Chapter 5. Hardware related
5.4.7 How can I optimize the second harmonic and other spurious signals created by my
own products?
The second harmonic mainly comes from the radiation generated by the RF link and PA (power am-
plier) power supply. The backplane (board size) and the product also make impact on the second
harmonic. Therefore, it is recommended to:
• Add a ground capacitor of approximately 2.4 pF to the RF matching circuit to reduce the spurious
radiation coming from the RF link.
• Add a series inductor to the PA power supply (Pins 3 and 4 of ESP32) to reduce the spurious
radiation coming from it.
5.4.8 How can I suppress the harmonics of 80 MHz?
If the harmonics of 80 MHz (160 MHz, 240 MHz, 320 MHz, etc.) exceed the allowable levels of
spurious emissions, you can add a resistor of approximately 470 Ω to the data transmission circuit (TXD)
to suppress those harmonics.
5.4.9 Is manual power calibration required for the Espressif modules that connect to ex-
ternal antennas?
No, it is not required. When an external antenna is used, please make sure it is connected properly before
the module is powered up. Then, the module performs a self-calibration, including power calibration.
5.4.10 What is the default duty cycle for the “default”level when using the “RF Test
Tool”to set the Wi-Fi “TX continues”mode?
• The default duty cycle for the “default”level is 98% or higher, and cannot be modied.
5.5 Process and ESD Protection
5.5.1 What should be paid attention to during the ESP32 ESD test?
• The Electrostatic Discharge (ESD) test for ESP32 is conducted to ensure that the device has sucient tolerance
to withstand electrostatic discharge. The precautions are as follows: - ESD testing should be conducted in
an ESD laboratory or ESD protection area, which should have good grounding protection and electrostatic
discharge protection facilities. - When conducting ESD testing, please use ESD testing equipment that meets
international standards, including ESD generators and ESD grounding mats, to ensure the accuracy of the test
results. - When conducting ESD testing, please make sure you are using a stable 3.3 V voltage. If the EN trace
is too long, it may cause a reboot. - ESP32 devices should be tested multiple times to verify the reliability of
their tolerance, and the test results should be recorded and analyzed. - If the module does not respond, please
check the voltage of the air discharge or contact discharge used in the test.
Espressif Systems 167
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