Test Plan for Measurements

0501-EX-ST-2013 Text Documents

National Public Radio

2013-05-23ELS_137266

Test Plan for Measurement of Interference Susceptibility Ratio to C-Band Receive Terminals to Potential IMT Signals John Kean, Senior Technologist 23 May 2013 ©2013 National Public Radio, Inc.

Procedure to Measure Interference Susceptibility Ratio of C-Band Satellite Receive Terminals with Signals from Potential IMT Services The World Radiocommunication Conference (WRC-2007), among other organizations representing wireless communications, has proposed additional globally-harmonized spectrum to support the expansion of International Mobile Telecommunications- Advanced (IMT-Advanced) services.1 These initiatives involve frequencies that may impact the operation of fixed satellite earth stations receiving in the 3400-4200 MHz range (known as C-Band). This test plan set forth a simplified procedure to test interference susceptibility margins with a standard earth station used by National Public Radio. It is believed that these margins are generally applicable to other C-Band earth stations having the same EIRP and antenna configuration. This study focuses on frequencies that are not shared with fixed satellite services (FSS), potentially operating on frequencies immediately below the C-Band downlink used in Region 2, which spans from 3700 to 4200 MHz. The exact nature of IMT-Advanced services are not yet known, but it is assumed that they will operate as either fixed or mobile transceivers on a blanket authorization for a given frequency band and geographic area. Even if an IMT operation avoids operation on the 36 MHz-wide transponder channels used by C-Band downlinks, it is possible for one or more IMT devices to operate in close proximity to C-Band downlink facilities with no prior coordination, which poses a risk for interference and desensitization effects. In the United States, 3.65 GHz is currently used for point-to-point and point-to-multipoint fixed services under Part 90 of the FCC rules. These stations operate with WiMAX protocols in accordance with the IEEE 802.16 standard with bandwidth of up to 7 MHz. The procedure in Appendix A is an initial draft plan that uses one or more standard downlinks employed by National Public Radio (NPR). The test would radiate a relatively-narrowband (no more than 10 MHz) signal near the downlink with known EIRP, and interference susceptibility ratios would be determined from the ratio of the received satellite signal to the interfering test signal, taking into account the EIRP and distance. The Eb/N0 of the satellite receiver would be observed; interference would be determined at the point at which the Eb/N0 is reduced. These ratios are intended to provide an indication of the maximum allowable powers of IMT-type emitters as a function of distance and azimuth from the earth terminal. No more radiated power will be emitted than is necessary to affect the Eb/N0 of the satellite receiver which is within a small distance (less than 50 meters) of the test transmitter. None of the proposed sites have other C-Band earth stations nearby, and the proposed sites are surrounded by trees or buildings that are taller than the test antenna (2m AGL), which will prevent the radiated signal from extending outside the local test area. 1 “ITU-R Radiocommunications Assembly Expands IMT-2000 3G Radio Interface Family with OFDMA technology”; http://www.itu.int/newsroom/wrc/2007/itur_web_flash/20071019.html, 19 October 2007.

Appendix A – Procedure for susceptibility tests Test Procedure Step # Description Objective FCC Experimental 1 It is expected that emissions will require File experimental request Authorization authority from the FCC Select satellite earth 2 The NPR earth terminal shall employ one of The terminal should be distant terminal the standard R/O antennas from other C-Band services and in a location that will minimize the radiation of the signal beyond the immediate vicinity. Collect test 3 A test antenna with known gain is used to NPR has secured an antenna instrumentation illuminate the R/O antenna. The antenna (Seavey SGA-40) having a gain of beam is oriented horizontally toward the 18 dBi and half-power beamwidth earth terminal under test and may be of 23 degrees. oriented at various azimuths around the We have identified an Agilent earth station. E4433B RF signal generator with The test should include the types of RF H97 software options that can signals used for mobile wireless generate the appropriate communication for stimulus. It is believed personalities in the target IMT and that this may be IS-95 CDMA, DECT or Part 90 bands. GSM/EDGE signals, for IMT, and 3.5 or We have identified a MiniCircuits 7 MHz wide OFDM for Part 90 WiMAX.. linear amplifier with a power The test system must produce clean, stable output of +20dBm (1 dB signals at an ERP of up to 1000 milliwatts, compression). With the selected requiring a TPO of 26 mW (+14 dBm). antenna, target EIRP will be 5 dB below this rating. Measure R/O receiver 4 Operate with normal receive conditions. Note the level of signal in dBm susceptibility threshold Set RF level of signal generator to zero into test antenna and distance output from R/O antenna Place interference test antenna at a known Tests may be repeated at the distance from the R/O antenna in a direct same bearing with different line with the R/O antenna’s main beam. distance to verify the directivity of the R/O antenna. Observe Eb/N0 of the satellite receiver and raise RF level of RF generator in small steps Tests may be repeated at the until and reduction is noted (if any). same bearing with different elevation Choose a distance and height to avoid reradiation of the signal from metallic objects within the beam width of the horn antenna 5 Repeat Step 4 with different bearing at the Note the level of signal in dBm same radial distance into test antenna and distance from R/O antenna Compile the data 6 Using the EIRP of the test transmission and the expected downlink EIRP of the R/O terminal, calculate the signal ratio for Eb/N0 degradation. Project to IMT operation 7 Using data available about IMT emissions, Determine clearance distances relate signal ratios to IMT transmissions necessary for IMT emissions to protect R/O terminals from interference as a function of downlink EIRP and distance from the R/O terminal


Document Created: 2013-05-23 13:35:17
Document Modified: 2013-05-23 13:35:17
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