of the Bluetooth audio interference test.
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
SMBV100A: IEEE 802.15.4
signal generator
SFU: ARB Bluetooth LE signal generator
Spectrum analyzer
+
I2C / UART
Trigger
RF cable
RF combiner
Figure 10. Bluetooth audio interference test setup
Signal definition
The following measurements can be made by capturing 1 channel (case 1) from a smartphone Bluetooth audio
stream:
•The Bluetooth interferer is set at a constant power level of -51.5 dBm. Its frequency is varied from -5 MHz to
+5 MHz on the IEEE 802.15.4 channel by step of 1 MHz. Duty cycle is forced to 5%.
•The IEEE 802.15.4 signal power is decreased until the criteria PER = 1% is met.
Figure 11 shows the settings required for the Bluetooth audio interference test.
Frequency
Power
5 MHz 1 MHz
Bluetooth
IEEE 802.15.4
Figure 11. Bluetooth audio interference test settings
4.2 Bluetooth audio interference test
Test method
Follow these steps to perform the Bluetooth audio interference test:
1. Configure the K32W148 radio as follows:
•RX mode
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NXP Semiconductors AN13887
K32W148 RF System Evaluation for IEEE 802.15.4 Applications with Interferer Coexistence
•Modulated
•Continuous mode
•Frequency: Channel 11 (2405 MHz), channel 18 (2440 MHz), channel 21 (2455 MHz), and channel 26
(2480 MHz)
2. Configure the desired signal on the signal generator as follows:
•IEEE 802.15.4 modulated signal (typically 1000 packets of 20 bytes)
•Continuous mode
•Frequency: Channel 11 (2405 MHz), channel 18 (2440 MHz), channel 21 (2455 MHz), and channel 26
(2480 MHz)
3. Check the power levels of the desired IEEE 802.15.4 signal and Bluetooth audio stream interference signal
on the spectrum analyzer, which performs power calibration on these signals.
4. Set the Bluetooth audio stream to -51.5 dBm, and then vary the frequency from -5 MHz to +5 MHz by step
of 1 MHz only on the existing Bluetooth channels (between 2402 MHz and 2480 MHz). Force duty cycle to
5%.
5. Decrease the IEEE 802.15.4 signal power until the criteria PER = 1% is met.
Test results
Figure 12 shows the results of the Bluetooth audio interference test with interferer Bluetooth audio Fs3MHz
where PER (sensitivity) is at 1%.
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
IEEE 802.15.4 minimum input power (dBm)
Interferer channel frequency offset (MHz)
Legend:
Channel 11
Channel 18
Channel 21
Channel 26
N-5 N-4 N-3 N-2 N-1 N N+1 N+2 N+3 N+4 N+5
Figure 12. IEEE 802.15.4 minimum input power vs Bluetooth audio test results
Conclusion
For co-channel, the carrier-to-interferer ratio (C/I) is +3 dB (IEEE 802.15.4 channel 11, 18, or 26).
5 Wi-Fi interference
This section is divided into the following subsections:
•Wi-Fi interference test setup
•Wi-Fi interference tests
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