Texas Instruments TIDA-010046, Design Manual

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10 100 1 10
3
u
0
10
20
30
40
50
60
70
FCC Class A QPK
FCC Class B QPK
CISPR 22 Clas s A QPK
CISPR 22 Clas s B QPK
Frequency (M Hz)
L
eve
l
(d
B
µ
V
/m
)
30
1 10 100
0
10
20
30
40
50
60
70
FCC Class A AVG
FCC Class B A VG
CISPR 22 Clas s A AVG
CISPR 22 Clas s B AVG
Frequency (GHz)
L
eve
l
(d
B
µ
V
/m
)
6 40
Frequency (MHz) Frequency (GHz)
L
e
ve
l
(d
B
V
/m
)
L
e
ve
l
(d
B
V
/m
)
Horn Antenna
(Above 1 GHz)
Support
Equipment
EUT
Measuring Receiver
Reference Ground Plane
3 m / 10 m
1
±
4 m
Variable
Search
Height
80 cm
Broadband Antenna
(30 MHz to 1 GHz)
Non-conducting Turntable
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Hardware, Software, Testing Requirements, and Test Results
33 TIDUES1A – October 2019 – Revised February 2020
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EMC Compliant 10/100-Mbps Ethernet PHY Reference Design With IEEE
802.3at Type-1 ( ≤ 12.95 W) PoE-PD
Then, how are class A or class B limits selected?
• Class A: Equipment, device and apparatus, that is marketed for use in commercial, business, and
industrial environments
• Class B: Equipment, device and apparatus, that is marketed for use in the home or a residential
environment by the customer
The emissions standards are more severe for Class B devices because they are more likely to be located
close to a radio or TV receiver in the home environment. Therefore, for Class B emission limits are more
restrictive than Class A by a factor of 3 (approximately 10 dB).
The radiated test setup shown in Figure 30 incorporates a measurement antenna that is placed 1 to 4 m
above the ground plane. The DUT is placed on a nonconductive table that is 80 cm high. The antenna and
DUT first should be separated by 3 m (or 10 m if required by the regulations). Both CISPR and ANSI
requirements call for the DUT to be in a worst-case operating mode, that is, a mode in which it is likely to
radiate an EM field.
Figure 31 shows the CISPR 22 / EN55022 and FCC Part 15 limits using quasi-peak
and average detectors, respectively. The test distance for radiated emission from the DUT to the antenna
is 3 m. The test was performed in an aneochic chamber, which conforms to the Volumetric Normalized
Site Attenuation (VNSA) for both 3- or 10-m measurements.
Figure 32 and Figure 33 show the actual
pictures of test setup for radiated emission test with antenna positioned at 3-m distance in horizontal and
vertical polarizations, respectively.
Figure 30. Radiated Emissions Measurement Setup for FCC Part 15 and CISPR 22
Figure 31. FCC Part 15 and CISPR 22 Radiated Limits for Class A and Class B Using QPK and AVG
Detectors