Spectrum Engineering Reports

The susceptibility of 3700– to 4200–MHz fixed–satellite service earth stations to interference from radar signals, and the mechanisms by which such interference can occur, are examined. It is shown that interference can occur even if all currently applicable NTIA and FCC spectrum engineering requirements for radar emissions and earth station receiver systems are satisfied.

This report provides the results of radio spectrum measurements performed to characterize the aggregate signal emissions present in the 2400–2500 MHz industrial, scientific, and medical (ISM) band and adjacent frequency bands. These measurements were performed at locations near Denver, Colorado and Los Angeles, California, and included various frequency domain and time domain tests utilizing omnidirectional and directive antennas. The information contained in this report can serve as an aid to designers developing equipments to operate in these frequency bands, as well as authorities seeking to enhance compatibility between ISM devices and other radio services. It should be noted that the frequency bands 2400–2402, 2402–2417 and 2417–2450 MHz have recently been reallocated from Federal use to non–Federal use in response to the requirements of Title IV — Communications Licensing and Spectrum Allocation Improvement — of the Omnibus Budget Reconciliation Act of 1993. This further enhances the attractiveness of these frequency bands to equipment manufacturers.

Keywords: microwave ovens; 2300-2600 MHz; Industrial, Scientific and Medical (ISM) Equipment; aggregate environment

TR 95-323.pdf

To request a reprint of this report, contact:

Ed Drocella, Chief,
Spectrum Engineering and Analysis Division
Office of Spectrum Management
National Telecommunications and Information Administration
(202) 482-1652
edrocella@ntia.doc.gov

For technical information concerning this report, contact:

Frank H. Sanders
Institute for Telecommunication Sciences
(303) 497-7600
fsanders@ntia.doc.gov

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

The Proposed Revision of Chapter 5 of the Manual of Regulations and Procedures for Federal Radio Frequency Management (Phase 1) report was released in September 1996.

This report addressed problems encountered by the Spectrum Planning Subcommittee of the Interdepartment Radio Advisory Committee and the Systems Review Branch of the Spectrum Engineering and Analysis Division, Office of Spectrum Management, in applying the spectrum standards of Chapter 5 to the NTIA Manual. Proposed revisions to Chapter 5 and a proposed new annex containing measurement methods are contained in the report.

This report contains the results of an NTIA study concerning the use of the Earth exploration-satellite service (EESS) in the frequency range 8025-8400 MHz for Government, non-Government and international operations. The intent of this report was to compile the current and proposed, national and international, spectrum usage in the 8025-8400 MHz frequency range (including the lower adjacent-band, 7900-8025 MHz, and the upper adjacent- band, 8400-8450 MHz), to identify potential sharing issues, and summarize some options available to alleviate the interference interaction that might occur. This report is intended to be a resource document for examining specific EESS issues within the frequency range of 8025-8400 MHz.

The major objective of the measurements and tests performed at Bath was to determine the mechanism by which interference is occurring, and to recommend technically feasible solutions to the interference problem. Technical feasibility of a solution does not necessarily mean that the solution will be considered to be practical or desirable from a standpoint of cost or other non-technical considerations; it only means that the solution will work under the limits of known laws of physics and current state-of-the art knowledge of electrical engineering principles. Our purpose in performing the tasks at Bath, performing analysis of the data from Bath, and in writing this report is to set forth all possible technical solutions that meet these criteria. The parties to the interference problem may use these recommendations to attempt to resolve the interference problem on a technical basis.

On behalf of the Secretary of Commerce, the National Telecommunications and Information Administration (NTIA) has prepared this report as required by Title III ­ Communication and Spectrum Allocation Provisions ­ of the Balanced Budget Act of 1997 (Title III of the BBA 97). This report identifies radio spectrum currently used by the Federal Government for reallocation to the private sector.

Title III of the BBA 97 requires the Secretary of Commerce to provide from the spectrum currently allocated for Federal use, an aggregate of at least 20 megahertz (MHz) below 3 gigahertz (GHz) for allocation and assignment by the Federal Communications Commission (FCC) to non-Federal users through the process of competitive bidding.

The National Table of Frequency Allocations allocate the 2025-2110 MHz band to Federal space science services and the entire 1990-2110 MHz band to the non-Federal government fixed and mobile communication services. The Federal space science services provide the tracking, telemetry, and command (TT&C) functions for near-Earth and geostationary-satellite network operated by the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA). The transmissions made to these satellites both from the surface of the Earth and from NASA’s Tracking and Data Relay Satellites (TDRS) in the 2025-2110 MHz band are essential to the success of the scientific and manned space programs.

The objectives of this report were to: 1) identify operational characteristics of representative Government radars operating in the 3.1-3.7 GHz frequency band, 2) outline a procedure for assessing the potential for EMI from these radars to adjacent-band FSS earth station receivers, and 3) identify methods for mitigating any received EMI.

The performance of the radios was evaluated using the SINAD histograms and by listening to the radio during the tests. Radios that had histograms which showed a distribution of SINAD measurements to higher values for a greater percentage of time performed better than those radios that had low SINAD values for higher percentages of time. Some radios performed better in Savannah than New Orleans.

Mariners in the United States and other countries are experiencing interference on channels allocated to the above functions. The Radio Technical Commission for Maritime Services (RTCM) established Special Committee 117 to investigate the interference and determine if the International Electrotechnical (IEC) standard 1097-7 “Global Maritime Distress and Safety System (GMDSS)-Part 7: Shipborne VHF Radiotelephone Transmitter and Receiver-Operational and Performance Requirements, Methods of Testing and Required Test Results” would be sufficient to protect marine VHF radios from interference. In support of this effort, NTIA, in coordination with the Coast Guard and RTCM SC-117, undertook a task to test nine commercial and recreational grade marine VHF radios to the IEC standard and perform radiated tests in areas where severe cases of interference are occurring. Laboratory testing of the radios to the IEC standard was performed in Boulder, Colorado. The radiated tests were performed in Savannah, Georgia on the Savannah River and on the Mississippi River in New Orleans, Louisiana. Mariners in both locations have been reporting cases of severe interference in the marine VHF band on the waterways for quite some time now. Some of the channels experiencing the interference are key channels used for safety and bridge-to-bridge communications. The interference is very disruptive to normal operations on the river and is distracting to the radio operators.