In the past few days, Xiaomi SU7 car owners have revealed that the triple-layer silver-plated windshield glass has caused mobile phone signal issues, igniting another online debate. However, I want to tell you: most people have actually misunderstood. By the end, you should be able to understand the truth!

01. Will silver-plated glass weaken mobile phone signals?

Will the triple-layer silver-plated windshield glass of Xiaomi SU7 affect the reception of mobile phone signals?

First, the conclusion: Yes, Yu Chengdong previously mentioned at a press conference that silver-plated glass can interfere with signals, which is correct, but it doesn't necessarily affect the use of mobile phones!

Why say "yes"?

Let's talk about the principle of silver-plated glass.

Silver-plated glass is essentially a process of plating silver on the surface of glass. Through vacuum coating technology, a layer of high-reflectivity silver film is evenly coated on the surface of the glass. This film enhances the absorption and reflection of solar radiation by the glass, achieving heat insulation and sun protection effects. This principle is the same as the silver-plated glass used on many buildings.

So what is the so-called triple-layer silver-plated glass?

The image below is from the ZIMI LS7. It actually has 3 layers of silver plating and 1 layer of PVB laminated film between two layers of glass. Among them, the nano-scale silver plating layer has a good direct reflection effect on infrared light, blocking a large amount of light energy from entering the car. Meanwhile, ultraviolet light is mainly absorbed by the graduated PVB layer. The two materials work together to achieve both sun protection and heat insulation.

According to Xiaomi's car launch data, the Xiaomi SU7's entire glass area is 5.35㎡, with double-layer silver plating on the roof glass and triple-layer silver plating on the windshield glass. The side windows have optical coatings that can isolate ultraviolet and infrared light.

Will such a design affect the normal use of mobile phone signals in the car?

Theoretically, silver-plated glass has a certain shielding effect on electromagnetic fields due to the silver plating, which will affect mobile phone signals to a certain extent. This is the most basic physics principle, but I believe its impact is limited and unlikely to reach the point of affecting mobile phone use in the car. There are four reasons:

First, this issue is not difficult to test, and Xiaomi has officially stated that they have conducted sufficient mobile phone signal testing and verification, covering 15 phone models from 6 brands and including 3 major operators. The conclusion is that it does not affect mobile phone network signals.

Moreover, to ensure the normal use of ETC, Xiaomi SU7's windshield glass has specifically undergone a desilvering process in local areas. If this aspect has been considered, surely the impact on mobile phone signals cannot be overlooked?

Second, since the launch of Xiaomi SU7, various testing teams have conducted hundreds of live broadcasts using this car, but so far, no large-scale complaints about mobile phone signal issues have been found;

Third, in addition to Xiaomi SU7, there is also the ZIMI LS7 in the industry. The windshield glass of ZIMI LS7 is the same as that of the C919 aircraft. Of course, I haven't found out which glass of the C919 uses triple-layer silver plating. If there were indeed issues, I believe it would not be an isolated case but a common phenomenon.

Fourth, it doesn't make sense scientifically. Why do I say that?

Here, I have to科普 again about the reception process of mobile phone signals!

I have provided a detailed introduction to microwave communication in "One Book to Understand Smart Connected Vehicles." Long-distance microwave communication relies on numerous microwave relay stations.

In other words, mobile phone signal reception does not directly transmit from a single signal tower to the phone. Otherwise, that tower would have to be infinitely tall. In reality, its transmission relies on various reflections, scatterings, and even diffractions.

Returning to the scenario of playing on a phone inside a car, the signal not only comes from the windshield but also enters through the ABCD pillars, roof, doors, seals, chassis, etc. In other words, it's omnipresent. Xiaomi SU7 only has triple-layer silver plating on the front windshield, and the roof glass is the more common double-layer silver plating. The four windows are not silver-plated. One front windshield cannot completely block the signal, just like the wireless signal of a router placed in the living room at home will not be blocked by the walls of the room. Moreover, even fully metal-enclosed elevators can now solve signal issues.

In fact, we played with Xiaomi SU7 for a long time when it was first launched, and sitting in the car, we didn't experience any issues with mobile phone signals.

Therefore, my conclusion is: The triple-layer silver-plated windshield glass of models like Xiaomi SU7 does have an impact on mobile phone signals compared to the double-layer silver-plated windshield glass of models like Wenjie M9, but it should not affect usage. In fact, the positive experience of sun protection it brings far outweighs the negative experience of weakening mobile phone signals. People who blame the triple-layer silver-plated windshield glass for poor mobile phone signals are either foolish or malicious!

If you encounter issues with using your phone in a Xiaomi car, please leave a comment.

So where does the problem really lie? Please continue to the next section!

02. Should the windshield be replaced for GPS signal issues?

The source of the recent controversy surrounding Xiaomi SU7 comes from a screenshot of a vehicle maintenance record showing that the front windshield assembly was replaced. As a result, many people hastily concluded that this triple-layer silver-plated windshield glass is the root cause of poor mobile phone signals.

However, please note: There is another crucial piece of information in the screenshot: Navigation experience technology upgrade. In other words, this is an issue with the car's navigation signal, not the mobile phone signal inside the car.

Let's look at other complaint cases. Some cases mention "Xiaomi SU7 car navigation lagging," while others say "network issues lead to the map not loading real-time traffic conditions, and the navigation route changes from green to blue." In addition, I've seen more cases of "navigation positioning not moving."

Now the problem is clearer: the main issue lies in the car's GPS signal.

From a principle standpoint, if the car loses GPS signal, it will not only lead to navigation malfunction but also prevent the activation of advanced driving assistance systems.

As a former layout engineer, I looked into the antenna layout of Xiaomi SU7 and found two pieces of information:

First, the GPS antenna module of Xiaomi SU7 is located just below the windshield near the roof glass seam area. The antenna can only be installed on the back of the windshield glass, which is the roof beam sheet metal, so it is covered by the triple-layer silver-plated windshield glass.

The 5G antenna module of Xiaomi SU7 is also located in the intersection area between the roof glass and the rear windshield glass, but it is an independent component.

Based on my conversations with automotive engineers over the past few days and my traditional experience, many models place the GPS antenna and 5G module within a shark fin or the rear spoiler (mainly for SUVs and MPVs) because such locations receive signals without obstruction, and both shark fins and spoilers are plastic parts that won't interfere with signal reception. If necessary, one can find a suitable location on the tailgate or D-pillar.

In the era of electrification, to optimize aerodynamic coefficients and improve range, many automakers have eliminated shark fins and adopted hidden antenna layouts. One common design is placing them in the instrument panel area, such as a new car launched last June that I know of, which was placed on the side of the passenger airbag.

After seeing that Xiaomi SU7 uses triple-layer silver-plated windshield glass, an engineer friend challenged me: Could it be that only the local area near the sun visor is triple-layer silver-plated?

With a pragmatic attitude, I consulted another friend in the automotive industry, and the answer was: the entire surface is silver-plated.

So, will the GPS antenna of Xiaomi SU7, which is located below the triple-layer silver-plated windshield glass, experience signal obstruction?

Based on my communication with engineer friends, we can preliminarily conclude that there will be some impact, but it's difficult to quantify how significant it is.

Why replace the windshield glass?

There are two possibilities: The first is that the windshield glass itself is fine, but it cannot be reused due to disassembly, so it must be replaced. The second is that the triple-layer silver plating of the windshield glass indeed has a negative impact on the signal reception of the GPS module.

Regarding this, I also consulted several other engineer friends, and the answers from engineers of different brands varied. Some said that the windshield glass can be reused after disassembly; others told me that a new glass needs to be replaced when encountering such issues because it's difficult to remove the glass adhesive after cutting, affecting the secondary adhesive fixation, including the previous positioning pins that would be damaged.

Since I don't have many friends in after-sales service, I welcome more professionals to correct me.

In fact, for the "navigation experience technology upgrade," replacing the windshield glass is not the only solution. Xiaomi's proposed solutions are: either replace the windshield or install a signal amplifier. In other words, while the GPS signal interference will have an impact, it can also be optimized through other means.

After analyzing all this, we find that there are still a lot of unresolved issues:

Is there a yield issue with the GPS antenna module itself?

Is there a tolerance in the assembly of the GPS module that affects its functionality?

Or perhaps there is an issue with the placement of the GPS antenna module, causing the three-layer silver front windshield to block the GPS antenna module from receiving signals and affecting the car's functions?

Or is it possible that the wiring harness of the GPS antenna is collinear with the camera wiring harness, causing signal interference?

Or is it that the GPS antenna module is too close to the high-power component of the LiDAR, causing interference in the signal?

Unfortunately, these issues cannot be analyzed solely based on the existing information on the internet, and we can only wait for the official announcement from Xiaomi.

After the video was posted, a friend of an engineer and I proposed a possibility: it is possible that the three layers of silver plated glass in the early stage did not have the film removed at the GPS antenna position. After sales, a windshield with the film removed will be used to solve the problem, because the glass coating is usually completely removed, and then the parts are removed. This will involve unit price and production speed, and of course, it may also depend on the specific process.

There are many factors that restrict GPS signals, such as surrounding buildings, clouds, ionosphere, different weather conditions, etc., so the test results of a vehicle at different times are also different.

As for the removal of film in the ETC area, this is a common practice in the industry. It is impossible to determine whether the GPS antenna module area has been removed from the surface.

Conclusion

I'm sorry, after consulting extensively and writing an analysis of nearly 3000 words, I found that there is still no accurate result to share with everyone. However, it can be confirmed that the impact of the three layers of silver plated glass on the front windshield on mobile phone signals is not significant. As for the impact on GPS module signal reception, how much is it? What is the essential purpose of replacing the front windshield? Next, let's see the official results of Xiaomi, and we look forward to getting the answer soon!