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NIST Technical Note 1521

Measurement Comparison of a

Low-Intermodulation

Termination for the

U.S. Wireless Industry

Jeffrey A. Jargon

i\sr

lonal Institute of Standards and Technology

lology Administration, U.S. Department of Commerce 1.1521

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NIST CINTINNIAl

NIST Technical Note 1521

Measurement Comparison of a

Low-Intermodulation

Termination for the U.S.

Wireless Industry

Jeffrey A. Jargon

Radio-Frequency Technology Division

Electronics and Electrical Engineering Laboratory

July 2001

Q WW- \

U.S. Department of Commerce

Donald L. Evans. Secretary

Technology Administration

Karen H. Brown. Acting Director

National Institute of Standards and Technolocv
National Institute of Standards and Technology Technical Note 1521

Natl. Inst. Stand. Technol. Tech. Note 1521, 18 pages (July 2001)

CODEN: NTNOEF
Measurement Comparison of a Low-Intermodulation

Termination for the U.S. Wireless Industry

Jeffrey A. Jargon

National Institute of Standards and Technology

Radio-Frequency Technology Division

325 Broadway

Boulder, CO 80305 USA

After the recent, successful completion of a passive intermodulation measurement

comparison for nonlinear two-port devices, the National Institute of Standards and Technology

was requested to perform a second comparison for a one-port termination. Whereas the first comparison allowed participants to determine the level of agreement in measurements of varying

levels of passive intermodulation (-1 10 dBm to -70 dBm), this comparison allows companies to check their systems at or near the noise floor level of most instruments (nominally -130 dBm).

Since March 2000, five U.S. companies have participated in this intercomparison and have

contributed ten data sets for four different commercial communications bands. This report

preserves company anonymity, and allows participants to determine how well their

measurements compare to ensemble averages. The study shows that the majority of the

participants report PIM levels within two standard deviations of the mean values, and none of the

participants' measurements fall outside of three standard deviations.

Key Words: communications, comparison, intermodulation, measurement, passive, termination,

third-order, wireless.
1. Introduction

Passive intermodulation (PIM) is a form of signal distortion that occurs whenever signals

at two or more frequencies conduct simultaneously in a passive device, such as a cable or connector that contains some nonlinear response. The nonlinear behavior produces spurious

signals whose frequencies are linear combinations of the frequencies of the original signals. The

lower odd-ordered intermodulation (IM) products [Q.g., J{IM3) = 2/i -fi] are usually the most

problematic in the wireless industry since their signal levels are usually stronger and have the

highest potential of falling within the receive band, or up-link, of a base station, creating rf

interference in the receiver [1]. Although frequency allocations are specifically designed to guard

against this problem, collocation of two or more base station transceivers at a single site substantially increases the possibility of PIM interference [2], as illustrated in Figure 1.

Base stations built for mobile communications systems such as Personal Communication

Service (PCS 1900), Advance Mobile Phone System (AMPS), Global System for Mobile

communications (GSM), and Digital Communications System (DCS 1800), use DIN (Deutsche

Industrinorm) 7-16 and Type N coaxial connectors to handle the high transmit power

requirements. At high (above 1 W) power, nonlinearities in coaxial connectors become apparent

and measurable [3]. The many possible causes of intermodulation in coaxial connectors and

cables include poor mechanical contact, dissimilar metals in direct contact, ferrous content in the

conductors, debris within the connector, poor surface finish, corrosion, vibration, and

temperature variations. The sources of PIM have been studied extensively at various laboratories

[4-18].

Base Station ReceiveBase Station TransmitBase Station Transmit

^^

IMS fi

o0000 O(N Q•^ Q05

OV Os Cn O000\

Frequency (MHz)

Figure 1. Potential third-order intermodulation in broadband PCS.

2
In 1998, the National Institute of Standards and Technology (NIST) initiated a PIM

measurement comparison [19-21] for the U.S. wireless industry, in response to requests by

industry and members of the International Electrotechnical Commission (lEC). The goal of this

comparison was to determine the level of agreement in measurements of PIM by U.S.

manufacturers and suppliers of passive components for wireless-communication base stations.

The study revealed not only the difficulties industry was having in measuring PIM, but also

provided U.S. companies with a tool to improve their measurement capabilities. Ten companies

participated in the PIM intercomparison, measuring four round-robin artifacts and contributing

nineteen data sets for four different commercial communications bands. The study showed that

the majority of the participants reported PIM levels within one standard deviation of the mean

values, but also revealed significant discrepancies reported by some participants.

After the successful completion of the first comparison for two-port devices, NIST was

requested to perform a second comparison for a one-port termination. Whereas the first comparison allowed participants to determine the level of agreement in measurements of varying

levels of passive intermodulation (-1 10 dBm to -70 dBm), this comparison allows companies to check their systems at or near the noise floor level of most instruments (nominally -130 dBm).

(Note that dBm is defined as decibels relative to 1 mW.) As in the previous study, this report

preserves company anonymity, and allows participants to determine how well their

measurements compare to ensemble averages.

2. Methodology

To conduct the comparison, NIST obtained a low-PIM 50 Q termination with a female

DIN 7-16 connector to be circulated among the participating companies. Following the

International Electrotechnical Commission's guidelines [22], the power levels for the third-order

IM products of the termination were measured with two cw signal sources, each measuring +43

dBm (20 W) at the test ports. The termination was measured within the base station receive (uplink) band of any or all of the four communications bands listed in Table 1, when the two +43

dBm signals were tuned to fall within the corresponding base-station transmit (down-link) band.

The minimum required data from each participant was a single third-order intermodulation

power in one communication band.

Participating companies were asked to measure the reflected intermodulation products, as

illustrated in Figure 2. They were instructed to connect the female connector of the termination

to the active test port of their systems by either a direct connection or a short cable or adapter.

Participants who had the ability to make swept-frequency measurements were encouraged to make additional measurements at specified frequencies. Those who had systems that could measure intermodulation products in more than one communication band and those who had

multiple systems were encouraged to measure the devices in as many different bands as possible.

Appendix A contains the Instructions for Participants, and Appendix B includes the Artifact

Measurement Form that each participant completed.
Table 1. Base-station receive and transmit frequencies for four communications bands.

Base station Base station

Communication receive transmit

band frequencies frequencies

(MHz) (MHz)

AMPS 824-849 869-894

PCS 1900 1850-1910 1930-1990

GSM 890-915 935-960

DCS 1800 1710-1785 1805-1880

The role of NIST in this comparison was to act as a pilot laboratory. Without Imowing

absolute PIM values, our tasks were to organize the comparison, measure the stability throughout

the study, keep a database of the measurements, and report the results. After each company

measured the termination, they sent it back to us, along with their data, and we re-measured it to ensure that it was still in working order, before sending it to the next company. Now that 5

companies have contributed 10 data sets over the past 14 months, we show how each of the

participants' measurements compare with the ensemble, keeping all companies' identities

confidential.

Figure 2. Configuration for measuring refiected passive intermodulation products.
3. Results

Of the five participants, one made measurements in the AMPS band, three in the GSM

band, four in the PCS band, and one in the DCS band. The data presented in this report span a

time period of 14 months from March 2000 to May 2001.

Tables 2 through 6 list the measured data, along with the mean values and standard

deviations, taken by the five participants. These data are also plotted in Figures 3 through 6,

where solid lines between measurement points indicate a sweep with source 1 held constant, and

dashed lines between measurement points indicate a sweep with source 2 held constant. The

mean value at each frequency was calculated by converting each of the measured PIM levels

fi-om dBm to watts before computing the mean, and then converting back to dBm. Likewise, the

standard deviation at each point was first computed in watts and then converted to decibels.

Below, we discuss the results obtained in each of the four communications bands.

3.1. PCS Band

We specified five particular IMS frequencies (1870, 1880, 1890, 1900, and 1910 MHz)

for measurements spanning the PCS band. Measurements at these frequencies could be obtained

in two ways: (1) holding source 1 at 1930 MHz and sweeping source 2 downward from 1990

MHz to 1950 MHz in steps of 10 MHz, or (2) holding source 2 at 1990 MHz and sweeping

source 1 upward fi-om 1930 MHz to 1950 MHz in steps of 5 MHz.

All four participants who made measurements in the PCS band made swept-frequency

measurements in both directions. Participant D made measurements on two separate systems, so they are designated separately as Dl and D2. Table 2 lists the measured data taken by the four

participants, and Table 3 lists the mean values and standard deviations calculated at each of the

five measured frequencies. These data are also plotted in Figure 3. The mean values measured

throughout the PCS band varied between -126.2 dBm and -129.8 dBm, with standard deviations

ranging from 3.9 dB to 5.5 dB.

3.2. DCS Band

We specified five particular IM3 frequencies (1730, 1740, 1750, 1760, and 1770 MHz)

for measurements spanning the DCS band. Measurements at these frequencies could be obtained

in two ways: (1) holding source 1 at 1805 MHz and sweeping source 2 downward from 1880

MHz to 1840 MHz in steps of 10 MHz, or (2) holding source 2 at 1880 MHz and sweeping

source 1 upward from 1805 MHz to 1825 MHz in steps of 5 MHz.

Participant B, the only one to measure the termination in the DCS band, made sweptfrequency measurements in both directions. Table 4 lists the measured data taken by Participant

B. Statistical computations were not performed since we received data from only one participant,

but measurements varied from -126.7 dBm to -134.8 dBm.
3.3. GSM Band

We specified five particular IMS fi-equencies (890, 895, 900, 905, and 910 MHz) for

measurements spanning the GSM band. Measurements at these frequencies could be obtained in

two ways: (1) holding source 1 at 925 MHz and sweeping source 2 downward fi*om 960 MHz to 940 MHz in steps of 5 MHz, or (2) holding source 2 at 960 MHz and sweeping source 1 upward

fi-om 925 MHz to 935 MHz in steps of 2.5 MHz.

Of the three participants who made measurements in the GSM band, one made sweptfrequency measurements in both directions, one made measurements at 890 and 895 MHz, and

the other made a measurement at 910 MHz. Table 5 lists the measured data taken by the three

participants. Statistical computations were not performed since we did not have adequate data at any one frequency, but measurements varied from -127.0 dBm to -138.5 dBm.

3.4. AMPS Band

We specified five particular IM3 frequencies (844, 845, 846, 847 and 848 MHz) for

measurements spanning the AMPS band. Measurements at these frequencies could be obtained

in two ways: (1) holding source 1 at 869 MHz and sweeping source 2 downward from 894 MHz

to 890 MHz in steps of 1 MHz, or (2) holding source 2 at 894 MHz and sweeping source 1 upward from 869 MHz to 871 MHz in steps of 0.5 MHz.

Participant E, the only one to measure the termination in the AMPS band, made sweptfrequency measurements in both directions. Table 6 lists the measured data taken by Participant

E. Statistical computations were not performed since we received data from only one participant,

but measurements did range from -130.5 dBm to -133.7 dBm.

3.5. Long-Term Stability

Throughout the period of the comparison (March 2000 through May 2001), we made

stability-check measurements on a PCS system. Prior to sending out the termination to each

participant, we measured it each time to make sure it was in working order and to verify the

long-term stability of the artifact and our system. The measurements of the termination have

remained stable to within a standard deviation of 2.6 dB on our system.

4. Discussion and Conclusions

Of the five PCS data sets received, most companies' measurements fell within 2 standard

deviations of the measured means, and none of the participants' measurements fell outside of

three standard deviations. And although we did not receive adequate data in the other

communications bands to warrant statistical analysis, none of the measurements we received in

those bands indicated significant discrepancies. We also found that measurements made by our system on the termination remained stable to within a standard deviation of 2,6 dB over a 14-

month period.
This comparison of passive intermodulation measurements has addressed a direct request

by U.S. base-station equipment manufacturers to check their systems at or near the noise floor

level of most instruments in an impartial manner while preserving each company's anonymity.

The author thanks Donald DeGroot, Charlie Spellman and David Weinstein for their

helpful comments regarding the preparation of this document.

5. References

[I] Nagel, R. and Audenaerde, K., Passive intermodulation in duplexed communication systems,

Semint97, Parana, Brazil; Oct. 1997.

[2] Lang, M., The intermodulation problem in mobile communications, Microwave Journal: 20-

28; May 1995.

[3] King, J., Intermodulation in coaxial connectors, RF Design: 68-71; Sep. 1996.

[4] Bayrak, M. and Benson, F. A., Intermodulation products from nonlinearities in transmission

lines and connectors at microwave frequencies. Proceedings of the DEE 122(4): 361-367; Apr.

1975.

[5] Young, C.E., The danger of intermodulation generation by rf connector hardware containing

ferromagnetic materials, Naval Research Laboratory Memorandum Report 4233, Presented at the

Ninth Annual Connector Symposium: 23-37; Oct. 1976.

[6] Amin, M.B. and Benson, F.A., Nonlinear effects in coaxial cables at microwave frequencies.

Electronics Letters 13(25): 768-770; Dec. 1977.

[7] Amin, M/B. and Benson, F.A., Coaxial cables as sources of intermodulation interference at microwave frequencies, IEEE Transactions on Electromagnetic Compatibility EMC-20(3); Aug.

1978.

[8] Arazm, F. and Benson, F.A., Nonlinearities in metal contacts at microwave frequencies,

IEEE Transactions on Electromagnetic Compatibility EMC-22(3): 142-149; Aug. 1980.

[9] Kumar, A., Passive IM products threaten high-power satcom systems. Microwaves & RF: 98-

103; Dec. 1987.

[10] Lui, P.L., Rawlins, A.D., and Watts, D.W., Measurement of intermodulation products

generated by structural components. Electronics Letters 24(16): 1005-1007; Aug. 1988.

[II] Foord, A.P. and Rawlins, A.D., A study of passive intermodulation interference in space rf

hardware, ESTEC Contract 1 1 1036 Final Report, University of Kent at Canterbury; May 1992.
[12] Carlson, B., RF/microwave connector design for low intermodulation generation,

Interconnection Technology: 23-27; Jul. 1993.

[13] Petit, J.S., Rawlins, A.D., and Mitchell, S.D., PIM characterisation of ESTEC CPTR for

ARTEMIS PIM testing, JSP/ESCTEC/03/96 Final Report, University of Kent at Canterbury;

Mar. 1996.

[14] Petit, J.S. and Rawlins, A.D., A study of multipaction in multicarrier rf components,

Volume 2 WP2100: Anomalous Effects; Sep. 1996.

[15] Petit, J.S. and Rawlins, A.D., The impact of passive intermodulation on specifying and

characterizing components, Proceedings Third ESA Electronic Components Conference: 45-49;

Jul. 1997.

[16] Deats, B. and Hartman, R., Measuring the passive-IM performance of rf cable assemblies,

Microwaves & RF: 108-114; Mar. 1997.

[17] Rosenberger, B., The measurement of intermodulation products on passive components and

transmission lines, 50th ARFTG Conference Digest: 13-22, Portland, OR; Dec. 1997.

[18] Helme, B.G.M., Interference in telecomm systems, from passive intermodulation product

generation: an overview, AMTA 22"^^ Meeting and Symposium Proceedings: 143-149,

Philadelphia, PA; Oct. 2000.

[19] Jargon, J.A., DeGroot, D.C., and Reed, K.L., NIST passive intermodulation measurement

comparison for wireless base station equipment, 52nd ARFTG Conference Digest: 128-139,

Rohnert Park, CA; Dec. 1998.

[20] Jargon, J.A. and DeGroot, D.C., Comparison of passive intermodulation measurements for

the U.S. wireless industry, NIST Technical Note 1515; Oct. 1999.

[21] Jargon, J.A. and DeGroot, D.C., NIST unveils status of PIM testing, Microwaves & RF: 72-

81; Jan. 2000.

[22] International Electrotechnical Commission, RF connectors, connector cable assemblies and

cables —intermodulation level measurement. Technical Committee 46, Working Group 6.
Table 2. Measurements of the low-PIM termination in the PCS band, by participant.

Src. 1 Src. 2 IM3 A B Dl D2 E

Freq Freq Freq PIM PIM PIM PIM PIM

(MHz) (MHz) (MHz) (dBm) (dBm) (dBm) (dBm) (dBm)

1930 1990 1870 -129.8 -135.8 -123.0 -136.0 -131.7

1930 1980 1880 -131.3 -130.7 -134.0 -135.0 -126.9

1930 1970 1890 -126.3 -127.8 -135.0 -137.0 -126.3

1930 1960 1900 -132.0 -135.0 -130.0 -129.0 -126.2

1930 1950 1910 -129.8 -127.9 -129.0 -133.0 -124.1

1930 1990 1870 -130.4 -138.1 -127.0 -135.0 -130.5

1935 1990 1880 -132.7 -133.8 -125.0 -134.0 -127.7

1940 1990 1890 -128.5 -135.7 -136.0 -128.0 -123.0

1945 1990 1900 -132.5 -140.5 -126.0 -131.0 -122.1

1950 1990 1910 -126.5 -134.1 -122.0 -133.0 -121.9

Table 3. Mean values and standard deviations of the low-PIM termination in the PCS band.

IM3

Freq Mean Std. Dev.

(MHz) (dBm) (dB)

1870 -129.4 5.5

1880 -129.8 3.9

1890 -128.1 4.2

1900 -128.0 5.0

1910 -126.2 4.2

Table 4. Measurements of the low-PIM termination in the DCS band, by participant.

Src. 1 Src. 2 IM3 B

Freq Freq Freq PIM

(MHz) (MHz) (MHz) (dBm)

1805 1880 1730 -134.5

1805 1870 1740 -133.6

1805 1860 1750 -131.3

1805 1850 1760 -129.5

1805 1840 1770 -126.7

1805 1880 1730 -134.8

1810 1880 1740 -131.8

1815 1880 1750 -129.9

1820 1880 1760 -127.2

1825 1880 1770 -128.2
Table 5. Measurements of the low-PDVI termination in the GSM band, by participant.

Src. 1 Src. 2 IM3 B C D

Freq Freq Freq PIM PIM PIM

(MHz) (MHz) (MHz) (dBm) (dBm) (dBm)

925.0 960.0 890.0 -130.4 -133.2

925.0 955.0 895.0 -137.8 -134.3

925.0 950.0 900.0 -132.3

925.0 945.0 905.0 -134.5

925.0 940.0 910.0 -131.0

925.0 960.0 890.0 -127.0

927.5 960.0 895.0 -133.9

930.0 960.0 900.0 -129.6

932.5 960.0 905.0 -132.1

935.0 960.0 910.0 -138.5 --- -131.7

Table 6. Measurements of the low-PIM termination in the AMPS band, by participant.

Src. 1 Src. 2 IM3 E

Freq Freq Freq PIM

(MHz) (MHz) (MHz) (dBm)

869.0 894.0 844.0 -130.5

869.0 893.0 845.0 -130.7

869.0 892.0 846.0 -132.5

869.0 891.0 847.0 -133.7

869.0 890.0 848.0 -131.5

869.0 894.0 844.0 -131.1

869.5 894.0 845.0 -130.8

870.0 894.0 846.0 -131.8

870.5 894.0 847.0 -132.9

871.0 894.0 848.0 -131.2

10
I

•120-1

•125-

-130-

•135-

-140-

•145

A

D2

1870

-- E

Dl

Mean

T T

1880 1890 1900

IM3 Frequency (MHz)

1910

Figure 3. Measurements of the low-PIM termination in the PCS band, along with the means and

standards deviations.

^

•120-1

•125-

•130-

•135-

-140-

-145

1730

B

T T

1740 1750

IM3 Frequency (MHz)

1760 1770

Figure 4. Measurements of the low-PIM termination in the DCS band.

11
IPQT3

120n

125-

-130-

135-

UO145

890

—w— c

~^r~ D

^ I 895 900

IM3 Frequency (MHz)

905 910

Figure 5. Measurements of the low-PIM termination in the GSM band.

•120-1

-125 -

^ -130-

Oh -135-

-140-

145

844 845 846 847

IM3 Frequency (MHz)

848

Figure 6. Measurements of the low-PIM termination in the AMPS band.

12
Appendix A. Instructions for Participants

NIST Passive Intermodulation Measurement

Comparison for Wireless Base-Station Equipment

Instructions for Participants

Low-PIM Termination

You will find enclosed a one-port low-PIM termination with a female DEN 7-16 connector to be

measured. Please make every effort to perform the measurements described below, and to send

the artifact along with the data back to NIST within one calendar week after receiving it. If for

some reason your laboratory cannot meet this deadline, contact us immediately so we can make

alternative arrangements.

Measurements

The power of the third order intermodulation products of this artifact are to be measured in a system with two cw signal sources, following the International Electrotechnical Commission's

guidelines (lEC Technical Committee 46, Working Group 6). The two test signals should each measure +43 dBm (20 W) at the test ports of your measurement system. All measurements

should be reported in dBm.

The third order intermodulation products of this artifact are to be measured within the receive

(up-link) band of any or all of the communication bands listed below when the two +43 dBm

signals are tuned to fall within the corresponding transmit (down-link) band. The minimum

required data is a single third order intermodulation power in one communication band. If your

system has the ability to make swept frequency measurements, please perform additional

measurements at the frequencies listed on the attached Artifact Measurement Form. In either case, please provide an overall intermodulation value for the entire band in the space provided.

Measure the reflected intermodulation product by connecting the female connector of the

termination to the active test port of your system by either a direct connection or by using a short

cable or adapter.

If your system has the capability of measuring intermodulation products in more than one communication band, or if you have multiple systems, we encourage you to measure the devices

in as many of the different bands as possible.

13
Communication band Receive frequencies Transmit frequencies

(MHz) (MHz)

AMPS 824-849 869-894

PCS 1900 1850-1910 1930-1990

GSM 890-915 935-960

DCS 1800 1710-1785 1805-1880

Reporting the Results

When you have finished your measurements, enter your measured data (in dBm) into the

provided Artifact Measurement Form replacing the zeroes with your data. Where you do

not make measurements, do not replace the zeroes. On the form, your contact information

and any comments you would like to share with us relating to your measurements, such

as environmental conditions, measurement system and termination used, uncertainty

bounds, and anything else you think appropriate.

Returning the Devices

Once you have completed the Artifact Measurement Form for this measured artifact, e- mail it to iiargon@nist.gov. and return the device with a hard copy of the data to:

NIST

c/o Puanani DeLara

325 Broadway, Mail Stop 813

Boulder, CO 80305

Contact Information

If you have any questions regarding these measurements, contact:

Jeffrey Jargon

NIST

325 Broadway, Mail Stop 813.01

Boulder, CO 80305

Tel: (303)497-3596

Fax: (303)497-3970

E-Mail: jjargon@nist.gov

Thank you for your participation. We will contact you in the near future showing you

how your measurements compared with everybody elses', keeping other companies'

identities confidential. Likewise, your identity will remain confidential in the reports we

send to other companies.

14
Appendix B. Artifact Measurement Form

! ARTIFACT MEASUREMENT FORM

! Artifact

! Date:

! Organization:

! Contact:

! Address Line 1)

:

! Address Line 2)

! Tel:

! Fax:

! E-Mail:

! Comments (Line 1)

:

! Comments (Line 2)

! Comments (Line 3)

! AMPS (824 -894 MHz) - Overall PIM leve 1: dBm

! Freql(MH2 ) Freq2(MHz) IM3Freq(MHz) Reflected PIM (dBm)

869.0 894.0 844.0

869.0 893.0 845.0

869.0 892.0 846.0

869.0 891.0 847.0

869.0 890.0 848.0

869.0 894.0 844.0

869.5 894.0 845.0

870.0 894.0 846.0

870.5 894.0 847.0

871.0 894.0 848.0

! PCS 1900 (1850-1990 MHz - Overall PIM level: dBm

! Freql (MHz ) Freq2(MHz) IM3Freq(MHz) Reflected PIM (dBm)

1930.0 1990.0 1870.0

1930.0 1980.0 1880.0

1930.0 1970.0 1890.0

1930.0 1960.0 1900.0

1930.0 1950.0 1910.0

1930.0 1990.0 1870.0

1935.0 1990.0 1880.0

1940.0 1990.0 1890.0

1945.0 1990.0 1900.0

1950.0 1990.0 1910.0

! GSM (880- 960 MHz) - Overall PIM level : dBm

! Freql (MHz ) Freq2(MHz) IM3Freq(MHz) Reflected PIM (dBm)

925.0 960.0 890.0

925.0 955.0 895.0

925.0 950.0 900.0

925.0 945.0 905.0

925.0 940.0 910.0

925.0 960.0 890.0

927.5 960.0 895.0

930.0 960.0 900.0

932.5 960.0 905.0

935.0 960.0 910.0

! DCS 1800 (1710-1880 MHz - Overall PIM level: dBm

! Freql (MHz ) Freq2(MHz) IM3Freq(MHz) Reflected PIM (dBm)

1805.0 1880.0 1730.0

1805.0 1870.0 1740.0

1805.0 1860.0 1750.0

1805.0 1850.0 1760.0

1805.0 1840.0 1770.0

1805.0 1880.0 1730.0

1810.0 1880.0 1740.0

1815.0 1880.0 1750.0

1820.0 1880.0 1760.0

1825.0 1880.0 1770.0

U.S. GPO 2001-0-673-019/40197 15



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of other government agencies.

Voluntary Product Standards—Developed under procedures published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The standards establish nationally recognized

requirements for products, and provide all concerned interests with a basis for common understanding of the characteristics of the products. NIST administers this program in support of the efforts of private-sector

standardizing organizations.

Consumer Information Series—Practical information, based on NIST research and experience, covering

areas of interest to the consumer. Easily understandable language and illustrations provide useful background

knowledge for shopping in today's technological marketplace.

Order the above NIST publications from: Superintendent of Documents, Government Printing Office,

Washington, DC 20402.

Order the following NISTpublications—FIPS and NISTIRs—from the National Technical Information Service,

Springfield, VA 22161.

Federal Information Processing Standards Publications (FIPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register. The Register serves as the

official source of information in the Federal Government regarding standards issued by NIST pursuant to the Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat. 1127),

and as implemented by Executive Order 11717 (38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal Regulations).

NIST Interagency Reports (NISTIR)—A special series of interim or final reports on work performed by

NIST for outside sponsors (both government and non-government). In general, initial distribution is handled

by the sponsor; public distribution is by the National Technical Information Service, Springfield, VA 22161

.

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