RF Exposure Info Collocated MPE.pdf

FCC ID: N7NMC7750

RF Exposure Info

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FCCID_2077244

1 Smart Grid Node Model: X-320e-xxx RF exposure calculations for Embedded Modules with collocated antennas according FCC 47 CFR 1.307(b)(1). Modules type: - Cellular/PCS GSM/EDGE/WCDMA/SDMA/700 MHz LTE modem, Sierra Wireless Inc., Mod: MC7750 (FCC ID: N7NMC7750) and - 802.11 a/b/g/n: Compex Systems Pte Ltd, Mod: WLE200NX (FCC ID: TK4-10-WLE200NX) The following calculations was made for RF exposure evaluation of the smart grid node Model: X-3200-xxx, which equipped with embedded Cellular/PCS GSM/EDGE/WCDMA/SDMA/700 MHz LTE module Model: MC7750 (Sierra Wireless Inc.) and 802.11 b/g/n module Model: WLE200NX (Compex Systems Pte Ltd). Both modules has been evaluated and comply with FCC RF exposure requirements separately, however in case of X- 320e, these antennas are collocated less then 20 cm for each other and therefore X-320e is a subject to cumulative RF exposure evaluation. The EUT will be only used with a separation of 20 cm or greater between the antennas and the user or nearby person and therefore can be consider a mobile transmitter per 47 CFR 2.1091(b). Due to deployment conditions, device has to comply with Maximum Permissible Exposure (MPE) limits for General Population/Uncontrolled Exposure. EUT contains: a) Cellular/PCS GSM/EDGE/WCDMA/SDMA/700 MHz LTE transmitter (FCC ID: N7NMC7750) operates under Parts 22E, 22H, 24E, 24H and Part 27 of the FCC Rules. Device transmitting characteristics has been showing in the Table1. Table1 Maximum Peak Antenna Numeric Peak FCC Gain (cable loss Antenna Gain Frequency output Duty Part included) for (cable loss Range (MHz) power Cycle calculation MPE included) for No. (W) (dBi) calculation MPE 24E 1850.2 - 1908.8 0.899 0.25 2.9 1.95 24E 1851.2 – 1908.8 0.34 1 2.9 1.95 24E 1852.4 – 1907.6 0.182 1 2.9 1.95 1851.25 – 24E 0.337 1 2.9 1.95 1908.75 22H 824.2 – 848.8 1.82 0.25 0.5 1.13 22H 824.2 – 848.8 0.419 1 0.5 1.13 22H 826.4 – 846.6 0.22 1 0.5 1.13 22H 824.7 – 848.31 0.34 1 0.5 1.13 27 779.5 – 784.5 0.224 1 -0.2 0.955 27 779.5 – 784.5 0.221 1 -0.2 0.955 Ambient Corporation Confidential and Proprietary

2 27 782.0 – 782.0 0.227 1 -0.2 0.995 27 782.0 – 782.0 0.226 1 -0.2 0.995 b) 802.11 a/b/g/n transmitter (FCC ID: TK4-10-WLE200NX) operates under Part 15C of FCC Rules in ISM band and has transmitting characteristics that are showing in Table2 Table2 Maximum Peak Antenna Numeric Peak FCC Frequency Gain ( cable Antenna Gain output Duty Part Modulation Range loss included) (cable loss power Cycle for calculation included) for No. (MHz) (mW) MPE (dBi) calculation MPE 2412.0 - 15C 802.11b/g/n 410 1 3.7 2.35 2462.0 2422.0 - 15C 802.11 b/g/n 240 1 3.7 2.35 2452.0 5745.0 - 15C 802.11a/n 410 1 4.3 2.70 5825.0 5755.0 - 15C 802.11a/n 300 1 4.3 2.70 5795.0 According 47 CFR 1.1310 FCC MPE limits for General population/Uncontrolled Exposure are showing in the Table3 Table3 Magnetic Electric Field Frequency Field Power density Averaging Strength [E] Range (MHz) Strength [S] (mW/cm²) time (min) (V/m) [H](A/m) 0.3 - 1.34 614 1.63 (100)* 30 1.34 - 30 824/f 2.19/f (180/f²)* 30 30 - 300 27.5 0.073 0.2 30 300 - 1500 ------- ------- f/1500 30 1500 -100,000 ------- ------- 1 30 f = frequency in MHz * = Plane-wave equivalent Power Density Based on FCC Bulletin OET 65, the MPE calculations in case of multiple transmitters have been e performed on the following and assumptions and equations: Ambient Corporation Confidential and Proprietary

3 1. For transmitters which operate in the frequency band with a same MPE limit the Power Densities are summed. The Total Power Density shall not exceed the Limit for this band 2. For transmitters which operate in frequency bands with a different MPE the Power Densities are calculated separately for each band, and then divided by Limit for each band. The sum of these ratios shall not exceed 1. 3. The calculation of the Power Density based on equation given in OET 65: E = √ (30 x P x DC x G) / d (Eq.1) and S = E² / 3770 (Eq.2) Where: E = field strength in volts/meter P = power in watts DC = numeric duty cycle G = numeric antenna gain d = distance in meters S = power density in milliwatts / square centimeter Combining (Eq.1) and (Eq.2), S may be calculated as: S = (30 x P x DC x G) / (3770 x d²) (Eq.3) By changing units for P to mW and distance to cm, (Eq.3) can be written as: S = [30 x (0.001 x P) x DC x G] / [3770 x (0.01 x d)²] (Eq.4) Or: S = (0.0795756 x P x DC x G) / d² (Eq.4) Where: P = power in mW DC = numeric duty cycle G = numeric antenna gain d = distance in cm S = power density in mW/cm² 4. According Table3, limit for the transmitter in 824.2 – 848.8 MHz band shall be calculated at the lowest frequency (worst case) as: 824.2 / 1500 = 0.55 mW/cm² Ambient Corporation Confidential and Proprietary

4 Correspondingly, the worst case limit for the transmitter in 779.5 – 784.5 MHz band shall be calculated as: : 779.5/ 1500 = 0.519 mW/cm² 1. For the all frequency bands the worst case combination of conducted power, duty cycle and antennas gain was used for calculation. The results of calculations for these cases are showing in Table 4. Table 4 Peak Numeric antenna Power Transmitting peak Ratio the Transmitting gain density at Device conductive Transmitter antenna of power frequency bands (cable 20 cm from (transmitter) power duty cycle gain (cable density to (MHz) loss antennas (mW) loss the limit included) (mW/cm²) included) (dBi) GPRS 824.2-848.8 1820 0.25 0.5 1.13 0.103 0.186 EV-DO 824.2-848.8 419 1 0.5 1.13 0.095 0.172 1850.2- GPRS 899 0.25 2.9 1.95 0.088 0.088 1909.8 1850.2- EV-DO 340 1 2.9 1.95 0.132 0.132 1900.8 LTE 782.0-782.0 227 1 -0.2 0.995 0.045 0.087 802.11 2412.0- 410 1 3.7 2.35 0.192 0.192 b/g/n 2462.0 802.11 2422.0- 240 1 3.7 2.35 0.113 0.113 b/g/n 2452.0 802.11 5745.0- 410 1 4.3 2.7 0.221 0.221 a/n 5825.0 802.11 5755.0- 300 1 4.3 2.7 0.162 0.162 a/n 5795.0 Ambient Corporation Confidential and Proprietary

5 1. Finally, the MPE calculations (worst cases) for collocated Cellular/PCS GSM/EDGE/WCDMA/SDMA/700 MHz LTE and 802.11 a/b/g/n transmitters are shown in the Table5 Table5 Active transmitters in frequency bands (MHz): Power density worst 824.2- 1850.2 - MPE Total Limit Margin Pass/ cases 5745.0- 848.8 1909.8 782.0 - 2.412.0 - (numerical) (numerical (numerical Fail (fraction of 5825.0 the limit) (EV- (EV-DO 782.0 2462.0 (802.11 DO or or (LTE) (802.11 b/g/n) a/n) GPRS) GPRS) GPRS (fraction of 0.186 0.192 0.378 1 -0.622 Pass the limit) GPRS (fraction of 0.186 0..221 0.407 1 -0.593 Pass the limit) GPRS (fraction of 0.088 0.192 0.28 1 -0.72 Pass the limit) GPRS (fraction of 0.088 0.221 0.309 1 -0.691 Pass the limit) EV-DO: (fraction of 0.172 0.192 0.364 1 -0.636 Pass the limit) EV-DO: (fraction of 0.172 0.221 0.393 1 -0.607 Pass the limit) EV-DO: (fraction of 0.132 0.192 0.324 1 -0.676 Pass the limit EV-DO: (fraction of 0.132 0.221 0.353 1 -0.647 Pass the limit LTE (fraction 0.087 0.192 0.279 1 -0.721 Pass of the limit) LTE (fraction 0.087 0.221 0.308 1 -0.692 Pass of the limit) 7. Conclusion. Calculated worst case MPE numbers are complying with FCC limits for General population/Uncontrolled Exposure as a mobile device. Ambient Corporation Confidential and Proprietary


Document Created: 2013-09-19 11:11:19
Document Modified: 2013-09-19 11:11:19
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