Q: The Power Ripple Is Small, But Rf Tx Performance Is Poor; Q: When Esp32-C6 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-C6 Series Hardware Design Manuallines

3 PCB Layout Design

3.10.2 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 itself. Poor quality and
big frequency offsets of the crystal decrease the RF TX performance. The crystal 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 traces and UART traces under the crystal, could also result in the malfunction of the crystal.
Besides, sensitive components or radiating 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 Section 3.4 for
details.
3.10.3 Q: When ESP32-C6 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 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.

3.10.4 Q: TX performance is not bad, but the RX sensitivity is low.

Analysis:
Good TX performance indicates proper RF impedance matching. Poor RX sensitivity may result from external
coupling to the antenna. For instance, the crystal signal harmonics could couple to the antenna. If the TX and RX
traces of UART cross over with RF trace, they will affect the RX performance, as well. If there are many
high-frequency interference sources on the board, signal integrity should be considered.
Solution:
Keep the antenna away from crystals. Do not route high-frequency signal traces close to the RF trace. Please
see Section 3.5 for details.
Espressif Systems 28
ESP32-C6 Series Hardware Design Guidelines v1.0
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