QPE6105A
FCC Certification Guide
– Bluetooth™ Low Energy Mode
Subject to change without notice | All rights reserved. © 2022-2023 Qorvo, Inc.
GP335_UM_20021 Version 1.00
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RX mode.
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Radio Information
3.1
Applicable Standard
CFR 47 PART 15, § 15.247 - Operation within the bands 902
– 928 MHz, 2400 - 2483.5 MHz, and 5725 -
5850 MHz. See reference [11].
For spurious emissions § 15.247 is calling §
15.205 “Restricted bands of operation” and § 15.209 “Radiated
emission limits;
general requirements”.
Please mind that § 15.209 (d) states:
“…
the frequency bands 9-90 kHz, 110-490 kHz and above 1000 MHz.
Radiated emission limits in these three bands are based on measurements employing an average detector.
”
Averaging can be done by choosing a narrow video bandwidth setting on the spectrum analyzer or by
averaging multiple traces.
3.2
Duty Cycle Correction Spurious Emission According Section 15.35(c)
Section 15.35 (c) states:
“Unless otherwise specified,
[...]
, when the radiated emission limits are expressed
in terms of the average value of the emission, and pulsed operation is employed, the measurement field
strength shall be determined by averaging over one complete pulse train, including blanking intervals, as
long as the pulse train does not exceed 0.1 seconds. As an alternative (provided the transmitter operates
for longer than 0.1 seconds) or in cases where the pulse train exceeds 0.1 seconds, the measured field
strength shall be determined from the average absolute voltage during a 0.1 second interval during which
the field strength is at its maximum value. The exact method of calculating the average field strength shall
be submitted with any application for certification or shall be retained in the measurement data file for
equipment subject to Supplier's Declaration of Conformity
.”
Details on applying duty cycle correction can be found in reference [12]
, in the “Frequently Asked Questions”
section at “Question 3”, “Answer 3 (c)”;
“Taking a RMS average measurement while EUT is transmitting continuously, i.e., greater than 98%, and
correcting for operational duty cycle
– When greater than 98% duty cycle is achieved for testing purposes,
applying average measurement techniques (e.g., average detector / reduced VBW) then adjusting for the
protocol limited duty factor to determine the average emission is acceptable. If the EUT supports more
than operational duty cycle the worst-case value should be used, i.e., the highest operational duty cycle.
This measurement refers to spectrum analyzer settings 11.12.2.5.1 (Trace averaging with continuous EUT
transmissions at full power) in ANSI C63.10
.”
See also reference [13].
This answer explains that duty cycle correction of average spurious emissions for protocol limited devices
is allowed under the condition that the average spurious emissions are measured with a continuous wave
signal.