Test on radiation performance of the whole machine
CTIAOTA'sRelevant standards。OTA test focuses on the radiation performance of the whole machine, and has gradually become a test item valued and recognized by mobile phone manufacturers.
Chinese name
Over the air download technology test
Foreign name
Over The Air
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CTIA
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Test on radiation performance of the whole machine
Currently onMobile radio frequencyperformance testing More and more attention is paid to the test of the radiation performance of the whole machine, which reflects the final transmission and reception performance of the mobile phone.At present, there are two main methods to investigate the radiation performance of mobile phones: one is to judge the radiation performance of the antenna, which is currently a more traditional antenna test method, called passive test;The other is whenMicrowave anechoic chamberTest the mobile phone'sRadiant powerandReceiving sensitivity, called active test.
Passive testing focuses onMobile phone antennaThe radiation performance of mobile phones is investigated in terms of antenna radiation parameters such as gain, efficiency and pattern.Although the passive test takes into account the impact of the environment of the whole antenna (such as the components around the antenna, the open cover and the close cover) on the antenna performance, the finalRadiated emissionHow about power and receiving sensitivity, from passivetest dataIt is impossible to know directly, and the test data is not very intuitive.
The active test focuses on the radiation performance of the mobile phone from the aspects of the transmission power and reception sensitivity of the whole mobile phone.Active test is to test the whole machine in a specific microwave anechoic chamberthree-dimensional spaceThe transmitting power and receiving sensitivity in all directions can more directly reflect the radiation performance of the whole mobile phone.
CTIA(CellularTelecommunicationAnd Internet Association)Relevant standards。OTA test focuses on the radiation performance of the whole machine, and has gradually become a test item valued and recognized by mobile phone manufacturers.
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Purpose of OTA test
At present, only throughFTA(Full Type Approval) Only the mobile phone models tested in the certification test can be marketed. In the FTA test,radio frequencyPerformance test is mainly used to test the RF performance of mobile phones in cable connection mode;As for the mobile phoneRadiated emissionThere is no clear regulation on the receiving performance and the receiving performance in FTA test, while the OTA test just makes up for the shortcomings of FTA test in this respect.At the same time, the terminal manufacturer must have a clear understanding of the radiation performance of the mobile phones produced and improve it through various measuresMobile phone radiationTransmission and reception indicators of.If the radiation performance of the mobile phone is poor, the mobile phone signal will be poorvoice call Poor quality, easy disconnection and other problems, which are alsoCustomer complaintsThere are many problems.
When talking on a mobile phone, because the human brain is close toMobile phone antenna, the transmitting and receiving performance of the mobile phone will be reduced, and the transmitting and receiving performance of the whole mobile phone radiation will be reduced.In the process of mobile phone research and development, the impact of human brain on the transmission and reception performance of mobile phones should be measured quantitativelyoptimal design So that the transmission and reception performance cannot be reduced too much, that is, the electromagnetic coupling effect between the human body and the antenna can be reduced.
In order to investigate the radiation performance of mobile phones, in addition to the passive performance of mobile phone antennas, the active performance of the whole machine is also an important aspect.At present, the active performance of the whole machine is paid more and more attention by terminal manufacturers, soMobile phone radiationPerformance under investigationTheThe two radiation properties are considered together.at presentTerminal antennaIn R&D, manufacturers generally require antenna suppliers to provide passive and active test reports.
Test and parameters
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Main points in OTA testTest parametersIn OTA test, radiation performance parameters are mainly divided into two categories: receiving parameters and transmitting parameters.
Transmitting parameters include TRP and NHPRP; receiving parameters include TIS and NHPIS.
TRP (Total Radiated Power):Area scoreAnd take the average.It reflects the transmission power of the mobile phone, and is related to the transmission power of the mobile phone in the conduction case and the antenna radiation performance.
NHPRP (Near Horizon Partial Radiated Power):H planeParameters of transmission power of nearby antenna.
TIS (Total Isotopic Sensitivity): reflected in the whole radiation spherical mobile phoneReceiving sensitivityIndicators.It reflects the reception sensitivity of the mobile phone, and is related to the conduction sensitivity of the mobile phone and the radiation performance of the antenna.
NHPIS (Near Horizon Partial Isotopic Sensitivity): a parameter reflecting the receiving sensitivity of the antenna near the H plane of the mobile phone.
aboutHandheld terminalThe OTA test will also examine the above parameters of the terminal with and without a simulated headRelated parametersChange of.
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Other relevant antenna parameters
When reviewing antenna performance, there are other parameters that need to be understood, such as APIPGain、Directivity、EIRP、ERP。
Gain(dBi）: In the sameInput powerThe radiation power of the antenna at a point in space is equal to that of the ideal zerodirectionalPoint source antennaThe power ratio at the same point, the gain unit is dBi,Mobile phone antennaAntenna provided by the manufacturerTest reportThe gain in is generally expressed in dBi.
Gain (dBd): under the same input powerRadiant powerAnd idealHalf waveDipole antennaThe ratio of power in the direction of maximum radiation, and the unit of this gain is dBd.
Direction: under the same radiation power, the ratio of the power generated by an antenna at a certain point in space to the power generated by an ideal point source antenna at the same point.
Efficiency: The ratio of antenna radiation power and antenna input power.
APIP (Antenna Port Input Power): The power added to the antenna port is the power output from the PA to the antenna port.This power is mainly related to theConducted emissionPower size.
EIRP(Effective Isotopic Radiated Power): equivalentOmnidirectional radiation powerIs the product of the power obtained by the antenna and the gain expressed in dBi of the antenna, reflecting the power radiated by the antenna in all directions.
ERP (Effective Radiated Power) has the same concept as EIRP, but ERP is the product of the power obtained by the antenna and the gain expressed in dBd.
Restriction of indicators
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TRP reflectsAntenna far-fieldRadiation performance, andSARReflected by antennanear fieldRadiation performance.For the TRP index in OTA, it is generally expected that the TRP is relatively large, so that the power entering the antenna from the PA will beEffective radiation, the connectivity of the wireless interface is better.In the SAR test, it is hoped that the SAR value is relatively small, so that the power absorbed by the human brain is relatively small, to ensure that it can pass the SAR test standard.Therefore, TRP index and SAR index are a pair of contradictory indexes. In antenna design, how to ensure that both indexes meet the relevant standards and meet the design needs should be considered at the beginning of antenna design.
Here are some solutions:
(1) It is most important to select the appropriate antenna form.For example, the Monopole in the built-in antenna has the characteristics of high efficiency but also high SAR. Therefore, we should know this before using it, that is, the Monopole and the human braincoupling effect Strong.PIFAAntenna synthesisGood performance, because the side close to the human brain is blocked by the PCB, its high-frequency band is in the human brainDirectional ratioThe maximum radiation direction has 5-6dB attenuation, so the SAR value of the PIFA antenna is relatively low, which is an ideal antenna form among the built-in antennas.
(2) SAR was considered at the beginning of antenna design, mainly on structural issues, and appropriate forms of antennas were selected in combination with the structure of mobile phones to ensure antenna performance while meeting SAR indicators, such as taking measures such as placing the antenna at the bottom of PCB.For externalSpiral antennaIn general, attention should be paid to the distance between the antenna and the human brain to ensure that it meets the needs of SAR testing.
(3) In the late design stage, SAR test is found to exceed the standard, which can be solved by lowering the antenna performance, such asUsage lossFor slightly larger materials and other methods, it needs to cooperate with the antenna manufacturer.
(4) Change antenna wiring mode and adjustPatternAnd other measures.
OTA antenna test darkroom complies withCTIAOTA test standard of SG24 and near-field conversion of SG24 adopted by the test systemfar fieldThe measurement scheme is the most accurate antenna at presenttest method。yesRepeatabilityHigh,AccuracyHigh,ResolutionAdvanced advantages.SG24 is one of the few test systems in the world that can fully meet the requirements of CTIA.Be able to provide the TRP/TIS test required by CTIA.Test scope: CTIA OTA (GSM900,DCS1800,Cellular850,PCS1900)；3D antenna field measurement, gainAntenna efficiency, patternpolarizationPerformance.
