Several common mobile phone antenna test methods in the development process of mobile antenna

With the rapid development and application of mobile communications, China's mobile phone industry has also continued to grow and develop. Of course, China's mobile phone users are also growing rapidly. In the RF devices of mobile phones, the mobile phone antenna is a passive device, and the mobile phone antenna is the only “tailor-made” device on the mobile phone. Its speciality and importance inevitably require that its R&D process requires very strict testing of the antenna performance. In order to ensure the normal use of mobile phones. Now briefly introduce some common mobile phone antenna test methods in the development process of mobile phone antenna:

1. Anechonic chamber

The anechoic chamber is also called a non-reflecting chamber and the anechoic chamber is abbreviated as a dark chamber. Microwave darkroom is composed of electromagnetic shielding room, filtering and isolation, grounding device, ventilation waveguide, indoor power distribution system, monitoring system, and wave absorbing material. It is a screened room with a wave-absorbing material as a lining. It can absorb most of the electromagnetic energy that strikes the six walls. The darkroom is a test equipment that all antenna design companies need to build. Because the test of the mobile phone antenna is more accurate and more systematic, the test index can be used to measure the performance of a mobile phone antenna. It is mainly used by antenna companies, but its cost is expensive.

2, TEM CELL test

Use TEM CELL to test the active index of the antenna, because the microwave darkroom and antenna test system is relatively expensive, generally more than one million, the general mobile phone design and R&D company does not have such equipment, and instead use TEM CELL (also more triangular cone) instead test. Just like the purpose of testing the microwave anechoic chamber, the TEM CELL is an antenna testing environment that simulates the ideal space. The metal box can provide enough shielding functions to eliminate the influence of external interference on the antenna, and the internal wave absorbing material can also absorb the incident wave. Small reflected waves. The TEM CELL cannot passively test the antenna and can only test the active indicator. Due to space limitations, the TEM CELL absorber material is relatively thin, and for the cymbal absorber material, the incident wave is absorbed by multiple reflections between the cusp tips. Therefore, the microwave absorption material in the anechoic chamber is relatively thick, and None of the TEM CELL's absorbing materials are thick, so the absorption of the incident wave is not sufficient and therefore results in inaccurate test results.

In addition, the height of TEM CELL is not enough, which is one of the reasons why TEM CELL cannot perform quantitative tests. According to the far-field test analysis of the antenna radiation, for the EGSM/DCS-band mobile phone antenna, the distance between the measured mobile phone and the antenna is at least 1 meter; therefore, we can see that almost all the 2D darkrooms are much larger than this distance. The TEM CELL is smaller than this distance, so this is also a reason why the TEM CELL is inaccurate to measure relative to the microwave darkroom.

Therefore, TEM CELL can only perform qualitative analysis of the antenna and cannot perform quantitative analysis. In the laboratory, we can qualitatively analyze the differences among several prototypes and compare their performance. However, we can't measure the performance of an antenna as an accurate standard value. We can only approximate it by comparing with other golden samples. Cell phone antenna performance. TEM CELL generally only finds the best square value, making the test result more sensitive to the location of the phone.

In addition, there is a test tool called shielding box, and some design companies are used to carry out active tests on the antenna of the mobile phone. This method is not feasible. On the one hand, because the test distance is too close, and because there is not enough absorbing material on the other hand, the influence of external interference on the test of the antenna is relatively large. As a result, the test result is more sensitive to the position. A slight change in the position results in a relatively large change. Therefore, this test method does not have much reference to the performance of the mobile phone antenna.

3, using the coupling test board to test the antenna performance

In order to ensure the product's production quality in the production process, antenna coupling tests are often performed. The test device to be used is: the shielding box, the coupling board and the integrated tester are connected, and the mobile phone is fixed on the fixture. In the early stage of production, according to the test results of several prototypes, a reasonable coupling compensation value is given, a power standard is determined, and then the maximum power of the mobile phone is tested. Above this power standard, the product meets the production requirements and is lower than the requirement. There is a problem with the antenna and related devices. Through the antenna coupling test you can find the following problems:

(1) Antenna matching circuit Weld and missing parts.

(2) There is a problem with the electronic/structural parts around the antenna.

(3) The antenna is not assembled.

(4) There is a problem with the quality of the antenna itself.

It should be pointed out that the antenna coupling test is a conformance test of the product and does not test the performance of the product. The previously mentioned antenna specifications are for far-field testing. Antenna coupling testing is for near-field testing. The antenna of the tested handset is very close to the antenna of the coupling fixture. In the near field, the antenna itself exists objectively. Once the structure and antenna of the entire mobile phone are determined, the near field can be determined. Therefore, whether or not there is a problem in the antenna part can be determined according to whether the test result is within a certain range. The antenna coupling test only tests the maximum power of the antenna and does not perform tests on other items. Even if it is tested, it does not make sense.

Antenna coupling testing is used to verify the performance of the antenna. Performance is judged based on the test results of different mobile phones. This is very wrong. At present, there are still many domestic mobile phone companies that determine the performance of the antenna by means of coupling tests. As a result, the antenna company has to pass the coupling test standard by tuning the resonant frequency.

In terms of the design of a mobile phone antenna, the antenna test is a very important part. There is no accurate design. There is nothing to measure the goodness or badness of the antenna design. Therefore, choosing a good test system is very important for the development of a mobile phone antenna. of.