A bare metal test

This time, the radiation noise of the iPhone 13 Pro 256G was tested. The mobile phone was tested with 4K video playback, sound and brightness adjusted to the maximum. The test standard is EN55032 Class B 3m. The test images and data are as follows:

Figure 1 Horizontal Orientation

Figure 2 Vertical Orientation

From the data in the figure above, we can see that the radiated noise of the bare metal is very low, close to the noise floor.

Two charging test

Next, we connected the Anker 20W fast charge to charge the mobile phone. At this time, the power of the mobile phone was 91%.

Figure 3 Horizontal Orientation

Figure 4 Vertical Orientation

From the data, we can find that after connecting the Anker 20W fast charge, the noise is much higher, especially the noise in the vertical direction approaches the limit of EN55032 Class B (green is the standard limit, and the blue test data cannot exceed this limit) ; Red is the 6dB margin limit, if the blue test data does not exceed this limit, it means at least 6dB margin).

There are two main reasons for the high radiation: 1. The noise of the AC-DC part of the Anker 20W fast charging head is radiated through the 1-meter-long power cord; 2. The DC-DC noise inside the Apple iPhone 13 Pro passes through the 1-meter-long power cord. Power lines radiate out.

Therefore, we can find that if the product contains AC-DC or DC-DC, and then there is a long power cord, it is easy to cause the radiation noise to exceed the standard.

Three adapter ring plus magnetic ring

By adding a magnetic ring on the adapter end (Anker 20W fast charging head end), we can judge how much common mode noise is on the adapter end. The following are the test results:

Figure 5 Horizontal direction – charging without magnetic ring

Figure 6 Horizontal Orientation – Charging and Magnetic Ring

Figure 7 Vertical direction – charging without magnetic ring

Figure 8 Vertical Orientation – Charging and Magnetic Ring

Through the test data, we can find that after the magnetic ring is added to the adapter end, the noise of 50-200MHz is significantly reduced, and the radiation test has a margin of more than 6dB.

Since I don’t have Apple’s original fast charging head on hand (because it’s green, you know), there is no noise to compare the fast charging head.

Nowadays, many consumer electronic products require AC-DC adapters, and the noise caused by different adapters is very different. I hope that friends will choose adapters with lower noise when testing their products.

Reviewing Editor: Peng Jing

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