Beware of a certain ESP32-S3 development board on Taobao with extremely poor WiFi signal, suspected of lacking impedance matching

Industry Exchange Product Review & Teardown
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First, let’s look at normal performance. This is LCSC’s ESP32-S3 development board, showing a Wi-Fi signal strength of -54dBm for network 905.

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Now, let’s check the ESP32-S3 development board purchased from Taobao. At the same location, the Wi-Fi signal strength for network 905 is only -77dBm, making it unable to connect to Wi-Fi.

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The board shown in the image below—three units of this exact model were bought from different Taobao sellers (Why insist on this model? Because its width fits breadboards, while others are wider and incompatible. LCSC’s board also fits breadboards but originally costs 35 RMB, which is slightly expensive; you need to gather likes on social media to get it discounted to 19.9 RMB. The Taobao version was bought for 25 RMB). All three exhibited similarly poor signal performance. It appears they’re based on an open-source design without proper impedance matching. All use the ESP32-S3R8 chip and ceramic antennas (the antenna itself likely isn’t the issue, as LCSC’s board also uses a ceramic antenna but performs well).

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:play_button: Electronics/Microcontroller Technical Discussion QQ Group: 2169025065

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By the way, there’s another issue with this development board from Taobao: the factory firmware seems to be faulty. It continuously resets and reboots upon powering up. The problem is resolved after pressing and holding the BOOT button while powering on, then flashing your own program. I bought three boards from different sellers, and all of them had this issue!

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Tried replacing the antenna, but there was no significant change. Then replaced the inductor in the antenna’s π-matching circuit with a 2.2nH one, which noticeably improved the signal. The performance is still somewhat suboptimal, but much better than before—the company Wi-Fi signal now reaches -67dBm. Still a bit weak compared to a previous board we developed at the company using the same ceramic antenna, which achieved -55dBm.

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Wow, I just realized that this ceramic antenna and the IPX connector are directly connected in parallel without using open pads to separate them (which is normally how it’s done). After plugging in an external antenna, the same Wi-Fi signal immediately improved from -67dBm to -52dBm—ridiculous!

Also, the component placement and routing of the π-type matching circuit are extremely unreasonable.

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Plugged in an external antenna, but still can’t connect to WiFi. Created an AP hotspot, yet my phone can’t detect the signal either (the same code works fine on another board from LCSC). Suspecting that due to impedance discontinuity, the transmitted signal is entirely reflected back, or perhaps the reflected signal has damaged the RF transmission section…

For such a design to actually enter mass production and be sold, it really shows—this world is one giant makeshift troupe…

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This design is kind of ridiculous :rofl:

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To add further, the ESP32-S3 chip on this board runs slightly hotter compared to a normal board. The thermal image below shows the boards operating in AP mode (Wi-Fi hotspot) after running for 5 minutes. On the left is the LCSC board, with the ESP chip at 48°C; on the right is the board from Taobao, with the ESP chip reaching 60.2°C—significantly higher. This suggests there may be an issue with the RF section, resulting in approximately 0.4 watts higher power consumption.

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