Generalized Method for the Determination of Wireless Device RF Interference Level (Simplified Explanation) ANSI C63.19 Working Group Submitted for discussion by Stephen Julstrom and Mead Killion UL, Northbrook, IL October 6, 2008 Note: This example incorporates proposed spectrum weighting only (either A-weighting or J-weighting). Additional improvement in predictability is obtained by adding temporal weighting, as shown in the last slides.

2 1.For the WD, measure the worst-case output level from the weighted, square-law detected, fast probe. In this example, the measured weighted ac voltage is 78 dBuV (7.9 mV). This measurement is repeated for a total of 9 locations. The worst of the 6 required becomes the target voltage for Step 2. RF Interference Level measurement (fast probe) and IRIL calculation:

3 Don’t touch the knob! This dB V/m E-field value is the RF Interference Level

4 Given the RF Interference Level. With the measured unmodulated carrier strengths (step 3) presented in dB(V/m) or dB(A/m), calculate the actual worst- case weighted HA IRIL in response to the WD’s RF modulation. Weighted IRIL (dB-SPL) = 2(RF Interference Level – Susceptibility) + 55 dB-SPL RF Interference Level measurement (fast probe) and IRIL calculation:

5 The following block diagram shows the previously proposed combined spectral and temporal weighting that reduces the across-modulation schemes by approximately 2:1 compared to simple A- weighting alone.

6 X2X2 X msec TC 550 msec T.C. Peak DetectorRMS Level MeasurementSpectral Weighting Similar to CISPR, ITU-R 468 Quasi-Peak DetectionSimilar to A-weighting from square- law detector to DC meter The weighting function: The weighting function consists of straightforward spectral weighting followed by temporal weighting. Each step is clearly mathematically definable. Implementation may be in hardware or software.

7 (In viewing the graphs, the 80-90% range in the distribution is the most significant for comparison, since it includes the most subjects while excluding the outliers in the top few percent.) Telecoil mode test results using A-weighting and New weighting A weighting only New weighting and temporal weighting