一、from 4G to 5G, cell phone antenna doubling the problem
1. The number of antennas and the number began to increase
5G (Fifth-Generation) is the fifth generation of mobile communication technology. It is a product of the development of communication technology from quantitative change to qualitative change over the years. Due to the millimeter-wave technology, transmission distance is short and obstacles are obstructed to connect. high. 4G to 4.5G Pro, and then to 4.9G and finally the gradual realization of a seamless transition to 5G, 4.5G Pro speeds up to 1.2Gbps, 4.9G will coexist with 5G. 4.5G network will be in terms of bandwidth, network capacity, delay and so on. Specifically, you can achieve 100Mbps connection speed anytime, anywhere, network latency will be reduced from the current tens of milliseconds 4G to 10 milliseconds, and can support 30 billion order of connections. Huawei P10 and Samsung start selling terminals.
The current 4.5G is 4x4 MIMO, its carrier aggregation demonstration, the rate of up to 1.2Gbps. 4.5Gadvance 4.5Gadvance following the 4.5G is 8x8MiMo, the rate of 2Gbps and above, the phone were more than 2 and 4 antennas, a substantial increase in the number of antennas, location requirements also increased, to 5G era, if in the high frequency mm band will increase The number of antennas. At present, 13 provinces have upgraded their systems to 4.5G, 3G has 5 bands, 4G has 40 bands, 5G has added more than 50 bands, and RF front-end modules and components have jumped from $ 10.1 billion in 2016 to 2022 Of the 227 billion U.S. dollars (estimated by Yole Developpement).
2. Antenna indicators are affected, the layout of the region need to re-consider
6Ghz, 4G-LET band transformed into 3D-MIMIO transmitting antenna, with the accompanying cell phone using 4x4 MIMO antenna. Multi-input and multi-output in MIMO in 4.5G, multi-antenna transmit / receive in transmit and receive, and capacity and reliability through spatial multiplexing and gain diversity. Antenna correlation and isolation seriously affect antenna specifications and how to decouple? MIMO antenna, split into pieces, there is isolation between multiple antennas! Is not a traditional metal line sub-band signal mode taken. However, mobile phone space is small, continuous piece design antenna area is limited, the back cover may be the best antenna layout area!
In short: At the beginning of the installation of the antenna, we must pay attention to find the right place in order to find the right frequency band, in the cell phone, the most suitable 5G antenna position is the two ends, especially the upper end. However, with the advent of 4.5G | 5G, the number and types of antennas increase, which means that the space between the two ends of the traditional antenna is crowded, the efficiency of the antenna is reduced, and some antennas need to be shifted to other places. Therefore, the structure and material of the mobile phone, Design brings new challenges. The back cover becomes a place to try.
二、the location of the antenna in the mobile migration: need to spread the distribution
Mobile phones, the camera began to change double and quadruple shot, continuous zoom; full screen mobile phone also began to spread, these factors lead to the traditional layout of the best antenna space crowded antenna, antenna efficiency decline, RF and structural engineers began to distress.
Mutual coupling of the antenna
Left, no mutual coupling; right, mutual coupling serious
To reduce the coupling between the original signal from an antenna to do different bands of ideas is not feasible, you need four antenna space to spread the layout, the farther the better! And the space misplaced layout.
4 antennas are distributed in 4 corners is the best choice!
The specific operation is as follows: machine metal frame is cut into 6-8 segments, four antennas each take a section to do the antenna exposed radiator. Due to the rear part of the phone, Harvatek consecutive piece of plastic space less, fragmented space, the use of "neutralization line" to decoupling, ground split decoupling technology, requires a continuous lead space, so a consideration Is not thickening the case of mobile phones, the circuit layout in the back cover, as the traditional process can not solve the RF index under a new choice! Or "catch" some of the other band antennas onto the back cover and out of the four corner spaces.
Radiation of the 3D map space misplaced
Figure antenna layout in the back cover
三、the antenna manufacturing process changes
New Manufacturing Technology: LDS ink process in back cover. Specific steps are as follows:
1) The inner side of the high-pressure film spray thermal curing black LDS ink, both light and play the role of circuit substrate
2) 3D laser scanning, to be activated;
3) Electroless copper or nickel plating
The advantages of this process are:
1, integration, eliminating the need to stick a large number of manpower FPC antenna;
2, the cost is cheaper;
3, high reliability;
4, contiguous space, from the internal electronic interference furthest, good performance.
Back cover made of composite antenna
Summary: Non-metallic phone back cover is an important antenna area, cell phone antenna engineers eager to make a difference, structural engineers are more conservative. Back cover and PCB connection need to use shrapnel or conductive foam. High-pressure diaphragm rear injection molding: IML, IMD? Easier to manufacture an antenna directly on the plastic housing?
Figure back cover and the PCB board connection should pay attention to the problem
