Q: The Power Ripple Is Small, But Rf Tx Performance Is Poor; Q: When Esp32 Sends Data Packages, The Power Value Is Much Higher Or Lower Than The Target Power Value, And The Evm Is Relatively Poor; Q: Tx Performance Is Not Bad, But The Rx Sensitivity Is Low - Espressif Systems ESP32 Series Manual

3.2 PCB Layout
Generally, the ripple should be <100 mV when ESP32 sends 11n MCS7 packets, and < 120 mV when ESP32
sends 11b 11m packets.
Solution:
Add a 10 µF filter capacitor to the branch of the power trace (the branch is ESP32's analog power pin). The 10 µF
capacitor should be as close to the analog power pin as possible for small and stable current ripples.
3.2.3.2

Q: The power ripple is small, but RF Tx performance is poor.

Analysis:
The RF Tx performance can be affected not only by power ripples, but also by the crystal oscillator itself. Poor
quality and big frequency offsets of the crystal oscillator decrease the RF Tx performance. The crystal oscillator
can be corrupted by other interfering signals, such as output or input signals. In addition, high-frequency signal
traces, such as the SDIO trace and UART trace under the crystal oscillator, could also result in the malfunction of
the crystal oscillator. Besides, sensitive components or radiation components, such as inductors and antennas,
may also decrease the RF performance.
Solution:
This problem is caused by improper layout and can be solved by re-layout. Please see Chapter
tails.
3.2.3.3 Q: When ESP32 sends data packages, the power value is much higher or lower than the target
power value, and the EVM is relatively poor.
Analysis:
The disparity between the tested value and the target value may be due to signal reflection caused by the impedance
mismatch on the transmission line between the RF pin and the antenna. Besides, the impedance mismatch will
affect the working state of the internal PA, making the PA prematurely access the saturated region in an abnormal
way. The EVM becomes poor as the signal distortion happens.
Solution:
Match the antenna's impedance with the reserved π-type circuit on the RF trace, so that the resistance of the RF
pin towards the antenna is similar to that of the chip.
3.2.3.4

Q: Tx performance is not bad, but the Rx sensitivity is low.

Analysis:
Good Tx performance indicates proper RF impedance matching. External coupling to the antenna can affect the
Rx performance. For instance, the crystal oscillator signal's harmonics could couple to the antenna. If the Tx and
Rx traces of UART cross over with RF trace, then, they will affect the Rx performance, as well. If ESP32 serves as a
slave device, there will be other high-frequency interferences on the board, which may affect the Rx performance.
Solution:
Keep the antenna away from crystal oscillators. Do not route high-frequency signal traces close to the RF trace.
Please see Chapter 3.2 for details.
Espressif Systems
3 SCHEMATICS AND PCB LAYOUT DESIGN
22 ESP32 Hardware Design Guideline V1.0
3.2 for de-