Calculating Total Exposure Ratios for Co Located Transmitters in Handheld Equipment
Multi-radio handheld exposure compliance requires summing normalized SAR values across concurrent transmitters to verify the total exposure ratio stays below unity.
Absorption Rate Summation
Meaning
Mathematical accumulation of electromagnetic energy deposition values from multiple co-located transmitters represents a critical compliance metric for wireless communication hardware. In multi-transmitter systems, absorption rate summation defines how individual local specific absorption rates add together when different antennas transmit simultaneously. The calculation prevents localized exposure from exceeding regulatory limits even if each individual antenna operates within its legal power envelope.
Evaluation Protocol
Certification testing uses the accumulated metrics of the system during simultaneous transmission modes to prove regulatory alignment. Engineers sum the peak spatial-coincident values or use more advanced volumetric interpolation techniques to determine the total exposure. When the aggregate calculation remains below the specified threshold, the device passes certification without requiring additional physical measurements.
This phase occurs during the final hardware integration before submitting the technical construction file to the notified body.
Boundary Limit
The threshold where simple addition stops being mandatory depends on the physical distance separating the active antenna structures. Close proximity requires a strict three-dimensional volumetric assessment to prevent overestimating the combined heating effect. For antennas separated by more than five centimeters, the process allows direct numerical summation of the individual maximum values because the fields do not overlap significantly.
Array Design
Antenna positioning within the device housing directly determines the outcome of the compliance calculation. Strategic separation of the primary cellular and secondary wireless local area network antennas minimizes the overlapping hot spots. This isolation reduces the compiled exposure value and allows both transmitters to operate at higher power levels.