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Electromagnetic MeasurementsRF, Microwave and Millimeter–Wave MeasurementsThermistor DetectorsTechnical Contacts: George M. Free Thomas P. Crowley Puanani L. DeLara Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
back to top of page | back to index of electromagnetic measurements General InformationCalibration services are available for thermistor detectors with GPC–7, Type N, and 3.5 mm coaxial connectors and several waveguide sizes (8.2 GHz to 96 GHz). Assistance is available for applying published, technically valid measurement techniques in lieu of previously available NIST calibration services for coaxial and waveguide calorimeters, thermoelectric power meters, and bolometer coupler units. The attainable limits of measurement uncertainty using these techniques are comparable to those of the previously available calibration services for these devices. The Reports of Calibration and Special Test give the magnitude and phase of the reflection coefficient, effective efficiency, and calibration factor of the thermistor detector. Definitions: Effective Efficiency The effective efficiency Bolometrically Substituted dc Power The bolometrically substituted dc power is the change in dc (or audio frequency) bias power required to maintain the resistance of the thermistor element at a constant value following the application of rf or microwave power. Calibration Factor, KB The calibration factor is the ratio of the
bolometrically substituted dc power in the thermistor detector to the
CW rf microwave power incident upon the thermistor detector. K B = Reflection Coefficient Magnitude, | The reflection coefficient magnitude and phase (argument of reflection coefficient) is the ratio of the reflected wave voltage amplitude to the incident wave voltage amplitude and phase. back to top of page | back to index of electromagnetic measurements Commercial Coaxial Thermistor Detectors (61110S–61136S)Specify frequencies in the range from 0.1
MHz to 10 MHz for special low–frequency thermistor detectors (Service
ID Number 61110S). Values for The following table lists the frequencies at which measurements are made on thermistor detectors with GPC–7 or Type N connectors. back to top of page | back to index of electromagnetic measurements Table 9.13. Measurement Ranges and Uncertainties for Coaxial Thermistor Detectors
Uncertainties for the effective efficiency and calibration factor depend on the frequency and the characteristics of the unit being calibrated such as connector type, reflection coefficient, and repeatability. back to top of page | back to index of electromagnetic measurements NIST Model CN Reference Standard (61137C–61138C)This premium service provides he measurements as a function of frequency for a NIST–designed coaxial reference standard with a Type N connector. The reference standard, designated Model CN (Coaxial with a Type N connector), is a bolometric, dc–substitution power detector that must be used with a NIST Type IV power meter (available from several commercial sources). The detector is designed as an optimum transfer standard which can be measured directly in the NIST coaxial microcalorimeter. To use this service, the customer needs to have a CN detector (contact Fred R. Clague for information).
Measurements are made at 124 frequencies over the range from 50 MHz to 18 GHz (Service ID Number 61137C) or customer specified frequencies (Service ID Number 61138C). Figure 9.1 compares the expanded uncertainty of the premium service with that of the regular service for coaxial thermistor detectors. back to top of page | back to index of electromagnetic measurements Waveguide Thermistor Detectors (61144S–61155S)Measurements of effective efficiency, efficiency factor, and reflection coefficient are made for various waveguide sizes as follows: Table 9.14. Measurement Range and Uncertainties for Waveguide Thermistor Detectors
back to top of page | back to index of electromagnetic measurements High–Power Wattmeter (61160S)A Special Test service is available for continuous wave (CW) high power wattmeters. Measurements are available at several frequencies from 1 MHz to 30 MHz (1 W to 1000 W) and 30 MHz to 400 MHz (1 W to 500 W). Wattmeters must be controllable via an IEEE–488 bus, have a Type N male input connector, and either have a Type N female output connector or an appropriate termination. The calibration factor, defined as the ratio of the wattmeter reading to the power incident upon it, will be supplied at each measurement point. The relative expanded uncertainty is typically less than 2%, depending on frequency, power level and electrical characteristics of the wattmeter/load combination. Call the technical contact for further information. back to top of page | back to index of electromagnetic measurements References—Thermistor DetectorsDirect Comparison Transfer of Microwave Power Sensor Calibration, M. Weidman, Natl. Inst. Stand. Technol. (U.S.), Tech. Note 1379 (January 1996). A Calibration Service for Reference Standards for Microwave Power, F. Clague, Natl. Inst. Stand. Technol., Tech. Note 1374 (May 1995). Microcalorimeter for GPC–7 Coaxial Transmission Line, F. Clague, Natl. Inst. Stand. Technol., Tech. Note 1358 (August 1993). Coaxial Reference Standard for Microwave Power, F. Clague and P. Voris, Natl. Inst. Stand. Technol., Tech. Note 1357 (April 1993). Measurement Service for High–Power CW Wattmeter at the National Institute of Standards and Technology, J. A. Jargon and G. Rebuldela, Proc. of the Meas. Sci. Conf., Anaheim, CA (Jan. 1993). Basic RF and Microwave Measurements: A Review of Selected Programs, A. J. Estin, J. R. Juroshek, R. B. Marks, F. R. Clague, and J. Wayde Allen, Metrologia 29, 135-151 (1992). High Power CW Wattmeter Calibration at NIST, G. Rebuldela and J. A. Jargon, J. Res. Natl. Inst. Stand. Technol., 97 (6), pp. 673-687 (Nov.-Dec. 1992). WR–10 Millimeter Wave Microcalorimeter, M. Weidman and P. Hudson, Natl. Bur. Stand. (U.S.), Tech. Note 1044 (June 1981). A Semiautomated Six–Port for Measuring Millimeter–Wave Power and Complex Reflection Coefficient, M. Weidman, IEEE Trans. Micro. Theory Tech. MTT-25, 12 (Dec. 1977). Performance Characteristics of an Automated Broad–Band Bolometer Unit Calibration System, E. Komarek, IEEE Trans. Micro. Theory Tech. MTT-25, 12 (Dec. 1977). Theory of UHF and Microwave Measurements Using the Power Equation Concept, G. F. Engen, Natl. Bur. Stand. (U.S.), Tech. Note 637 (Apr. 1973). Application of an Arbitrary Six–Port Junction to Power Measurement Problems, G. Engen and C. Hoer, IEEE Trans. Instrum. Meas. IM-21, 470 (Nov. 1972). WR–15 Microwave Calorimeter and Bolometer Unit, M. Harvey, Natl. Bur. Stand. (U.S.), Tech. Note 618 (May 1972). Accurate Microwave High–Power Measurements Using a Cascaded Coupler Method, K. E. Bramall, J. Res. Natl. Bur. Stand. (U.S.), 75C (3 and 4), 185 (July-Dec. 1971). back to top of page | back to index of electromagnetic measurements Scattering Parameters of Passive Multi–Port DevicesTechnical Contacts: Puanani L. DeLara Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
back to top of page | back to index of electromagnetic measurements General InformationMicrowave devices are characterized by their reflection and transmission properties. Single port devices such as matched terminations and offset shorts are characterized by measuring their reflection properties or voltage reflection coefficient. Multiport devices such as attenuators are characterized by measuring both their reflection and transmission properties. Figure 9.2 shows the reflected and transmitted voltage waves for a typical two–port device. The voltage waves incident to the device are defined as a1 and a2. The voltage waves reflected from the device are defined as b1 and b2.
The scattering parameters specify the relationship between the incident and reflected waves. In the case of the two–port in Figure 9.2, the scattering matrix is, [b1] = [S11 S12] [a1] The scattering matrices shown are complex quantities conveying information on both the magnitude and phase of the quantities of interest. The attenuation of a two–port device is defined as S12 and S21. Most passive microwave devices are reciprocal where S12 = S21. The magnitude of the attenuation for a reciprocal device is commonly expressed in dB as A = –20 log10 ( | S12 | ), dB = –20 log10 ( | S21 | ), dB Similar definitions exist for single port devices such as terminations and offset shorts. A one port device can be thought of as the special case of a two port device where S12 = S21 = 0. The voltage reflection coefficient for a one port device is commonly given as
where a is the voltage wave incident on the device, and b is the voltage wave reflected from the device. All scattering parameters are referenced
to some idealized transmission line. At NIST, all coaxial measurements
are referenced to an idealized, air dielectric, 50 Standards submitted for calibration should be in good repair and require only very minor cleaning of connector surfaces. NIST does not provide repair services. Items received requiring maintenance will be returned to the customer, and a handling fee will be charged. back to top of page | back to index of electromagnetic measurements Coaxial Fixed and Variable Attenuators (61210S–61221S)Coaxial fixed and variable attenuators are measured on either a NIST Dual Six–Port Vector Network Analyzer (VNA) over the frequency range from 10 MHz to 26.5 GHz or on a commercial VNA over the frequency range from 50 MHz to 50 GHz. Coaxial attenuators are normally measured
relative to a reference characteristic impedance of 50 For variable attenuators, normally only the change in attenuation from the zero setting is of interest. The test report for variable attenuators show the change in the magnitude of S12 from the zero setting versus frequency for selected attenuator settings. Complete scattering parameter measurements for variable attenuators are available by special request. Uncertainties depend on the nominal attenuation, connector type, and frequency. Attenuation measurements are available for devices with 2.4 mm, 2.92 mm, 3.5 mm, GPC–7, 14 mm, and Type N connectors as shown in Table 9.15. Measurements not listed may be available and you should call the technical contact to discuss the availability. The cost of such services must be negotiated and will, in general, be higher than other established services. Consultation is available by telephone. back to top of page | back to index of electromagnetic measurements Table 9.15. Measurement Ranges and Uncertainties for Coaxial Two–Port Devices
back to top of page | back to index of electromagnetic measurements Rectangular Waveguide Fixed and Variable Attenuators (61230S–61249S)Fixed and variable (usually rotary vane) waveguide attenuators are calibrated on the NIST Dual 6–Port VNA. Service is available for frequencies corresponding to waveguide sizes WR10, WR15, WR22, WR28, WR42, WR62, and WR90 as shown in Table 9.16. Table 9.16. Measurement Ranges and Uncertainties for Waveguide Two–Port Devices
back to top of page | back to index of electromagnetic measurements Time Delay, Coaxial and Waveguide (61250S)Time delay calibration services are available for both coaxial and waveguide delay lines. The time delay for the device under test is determined from phase measurements that are made on a vector network analyzer. The frequency range for the measurements ranges from 0.1 GHz to 100 GHz depending on the connectors involved. Devices submitted for calibration should be equipped with either precision coaxial connectors or precision waveguide flanges. The length of the device should typically be less than 30 cm. However, delay measurements can be made on longer devices in certain circumstances. Because of the specialized nature of these measurements, prior discussions should be held with NIST staff before submission of any device for testing. back to top of page | back to index of electromagnetic measurements Coaxial One–Port Devices (61260S–61271S)Services are available for complex reflection coefficient of passive devices with 2.4 mm, 2.92 mm, 3.5 mm, GPC–7, Type N and GR900 connectors. Available calibration frequencies are listed in Table 9.17. Table 9.17. Measurement Ranges and Uncertainties for Coaxial One–Port Devices
back to top of page | back to index of electromagnetic measurements Waveguide One–Port Devices (61280S–61294S)The terminations must be fitted with standard waveguide flange connectors. The faces of these flanges should be machined flat and smooth and should not contain protrusions or indentations. Considerable care must be exercised in keeping the mating connector flange surfaces smooth and clean. Accurate alignment of the waveguide joint and flanges is also very important. The back of the flange which makes contact with the connecting bolts should be nominally flat and free of soft materials, including paint. The connecting holes of the flange should be symmetrically and accurately aligned to the rectangular waveguide opening. Available calibration frequencies are listed in Table 9.18. Table 9.18. Measurement Ranges and Uncertainties for Waveguide One–Port Devices
back to top of page | back to index of electromagnetic measurements Phase Shifters, RF and Microwave (61295S–61297S)The specific phase shift services are available
on a limited basis. Because of the specialized nature of coaxial phase
shifting components, prior discussions should be held with NIST staff
before submission of any devices to NIST. Items to be calibrated must
be fitted with connectors having a know plane of reference, such as sexless
precision connectors, or Type N connectors meeting Mil. Std. C39012. The
phase angle is For rectangular waveguide, the measurement services are normally limited to phase shift difference. Measurements are made on continuously variable waveguide phase shifters with the zero value of the scale as the nominal reference position. The expanded uncertainty is typically 0.5 °. back to top of page | back to index of electromagnetic measurements References—CS–Parameters of Passive 1– and 2–Port DevicesMeasurements of the Characteristic Impedance of Coaxial Air Line Standards, J. R. Juroshek and G. M. Free, IEEE Trans. on MTT, 42 (2), 186-191 (Feb. 1994). Basic RF and Microwave Measurements: A Review of Selected Programs, A. J. Estin, J. R. Juroshek, R. B. Marks, F.R. Clague, and J. Wayde Allen, Metrologia 29, 135-151 (1992). "Thru–Reflect–Line": An Improved Technique for Calibrating the dual Six–Port Automatic Network Analyzer, G. F. Engen and C. A. Hoer, IEEE Trans. Micr. Theory Tech. MTT-27, 987 (Dec. 1979). A Network Analyzer Incorporating Two Six–Port Reflectometers, C. A. Hoer, IEEE Trans. Micr. Tech. MTT-25, 1070 (Dec. 1977). The Six–Port Reflectometer: An Alternative Network Analyzer, G. F. Engen, IEEE Trans. Micr. Theory Tech. MTT-25, 1075 (Dec. 1977). Application of Waveguide and Circuit Theory to the Development of Accurate Microwave Measurement Methods and Standards, R. W. Beatty, Natl. Bur. Stand. (U.S.), Monogr. 137 (Aug. 1973). Specifications and Test Methods for Fixed and Variable Attenuators, dc to 40 GHz, IEEE Standard 474 (1973). Basic Theory of Waveguide Junctions and Introductory Microwave network Analysis, D. M. Kearns and R. W. Beatty, Intl. Ser. of Monogr. in Electromag. Waves 13, 59, Pergammon Press, New York, NY (1967). Electrical Parameters of Precision, Coaxial, Air Dielectric Transmission Lines, R. E. Nelson and M. R. Coryell, Natl. Bur. Stand. (U.S.), Monogr. 96 (June 1966). back to top of page | back to index of electromagnetic measurements High Accuracy Attenuation MeasurementsTechnical Contacts: Jeff A. Jargon Puanani L. DeLara Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
back to top of page | back to index of electromagnetic measurements Coaxial Fixed and Variable Attenuators (61310C)Coaxial fixed and variable attenuators are measured with reference to the NIST waveguide–below–cutoff (piston) attenuator at a fixed frequency of 30 MHz. Coaxial attenuators are normally measured
in a system having a characteristic impedance of 50 back to top of page | back to index of electromagnetic measurements Waveguide–Below–Cutoff (Piston) Attenuator Measurements at 30 MHz (61320S)Incremental attenuation is the change in attenuation of an adjustable attenuator between a reference setting (usually zero) and any other setting. The same restraints of system conditions apply as for attenuation. The term "attenuation difference" is sometimes applied to this case and usually refers to two nonzero settings. Measurements on waveguide below–cutoff (piston) attenuators are performed at 30 MHz. In any measurement, the maximum power delivered to the test attenuator is 400 mW. If the attenuator cannot tolerate this power level, some reduction of measurement range will be required. Piston attenuators are normally calibrated
in a system having a characteristic impedance of 50 back to top of page | back to index of electromagnetic measurements Attenuation Measurements at 1.25 MHz (61330S)An additional measurement service is available for attenuation measurements of special three–port devices at 1.25 MHz. A measurement system has been developed to measure the change in the ratio S21/S31 of special stable two–position, three–port devices sometimes called voltage doublers, at 1.25 MHz. The device must have an input for a 1.25 MHz source (port 1), a reference output (port 3), and an output (port 2) with a level switchable to two different values. The two levels of the bi–level output have a nominal ratio of 6.0206 dB. If Pr1 is the reference
power level when the bi–level output is at level 1 (Pb1),
and Pr2 is the reference power level when the bi–level
output is at level 2 (Pb2), then the parameter
measured is given by the following equation: The Type A standard uncertainty of the measurement system in measuring a 6 dB change in attenuation is 8.2 µB. Typical Type B standard uncertainties are on the order of 0.3 µB to 0.5 µB (1 µB = 10–5 dB). Two–port step attenuators having a nominal change in attenuation of 6 dB can also be measured by this system at 1.25 MHz. back to top of page | back to index of electromagnetic measurements Phase Shifters (61350C)The specific phase shift services are available on a limited basis depending on other demands and staff availability. Measurements not listed may possibly be provided if sufficient advance notice is given. The cost of such services must be negotiated and will, in general, be higher than the established phase shift services. Consultation by telephone or written correspondence is suggested. Often a measurement technique can be suggested that will permit the customer to perform calibrations in–house with appropriate reference to other NIST–supported standards. The expanded uncertainty is 0.5°. back to top of page | back to index of electromagnetic measurements References—High Accuracy Attenuation MeasurementsA 30 MHz Comparison Receiver, J. A. Jargon, Asia–Pacific Microwave Conf. Proc., Taejon, Korea (Oct. 1995). A Revised Uncertainty Analysis for the NIST 30 MHz Attenuation Calibration System, J. A. Jargon, Proc. of the Meas. Sci. Conf., Pasadena, CA (Jan. 1994). Basic RF and Microwave Measurements: A Review of Selected Programs, A. J. Estin, J. R. Juroshek, R. B. Marks, F. R. Clague, and J. Wayde Allen, Metrologia 29, 135-151 (1992). A Calibration Service for 30 MHz Attenuation and Phase Shift, R.T. Adair and D. H Russell, Natl. Bur. Stand. (U.S.), SP 250-32 (1988). 1.25 MHz Attenuation Measurement System, R. A. Ginley and C. M. Allred, IEEE Trans. Instrum. Meas., IM-35 (4), Pt. 1 (Dec. 1986). Specifications and Test Methods for Fixed and Variable Attenuators, dc to 40 GHz, IEEE Standard 474 (1973). UHF and Microwave Phase–Shift Measurements, D. A. Ellerbach, Proc. IEEE 55 (6), 960 (June 1967). back to top of page | back to index of electromagnetic measurements Thermal Noise MeasurementsTechnical Contacts: George M. Free Puanani L. DeLara Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
back to top of page | back to index of electromagnetic measurements Noise Temperature Measurements (61410S–61465S)Noise temperature measurements are available on single–port, coaxial and rectangular–waveguide noise sources under conditions of continuous, unmodulated operation. Precision coaxial connectors or clean, smooth, and flat standard EIA waveguide flanges are required. Measurement results on devices submitted with adapters attached may apply only to the source/ adapter combination. Complete operating instructions and special electronic connectors should be supplied, and pertinent operating conditions (voltages, circuits, etc.) should be specified for the noise source to be measured. Devices submitted that are not of sufficient quality or not mechanically compatible with the measuring system will be rejected, and an appropriate fee will be charged. Availability of measurements at specific frequencies and for various connector types is specified above. The measurement uncertainty varies with noise temperature, reflection coefficient, connector type, and source stability. The relative expanded uncertainty typically lies between 0.9 % and 1.5 % of the noise temperature. The noise temperature measured and reported
is the available noise temperature, defined to be the available
noise power per unit bandwidth divided by Boltzmann's constant. For noise
temperatures above T0=
290K, we also report the excess noise ratio delivered into a reflectionless
load (ENR0). It is defined by NIST noise–temperature measurements are performed on total–power radiometers, using two primary thermal noise standards, one of which is at ambient temperature and one of which is at cryogenic (liquid nitrogen) temperature. For measurements at 30 and 60 MHz, tunable coaxial standards [1] are used. From 1 to 12.4 GHz, coaxial standards [2] are used, and for 12.4 GHz and above, waveguide/horn standards [3,4] are used. The radiometers themselves are described in references [1,5–7]. The NIST radiometers are double–sideband, total–power radiometers. The IF frequency is 0 (i.e., the LO frequency is set to the measurement frequency), and the IF bandwidth BIF ranges from 5 MHz to 20 MHz, depending on the particular radiometer. Thus the reported noise temperature represents an average over a frequency range of 2BIF centered at the measurement frequency. At least three independent measurements (including separate system calibrations, where applicable) of the noise temperature are made at each frequency. The noise source is allowed to warm up before any measurements are made. For many connector types and frequencies, the measurements are made through adapters. The procedure for characterizing the adapter and removing its effect is described in references [8,9]. The combined standard uncertainty is composed
of type–A and type–B uncertainties [10,11]. Type–A uncertainties
(uA) are those that are measured and determined by statistical
methods, such as the standard deviation of the means of several independent
measurements of the quantity of interest. Type–B uncertainties (uB)
are those determined by other means, such as estimates of systematic uncertainties.
The uncertainty reported is the expanded uncertainty, given by back to top of page | back to index of electromagnetic measurements Special Noise Temperature Measurements (61495S)Measurements of electromagnetic thermal noise other than those listed above can sometimes be arranged on a case–by–case basis. These may include measurements through adapters, measurements out of the parameter ranges specified above, and measurements on systems currently under development. Such measurements should be discussed with one of the technical contacts before submitting a device for calibration. back to top of page | back to index of electromagnetic measurements References—Noise Temperature Measurements[1] NBS 30/60 Megahertz Noise Measurement System Operation and Service Manual, G. J. Counas and T. H. Bremer, NBSIR 81-1656 (Dec. 1981). [2] A Coaxial Noise Standard for the 1 GHz to 12.4 GHz Frequency Range, W. C. Daywitt, NBS Tech. Note 1074 (Mar. 1984). [3] Design and Error Analysis for the WR10 Thermal Noise Standard, W. C. Daywitt, NBS Tech. Note 1071 (Dec. 1993). [4] The noise temperature of an arbitrarily shaped microwave cavity with application to a set of millimetre wave primary standards, Metrologia, 30 (5) 471-478 (Oct./Nov. 1993). [5] The 30/60 MHz Tuned Radiometer—The NIST System for Noise Temperature Measurements, C. A. Grosvenor and R. L. Billinger, NIST Tech. Note 1525 (Mar. 2002). [6] Design and Testing of NFRad—A New Noise Measurement System, C. A. Grosvenor, J. Randa, and R. L. Billinger, NIST Tech. Note 1518 (Mar. 2000). [7] Noise–Temperature Measurement System for the WR–28 Band, J. Randa and L. A. Terrell, NIST Tech. Note 1395 (Aug. 1997). [8] Determining adapter efficiency by envelope averaging swept frequency reflection data, W. C. Daywitt, IEEE Trans. on Microwave Theory and Techniques, MTT–38 (11) 1748-1752 (Nov. 1990). [9] Single–port technique for adaptor efficiency evaluation, S. P. Pucic and W. C. Daywitt, 45th ARFTG Conference Digest, 113-118, Orlando, FL (May 1995). [10] Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, B. N. Taylor and C. E. Kuyatt, NIST Tech. Note 1297 (Sept. 1994). [11] ISO Guide to the Expression of Uncertainty in Measurement, Intl. Org. for Standardization; Geneva, Switzerland (1993). [12] Uncertainties in NIST Noise–Temperature Measurements, J. Randa, NIST Tech. Note 1502 (Mar. 1998). back to top of page | back to index of electromagnetic measurements Dimensional Verification of Coaxial Air Line StandardsTechnical Contacts: Puanani L. DeLara Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
back to top of page | back to index of electromagnetic measurements Coaxial Air Lines (61510S)Dimensional measurements are made on the inner and outer conductors of a beadless, coaxial, air line standard. The characteristic impedance of the air line standard is then computed from these dimensional measurements. The service is currently available for 1.85 mm, 2.4 mm, 2.92 mm, 3.5 mm, GPC–7, 14 mm, and Type N air line standards. The computations for characteristic impedance is made over the normal operating frequency range of the air line standard. Consultation is available by telephone. back to top of page | back to index of electromagnetic measurements Dielectric and Magnetic Material MeasurementsTechnical Contact: Puanani L. DeLara Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
back to top of page | back to index of electromagnetic measurements Special Tests for Dielectric and Magnetic Materials (61620S) A special–test
measurement service is available for measuring the complex permittivity,
Upon request, NIST staff will prepare a detailed cost quotation that includes estimates of the measurement uncertainties. For the case of solids, each measurement method requires accurately machined test samples with optical–standard tolerances for dimensions, flatness and parallelism. NIST can either perform the machining of test samples, the cost of which is included in the price quotation, or furnish drawings of sample specifications for the customer to perform the necessary machining. The measurement techniques available at
NIST can be divided into three categories: a) cavity resonator methods
for low–loss materials (tan Broadband transmission line techniques include
coaxial air lines and waveguides of various dimensions, as well as 1–
and 2–port open–ended coaxial probe methods. Measured broad–band
data are normally provided as linear or logarithmic plots of back to top of page | back to index of electromagnetic measurements References—Dielectric and Magnetic Material MeasurementsComplex Permeability of Demagnetized Microwave Ferrites Near and Above Gyromagnetic Resonance, J. Krupka et al, IEEE Trans. Mag. 32 (3) pp. 1924-1933 (May 1996). Dielectric and Magnetic Measurements from –50 °C to 200 °C and in the Frequency Band 50 MHz to 2 GHz, J. Baker–Jarvis et al, NIST Internal Report 5045 (Mar. 1996). Dielectric Measurements of Printed–Wiring and Circuit Boards, Thin Films, and Substrates: An Overview, J. Baker–Jarvis and C. A. Jones, Mat. Res. Soc. Symp. Proc. 381, pp. 153-164 (April 1995). Analysis of an Open–Ended Coaxial Probe with Lift–Off for Nondestructive Testing, J. Baker-Jarvis et al, IEEE Trans I&M, 43 (5) pp 711-718 (Oct. 1994). Transmission/Reflection and Short–Circuit Line Methods for Measuring Permittivity and Permeability, J. Baker–Jarvis et al, NIST Tech. Note 1355-R (Dec. 1993). The NIST 60–mm Diameter Cylindrical Cavity Resonator: Performance Evaluation for Permittivity Measurements, E .J. Vanzura et al, NIST Tech. Note 1354 (Aug. 1993). NIST Measurement Service for Electromagnetic Characterization of Materials, J. H. Grosvenor, NISTIR 5006 (Aug. 1993). Shielded Open–Circuited Sample Holders for Dielectric and Magnetic Measurements of Liquids and Powders, J. Baker–Jarvis et al, NISTIR 5001 (Mar. 1993). back to top of page | back to index of electromagnetic measurements Calibration Services, NIST,
100 Bureau Drive, Stop 2330, Gaithersburg, MD 20899-2330 Date created: 06/30/1999 |
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e
| 2 ). 
transmission line of specified dimensions. Similarly, all waveguide measurements
are referenced to an idealized, air dielectric, precision waveguide section
of specified dimensions. Details of the reference standard are available
on request. 
+ 360 n, where n is an integer. The value
of n is not determined. The expanded uncertainty is 0.5 °.
is the available noise
temperature, and 
* and permeability, µ* of dielectric and magnetic materials, as
well as the surface resistance of conductors, at selected RF/microwave
frequencies in the spectral range 1 kHz to 60 GHz. The service
is capable of characterizing fluids, powders, or bulk solids at room temperatures
(23 °C) and, in some cases, over a temperature range of approximately
–80 °C to 150 °C. Customers interested in high
frequency material characterization measurements should contact NIST staff
to discuss their specific needs. The optimal measurement technique used
is selected from a number of measurement techniques developed at NIST.
The selection depends on a number of factors including whether the material
is in fluid, powder or solid form, the volume of material available, its
shape factor (for solids), its anticipated loss factor, whether the material
is anisotropic, and the desired measurement frequencies and ambient temperature.
The resulting measurement uncertainties depend on the technique selected
as well as the nominal permittivity of the material under test. 
<
0.01), b) broadband transmission line methods for medium to high–loss
materials, and c) low–frequency impedance measuring methods. Most
cavity resonators operate at frequencies above 100 MHz and usually provide
single–frequency data, unless the resonators are tunable or can be
operated on higher–order modes. Data are usually provided in tabular
form. In general, better measurement uncertainties are achievable using
cavities and are about 0.5% for