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 Hardware Design Manuallines

2. SCHEMATIC CHECKLIST AND PCB LAYOUT DESIGN
Solution:
Add a 10 µF filter capacitor to the branch of the power trace (the branch powering the ESP32 analog power
pin). The 10 µF capacitor should be as close to the analog power pin as possible for small and stable current
ripples.
2.2.3.2

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
clock may be corrupted by other interfering signals, such as high-speed 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.
2.2.3.3 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 connecting 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 impedance of the antenna
as seen from the RF pin matches closely with that of the chip. This reduces reflections to the minimum.
2.2.3.4

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 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 interference sources 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.
High performance digital circuitry should be placed away from the RF block on large board designs. Please see
Chapter 2.2 for details.
Espressif Systems 22 ESP32 Hardware Design Guidelines V2.1
2.2 for de-