ITS UWB Test Plan

June 14, 2000

Ultra-Wideband Signals for Sensing and Communication:

A Master Plan for Developing Measurement Methods, Characterizing the Signals and Estimating Their Effects on Existing Systems

ITS Ultra-Wideband Measurement Plan

(Master Plan Task 1.2)

August 25, 2000 (1:13pm)

1. INTRODUCTION

This measurement plan includes tasks that will be performed by personnel from the National Telecommunications and Information Administration (NTIA) Institute of Telecommunication Sciences (ITS) in Boulder, Colorado, the Department of Commerce National Institute of Science and Technology (NIST) which is also in Boulder, and the NTIA Office of Spectrum Management (OSM) in Washington, DC.

The measurement procedures contained in this plan are intended as guidance. As we gain experience in understanding the characteristics of UWB emissions and their transfer properties in receiver systems, we may develop alternative measurement procedures or make additional measurements to those described here. Modifications to this measurement plan will be coordinated between OSM and ITS, and will be noted in the final NTIA Report on this tasking.

2. MEASUREMENT PLAN OBJECTIVES

The objectives of this plan are to:

develop measurement procedures that use commercial-off-the-shelf (COTS) measurement equipment to accurately portray UWB emission characteristics;
observe effects of UWB signals in the IF sections of selected receivers, and determine the susceptibility of conventional radio receivers to UWB emissions;
provide a basis for development of a one-on-one interference analysis procedure to determine the minimum needed separation distances or the maximum peak and average EIRP of UWB devices to ensure compatibility;
perform a limited set of measurements to validate the one-on-one interference analysis (above) between UWB signals and selected Federal radio receivers, particularly radio navigation and safety-of-life systems;
show how multiple UWB emissions add together within a single receiver.

3. APPROACH

In order to accomplish the objectives of this measurement plan, the following approach will be taken:

Acquire several UWB devices from manufacturers, and acquire several UWB simulators. The UWB devices will be representative of typical ranges of UWB system characteristics (PRF, non-dithered, dithered and gated). The UWB simulators should produce sub-nanosecond pulsewidths, PRFs up to 40 MHz, frequency range up to 4 GHz, peak power of +30 dBm, and be capable of being triggered to produce dithered and/or gated pulse sequences.
Ensure that the UWB simulators accurately reproduce UWB device signals when programmed to simulate them.
Measure the time and frequency domain characteristics (e.g., RF emission spectra, total peak power and average power, pulsewidth, PRF, percent dither, and gating) of several UWB devices using full bandwidth (i.e., measurements in the time domain) and bandwidth-limited COTS measurement equipment.
Identify measurement procedures to accurately characterize UWB devices using bandwidth limited measurements made with COTS test equipment combined with analytical calculations.
Measure receiver IF output time waveform, peak and average power responses, and amplitude probability distributions (APDs) for a range of UWB signal characteristics and receiver IF bandwidths. Develop interference analysis procedures using this information.
Perform interference protection measurements on a limited number of Federal radio systems to assess the accuracy of the interference analysis procedures.
Perform measurements to determine if emissions from multiple UWB transmitters can have an aggregate or cumulative effect at the receiver IF output. These measurements will be performed using the three UWB simulators.

In addition to the above, some measurement results will be compared with simulated and analytical analysis results of single and multiple UWB sources including responses in a range of IF bandwidths.

4. MEASUREMENT PLAN

Figure 1 is a block diagram of the test plan showing the relationship between the various individual tasks in the test plan. Individual blocks or groups of blocks represent the major tasks, which are described in more detail in the following paragraphs. The test blocks outside of the dashed line are not part of this test plan.

4.1. Full Bandwidth Time Domain Measurements (NIST and ITS) - Master Plan Task 3.

The objectives of these measurements are to quantify UWB device and UWB simulator characteristics that cannot be measured directly with commercial-off-the shelf (COTS) equipment, and to compare with measurements performed with COTS equipment. NTIA/ITS will assess the effects and limits of using COTS bandwidth limited equipment in determining UWB device characteristics.

Figure - UWB Test Plan Block Diagram

Figure - Full Bandwidth Measurement System Block Diagram

Figure 2 shows the measurement setup for full bandwidth measurements. These measurements will be made on a radiated and conducted basis, and the results compared. A comparison of these test results is expected to give additional insight into changes in the signal characteristics that occur when the UWB device antenna is replaced by a coaxial connection to the measuring device.

Characterize the UWB devices and the UWB pulse generator simulator using the NIST RF Technology Division's Radiated Time-Domain Laboratory to acquire sampled time domain representation of the UWB signal without band-limiting the signal. From these data, ITS will determine the total peak power, and total average power of a UWB device over its entire bandwidth. Radiated and conducted measurements will be performed. The measurements will be performed on all UWB devices under test and selected emission modes.
Using the full bandwidth time domain data of the UWB devices and fast fourier transforms (FFTs), determine the RF emission spectrum of each UWB device and identify the -10 and -20 dB RF bandwidths. (ITS)
Using the full bandwidth time domain data of the UWB devices and FFTs, determine the peak power in a 50 MHz IF bandwidth. (ITS)
Document rationale for the choice of antenna types that were used to make time domain measurements.

4.2 Development of COTS Techniques for Bandwidth Limited Measurements (ITS) - Master Plan Task 4

The objectives of these measurements are to:

develop measurement procedures using COTS equipment to quantify UWB emission characteristics (e.g., RF emission spectra, total peak and total average power, pulse width, PRF, percent dither, gating, etc.) for verifying compliance with Federal standards or rules and;
develop measurement procedures for determining the peak and average power of UWB signals measured in various IF bandwidths, including 1 MHz.

The general laboratory test equipment configuration for the development of COTS techniques is shown in Figure 3. Many of the measurements will not require the use of all of the measurement equipment shown. Most of these measurements will be made on a radiated basis (with appropriate corrections for antenna gain factors), with conducted measurements performed as necessary.

Measurements and analysis will include:

Those shown in TABLE 1 (below). However, measurements may not be limited to only those in TABLE 1. Results of these measurements will be compared with the UWB device measurements made with the NIST system. See the description of full bandwidth time domain measurements in section 4.1.
Using the procedures developed in item 1 above, measure the signal characteristics of various UWB devices and UWB pulse generator parameter settings.
The results from the various measurement procedures will be compared to determine the relative accuracy and range of applicability of alternative emission spectrum measurement techniques.
Determine whether the Commission's proposed measurement procedure using video filtering with a resolution bandwidth (RBW) of 1 MHz and a video bandwidth (VBW) of no greater than 10 kHz or less than 10 Hz in conjunction with log-detected peak hold (see Annex A) yields an accurate average power value (as determined under "average power" in TABLE 1). These measurements should be performed for UWB signals of noise-like, pulse-like and CW-like responses in a 1 MHz RBW (may require UWB simulator). If the Commission's video filtering technique does not provide an accurate average power value for all types of UWB signals, identify alternate techniques to determine average power in a 1 MHz bandwidth (e.g., video averaging).

TABLE 1

Bandwidth Limited Measurements with COTS Equipment

Parameter	Proposed COTS Measurement
RF Emission Spectrum	The radiated emission spectrum of each UWB device will be measured to determine the -10 & -20 dB bandwidths. The spectra will be measured down to the noise limit of the measurement system (with typical noise figure not to exceed 10 dB). Low-noise, bandpass-preselected front-ends will be used to maximize dynamic range of the measurements. Depending upon the EIRP and emission bandwidth of the UWB units, efforts should be made to measure 20 dB below the peak emission level. RF emission spectra will be measured with several techniques, including: peak-detected in a 1 MHz resolution and video bandwidth with stepped-frequency or swept-frequency maximum-hold algorithm to ensure that the peak level in 1 MHz and other bandwidths is determined at each measured frequency. Other possible techniques may include narrowband measurements in a CW/Gaussian mode, and wideband measurements in an impulsive mode. These results will be compared to each other and the NIST full-bandwidth data. Results will be used in the computation of peak and average power (below).
Pulse width	Compare the reciprocal of the -10 dB and the -20 dB bandwidths of the measured RF emission spectra with the NIST-measured pulse width values. Determine level on time waveform (e.g., 3-dB point, 6-dB point, etc.) that corresponds to 10-dB spectrum bandwidth.
Average PRF	a) If measurable spectrum lines are present (e.g., if PRF is fixed), measure frequency separation between them. b) If lines are not present (or are present but for some reason not measurable) then use a wideband detector to couple signal into an oscilloscope and measure average PRF from measured intervals within pulse trains.
Total Peak Power	Definition: Total peak power is the peak power while the pulse is on, measured with a bandwidth equal to or greater than one over the pulse width. Some techniques to be investigated include: a) If measurable lines are present, measure power in maximum-amplitude spectral line. Calculate total power, P_T, from this power level and the duty cycle (pulse width and repetition rate determined as above): P_T = P_line - 20log(duty cycle). b) Measure peak spectrum power density in a bandwidth and extrapolate to total power within the 3-dB and 10-dB points of the spectrum. c) Measure average power with a thermistor power meter, and calculate total power. P_T = P_ave - 10log(duty cycle).
Peak Power in a bandwidth (Power spectral density, PSD)	For each UWB device, measure the peak power in a wide bandwidth (e.g., 20 MHz) and extrapolate to 50 MHz resolution bandwidth. Extrapolation will be performed using measured bandwidth correction factors. Also, measure the average power using Part 15 measurement procedures for UWB systems operating above 1000 MHz (i.e., 1 MHz resolution bandwidth and 10 Hz video bandwidth (See Annex A). Record the difference in power in dB between the peak power in a 50 MHz resolution bandwidth and the Part 15 average power. Compare the results with the NIST measurements.
Total Average Power	Definition: Average power is the RMS power averaged over multiple pulse periods measured with a bandwidth greater than one over the pulsewidth. Some techniques to be investigated include: a) Using pulse width, average PRF, and P_T from above, calculate P_ave using P_ave = P_T + 10log(duty cycle). b) Using power measured in maximum spectral line (if available), calculate P_ave = P_line - 10log(duty cycle). c) Measure P_ave directly with a thermistor power meter. Compare these determinations of total P_ave to each other.
Average Power in a bandwidth (average PSD)	Definition: Average power is the rms power averaged over multiple pulse periods measured in a given bandwidth. Often referred to as average power spectral density (PSD). Some techniques to be investigated include: a) Log-detected narrowband video filtering (video bandwidth 1/100 of resolution bandwidth). Also, see Section 4.2 item 4 above. b) Video averaging (spectrum analyzer firmware algorithm). c) Determine average PSD using amplitude probability distributions in a variety of bandwidths, including 1 MHz.
Percent Dither	Attempt to measure wideband-detected signal pulse-to-pulse intervals on a COTS oscilloscope.
Pulse Gating	Wideband-detected signal will be coupled to an oscilloscope or the signal will be measured with a spectrum analyzer in 0-Hz span mode to observe the intervals between pulse bursts. An oscilloscope will be used if the intervals are too short to be resolvable on a spectrum analyzer.

4.3. IF Envelope Time Waveform and Bandwidth Correction Factor Measurements (ITS) - Master Plan Task 5

The objectives of this task are to:

determine the UWB time waveform characteristics and their associated amplitude probability distributions (APDs) at the IF output as a function of receiver IF bandwidths, and;
determine the average and peak power of UWB signals at the output of the receiver IF as a function of receiver bandwidth (bandwidth correction factor, BWCF). The UWB devices' IF envelope time waveform characterization measurements, APDs, and BWCFs should include non-dithered, dithered and gated UWB devices. This data will be used to develop a one-on-one interference analysis procedure.

Figure 3 shows the general laboratory test equipment configuration for these measurements. UWB signals will be provided by UWB devices or by the UWB pulse generator triggered by an arbitrary waveform generator (which determines the patterns of exact times when impulses are generated). Measurements shall be performed on all UWB devices in selected modes which have different emission characteristics. The UWB pulse generator will be used to simulate UWB devices if actual UWB devices are not easily available to include a full range of UWB parameter characteristics (e.g., PRF, non-dithered, dithered, and gating). One set of measurements with the UWB pulse generator will include a PRF of 30 kHz with 0% and 50% dithering.

Digitized waveforms of UWB signals will be obtained from the internal spectrum analyzer digitizer (narrower bandwidths), a digital oscilloscope connected to the spectrum analyzer log video output (medium bandwidths), or a digital oscilloscope connected to an external wideband detector or logarithmic amplifier processing the spectrum analyzer IF output.

4.3.1. General Measurement Procedure

These general measurement procedures are key to providing meaningful IF envelope time waveforms, APD and BWCF data, and will include:

Prior to performing these measurements, the actual spectrum analyzer or measurement instrument system inherent noise level should be determined for various resolution bandwidths (RBWs). For example, a spectrum analyzer display showing the change in peak noise level every few graticules for RBWs between 10 kHz and 3 MHz should be provided. This information will be used to assess spectrum analyzer IF resolution bandwidth characteristics.
All IF envelope time waveforms, APD and BWCF measurements should be made at the frequency of maximum amplitude of each UWB device. Occasional additional measurements should be made near the upper and lower 10 dB points to ensure that the characteristics of UWB signals are constant over a frequency range.
The UWB signal level shall be at least 10 dB above the measurement receiver inherent noise level for the largest measurement bandwidth.
Spectrum analyzer video bandwidth (VBW) should be greater than or equal to the resolution bandwidth.
For non-dithered UWB devices measured in narrow bandwidths (bandwidths less than the PRF), the measurement instrument should be tuned to an emission line. For dithered UWB devices, the measurement instrument should be tuned to the center of a cluster of line spectra if they exist.

4.3.2. IF Envelope Time Waveform Measurements

IF envelope time waveforms as a function of receiver IF bandwidth for non-dithered, dithered and gated UWB signals should be measured. Particular attention should be given to the ratio of the UWB signal PRF and the receiver IF bandwidth. Receiver IF output time waveforms should be described as noise-like, CW-like, pulsed.

Time waveform measurements should be made for receiver bandwidths of 10 kHz to at least 50 MHz in 1/3/10 log progression. (Note: The maximum available bandwidth will be less than 50 MHz at some frequencies.)
All time waveforms should be measured and recorded digitally.

4.3.3. IF Envelope Amplitude Probability Distribution (APD) Measurements

Using the same equipment set-up and UWB sources used in the time waveform measurements in 4.3.2 above, data from multiple digital traces at each given bandwidth/UWB device mode will be measured and combined into amplitude probability distributions (APDs). The total number of data samples from each measured UWB signal mode will be determined by considering the number of samples required to accurately resolve the expected impulsive duty cycle for that PRF and effective pulsewidth in the receiver bandpass.

These APD data will be plotted and the readings will be analyzed to compute various simulated detector functions. Included in these detector functions will be RMS, average voltage, and average logarithm.

An APD measurement of the measurement system inherent noise level (UWB device off) will be performed for each IF bandwidth. Measurement system noise APDs will be included in the plots for each UWB device.
APDs will be measured for each UWB device with maximum dynamic range. In addition, and to verify that APD curves vary linearly with measurement dynamic range, APD measurements will be made in bandwidths giving noise-like, CW, and impulse-like responses for the following peak interference-to-RMS-noise ratios: -10 dB, -6 dB, 0 dB for selected UWB devices. See ANNEX B for the procedure for establishing the peak interference-to-RMS-noise ratio.

4.3.4. Bandwidth Correction Factor and Part 15 Measurements

Receiver IF bandwidth correction factor (BWCF) measurements will be made for all UWB device modes measured in Part 4.3.2. These measurements should determine the UWB peak and average signal levels at a receiver IF output as a function of the UWB signal characteristics (PRF, non-dithered/dithered, etc) and the receiver IF bandwidth. For each bandwidth correction factor measurement:

Set the spectrum analyzer in the zero span mode at a UWB emission frequency identified as in the Part 15 procedure of Annex A.
Measure the UWB signal average power level using Part 15 measurement procedure (Annex A). This will be one of the reference levels or normalization power level(s) for subsequent analysis.
Plot UWB device peak and average (RMS, voltage, and log detector functions) levels derived from APD measurement curves (see 4.3.3) for resolution bandwidths from 10 kHz to at least 3 MHz in 1/3/10 log progression.
If possible, make average and peak power measurements similar to (c) with bandwidths of 3 MHz, 10 MHz, 30 MHz, and 50 MHz. Combine these measurements with measurements made in (c) to produce a single graph for 10 kHz to 50 MHz range.

4.4. Receiver Interference Protection Measurements - Master Plan Task 6 & 7

The objectives of this task are to:

determine what emission limits are necessary to protect selected Federal radio systems. Testing will include but not be limited to power levels meeting the general emission limits contained in 47 C.F.R. Section 15.209;
identify specific interference coupling mechanisms; and
validate the one-on-one interference analysis procedure by determining the minimum distance separation and/or the maximum UWB EIRP to ensure compatibility between UWB devices and selected Federal radionavigation and safety-of-life systems which operate in restricted bands.

These measurements will use accepted National and International interference protection criteria. The measurements will use the UWB simulator as the interference source. Both closed system and radiated measurements will be performed. Three to four of the following systems will be measured.

TABLE 2

Candidate Systems⁽¹⁾

System	Frequency Band of Operation (MHz)
1. Instrument Landing System (Localizer and Glideslope)	108-112 328.6-335.4
2. Distance Measuring Equipment (Interrogator and Transponder)	960-1215
3. ATCRBS Systems (Interrogator and Transponder) (Selected for Measurement)	1030, 1090
4. SARSAT Receivers	1,544.5
5. Air Route Surveillance Radar (Selected for Measurement)	1260-1400
5. Fixed Microwave System	1755-1850
6. Airport Surveillance Radars (Selected for Measurement)	2700-2900
7. Earth Station Receiver (Selected for Measurement)	3700-4200
8. Radar Altimeters	4200-4400
9. Microwave Landing System	5030-5090
10. Terminal Doppler Weather Radars	5600-5650
11. Microwave Landing System	5030-5090
12. Terminal Doppler Weather Radars	5600-5650

Measurements will be performed for the UWB simulator parameters or conditions shown in TABLE 3, and on other UWB parameters based on measured data from Section 4.3 .

TABLE 3

UWB Simulator Parameters for Protection Measurements

TEST #	PRF/BW RATIO	DITHER (%)	GATING (%)	RECEIVER IF OUTPUT RESPONSE TO UWB SIGNAL
1	10/1	YES(50%)	TBD	Noise-like
2	10/1	No	TBD	CW-like
3	1/10	No	TBD	Pulse-like

4.4.1. Closed System Measurements

Figure 4 shows a block diagram of the closed system measurement setup.

For each victim receiver, perform the following procedures:

Select UWB parameters that will be used for each receiver test (see Table 3).
With a spectrum analyzer, Perform Part 15 measurement on UWB signal (Annex A) at frequency of victim receiver. This will identify the ratio of peak to Part 15 average. Table 3 gives the appropriate Part 15 detector, resolution and video bandwidths for measuring the equivalent Part 15.209 power level.
Measure the receiver RMS inherent noise level (using video averaging technique).
Connect a CW signal generator to the RF input and sweep the signal generator to determine the receiver IF selectivity response. Record the shape of the IF selectivity response.
Connect the UWB simulator to the RF input of the receiver being tested. Increase the power level of the simulator output to a high SNR at the IF output. Record the undetected UWB time waveform at the IF output with an oscilloscope. Measure an APD in this configuration using a spectrum analyzer with a wider resolution bandwidth than the victim receiver IF bandwidth. APD will later be used to determine peak and average levels in this IF.
Adjust the UWB simulator attenuator setting to produce a peak interference to RMS noise ratio at the receiver IF output of 0 dB, hardline coupled. See Annex B for procedure. This will be used to understand the appearance of UWB interference in the receiver. Record oscilloscope or spectrum analyzer traces as appropriate to document this appearance.
Disconnect the UWB simulator from the receiver RF input and measure the PART 15 power level (see Annex A) with a spectrum analyzer. This may require removing attenuation and basing the Part 15 average power level on the peak-to-average ratio in Step "2" above taking into account the decreased attenuation.
Repeat the above steps for various parameter settings on the UWB simulator (See TABLE 3).
To determine the required distance separation to ensure compatibility, the propagation path loss required to preclude interference can be determined from:

L_P = EIRP + G_R() - L_R - P_r

where:

L_P = the propagation loss between transmitting and receiving antennas necessary to preclude interference from the Part 15 UWB device, in dB

EIRP = the equivalent isotropic radiated power limit under Part 15.209, in dBm. The EIRP value as a function of frequency can be determined from Table 4 below.

G_R() = the victim receiver antenna gain in the direction of the Part 15 device, in dBi.

L_R = the insertion loss (loss between the receiver antenna and receiver input) in the victim receiver, in dB.

P_r = received power of the UWB device at the victim receiver input measured using the Part 15 measurement procedure (See Annex A), in dBm. NOTE: the measured value of P_r is an average UWB signal level at the receiver RF input which corresponds to a peak I/N of 0 dB at the receiver IF output . For distance separation calculations of peak I/N protection ratios of -6 and -10 dB, an additional 6 or 10 dB must be subtracted from P_r, respectively.

Once the required propagation loss (L_P) is determined for the appropriate interference protection criteria, an appropriate smooth earth propagation model should be used to determine the required separation distance.

TABLE 4

Section 15.209 Radiated Emission Limits

Frequency (MHz)	Field Strength^a (microvolts/meter)	Measurement Distance (m)	FCC Measurement Bandwidth (kHz)	EIRP^b (dBm)
0.009 - 0.015	2400/F(kHz)	300	0.3	11.8 -20log₁₀F(kHz)
0.015 - 0.490	2400/F(kHz)	300	10	11.8 -20log₁₀F(kHz)
0.490 - 1.705	24000/F(kHz)	30	10	12.3 -20log₁₀F(kHz)
1.705 - 30.0	30	30	10	-45.7
30 - 88	100^c	3	100	-55.3
88 - 216	150^c	3	100	-51.7
216 - 960	200^c	3	100	-49.2
960-1000	500	3	100	-41.3
above 1000	500	3	1000	-41.3
a) The field strength emission limits specified are based on measurements employing a CISPR quasi-peak detector, except for the frequency bands, 9-90 kHz, 110-490 kHz, and above 1000 MHz. Emission limits in these three bands are based on measurements employing an average detector. b) The field strength emission limits were converted to an equivalent isotropic radiated power level in dBm using the following equation. EIRP(dBm) = E_o(dBV/m) + 20log₁₀D(m) - 104.8 c) Except for perimeter protection systems and biomedical telemetry systems, fundamental emissions from intentional radiators operating under Section 15.209 shall not be located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz, or 470-806 MHz, except as specified in 15.231 & 15.241.

4.4.2 Radiated Measurements

Radiated measurements are made as follows:

Set UWB pulse generator to radiate at the Part 15 level of Table 4 using Annex A procedures.
Begin radiating the UWB signal at a separation distance that is small, and gradually drive the transmitter away from the receiver (maintaining line-of-sight propagation) until interference drops to the point that it appears the same as the previously observed 0 dB interference level (see section 4.4.1.6). Note the distance from the receiver (as with a GPS unit).
Analytically, this distance will be adjusted for other protection levels (e.g., -6 dB, -10 dB).
Repeat the above steps for various parameter settings on the UWB simulator (See TABLE 3).

4.5. Aggregate Effects Measurements - Master PlanTask 8

The objective of these measurements is to determine if emissions from multiple UWB transmitters can have an aggregate or cumulative effect at a receiver IF output when multiple UWB signals are present at a receiver input. This information will also be applied to the aggregate modeling and analysis efforts.

These aggregate measurements will be closed-system using up to three UWB simulators. Figure 5 shows the aggregate effects measurement test setup. Tests will be made with signal combinations as shown in Table 5. Some measurements will be made to test the validity of the ITS aggregate APD model.

TABLE 5

UWB Simulator Parameters for Aggregate Measurements

TEST #	SIGNAL #	PRF/BW RATIO	DITHER (%)	GATING (%)	RECEIVER IF OUTPUT RESPONSE TO UWB SIGNAL
1	1	36,799	Yes (50%)	TBD	Noise-like
	2	10/1	Yes (50%)	TBD	Noise-like
	3	10/1	Yes (50%)	TBD	Noise-like
2	1	10/1	No	TBD	CW-like¹
	2	10/1	No	TBD	CW-like¹
	3	10/1	No	TBD	CW-like¹
3	1	1/10	No	TBD	Pulse-like
		1/10	No	TBD	Pulse-like
	2	1/10	No	TBD	Pulse-like
4	1	10/1	Yes	TBD	Noise-like
	2	10/1	No	TBD	CW-like¹
	3	1/10	No	TBD	Pulse-like
1. Spectrum analyzer should be tuned to center of PRF line spectra.

The following measured data will be taken.

1. For each source, set the spectrum analyzer resolution and video bandwidths to 1 MHz, and record the APD at the spectrum analyzer IF output. Plot all three APDs on a single graph. Maintain equal output levels for the three simulator outputs.

2. Combine two simulator outputs and measure the resulting APD in 1 MHz bandwidth.

3. Combine three simulator outputs and repeat.

4. For UWB noise-like and CW-like signals at the spectrum analyzer output, use video averaging technique (VBW=1/100 of RBW) on the spectrum analyzer to observe the aggregate effect. Perform stair-step measurement with one, two, and three simulators combined, and record.

5. Compare APDs of measured aggregates to results obtained by mathematically combining individual APDs.

ANNEX A

FCC UWB Measurement Procedures

General Procedure:

With the device under test (DUT) off, the spectrum analyzer (SA) is set to a frequency span that would encompass the known or suspected emission spectrum of the DUT. The SA is set to log scale (dBµV/m), with a peak detector. Because Part 15 emission limits for frequencies above 1 GHz are in terms of the average level of the emission, a resolution bandwidth (RBW) of 1 MHz with the video bandwidth (VBW) set to 10 Hz is used if the frequency is above 1 GHz. A VBW of 1 MHz is used if the frequencies of interest are below 1 GHz. A preamplifier (at least 26 dB gain) is used to assure that the signal is well above the noise floor of the SA. A calibrated antenna commensurate with the frequency range of the DUT is connected to the preamp. The ambient signal levels over the frequency range are noted/measured as a baseline.
The orientation of both the antenna and DUT are adjusted to ensure that the maximum signal strength is measured. The polarization antenna is set in the horizontal plane one meter from the ground plane and the distance between the antenna and DUT is set to 3 meters. The DUT is rotated through 360 degrees while observing the both the frequency and level of the emissions on the SA. The antenna is raised and the process repeated until the maximum emission level and it's frequency are found. The antenna polarization is changed to vertical and the process of rotation of the DUT and raising and lowering the antenna is repeated until the maximum emission level and it's frequency are obtained.
After maximizing the emission by the procedure outlined above, the signal strength and frequency are recorded. A signal substitution method is used to determine the actual field strength. The antenna is removed and replaced with a calibrated signal generator and the signal substitution method is used to account for system gains and losses. The frequency of the signal generator is set to the same frequency at which the DUT produces the maximum emission. The power level of the signal generator is adjusted to give the same reading as the previous configuration. The signal generator power level is recorded and the field strength is computed by converting the power level to field strength using the equation E(dBV/m) = 107 + signal generator output power in dBm + Antenna Factor at the frequency of maximum emission level. The calculated field strength is compared to the Part 15 limit at the appropriate frequency.

Note: If a measurement below 1 GHz does not comply with the Part 15 limits, the above procedure is repeated with using a quasi-peak detector, as Part 15 emission limits for frequencies below 1 GHz are in terms of quasi-peak.

ANNEX B

Interference Protection Criteria Measurements (ITS)

The objective of this procedure is to establish an I/N of 0 dB at the victim receiver IF output across a wide range of UWB parameters. When I/N of 0 is established, other levels (e.g., -6 dB, -10 dB) can be set by adjusting input attenuation accordingly.

Technique:

1) For each bandwidth, determine spectrum analyzer RMS noise level using lowpass video filtering (RBW 100 × VBW).

2) For UWB signal with noise-like characteristics at IF output, couple into spectrum analyzer at a level at least 10 dB above the spectrum analyzer video filtered noise established in step 1. Determine level using lowpass video filtering. Then add attenuation at spectrum analyzer input to achieve desired 0 dB I/N ratio. Verify that new level is 3 dB higher than inherent noise level.

3) For UWB signal with CW-like characteristics at IF output, couple into spectrum analyzer at a level 10 dB or more higher than spectrum analyzer noise established in Step 1. Determine level using lowpass video filtering. Then add attenuation at spectrum analyzer input to achieve 0 dB I/N ratio, taking into account that the log average of noise is measured 2.5 dB lower than the actual RMS level.

4) For UWB signal with pulse-like characteristics at IF output, couple into spectrum analyzer at a peak-detected level 10 dB or more higher than spectrum analyzer noise established in Step 1. Then add attenuation at spectrum analyzer input to achieve 0 dB I/N ratio, taking into account that the log average of noise is measured 2.5 dB lower than the actual RMS level.

ENDNOTE:

1. ¹ Pending FAA response to NTIA.

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