Among the radio frequency components of mobile phones, the cellular antenna is a passive component. As the only customized device on the mobile phone, its particularity and importance inevitably put forward very strict requirements on the antenna performance test during the development process to ensure normal use.
Here is a brief introduction to three common cellular antenna testing methods in the development of cellular antennas.
The microwave anechoic chamber is composed of an electromagnetic shielding room, filter isolation, grounding device, ventilation waveguide, indoor power distribution system, monitoring system, and wave absorbing materials.
This is a shielded room backed by absorptive materials, which can absorb most of the electromagnetic energy incident on the six walls. This is a good simulation of free-space conditions.
The darkroom is the test equipment that the antenna design company needs to build, because the cellular antenna test is more accurate and systematic, and its test indicators can be used to measure the performance of the cellular antenna.
Use TEM CELL to test antenna active indicator, because the cost of microwave anechoic chamber and antenna test system is relatively expensive, usually more than 100w RMB. Ordinary mobile phone design and development companies do not have such equipment but use TEM CELL instead of testing.
Similar to the test purpose of a microwave anechoic chamber, TEM CELL is also a 5G radio antenna test environment that simulates an ideal space. The metal box can provide a sufficient shielding function to eliminate the influence of external interference on the antenna, and the internal absorbing material can also absorb incident waves and reduce small reflected waves.
TEM CELL cannot perform passive testing on the antenna, but can only perform active indicators. In addition, the height of the TEM CELL is not enough and can only perform qualitative analysis on the 5G radio antenna, but not quantitative analysis.
TEM CELL usually only finds the best square value, which makes the test results more sensitive to the location of the phone.
In order to ensure the production quality of products during the production process, antenna coupling tests are often performed. In the early stage of production, a reasonable coupling compensation value is determined based on the test results of several prototypes, a power standard is determined, and then the maximum power of the mobile phone is tested. Here the power standard means that the product meets the production requirements.
The antenna coupling test is suitable for the near field. The near field is the objective existence of the cellular antenna itself. Once the structure and antenna of the entire mobile phone are determined, the near field can be determined. Therefore, it can be judged whether there is a problem with the antenna part according to whether the test result is within a certain range.
At present, many Chinese mobile phone companies judge the performance of antennas through coupling tests, which makes antenna companies have to adjust the resonant frequency offset to pass the coupling test standards.
As far as cellular antenna design is concerned, antenna testing is a very important part. Without precise design, the quality of antenna design cannot be measured. Therefore, choosing a good test system is also very important for the development of cellular antennas.