ZHCU623 January   2019

 

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3.2.1.2 Range

Traditionally a measurement of effective isotropic radiated power (EIRP) would be a good tool to estimate the total range of an RF system, but with a wearable medical patch, there will be significant absorption of the RF signal from the human body. Therefore, the best method for verifying the range of the patch was determined to be demonstration. The output power of the patch while worn was measured using a Bluetooth explorer app from a smartphone, and the range of the patch in open air can be calculated based on an assumed receiver quality. To verify this, one of the patches was worn for an extended period, adhered to the engineer using an FDA-approved TegaDerm ™ patch. The range of the device was periodically tested using the detection of regular temperature updates from the auto-advertisement pulses as indication, and was used to confirm the initial calculations.