NRSC GUIDELINE NATIONAL RADIO SYSTEMS COMMITTEE NRSC-G201 NRSC-5 RF Mask Compliance: Measurement Methods and Practice April, 2009 NAB: 1771 N Street, N.W. CEA: 1919 South Eads Street Washington, DC 20036 Arlington, VA 22202 Tel: (202) 429-5356 Fax: (202) 775-4981 Tel: (703) 907-7660 Fax: (703) 907-8113 Co-sponsored by the Consumer Electronics Association and the National Association of Broadcasters http://www.nrscstandards.org NRSC-G201 NOTICE NRSC Standards, Guidelines, Reports and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards, Guidelines, Reports and other technical publications shall not in any respect preclude any member or nonmember of the Consumer Electronics Association (CEA) or the National Association of Broadcasters (NAB) from manufacturing or selling products not conforming to such Standards, Guidelines, Reports and other technical publications, nor shall the existence of such Standards, Guidelines, Reports and other technical publications preclude their voluntary use by those other than CEA or NAB members, whether to be used either domestically or internationally. Standards, Guidelines, Reports and other technical publications are adopted by the NRSC in accordance with the NRSC patent policy. By such action, CEA and NAB do not assume any liability to any patent owner, nor do they assume any obligation whatever to parties adopting the Standard, Guideline, Report or other technical publication. This Guideline does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Guideline to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. Published by CONSUMER ELECTRONICS ASSOCIATION Technology & Standards Department 1919 S. Eads St. Arlington, VA 22202 NATIONAL ASSOCIATION OF BROADCASTERS Science and Technology Department 1771 N Street, NW Washington, DC 20036 ©2009 CEA & NAB. All rights reserved. This document is available free of charge via the NRSC website at www.nrscstandards.org. Republication or further distribution of this document, in whole or in part, requires prior permission of CEA or NAB. Page 2 NRSC-G201 FOREWORD The NRSC-5 in-band/on-channel (IBOC) Digital Radio Broadcasting Standard specifies IBOC systems for both the AM and FM bands, including detailed specification of the parameters which must be met by the radio frequency (RF) signal which is ultimately broadcast by an IBOC facility. The most common graphical expression of some of these parameters is the so-called “RF mask” which can be thought of as a template within which the IBOC RF signal must fit. Given the variety of transmission facility configurations suitable for IBOC signal generation as well as the need to characterize IBOC RF signals by both equipment manufacturers (during construction and testing of IBOC transmission equipment) and broadcasters, various methods must be utilized to determine whether an RF signal is compliant with the RF masks specified by NRSC-5. The purpose of the NRSC Guideline is to provide background information as well as detailed instructions on the best methods and practices for determining RF mask compliance for the situations most likely to be encountered by equipment manufacturers and broadcasters. The information contained in this NRSC Guideline is the work of the IBOC Standards Development Working Group (ISDWG), a subgroup of the Digital Radio Broadcasting (DRB) Subcommittee of the NRSC. At the time of first adoption of this Guideline, the ISDWG was chaired by Dom Bordonaro, Cox Radio, and the DRB Subcommittee was co-chaired by Mike Bergman, Kenwood, Americas Corporation, and Andy Laird, Journal Broadcast Group. The NRSC chairman at the time of adoption of NRSC-G201 was Milford Smith, Greater Media, Inc. The NRSC is jointly sponsored by the Consumer Electronics Association and the National Association of Broadcasters. It serves as an industry-wide standards-setting body for technical aspects of terrestrial over-the-air radio broadcasting systems in the United States. Page 3 NRSC-G201 CONTENTS 1 SCOPE .................................................................................................................................................7 2 REFERENCES.....................................................................................................................................7 2.1 NORMATIVE REFERENCES ..............................................................................................................7 2.2 INFORMATIVE REFERENCES ............................................................................................................7 2.3 SYMBOLS AND ABBREVIATIONS .......................................................................................................8 2.4 DEFINITIONS ..................................................................................................................................9 3 BACKGROUND .................................................................................................................................11 4 HYBRID FM IBOC MASK COMPLIANCE MEASUREMENTS.........................................................12 4.1 OVERVIEW...................................................................................................................................12 4.2 MODULATING SIGNALS AND COMPLIANCE MEASUREMENTS..............................................................13 4.3 OPERATIONAL FACILITIES..............................................................................................................13 4.3.1 Common-line facilities ...........................................................................................................15 4.3.1.1 Measurement location and sampling method .............................................................................15 4.3.1.2 Instrument configuration .............................................................................................................16 4.3.1.3 Spurious emissions.....................................................................................................................16 4.3.2 Separate-line facilities ...........................................................................................................18 4.3.2.1 Measurement location and sampling method .............................................................................18 4.3.2.2 Instrument configuration .............................................................................................................19 4.3.2.3 Spurious emissions.....................................................................................................................19 4.4 TROUBLESHOOTING (VARIOUS OUT-OF-SPEC CONDITIONS AND POSSIBLE REMEDIES).......................20 4.4.1 Pre-correction and clipping discussion..................................................................................21 4.4.2 Evaluating ingress of unwanted signals ................................................................................21 4.4.3 Error rate testing....................................................................................................................23 5 HYBRID AM IBOC MASK COMPLIANCE MEASUREMENTS ........................................................24 5.1 OVERVIEW...................................................................................................................................24 5.2 OPERATIONAL FACILITIES..............................................................................................................25 5.2.1 Directional and non-directional antenna systems .................................................................26 5.2.2 Measurement locations and sampling methods....................................................................26 5.2.2.1 Field measurement .....................................................................................................................26 5.2.2.2 True power measurement at transmitter.....................................................................................27 5.2.2.3 Impact of pattern bandwidth........................................................................................................28 5.2.2.4 Directional coupler measurements not for compliance assessment ...........................................28 5.2.3 Analog signal and digital sidebands......................................................................................28 5.2.4 Spurious emissions ...............................................................................................................29 5.2.5 AM IBOC mask compliance measurement procedures ........................................................30 5.2.5.1 Additional legacy mask on full hybrid signal measurement.........................................................31 5.2.5.2 Harmonics...................................................................................................................................31 5.2.5.3 Testing for instrument-induced harmonic and spurious content..................................................31 5.3 TROUBLESHOOTING (VARIOUS OUT-OF-SPEC CONDITIONS AND POSSIBLE