**DA 00-705**

**Released March 30, 2000**

**[Filing and Measurement Guidelines]{.underline}**

**[for Frequency Hopping Spread Spectrum Systems]{.underline}**

Part 15.247 of the FCC Rules provides for operation of frequency hopping
spread spectrum transmitters. Examples of devices that operate under
these rules include wireless local area networks, cordless telephones,
wireless cash registers and wireless inventory tracking systems.

The FCC has no established test procedure for frequency hopping spread
spectrum devices. Such tests are to be performed following the general
guidance in Section 15.31 of the FCC Rules, using good engineering
practice. The following provides both information on the measurement
techniques that have been accepted in the past for equipment
authorization purposes, as well as general filing guidelines which may
be used to address the various technical requirements for frequency
hopping spread spectrum transmitters.

NOTE: Unless otherwise specified, the following measurements should be
made in an RF conducted manner, with a direct connection between the
antenna port of the EUT and the measuring instrument. If any attenuation
is required between the EUT and the measuring instrument, this value, in
addition to the measured cable loss, must be added to the measured
levels. If a direct connection cannot be made to the antenna port,
alternative procedures are outlined at the end of this document. All
measurement results should be consistent with the technical
specifications and descriptions of the EUT with respect to frequency
range of operation, peak output power, etc.

**[Section 15.31(m)]{.underline}:**

This rule specifies the number of operating frequencies to be examined
for tunable equipment. Unless otherwise specified, the hopping function
must be disabled for the following tests, which should be performed with
the EUT transmitting on the number of frequencies specified in this
Section. The measurements made at the upper and lower ends of the band
of operation should be made with the EUT tuned to the highest and lowest
available channels.

**[Section 15.203:]{.underline}**

Describe how the EUT complies with the requirement that either its
antenna is permanently attached, or that it employs a unique antenna
connector, for every antenna proposed for use with the EUT. The
exception is in those cases where the EUT must be professionally
installed. In order to demonstrate that professional installation is
required, the following three points must be addressed: (a) the
application (or intended use) of the EUT, (b) the installation
requirements of the EUT, and (c) the method by which the EUT will be
marketed.

**[Section 15.204:]{.underline}**

Provide the following information for every antenna proposed for use
with the EUT: (a) type (e.g., Yagi, patch, grid, dish, etc.), (b)
manufacturer and model number, and (c) gain with reference to an
isotropic radiator.

**[Section 15.207:]{.underline}**

If the unit is designed to be connected to the public utility power
line, the voltage conducted back onto the AC power line must be
measured, in order to demonstrate compliance with the limit specified in
this Section. See ANSI C63.4-1992 for the proper set up and procedures.

**[Section 15.247(a):]{.underline}**

Describe how the EUT meets the definition of a frequency hopping spread
spectrum system, found in Section 2.1, based on the technical
description.

**[Carrier Frequency Separation]{.underline}**

The EUT must have its hopping function enabled. Use the following
spectrum analyzer settings:

Span = wide enough to capture the peaks of two adjacent channels

Resolution (or IF) Bandwidth (RBW) 1% of the span

Video (or Average) Bandwidth (VBW) RBW

Sweep = auto

Detector function = peak

Trace = max hold

Allow the trace to stabilize. Use the marker-delta function to determine
the separation between the peaks of the adjacent channels. The limit is
specified in one of the subparagraphs of this Section. Submit this plot.

**[Number of Hopping Frequencies]{.underline}**

The EUT must have its hopping function enabled. Use the following
spectrum analyzer settings:

Span = the frequency band of operation

RBW 1% of the span

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

Allow the trace to stabilize. It may prove necessary to break the span
up to sections, in order to clearly show all of the hopping frequencies.
The limit is specified in one of the subparagraphs of this Section.
Submit this plot(s).

**[Time of Occupancy (Dwell Time)]{.underline}**

The EUT must have its hopping function enabled. Use the following
spectrum analyzer settings:

Span = zero span, centered on a hopping channel

RBW = 1 MHz

VBW RBW

Sweep = as necessary to capture the entire dwell time per hopping
channel

Detector function = peak

Trace = max hold

If possible, use the marker-delta function to determine the dwell time.
If this value varies with different modes of operation (e.g., data rate,
modulation format, etc.), repeat this test for each variation. The limit
is specified in one of the subparagraphs of this Section. Submit this
plot(s). An oscilloscope may be used instead of a spectrum analyzer.

**[20 dB Bandwidth]{.underline}**

Use the following spectrum analyzer settings:

Span = approximately 2 to 3 times the 20 dB bandwidth, centered on a
hopping channel

RBW 1% of the 20 dB bandwidth

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

The EUT should be transmitting at its maximum data rate. Allow the trace
to stabilize. Use the marker-to-peak function to set the marker to the
peak of the emission. Use the marker-delta function to measure 20 dB
down one side of the emission. Reset the marker-delta function, and move
the marker to the other side of the emission, until it is (as close as
possible to) even with the reference marker level. The marker-delta
reading at this point is the 20 dB bandwidth of the emission. If this
value varies with different modes of operation (e.g., data rate,
modulation format, etc.), repeat this test for each variation. The limit
is specified in one of the subparagraphs of this Section. Submit this
plot(s).

**[Pseudorandom Frequency Hopping Sequence]{.underline}**

Describe how the hopping sequence is generated. Provide an example of
the hopping sequence channels, in order to demonstrate that the sequence
meets the requirement specified in the definition of a frequency hopping
spread spectrum system, found in Section 2.1.

**[Equal Hopping Frequency Use]{.underline}**

Describe how each individual EUT meets the requirement that each of its
hopping channels is used equally on average (e.g., that each new
transmission event begins on the next channel in the hopping sequence
after the final channel used in the previous transmission event).

**[System Receiver Input Bandwidth]{.underline}**

Describe how the associated receiver(s) complies with the requirement
that its input bandwidth (either RF or IF) matches the bandwidth of the
transmitted signal.

**[System Receiver Hopping Capability]{.underline}**

Describe how the associated receiver(s) has the ability to shift
frequencies in synchronization with the transmitted signals.

**[Section 15.247(b):]{.underline}**

**[Peak Output Power]{.underline}**

Use the following spectrum analyzer settings:

Span = approximately 5 times the 20 dB bandwidth, centered on a hopping
channel

RBW \> the 20 dB bandwidth of the emission being measured

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

Allow the trace to stabilize. Use the marker-to-peak function to set the
marker to the peak of the emission. The indicated level is the peak
output power (see the NOTE above regarding external attenuation and
cable loss). The limit is specified in one of the subparagraphs of this
Section. Submit this plot. A peak responding power meter may be used
instead of a spectrum analyzer.

**[*De Facto* EIRP Limit]{.underline}**

Describe how the EUT complies with the *de facto* EIRP limit for every
antenna proposed for use with the EUT. This includes those devices that
will be used in point-to-point applications. If the peak output power,
as measured above, must be reduced so that the *de facto* EIRP limit may
be met for a particular antenna, describe exactly how much it will be
reduced for that antenna. If the peak output power level is raised above
the limit in order to compensate for cable loss between the EUT and the
antenna, specify the minimum length of cable which will always be used,
the type of cable, and its loss, in dB per unit length, for the
frequency of the emission. The limit is specified in one of the
subparagraphs of this Section. Also, specify who will be responsible for
ensuring that compliant operation is maintained for every antenna that
will be used with the EUT.

**[Point-to-Point Operation]{.underline}**

If the EIRP relaxation for point-to-point operation is proposed for any
particular antenna, describe who will be responsible for ensuring that
the EUT is only used in such an application.

**[RF Exposure Compliance Requirements]{.underline}**

Spread spectrum transmitters operating under Section 15.247 are
categorically excluded from routine environmental evaluation for
demonstrating RF exposure compliance with respect to MPE and/or SAR
limits. These devices are not exempted from compliance. As indicated in
Section 15.247(b)(4), these transmitters are required to operate in a
manner that ensures that exposure to the public (users and nearby
persons) does not exceed the Commission\'s RF exposure guidelines (see
Sections 1.1307, 2.1091 and 2.1093). Unless a device operates at
substantially low output power levels, with a low gain antenna(s),
supporting information is generally needed to establish the various
potential operating configurations and exposure conditions of a
transmitter and its antenna(s), in order to determine compliance with
the RF exposure guidelines.

In order to demonstrate compliance with MPE requirements (see Section
2.1091), the following information is typically needed: (1) calculations
that estimate the minimum separation distance (20 cm or more) between an
antenna and persons required to satisfy power density limits (defined
for free-space), (2) antenna installation and device operating
instructions for installers (professional and/or unskilled users), and
the parties responsible for ensuring compliance with the RF exposure
requirements, (3) any caution statements and/or warning labels that are
necessary in order for a device to comply with the exposure limits, and
(4) any other RF exposure related issues that may affect MPE compliance.

For portable transmitters (see Section 2.1093), or devices deigned to
operate next to a person\'s body, compliance is determined with respect
to the SAR limit (defined in body tissues) for near-field exposure
conditions. If the maximum average output power, operating
configurations, and exposure conditions are comparable to those of
existing cellular and PCS phones, an SAR evaluation may be required in
order to determine if such a device complies with the SAR limit. When
SAR data is not available, and the additional supporting information
cannot assure compliance, the Commission may request that an SAR
evaluation be performed, as provided for in Section 1.1307(d).

**[Installation/Operation Manual Requirements]{.underline}**

Submit a copy of the information/instructions that will be included in
the installation/operation manual pertaining to: (a) correct peak output
power settings required for compliant operation for every antenna
proposed for use with the EUT, (b) point-to-point operational
requirements and responsibilities, (c) any RF exposure compliance
requirements.

**[Section 15.247(c):]{.underline}**

**[Band-edge Compliance of RF Conducted Emissions]{.underline}**

Use the following spectrum analyzer settings:

Span = wide enough to capture the peak level of the emission operating
on the channel closest to the bandedge, as well as any modulation
products which fall outside of the authorized band of operation

RBW 1% of the span

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

Allow the trace to stabilize. Set the marker on the emission at the
bandedge, or on the highest modulation product outside of the band, if
this level is greater than that at the bandedge. Enable the marker-delta
function, then use the marker-to-peak function to move the marker to the
peak of the in-band emission. The marker-delta value now displayed must
comply with the limit specified in this Section. Submit this plot.

Now, using the same instrument settings, enable the hopping function of
the EUT. Allow the trace to stabilize. Follow the same procedure listed
above to determine if any spurious emissions caused by the hopping
function also comply with the specified limit. Submit this plot.

**[Spurious RF Conducted Emissions]{.underline}**

Use the following spectrum analyzer settings:

Span = wide enough to capture the peak level of the in-band emission and
all spurious emissions (e.g., harmonics) from the lowest frequency
generated in the EUT up through the 10^th^ harmonic. Typically, several
plots are required to cover this entire span.

RBW = 100 kHz

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

Allow the trace to stabilize. Set the marker on the peak of any spurious
emission recorded. The level displayed must comply with the limit
specified in this Section. Submit these plots.

**[Spurious Radiated Emissions]{.underline}**

This test is required for any spurious emission or modulation product
that falls in a Restricted Band, as defined in Section 15.205. It must
be performed with the highest gain of each type of antenna proposed for
use with the EUT. Use the following spectrum analyzer settings:

Span = wide enough to fully capture the emission being measured

RBW = 1 MHz for f 1 GHz, 100 kHz for f \< 1 GHz

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

Follow the guidelines in ANSI C63.4-1992 with respect to maximizing the
emission by rotating the EUT, measuring the emission while the EUT is
situated in three orthogonal planes (if appropriate), adjusting the
measurement antenna height and polarization, etc. A pre-amp and a high
pass filter are required for this test, in order to provide the
measuring system with sufficient sensitivity. Allow the trace to
stabilize. The peak reading of the emission, after being corrected by
the antenna factor, cable loss, pre-amp gain, etc., is the peak field
strength, which must comply with the limit specified in Section
15.35(b). Submit this data.

Now set the VBW to 10 Hz, while maintaining all of the other instrument
settings. This peak level, once corrected, must comply with the limit
specified in Section 15.209. If the dwell time per channel of the
hopping signal is less than 100 ms, then the reading obtained with the
10 Hz VBW may be further adjusted by a "duty cycle correction factor",
derived from 20log(dwell time/100 ms), in an effort to demonstrate
compliance with the 15.209 limit. Submit this data.

If the emission on which a radiated measurement must be made is located
at the edge of the authorized band of operation, then the alternative
"marker-delta" method, listed at the end of this document, may be
employed.

**[Section 15.247(g):]{.underline}**

Describe how the EUT complies with the requirement that it be designed
to be capable of operating as a true frequency hopping system.

**[Section 15.247(h):]{.underline}**

Describe how the EUT complies with the requirement that it not have the
ability to be coordinated with other FHSS systems in an effort to avoid
the simultaneous occupancy of individual hopping frequencies by multiple
transmitters.

**[ALTERNATIVE TEST PROCEDURES]{.underline}**

If antenna conducted tests cannot be performed on this device, radiated
tests to show compliance with the peak output power limit specified in
Section 15.247(b) and the spurious RF conducted emission limit specified
in Section 15.247(c) are acceptable. As stated previously, a pre-amp,
and, in the latter case, a high pass filter, are required for the
following measurements.

1\) Calculate the transmitter\'s peak power using the following
equation:

E = [30PG]{.underline}

d

Where: E is the measured maximum fundamental field strength in V/m,
utilizing a RBW the 20 dB bandwidth of the emission, VBW \> RBW, peak
detector function. Follow the procedures in C63.4-1992 with respect to
maximizing the emission.

> G is the numeric gain of the transmitting antenna with reference to an
> isotropic radiator.
>
> d is the distance in meters from which the field strength was
> measured.

P is the power in watts for which you are solving:

P = [(Ed)^2^]{.underline}

30G

# 

2\) To demonstrate compliance with the spurious RF conducted emission
requirement of Section 15.247(c), use the following spectrum analyzer
settings:

Span = wide enough to fully capture the emission being measured

RBW = 100 kHz

VBW RBW

Sweep = auto

Detector function = peak

Trace = max hold

# Measure the field strength of both the fundamental emission and all spurious emissions with these settings. Follow the procedures in C63.4-1992 with respect to maximizing the emissions. The measured field strength of all spurious emissions must be below the measured field strength of the fundamental emission by the amount specified in Section 15.247(c). Note that if the emission falls in a Restricted Band, as defined in Section 15.205, the procedure for measuring spurious radiated emissions, listed above, must be followed.

#  

# 

# **Marker-Delta Method**

In making radiated band-edge measurements, there can be a problem
obtaining meaningful data since a measurement instrument that is tuned
to a band-edge frequency may also capture some in‑band signals when
using the resolution bandwidth (RBW) required by measurement procedure
ANSI C63.4-1992 (hereafter C63.4). In an effort to compensate for this
problem, we have developed the following technique for determining
band‑edge compliance.

STEP 1) Perform an in‑band field strength measurement of the fundamental
emission using the RBW and detector function required by C63.4 and our
Rules for the frequency being measured. For example, for a device
operating in the 902-928 MHz band under Section 15.249, use a 120 kHz
RBW with a CISPR QP detector (a peak detector with 100 kHz RBW may
alternatively be used). For transmitters operating above 1 GHz, use a 1
MHz RBW, a 1 MHz VBW, and a peak detector (as required by Section
15.35). Repeat the measurement with an average detector (i.e., 1 MHz RBW
with 10 Hz VBW). Note: For pulsed emissions, other factors must be
included. Please contact the FCC Lab for details if the emission under
investigation is pulsed. Also, please note that radiated measurements of
the fundamental emission of a transmitter operating under 15.247 are not
normally required, but they are necessary in connection with this
procedure.

STEP 2) Choose a spectrum analyzer span that encompasses both the peak
of the fundamental emission and the band-edge emission under
investigation. Set the analyzer RBW to 1% of the total span (but never
less than 30 kHz) with a video bandwidth equal to or greater than the
RBW. Record the peak levels of the fundamental emission and the relevant
band-edge emission (i.e., run several sweeps in peak hold mode). Observe
the stored trace and measure the amplitude delta between the peak of the
fundamental and the peak of the band-edge emission. This is not a field
strength measurement, it is only a relative measurement to determine the
amount by which the emission drops at the band‑edge relative to the
highest fundamental emission level.

STEP 3) Subtract the delta measured in step (2) from the field strengths
measured in step (1). The resultant field strengths (CISPR QP, average,
or peak, as appropriate) are then used to determine band‑edge compliance
as required by Section 15.205.

STEP 4) The above \"delta\" measurement technique may be used for
measuring emissions that are up to two \"standard\" bandwidths away from
the band‑edge, where a \"standard\" bandwidth is the bandwidth specified
by C63.4 for the frequency being measured. For example, for band-edge
measurements in the restricted band that begins at 2483.5 MHz, C63.4
specifies a measurement bandwidth of at least 1 MHz. Therefore you may
use the \"delta\" technique for measuring emissions up to 2 MHz removed
from the band-edge. Radiated emissions that are removed by more than two
"standard" bandwidths must be measured in the conventional manner.

Questions pertaining to this document may be directed to Gregory Czumak,
phone: (301) 362-3052, e-mail: GCZUMAK@FCC.GOV