Since wireless communication devices operate at the highest power state, they can cause severe electromagnetic interference to surrounding electronic products. Among them, the interference caused by the hearing aids used by the disabled is the most serious, and it will directly affect the normal use of the users. According to this situation, the test requirements of the HAC (hearing aid compaTIbility) part are specified in the ANSI C63.19 standard, in which the RF electric field radiation and the radio frequency magnetic field radiation of the HAC are one of the most important components. Below we briefly introduce the approximate method of RF electric field radiation and RF magnetic field radiation of HAC.
The instruments used in the HAC test mainly include:
1. Near field electric field probe;
2. Near field magnetic field probe;
3. Probe positioning device;
4. WD (Wireless Devices) support system;
5. Other auxiliary equipment such as RF shielding room;
The test needs to adjust the wireless communication device (WD-Wireless Devices) to work at the maximum rated output power, and the test needs to be performed under high, medium and low channels. At the same time, it is necessary to confirm that the field strength probe and the test system and other equipment are in normal working condition, and the position of the probe needs to be positioned and calibrated.
The HAC test is performed in a 5 cm area, using the electric field probe to scan the surface to measure the maximum field strength, in the period of multiple pulses, through the peak measurement, and then based on the measured average and the constant duty cycle calculation of the infinite communication device. Average field strength. In order to accurately scan the entire area, the center of the probe must be scanned within the test area. The distance from the reference plane of the object to the probe element is 1.0 cm.
The brief test procedure is as shown in (Figure 1):
The test result is the maximum peak reading and is converted into an equal amount of peaks in V/m or A/m. The tested values ​​are converted to the corresponding grade according to the ANSI C63.19 limit.
The ANSI C63.19 standard also provides tests and classification methods for electromagnetic compatibility of hearing aids and digital mobile phones. Different models have been tested to classify the electromagnetic compatibility of hearing aids and digital mobile phones into 1, 2, 3, and 4 categories. When the number of categories of the hearing aid and the number of mobile phones are equal to 4, the resolution index reaches 0.3. Call; greater than 5 when the sharpness index reaches 0.5, can be used normally; greater than or equal to 6 when the sharpness index reaches 0.7, the call is very good.
Electromagnetic compatibility testing and classification methods
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