Since the 19th year since 2007, the smartphone is constantly increasing, and its "culprit" is forced to increase the screen size.
Take a look at the average data of the screen: the average screen size of your smartphone is extended from 3 inches to 4 inch for 5 years, but it has been expanded from 4 inches to the current 5 inches for two years.
Although these years have always been evolved in large-size direction, the screen is not conducive to user operation and experience, so after 5.5 inches, the size of the screen begins to slow. In 2017, the full-screen mobile phone began to receive attention from the manufacturer.
Compared to ordinary phones, the full screen phone has a narrower top and tail area and narrower borders. In the case where the whole machine is not changed, reduce the border of the mobile phone screen, the growth ratio, increase the screen, allowing the user to have a larger screen's experience.
From the perspective of human-computer engineering: 18: 9 will more in line with one-handed operation, and the bigger screen can meet both software and divide the screen operation, the recent Android 7.0 version, add the technology of the system under the multi-window Support, split screen operations will slowly become user habits due to the launch of full-screen mobile phones.
From the perspective of the whole machine size: 5.7-inch full screen mobile phone is relatively close to the machine size of the normal 5.2-inch mobile phone, but the display area has increased, and the display is more, which makes it easier to reduce the number of floppages, making the operation more convenient.
The core advantage of the full screen is that the ultra-high screen prevail, which not only brings a better visual experience, but also the appearance is more simple and beautiful. However, the full screen also brings a lot of problems to the mobile phone machine, such as front camera, fingerprint identification, handset, distance sensor, and even antennas, need to follow up adjustment design. The antenna is an important part of the mobile phone for transmission and reception signals, which is affected.
Mobile phone antenna is full, requiring a clearance area
The antenna is a device that receives and transmits signal (electromagnetic waves), is the most critical part of wireless communication. Although the physical composition of the antenna is relatively simple, its design and construction is complex, and it is necessary to consider many factors in all aspects of the internal environment of the mobile phone.
The directionality of the antenna refers to the intensity of the signal of the antenna radiation in a particular direction. The mobile phone antenna is a full-to-directional antenna, which means that the signal radiation intensity in the 360 ° direction in the antenna cross section is the same as the optimum communication effect. To achieve full-to-direction communication, there is a sufficient open space around the antenna in the phone, and it is not possible to shield or interference.
Radiation diagram of the full-to-directional antenna
Electromagnetic waves can be masked by metal, electrically conductive metal can generate reflection, absorption, and offset of electromagnetic waves, so when designing antenna, should be kept away from metal components, and avoid contacting other noise reduction elements.
At the same time, electromagnetic waves are easily interfered. Electromagnetic wave interference transmission can primarily be divided into two forms: conductive transmission and radiation transmission.
The transfer transmission, that is, there is a complete circuit connection between the interference source and the antenna, and the interference signal is passed to the antenna via this connection circuit. This transmission circuit can include a series of components such as wires, power, resistors, inductors, and capacitors.
The radiation transmission, that is, the interference energy is in the form of an electromagnetic field, and the interference form mainly includes three: signals from other antenna (coupled to the antenna), the spatial electromagnetic field of the current (coupling of the field pair), two shares The induction between the parallel current (the coupling of linear lines).
Electromagnetic wave will be masked by metal
Therefore, when the mobile phone antenna is designed, it should not only be away from the metal components, but also isolate the battery, oscillator, shield, camera and other parts, and leave a clean space for the antenna (referred to as clearance, clearance), guarantee the antenna. The full-directional communication effect.
In the mobile phone antenna design, the clearance of the antenna is one of the key considerations. In general, the environmental design requirements of the antenna are summarized as follows:
Metal housing, decoration, conductive spraying, etc. should be 20 mm from the antenna because the mobile phone built-in antenna is more sensitive to the medium near it;
The distance between the battery (the electrical connection) and the antenna should be 5mm or more;
When the antenna RF dual-foil is, the center distance of the RF and the ground pad should be between 4 to 5 mm;
Application conditions and partial performance comparison of PIFA antenna and single-pole antenna scheme
Comprehensive screen mobile phone clearance area reduces, antenna design is difficult to improve
Since the bottom of the mobile phone screen becomes narrower, the distance between the antenna and the metal is closer to the metal, and "clearance" is less than the traditional screen. In addition, the full-screen mobile phone receiver, camera and other devices require higher integration, closer to the antenna, and the "clearance" area left by the antenna is less than the traditional screen, higher for RF challenge.
Previously 16: 9 screen, the clearance that was finally left to the antenna at 7-9 mm (LCM backlight module to the bottom of the whole machine, generally 9mm main short air), now to 18: 9 screen, left The space of the antenna is about only 3-5 mm (such as the LCM backlight of Samsung S8, only less than 5mm main shortline), even narrower.
In general, the antenna is from the outer frame of the mobile phone, one of the main antennas, one below, from the antenna. "The part of the maximum performance of the antenna is how many spaces left to the antenna", "Qorvo China Mobile Products Division Sales Director is explained," If the space space is large, it covers the frequency band, the efficiency, its performance It is also better. However, the full screen extrudes the space of the antenna. The result of the extrusion makes the antenna efficiency, and ultimately affects the TRP (Total Radiated Power) is the overall emission power of the antenna. "TRP standard is made by operators It is stipulated that the frequency band has a predetermined value, and the TRP must be done to meet the requirements of the supplier through field testing, or you can't do it.
It can be said that this will test the process level of each antenna manufacturer, and strive to make the space you leave the smartphone screen, the better, otherwise the loss of the antenna part is relatively large.
From the frequency band, the longer the antenna can cover a lower frequency band, and the high frequency section is not high on the size of the antenna. Therefore, once the antenna space is squeezed, the maximum influence is low frequency, so that the bandwidth is narrowed. From the digital, the value of TRP is dropped, and from 16: 9. The number of TRPs like LTE B1, LTE B3, LTE B5 actually does not conform to CMCC requirements, than CMCC requirements. Low.
From smartphones to MIMO, 2CA, 3CA, 4CA and 5G, and low frequency 600 trillion, the number of antennas is increasing. If all of the above features, the smartphone is only 2-4 antennas, and it is necessary to increase the full screen to 4-7 antennas, and the number of antennas is increasing.
Comprehensive screen mobile phone clearance area reduces, how to break through antenna design
Currently there are three metal resection, LDS antenna technology and integrated antennas with other parts. There are two ideas for the aircraft of antennas under the full screen, and a idea is to expand the clearance area inside the phone, and the corresponding solution is the back metal resection. The second idea is to reduce the clearance area required for antennas, and the corresponding solution has LDS antenna technology, integrated antenna and other parts.
Metal resection behind the screen: increase the internal clearance area of the phone
The backplane metal can be hollowed to ensure sufficient clearance. The end of the phone screen will generally have a metal backplane, which acts as a protection screen, heat dissipation. The antenna is generally installed on the motherboard, but due to the presence of metal backplane, its position generally cannot be placed behind the screen. Under the full screen era, you can dig off the metal backplane of the upper and lower frames and leave enough space for the antenna. However, this method can cause the strength of the screen to be low and increase processing costs.
iPhone 5S metal screen backplane
Some metal backplane where the antenna is located
In addition, in order to achieve better antenna space, the three-ring and the buckle ceramic cover, and the trusted glass cover provides a better environment for mobile phone antenna design.
Solve the comprehensive screen antenna design problem, except for terminal manufacturers, RF device manufacturers are constantly trying, such as: The first is open source, improve PA's power, even if the power of PA is large, even absorbed, final release Out of it or more. The second is the mode of ET or Boost, by elevating the voltage to enhance the power of the PA. (If the power of the entire circuit is improved, there is also a special requirement for the filter, the duplexer, it is necessary to support higher power, high power filter.) Is useful to use the Impedance Tuner (impedance tuning) and Aperture Tuner (tuning) Help to increase the efficiency of the antenna.
Original address: https://www.eeboard.com/news/quanmianping-12/
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