Research On The Principle And Methods Of 4G Mobile Phone Testing Based On American HAC Standard

With the rapid development of mobile communication technology,mobile phone has become an inseparable part of people's life.But for some special groups,mobile phones have brought convenience and trouble to them.For example,some people need to use a hearing aid to use a cell phone,and the near field electromagnetic field generated by a normal call will interfere with the work of the hearing aid.In order to protect the rights of these people to use mobile phones,various countries have issued laws and regulations to guide manufacturers of mobile phones to achieve Hearing Aid Compatibility(HAC).For HAC test,the United States is in front of countries.In October 3,2018,at least 66% of the mobile phones exported to the US market need to be tested by HAC.This will bring some challenges to Chinese mobile phone manufacturers.Based on this consideration,this paper will study the HAC test principle and method of mobile phone.The HAC test of mobile phone is divided into two modes: audio coupling mode(RF mode)and T-coil coupling mode(Telecoil,T-coil mode).In this paper,the principle and method of HAC test on RF mode based on indirect method,and HAC test on T-coil mode based on the analog base station method are studied.Finally,by designing a multi band 4G mobile phone,we select the 4 frequency bands of GSM 850 MHz,WCDMA 1900 MHz,LTE Band 4 and WIFI 2.4G 802.11n(40 MHz),respectively.The results of verification can meet the requirements of HAC certification in the United States,which shows that the research of two kinds of mode test principles and the construction of test scenarios are reasonable.At the same time,some reasonable suggestions are provided for manufacturers to design HAC specifications mobile phones.For example,in the RF mode,the intensity of the RF signal near the receiver can be reduced by the way that the main radiation antenna is far away from the mobile phone receiver or shielded.In view of the T-coil mode,the main board line of the main board of LAYOUT is as far away from the phone receiver as possible.When designing the mobile phone battery management program,it is necessary to prevent the battery from causing a large current to cataclysm,and adopt a special HAC headset to improve the effective magnetic signal intensity.