MPE Prediction

FCC ID: XNA-WS-40

RF Exposure Info

Download: PDF

FCCID_1844804

FCC ID: XNA-WS-40

RF Exposure Evaluation
of
E.U.T. : Smart Kid Scale

FCC ID. : XNA-WS-40

MODEL : WS-40

for

APPLICANT : Withings

ADDRESS : 20, rue Rouget de Lisle, 92130 Issy les
Moulineaux, FRANCE

Prepared by

ELECTRONICS TESTING CENTER, TAIWAN
NO. 34. LIN 5, DINGFU VIL., LINKOU DIST.,
NEW TAIPEI CITY, TAIWAN, 24442, R.O.C.
Tel:(02)26023052 Fax:(02)26010910
http://www.etc.org.tw ; e-mail: emc@etc.org.tw
Report Number : 12-10-RBF-028-MPE

FCC ID: XNA-WS-40

Product Information:
Type of EUT: Smart Kid Scale
FCC ID: XNA-WS-40
Manufacturer: Withings
Model: WS-40
Description: Smart Kid Scale with 802.11b/g/n and Bluetooth

Maximum conducted output power (measured): 14.9 dBm or 30.903mW

The following table lists the provided authorized antennas:
Model Antenna Type Antenna Gain
(dBi) Numeric
N/A 2.4 GHz Inverted F Antenna 3.3 2.14

Below is an example of the RF Exposure Statement:

IMPORTANT NOTE: To comply with the FCC RF exposure compliance requirements,
the antenna(s) used for this transmitter must be installed to provide a separation
distance of at least 20 cm from all persons and must not be co-located or operating in
conjunction with any other antenna or transmitter. No change to the antenna or the
device is permitted. Any change to the antenna or the device could result in the
device exceeding the RF exposure requirements and void user’s authority to operate
the device.

FCC ID: XNA-WS-40

Relative Requirement for Compliance
According to section 1.1310 of FCC 47 CFR Part 1, limits for maximum permissible
exposure (MPE) are as following:

TABLE 1 – LIMITS FOR MAXIMUN PERMISSIBLE EXPOSURE (MPE)
Frequency Range Electric Field Magnetic Field Power Density Averaging Time
(MHz) Strength Strength
(V/m) (A/m) (mW/cm2) (minutes)
(A) Limits for Occupational/Controlled Exposures
0.3-3.0 ……………… 614 1.63 *(100) 6
3-30 ………………… 1842/f 4.89/f *(900/f2) 6
30-300 ……………… 61.4 0.163 1.0 6
300-1500 …………... …………………. …………………. f/300 6
1500-100,000 ……… …………………. …………………. 5 6
(B) Limits for General Population/Uncontrolled Exposure
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 ……… …………………. …………………. 1.0 30
f = frequency in MHz
* = Plane-wave equivalent power density
NOTE 1 TO TABLE 1: Occupational/controlled limits apply in situations in which persons are exposed as a
consequence of their employment provided those persons are fully aware of the potential for exposure and can
exercise control over their exposure. Limits for occupational/controlled exposure also apply in situations when
an individual is transient through a location where occupational / controlled limits apply provided he or she is
made aware of the potential for exposure.
NOTE 2 TO TABLE 1: General population/uncontrolled exposures apply in situations in which the general
public may be exposed, or in which persons that are exposed as a consequence of their employment may not
be fully aware of the potential for exposure or can not exercise control over their exposure.

FCC ID: XNA-WS-40

RF Exposure Calculations:
The following information provides the minimum separation distance for the highest
gain antenna provided. This calculation is based on the highest EIRP possible from
the system, considering maximum power and antenna gain, and considering a 1.0
mW/cm2 uncontrolled exposure limit. The formula shown in OET Bulletin 65 is used in
the calculation.
Equation from page 19 of OET Bulletin 65, Edition 97-01 is:

S= PG / 4πR2
where: S = power density (in appropriate units, e.g. mW/cm2)
P = power input to the antenna (in appropriate units, e.g., mW)
G = power gain of the antenna in the direction of interest relative to
an isotropic radiator
R = distance to the center of radiation of the antenna (appropriate
units, e.g., cm)
hence

R= (PG / 4πS)1/2
For our device
P = 30.903mW
G = 2.14
R = 20 cm
S = (30.903 * 2.14) / (4*π*202) = 0.0131 mW/cm2 < 1.0 mW/cm2

For complying the FCC limits for general population/uncontrolled exposure, the
power density limit is 1.0 mW/cm2. The calculation result of the power density at a
distance of 20 cm of our device is less than the limit.
This means that according to OET Bulletin 65 (Edition 97-01), Supplement C (Edition
01-01), the equipment fulfills the requirements on power density for general
population/uncontrolled exposure and therefore fulfills the requirements of 47 CFR
Part 15.247 (b)(5).

Document Created: 2012-11-08 09:46:47
Document Modified: 2012-11-08 09:46:47

© 2024 FCC.report
This site is not affiliated with or endorsed by the FCC