In the ten years of the iPhone, what changes have taken place from the appearance process to the antenna design?

Lei Feng network (search "Lei Feng network" public concern) : Author RFsister Maker RF space Xia Zende, this article describes the iPhone from the first generation 10 years ago, iPhone's appearance process and antenna design changes. Lei Feng network has been authorized by the author, reproduced please contact the authorization.

The iPhone has always been unique in its simple appearance, outline, and exquisite craftsmanship. From the first generation iPhone to the latest iPhone 7/7 Plus, ten years, each generation of the iPhone brings different surprises to each other, although it is easy to encounter the antenna door, curved door and paint door every time. Deal with it and take it with ease.

It can be said that Apple has compromised the visual, touch and process technologies in many product designs. The iPhone has changed for a decade, and its antenna design changes from the appearance process. Perhaps we may learn more.

From the first generation iPhone to iPhone 3G, iPhone 3GS, the three generations of back covers are all made of non-metal materials. Before the appearance of the iPhone 4 border antenna, all three generations of products have adopted the FPC antenna design structure.

The first iPhone's back shell, the upper part of the silver is metal, the lower part is plastic.

iPhone

Wireless signals cannot penetrate aluminum alloys, but they can penetrate plastics. Therefore, this generation of iPhone uses electroplated aluminum alloy with plastic backshell materials, which was a compromise made by the technical limitations and aesthetic philosophy at that time.

Take a look at the internal antenna structure of the iPhone

Remove the battery, you can see two connected to the logic board (logic board is also called the screen driver board, the central control board, TCON board. The LCD screen can not directly identify the output signal of the motherboard, the signal of the motherboard must be processed through the logic board and then transmitted Antenna wiring to the LCD screen).

Unplug the antenna connection to the left base connector

Can only see the antenna using FPC + bracket

Remove the antenna bracket

The iPhone uses a metal material to obtain a more beautiful, wear-resistant and excellent touch experience, but at the same time due to the signal shielding properties of the metal material, the device can not receive and send wireless signals normally, so the metal and glass are used in the subsequent iPhone. The design of plastic materials combined.

The iPhone 3G and iPhone 3GS have more support for 3G networks. In order to ensure the stable transmission of wireless signals, both have also adopted plastic housings.

iPhone 3G (Black) iPhone 3GS (White)

Looking at the internal structure of the iPhone 3GS, it is found that the antenna designed by FPC relies on copper foil to radiate signals. Its advantages are relatively simple design and low production cost. The disadvantage is that it easily receives the impact of hardware and assembly accuracy, and the antenna connection of the iPhone 3GS. There has been a weak situation.

iPhone 3GS

The iPhone 4 case consists of three basic parts: two smooth, high-strength glass, and a stainless steel band that surrounds the perimeter. The same iPhone4S appearance continues the iPhone 4 style.

iPhone4 front and rear glass panels, metal frame

The iPhone 4 metal frame uses a CNC stainless steel process. The two gaps on the left and top divide it into two sections. The frame not only plays the role of the frame of the fuselage, but also the wireless antenna of the mobile phone. The left half of the two sections serve as WiFi, Bluetooth, and GPS antennas, and the right half is the UMTS/GSM mobile network antenna.

iPhone4 metal frame structure

The new antenna design form is a major highlight of the iPhone 4 innovation. To increase sensitivity, engineers placed the antenna position from the inside of the front model to the side of the chassis (metal frame). However, antenna engineers are all shy. This brand-new iPhone 4 that claims to change everything is exploding the most basic communication defect --- "antenna door".

iPhone 4 bold antenna design analysis

The main antenna used in the iPhone 4 mobile phone network is not only formed on the side of the casing but also combined with another antenna inside the mobile phone. The side of the casing is welded with a complex shape of metal sheet, which is considered to support different bands in different countries.

According to the antenna engineer of the Nikkei Electronics Co., Ltd., the reason why the iPhone 4 antenna is composed of two components is "because when the frequency characteristics, etc., need to be fine-tuned, if the antenna is only part of the housing, it needs to be remade from the mold. do". In fact, the antenna inside the mobile phone is equipped with one coil and one capacitor each for the purpose of adjusting characteristics. The electrode equipped therefor is extremely small as a single-cell antenna supporting a plurality of frequency bands, so it is appropriate to regard it as a fine-tuned antenna that assists the side antenna of the casing.

The structure of the main antenna (picture from Nikkei Electronics)

The main antenna is located below the fuselage and consists of two antennas. Respectively, an antenna that uses the antenna on the side of the housing, and an antenna that is wired on the thin resin member above the speaker module.

However, this innovative design has an unexpected side effect: due to the way users hold mobile phones, reception instability has occurred. This "problem" may be due to the antenna structure: the proximity of the slot near the bottom left of the phone, which is likely to cause reception instability, and the radiation electrode exposed at the side of the cover, are the junctions of the two antennas (below).

The picture shows the structure and circuit diagram of the primary and secondary antennas of the iPhone 4, and some cases of the iPhone 4 are used as antennas (picture from Nikkei Electronics)

The sub-antenna (for WLAN, Bluetooth, GPS) is used as the radiation electrode on the upper side of the housing (above). The side of the radiation electrode side of both sides of the radiation electrode slit at the top of the housing is equipped with only a power button, and the other end is a headphone jack, volume control and the like. The power button is different from the headphone jack and volume control buttons and will not be used during communication. Therefore, it seems that the position of the antenna and the button are all adjusted so as not to affect the communication function.

The final solution: Apple's later release of the CDMA version of the iPhone 4 and the upgraded version of the 4S, will be more than a metal frame, to solve this problem.

How does the iPhone 4S improve reception sensitivity compared to the iPhone 4? During the analysis, engineers discovered that the iPhone 4S in CDMA2000 mode added a receive diversity function.

By testing the TRP (Total Radiated Power) and TIS (Total Omnidirectional Sensitivity) of the iPhone 4S , we can see how the improvement of the signal is, and the three-dimensional receiving sensitivity of the iPhone 4S is detected in the state of rotation of the mobile phone. The more obvious the red part, the better the receiving sensitivity .

Good wireless characteristics (picture from Nikkei Electronics)

Based on the detection of the iPhone 4S's signal reception sensitivity, it can be concluded that the iPhone 4S has excellent wireless characteristics and the signal reception sensitivity has deteriorated when hand-held. In addition, the CDMA2000 version of the iPhone 4S also introduces new technologies that can reduce the deterioration of the receiving sensitivity when hand-held.

Comparison of radiated power and sensitivity test data for iPhone4, iPhone4s

The iPhone 4S has excellent wireless characteristics, and the drop in the receiving sensitivity of the handheld is controlled at 7 to 18 dB.

Test data shows that the iPhone 4S signal problem has been well resolved. Next, we will learn more about the design changes that the iPhone 4S solves the signal problem from the inside out.

iPhone 4/iPhone 4S Black Seat and Mute Button Locations

When the iPhone 4 is configured to block the black gap on the left side of the body by hand, the power supply point and the ground are short-circuited. While the iPhone 4S has improved grounding, the internal structure of the iPhone 4S has been partially changed, thereby solving the problem of reduced reception sensitivity.

For example, the iPhone 4S adds a leaf spring to the speaker module next to the antenna. This is estimated to ensure contact with the ground portion, thereby reducing the potential difference. In addition, the estimation also implements optimization of the antenna impedance so that it is not easily affected by the hand.

iPhone 4S additional leaf spring reinforced ground

The progress of a dismantling iPhone 4S found that the lithium ion rechargeable battery width shortened by about 1mm, while the width of the substrate has increased accordingly, while the widening part is due to the antenna through. The antenna is fixed on a metal housing that prevents electromagnetic noise and is arranged along the longitudinal direction of the substrate. There is a metal terminal in the middle of the antenna. This part is connected to the metal housing. The iPhone 4S solves the problem that the iPhone 4 has an antenna design that causes the gripping method to affect the signal reception sensitivity by adding an antenna design.

The portion where the substrate width is increased is the antenna channel (comparison when the iPhone 4 substrate is overlaid with the iPhone 4 substrate)

In Japan, Apple has newly added CDMA2000 models from the iPhone 4S. So this time also using au's iPhone 4S to implement CDMA2000 mode evaluation. As a result, it has been found that the CDMA2000 method embeds a receive diversity function for improving the receiving sensitivity. The engineer dismantling speculated that there are four slots on the iPhone 4S, and a new coaxial cable has been added to the power amplifier IC section. It can be imagined that the four slits divide the frame roughly into three parts: the upper part, the middle part, and the lower part at a high frequency. The term "high-frequency state" is used here because the high-frequency circuit achieves ground sharing and achieves electrical connection with a certain point on all components.

If the lower part of the fuselage is regarded as the main antenna and the upper part of the fuselage is regarded as the sub antenna, then a new coaxial cable can be reasonably explained in the power amplifier IC part. In other words, Apple is equipped with CDMA2000-supported "receiving diversity" capabilities on the iPhone 4S.

Equipped with receive diversity function (picture from Nikkei Electronics)

The iPhone 4S has a connection cable that connects the upper antenna to the RF IC on the substrate. The CDMA2000 version estimation is equipped with a receive diversity function that uses the upper and lower antennas to be differentiated depending on the situation.

Receive diversity is a receiving sensitivity improvement technique that was used very early in the field of wireless communications. The principle is to prepare a plurality of receiving antennas in advance, selecting an antenna with a good radio wave state to receive a signal, or uniformly performing phase synthesis processing on signals received by all antennas.

iPhone 5 does not extend the design of the iPhone 4S's glass panel + steel metal frame, but instead uses an aluminum alloy material made of anodized aluminum. Of course, iPhone 5S design continues this style.

iPhone5

The 3G/3GS back cover is a large plastic, the antenna is not on the shell, 4/4s use the side frame to do the antenna. In order to ensure signal stability, the iPhone 5 metal back adopts a three-stage design. The upper and lower parts are ceramic glass. This is also a compromise that must be made to prevent the metal from shielding electromagnetic waves.

The front and back of the iPhone 5

iPhone 5, iPhone 5S, iPhone 5c dismantling contrast

After the display was removed, the basic layout of the interiors of the three was not much different.

The arrangement is basically the same, one side is the battery, the other side is the motherboard

After removing the battery, you can see the difference between the three, iPhone 5 and iPhone 5C almost no change.

5S, 5C Antenna Design Analysis

The technicians analyzed the dismantling of the iPhone 5s and the iPhone 5c. The three antennas of mobile communication, wireless LAN/Bluetooth, and GPS were integrated in the upper part of the body, and the sub antenna for mobile communication was located in the lower part of the body.

5c and 5s antenna basic configuration has not changed (picture from Nikkei Electronics)

The iPhone 5s also uses a partially external metal component as an antenna structure, while the iPhone 5c, which uses a resin case, is internally equipped with a sheet metal component (a) that performs the same function. The 5s and 5c wireless LAN/Bluetooth antennas are slightly different (b).

The main antenna for mobile communications and the GPS antenna are connected via terminals provided on the front and back of the uppermost part of the substrate. The iPhone 5s uses the metal frame of the case as an antenna, and the iPhone 5c implements the same function using the gold plated components inside the case. The wireless LAN/Bluetooth antenna is connected to the connector of the main board protrusion. In this connection, the iPhone 5s uses an antenna module integrated cable based on a flexible substrate (FPC), while the iPhone 5c uses a relatively inexpensive coaxial cable, and the same functional module has subtle differences. "There should be almost no difference in performance. It is only different from the supplier of the antenna module" ("Nikkei Electronics" RF technician).

The iPhone 6s/6s Plus looks the same as the iPhone 6/6 Plus, with the same rounding machine, unchanged three-piece design, and the same white belt (injected bar). For the iPhone 6s/6s Plus integrated back metal shell shielding of electromagnetic signals, engineers can only export the antenna, which seems to draw on the iPhone 5 three-stage design.

iPhone6, iPhone6S back contrast

iPhone 6 has "Complete Netcom" capabilities (public version of iPhone 6 Cellular supports China Mobile/China Unicom/Telecom 2G/3G/4G), and supports 802.11a/b/g/n/ac wireless networks (single antenna, dual-band 2.4 GHz/5GHz) and Bluetooth 4.0, and joined NFC. All of the above shows that the iPhone 6's antenna design is more difficult than ever.

Open the panel can see, iPhone 6s's internal body layout and iPhone 6 highly similar, so, we disassemble the analysis of IPhone6 ​​antenna design, you can also see the iPhone 6s antenna design ideas.

iPhone 6 and iPhone 6s internal layout comparison

Let's take a look at the dismantling of GeekBar. The seemingly one-piece metal backshell, which is filled with plastic, is in fact divided into three sections A/BCD/E. A and E are the upper part antenna and the lower part antenna, respectively. The middle BCD part is connected to each other and serves as Antenna grounding section.

Tucao back split design

The upper part of the iPhone 6 antenna relates to Cellular secondary antennas, dual-band WLAN, Bluetooth, GPS, NFC and other functions.

Upper antenna feed port (front) of iPhone 6 motherboard

i

Phone 6 upper antenna feed port (front)

Upper antenna feed port (front) of iPhone 6 motherboard

The upper antenna includes one feed port for UAT1, UAT2, and UAT3 and two ports for NFC.

UAT1 is the antenna Tunning port and affects UAT3.

UAT2 is a WLAN 5GHz band antenna;

UAT3 features more, including WLAN 2.4GHz, Bluetooth, GPS, Cellular secondary antennas.

iPhone5 Schematic 5GHz Wi-Fi Antenna Feed Port (Photo by GeekBar)

The lower antenna of the iPhone 6 involves the Cellular main antenna.

Mobile phones, as a communication tool, cannot be accessed without a network. Wireless networks in different frequency bands are carried on radio waves in different frequency bands. It is impractical to use one antenna to receive all the radio waves in different frequency bands. Therefore, Apple designed the iPhone 6 to take into consideration the design of the leucorrhea on the premise of guaranteeing signal quality.

iPhone 7 and iPhone 7 Plus adopt a brand-new process, a more concise design, and after 3D polishing, feel more comfortable. The whole body is round and seamless, while the shell is made of solid 7000 series aluminum metal. From the perspective of the back, the iPhone 7/7 Plus is no longer a three-stage design. It only retains the top and bottom of the leucorrhea, and the sense of visual fragmentation is no longer so obvious.

iPhone 6s, iPhone 7

The antenna leucorrhea also changed to the upper and lower edges, and the double bars were changed to a single bar, but it looked thicker.

Bright black version of the iPhone 7, iPhone 7 Plus, you can hardly see the plastic antenna strip, in addition to the color of the plastic itself similar to the metal anode (electrophoretic coloring), but also because these two materials have almost the same gloss, This is a manifestation of the level of plastic sanding.

iPhone 7 bright black version

Analyze the iPhone 7 (2G+128G TLC) by GeekBar and look at its antenna section.

Remove the antenna connector

Tail line picks up, pay attention to the two antenna connection lines to be disconnected

iPhone 7 motherboard unit

Picture from GeekBar

The top is the Wi-Fi chip. The iPhone 7 Wi-Fi chip is a profiled Wi-Fi chip that supports 801.1a/b/g/n/ac. Underneath it is a square NXP NFC chip for Apple Pay payments . Next is the phone's power management chip, which is responsible for powering the entire iPhone circuit.

TI has the lower half of the main board USB controller chip custom chip and charge, and display chip. The other half is the radio frequency circuit, baseband power supply chips and modems, antenna switches, filters, etc., responsible for the radio frequency part of the mobile phone.

Summary: From the iPhone 7 dismantling point of view, its internal precision is difficult for domestic friends. It is no exaggeration to say that the iPhone 7 is still the best mobile phone in the industry.

Recently, it was passed that the next-generation iPhone may adopt a ceramic casing, but the technology still faces many bottlenecks.

Although Apple has performed the aluminum alloy case to the extreme, the inherent disadvantage of the metal case is that it will shield the electromagnetic signal. This makes the antenna (radiation) bar inevitably appear on the mobile phone, and on the other hand it cannot be wirelessly charged.

As early as in 2012, Apple registered a design patent for incorporating an antenna in a ceramic housing. Some domestic manufacturers have already introduced a mobile phone using a ceramic back cover, which is a zirconia ceramic. Compared with metals and plastics, zirconium oxide ceramics have the advantages of wear resistance, skin-friendly, airtightness, and small electromagnetic shielding. Therefore, zirconium oxide ceramics are expected to become the third largest mobile phone back cover material after plastics and metals.