Final report EURAMET Supplementary Comparison EURAMET.EM.RF-S27 “Antenna factor for Loop Antennas” Frédéric Pythoud(1), Michele Borsero(2), Daniel Bownds(3), Soydan ÇAKIR(4), Mustafa ÇETİNTAŞ(4), Karel Dražil(5), David Gentle(3), Domenico Giordano(2), Stuart Harmon(3), Josef Kupec(5), Yannick Le Sage(6), Beat Mühlemann(1), Michal Ulvr(5), Giuseppe Vizio(2), Dongsheng Zhao(7) Mai 2014 1Federal Institute of Metrology METAS, Lindenweg 50, 3003 Bern-Wabern, Switzerland, [email protected] 2Istituto Nazionale di Ricerca Metrologica (INRIM), Italy 3National Physical Laboratory (NPL), United Kingdom 4TÜBİTAK Ulusal Metroloji Enstitüsü (TÜBİTAK UME), Turkey 5Czech Metrology Institute (CMI), Czech Republic 6Laboratoire National de Métrologie et d’Essais (LNE), France 7VSL Dutch Metrology Institute (VSL), Netherlands EURAMET Supplementary Comparison EURAMET.EM.RF-S27 1/37 Abstract The comparison of a loop antenna factor measurement has been performed. One of the mo- tivations for this comparison was that since the last comparison in this field (CCEM.RF- S21.F), several National Metrology Institutes have implemented the calibration capabilities for antenna measurements. The second motivation is that the loop antennas are typically working over a large frequency range, in this case 10 Hz to 30 MHz. For the calibration over this frequency span, two ranges are distinguished: the low frequency range where Alternat- ing Current (AC) techniques should be used, and the high frequency range where Radio- Frequency (RF) measurement techniques are applied. The comparison shows that the par- ticipants were able to measure within the declared uncertainties. EURAMET Supplementary Comparison EURAMET.EM.RF-S27 2/37 Table of contents 1 Introduction ..................................................................................................................... 4 1.1 Historical background ........................................................................................ 4 1.2 Technical background ....................................................................................... 4 1.3 Motivation .......................................................................................................... 4 2 Organisation ................................................................................................................... 5 2.1 Participants ........................................................................................................ 5 2.2 Schedule ........................................................................................................... 6 2.3 Unexpected incidents ........................................................................................ 6 3 Travelling standard ......................................................................................................... 7 3.1 Description ........................................................................................................ 7 3.2 Quantities to be measured: ............................................................................... 7 3.2.1 Quantity 1: The antenna factor .......................................................................... 7 3.2.2 Quantity 2: The complex reflection coefficient S11 ........................................... 8 3.3 Measurement instructions ................................................................................. 8 3.4 Deviation from the protocol ................................................................................ 8 4 Method of measurements ............................................................................................... 9 5 Stability of the standard ................................................................................................ 11 6 Measurement results .................................................................................................... 12 6.1 Results ............................................................................................................ 12 6.2 Normalization of the results ............................................................................. 13 6.3 Method of computation of the reference value ................................................ 13 6.4 Degrees of equivalence ................................................................................... 15 7 Summary and conclusions ........................................................................................... 18 8 References ................................................................................................................... 19 9 Annex A: Graphical results for non-mandatory frequencies ......................................... 20 10 Annex B: Graphical S11 at mandatory frequencies ..................................................... 33 11 Annex C: Participants protocol and uncertainty budget................................................ 37 EURAMET Supplementary Comparison EURAMET.EM.RF-S27 3/37 1 Introduction 1.1 Historical background In 2002-2004, the key comparison CCEM.RF-K21.F as well as the supplementary compari- son CCEM.RF-S21.F [3] took place. The aim of theses comparisons was to determine an- tenna factors of different kinds of antennas A. Schwarzbeck tuneable dipole, model UHAP: 300 MHz to 1 GHz B. Rohde & Schwarz log-periodic, model HL223: 200 MHz to 1.3 GHz C. Schaffner Chase bilog, model CBL 6112B: 30 MHz to 2 GHz D. Rohde & Schwarz active monopole HFH2-Z1: 9 kHz to 30 MHz E. EMCO active shielded loop, model 6507: 1 kHz to 30 MHz F. EMCO passive shielded loop, model 7604: 20 Hz to 150 kHz At that time, only four laboratories participated in the comparison: NMi-VSL, AIST, KRISS and NPL. The frequency points were: 20 Hz, 500 Hz, 10 kHz, 100 kHz, 1 MHz, 30 MHz. Since 2003, other National Metrology Institutes (NMI) like CMI, INRIM, LNE, UME, and METAS have implemented the calibration capabilities for loop antennas, so that it would be beneficial to perform a comparison again. 1.2 Technical background A typical loop antenna may cover the frequency range from 10 Hz to 30 MHz. To cover this wide frequency range, Alternating Current (AC) measurement techniques and Radio- Frequency (RF) measurement techniques are needed. The radiation of the antenna may be produced using: - Helmholtz coils - 3 antenna technique - TEM cells A typical broadband antenna calibration may be performed by combining different calibration methods. 1.3 Motivation Due to the time span since the last comparison, and to the technical wide spectrum of this magnetic antenna calibration, it was decided to perform a new comparison for European NMIs. EURAMET Supplementary Comparison EURAMET.EM.RF-S27 4/37 2 Organisation 2.1 Participants The pilot laboratory was METAS: The members of the support group: David Gentle (NPL) Dongsheng Zhao (VSL) The following NMIs participated in the comparison: Acronym Laboratory Contact CMI Czech Metrology Institute Mr Karel Drazil Microwave Measurement Laboratory e-mail: [email protected] Regional Inspectorate Praha phone: +420 266 020 173 (personal) Radiova 3 102 00 Praha CZECH REPUBLIC INRIM Istituto Nazionale di Ricerca Mr Michele Borsero Metrologica e-mail: [email protected] Strada delle Cace 91 phone: +39 011 3919 348 (personal) 10135 Torino +39 011 3919.1 (central) ITALY LNE Laboratoire national de métrologie et Mr Yannick Le Sage d’essais e-mail: [email protected] 29, avenue Roger Hennequin phone: +33 1 30 69 32 37 (personal) 78197 Trappes cedex +33 1 30 69 10 00 (central) FRANCE METAS Federal Institute of Metrology METAS Mr Frédéric Pythoud EMC Laboratory e-mail: [email protected] Lindenweg 50 phone: +41 58 38 70 335 (personal) 3003 Bern-Wabern +41 58 38 70 111 (central) SWITZERLAND VSL VSL Mr Dongsheng Zhao Dutch Metrology Institute e-mail: [email protected] Thijsseweg 11 phone: + 31 15 269 1741 (office) 2629JA Delft + 31 15 269 1635 (lab) The Netherlands + 31 15 269 1636 (lab) + 31 15 269 1500 (central) NPL National Physical Laboratory Mr David Gentle Hampton Road e-mail: [email protected] Teddington phone: +44 20 8943 6717 (personal) Middlesex UK +44 20 8977 3222 (central) TW11 0LW UME TÜBİTAK UME Mr Mustafa Cetintas PO 54 e-mail: [email protected] 41470 Gebze - KOCAELİ phone: +90 533 460 79 74 (mobile) TURKEY +90 262 679 50 00 (central) EURAMET Supplementary Comparison EURAMET.EM.RF-S27 5/37 2.2 Schedule The measurements were performed, starting in August of the year 2011, according to the following time plan. Measurement Time Participant August 2011 1. July to 26. August 2011 METAS September 2011 5. to 25. September 2011 NPL October 2011 3. to 21. October 2011 VSL 31. October to 18. November November 2011 - 2011 28. November to 16. December December 2011 METAS (stability control) 2011 January 2012 9. January to 3 February 2012 INRIM February 2012 6. February to 24 February 2012 LNE March 2012 5. March to 23. March 2012 CMI April 2012 METAS (stability control) May - July 2012 14. May to 15. July 2012 UME October 2012 1. October to 30. October 2012 METAS (stability control) Transportation and dispatch No special circulation method has been implemented. The transports were performed by post. On arrival at the participating laboratory, the devices and their packaging were carefully checked for any damage caused during transit. 2.3 Unexpected incidents No incident to the travelling standard was reported. EURAMET Supplementary Comparison EURAMET.EM.RF-S27 6/37 3 Travelling standard 3.1 Description The travelling standard is a shielded passive loop antenna: Magnetic Field Pickup