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1、 Business and General Aviation RA Lab Test Report October 30,2023 2 Table of Contents 1.Executive Summary.3 2.Introduction.5 3.Radio Altimeter Specifications.8 4.Bandpass Filter Design.10 5.CTIA Radio Altimeter Laboratory Test Setup and Inputs.12 5.1 DEKRA Facility.12 5.2 Radio Altimeters Tested.12
2、5.3 Test Setup.12 5.4 RA Transmitter Leakage.13 5.5 Test Pass/Fail Criteria.14 5.6 Test Heights and Loop Loss.14 5.6.1.Loop Losses in Aviation Studies.15 5.6.2.Loop Losses in CTIA Testing.15 5.7 Receiver Blocking Test Inputs.16 5.8 Spurious Emissions Test Inputs.18 6.Fundamental Emissions Test Resul
3、ts.19 7.Spurious Emissions Test Results.20 8.Conclusions.21 3 1.Executive Summary The exponential growth in wireless broadband has prompted spectrum regulators in dozens of countries to reallocate mid-band spectrum for 5G.Many countries are operating standard-power base stations within 3400-3800 MHz
4、,with some extending operations below 3400 MHz.Other countries are expanding International Mobile Telecommunications(IMT)allocations to frequencies above 3800 MHz;Canada,Australia and Korea have allocated spectrum up to 4000 MHz.Japan has 5G operations within 3600-4100 MHz and 4500-4600 MHz1 and is
5、planning future allocations up to 5000 MHz.Other countries are using spectrum above the RA band,including China,which uses 4800-4960 MHz,and Australia,Singapore,Vietnam,and Korea are considering spectrum allocations above 4400 MHz.2 In the United States,federal government systems operate within 4400
6、-4940 MHz and transmit high power levels above horizon.For example,since 2002,the U.S.Navy has operated the Cooperative Engagement Capability(CEC),a communications system that helps to integrate multiple radar sensor measurements into a single air defense view shared across a battlegroup.3 The evolv
7、ing spectrum landscape has prompted the consideration of coexistence between aviations radio altimeter(RA)band at 4200-4400 MHz and nearby spectrum services.Since 2022,the Federal Aviation Administration(FAA)partnered with wireless and aviation companies to model C-Band 5G base station signals near
8、airports and evaluate the performance of commercial and transport RA models.U.S.wireless carriers agreed to voluntary mitigations around airports until 2028.4 The FAA issued airworthiness directives requiring installation of filters or RA upgrades to some aircraft,to complement the environment creat
9、ed by the voluntary mitigations.5 Recent aviation standards efforts are focused on future-proofing the next generation of RAs for the evolving spectrum environment.The U.S.-based aviation standards-setting organization,RTCA,and the European Organization for Civil Aviation Equipment(EUROCAE),are prep
10、aring new Minimum Operational 1 NTT DOCOMO 5G Initiatives for Solving Social Problems and Achieving Social Transformation,NTT Technical Review,Vol.18,No.12,pp.8696,Dec.2020,last visited 07/20/2023 at https:/doi.org/10.53829/ntr202012fa13.Japan operates 5G base stations up to 4100 MHz and within 4500
11、-4600 MHz.2 Global 5G Spectrum Update and Innovations for Future Wireless Systems,Qualcomm Research,May 2023,at https:/ WT Docket No.00-32,Notice of Proposed Rulemaking,The 4.9 GHz Band Transferred from Federal Government Use,February 29,2000 at 35.The CEC transceivers use 22 MHz channels with a max
12、imum Effective Isotropic Radiated Power(EIRP)of 88 dBm,and are mounted on ships,aircraft,and mobile ground-based units.4 Ex parte letter,AT&T Services,Inc.,T-Mobile,US Cellular,and Verizon,GN Docket No.18-122,March 31,2023;and Agri-Valley Communications,Inc.,Carolina West Wireless,New Level II L.P.,
13、Nex-Tech Wireless,and Nsight Spectrum,LLC,GN Docket No.18-122,June 13,2023.5 FAA AD 2023-10-2,effective May 26,2023,at https:/drs.faa.gov/browse/excelExternalWindow/FR-ADFRAWD-2023-.0001.4 Performance Standards(MOPS)for radio altimeters,including requirements for resiliency to strong
14、 signals near the RA band.The joint committee also drafted DO-399,exploring RA performance in the presence of C-Band 5G signals.DO-399 is currently undergoing comment resolution.A thorough assessment of C-Band/RA coexistence requires a clear understanding of current RA performance and the potential
15、improvements achievable through bandpass filter and transceiver design.The next generation of RAs must operate robustly in the presence of other services immediately adjacent to the RA band.CTIA initiated laboratory testing of several RA models to assess the potential improvement achieved with custo
16、m bandpass filters designed to reject energy adjacent to the RA band.CTIA replicated the laboratory test environment established by the Aviation Vehicle Systems Institute(AVSI)in prior aviation testing.The test setup included conditions beyond worst case,exceeding the requirements established by RTC
17、A DO-155 and EUROCAE ED-30.CTIAs test results show that RAs equipped with custom bandpass filters achieve excellent tolerance of strong signals in spectrum adjacent to the RA band.Some RA models exhibited excellent performance today,without modification.A few RA models exhibited less robust performa
18、nce.However,with a custom bandpass filter in place,all RAs showed excellent rejection of energy outside the RA band.RA transmitter power also plays an important role in improving performance.The less robust RAs were generally equipped with lower power transmitters,and performance could improve beyon
19、d the levels shown here should the transmitter power increase.Designing future RAs with robust bandpass filters and higher transmitter power levels consistent with the better-performing models will future-proof RA performance within the ever-evolving wireless landscape,including the eventual expansi
20、on of full power IMT services within spectrum immediately adjacent to the RA band.5 2.Introduction Additional mid-band spectrum is essential to meeting the growth in wireless demand.A recent Accenture study highlighted the significant disparity in the amount of licensed versus unlicensed and federal
21、 spectrum allocations.6 A Brattle Group study released in April 2023 identified a spectrum shortfall of more than 1400 MHz of standard-power,licensed mid-band spectrum by 2032.7 The spectrum deficit was similarly underscored in an earlier GSMA report identifying a need for a total of two gigahertz o
22、f mid-band spectrum to meet the IMT wireless broadband requirements by 2030.8 With promising spectrum pipeline bands like 6 GHz already foreclosed to standard power wireless operations in the United States,9 the 3300-4200 MHz and 4400-5000 MHz bands10 are essential to address future wireless broadba
23、nd demand.Future RA designs must be sufficiently resilient to enable the efficient use of spectrum adjacent to the RA band for standard-power mobile broadband services.The wireless and aviation industries have worked cooperatively since 2020,participating in working groups11 and RTCA plenary meeting
24、s,sharing technical information,and discussing RA performance.In the fall of 2022,RTCA and EUROCAE released a draft guidance document of RA performance in the presence of IMT signals,DO-399.DO-399 is intended to provide one of the technical inputs to RTCA/EUROCAEs work program developing new RA MOPS
25、,12 which will be the first major revision to RA 6 Accenture,Spectrum Allocations in the United States,https:/www.ctia.org/news/spectrum-allocation-in-the-united-states,September 2022.7 The Brattle Group,Coleman Bazelon and Paroma Sanyal,How Much Licensed Spectrum is Needed to Meet Future Demands fo
26、r Network Capacity?,https:/api.ctia.org/wp-content/uploads/2023/04/Network-Capacity-Constraints-and-the-Need-for-Spectrum-Brattle.pdf,April 17,2023.8 GSMA Calls for 2 GHz of Mid-Band Spectrum to Meet UN Targets,GSMA,https:/ 8,2021.9 FCC Adopts New Rules for the 6 GHz Band,Unleashing 1,200 Megahertz
27、of Spectrum for Unlicensed Use,https:/docs.fcc.gov/public/attachments/DOC-363945A1.pdf,April 23,2020.10 3GPP TS 38.101-1 v18.1.0(2023-03),User Equipment(UE)radio transmission and reception,Part 1:Range 1 Standalone(Release 18),section 5.2,Table 5.2-1:NR operating bands in FR1,n77 3300 MHz 4200 MHz.T
28、he 3GPP FR1 N79 band class covers 4400-5000 MHz and is a similarly important spectrum band for future IMT services.11 As recommended by the Federal Communications Commission,wireless and aviation companies and associations formed the Technical Working Group 3(TWG-3)work group and met regularly over
29、a several month period,sharing wireless and radio altimeter technical information.The final TWG-3 report may be found at https:/www.fcc.gov/ecfs/document/1/1.Wireless and aviation groups also participated in the Department of Defense-led program known as the Joint Interagency Fifth Genera
30、tion Radar Altimeter Interference(JI-FRAI),which successfully evaluated military radio altimeter performance through laboratory and flight testing.The only publicly available test report from JI-FRAI,NTIA Report 22-562,may be found at https:/its.ntia.gov/umbraco/surface/download/publication?reportNu
31、mber=TR-22-562.pdf.The JI-FRAI program concluded with no further action required by the U.S.wireless carriers.12 The goal of the new MOPS is“to enable the efficient use of near-band spectrum by setting a standard for new radar altimeters that provide state-of-the-art near-band rejection while mainta
32、ining the current intended functions 6 performance requirements since 1980 when ED-30 was released.13 Draft DO-399,at the time of the RTCA Plenary in December 2022,included“best achievable”performance curves for Mainline Transport(MT),Regional Group(RG),and Unmanned Aerial Systems and Rotorcraft(UR)
33、RAs.14 Table 2-1 shows the draft DO-399 signal levels,referenced at the RA receiver port,for the Commercial/Transport RAs.15 Table 2-1:Commercial/Transport RA Receiver Blocking Thresholds(dBm/100 MHz)(Draft DO-399)Table 2-1:Commercial/Transport RA Receiver Blocking Thresholds(dBm/100 MHz)(Draft DO-3
34、99)All C/T RAs showed excellent rejection of IMT signals below 4000 MHz.Most C/T RAs showed excellent tolerance of signals within 200 MHz of the RA band.One RA showed somewhat less tolerance in the nearest 100 MHz.Table 2-2 similarly shows the signal levels from draft DO-399 for the Business and Gen
35、eral Aviation RAs,converted to the reference point of the RA receiver port.Table 2-2:Business/General Aviation RA Receiver Blocking Thresholds(dBm/100 MHz)(Draft DO-399)Table 2-2:Business/General Aviation RA Receiver Blocking Thresholds(dBm/100 MHz)(Draft DO-399)All of the BA/GA RAs showed excellent
36、 tolerance to IMT signals below 4000 MHz.Most of the BA/GA RAs showed good tolerance to IMT signals more than 100 MHz away from the RA band.Within 100 MHz of the RA band,all BA/GA RAs showed less tolerance.of the radar altimeters.”RTCA Paper No.339-22/PMC-2378,Terms of Reference,Special Committee(SC
37、)239 Low Range Radar Altimeter,Revision 3,December 15,2022,at 2.13 Minimum Performance Specification for Airborne Low Range Radio(RADAR)Altimeter Equipment,ED-30,EUROCAE,March 1980.14 As defined in the draft DO-399 document as of December 2022,Mainline Transport aircraft include“large fixed-wing air
38、craft used for mainline air transport applications(including both passenger air travel and air cargo)”.Draft DO-399,at 22.Other RA models are used on regional airplanes,business and general aviation airplanes,and helicopters.These other RA models will be referred to as Business/General Aviation,or B
39、A/GA models,herein.15 Draft DO-399 provided power flux density levels referenced to the RA antenna face and including all margins.To facilitate comparison of the RA manufacturer PFD levels to the CTIA test data,we converted the PFD values to the power level at the RA receiver port.The conversion use
40、d the manufacturer-provided antenna gain and cable loss,backed out margins to reflect DO-399 breakpoints,and then converted the power level to dBm/100 MHz.Manufacturer 3.35 GHz 3.45 GHz 3.55 GHz 3.65 GHz 3.75 GHz 3.85 GHz 3.95 GHz 4.05 GHz 4.15 GHz 4.45 GHz 4.55 GHz 4.65 GHzManufacturer 3.35 GHz 3.4
41、5 GHz 3.55 GHz 3.65 GHz 3.75 GHz 3.85 GHz 3.95 GHz 4.05 GHz 4.15 GHz 4.45 GHz 4.55 GHz 4.65 GHzHotel30.0530.3030.0529.8129.5730.8429.624.403.3924.00Papa22.5522.3022.0521.8121.5720.7420.521.491.30Tango 134.9232.7835.5735.5735.0937.0034.5125.44-5.15-17.0816.1530.35Tango 233.9437.0137.0131.1331.7934.44
42、33.3434.909.452.2327.6633.00Whiskey33.4533.2032.5532.3130.7730.8430.4230.404.294.2829.5929.90Manufacturer 3.35 GHz 3.45 GHz 3.55 GHz 3.65 GHz 3.75 GHz 3.85 GHz 3.95 GHz 4.05 GHz 4.15 GHz 4.45 GHz 4.55 GHz 4.65 GHzManufacturer 3.35 GHz 3.45 GHz 3.55 GHz 3.65 GHz 3.75 GHz 3.85 GHz 3.95 GHz 4.05 GHz 4.
43、15 GHz 4.45 GHz 4.55 GHz 4.65 GHzMike38.038.038.038.038.035.832.111.4-10.8-15.48.427.5Papa24.624.324.023.821.620.720.51.51.3Tango36.537.338.833.631.134.033.627.23.0-12.221.332.3Whiskey 139.539.238.538.330.830.830.4-9.7-18.7-17.7-4.729.9Whiskey 239.539.238.538.330.830.825.410.8-33.7-24.716.329.97 Wir
44、eless industry stakeholders participating in the DO-399 Final Review and Comment process encouraged RTCA and EUROCAE to further research bandpass filter,antenna,transmitter,and receiver design to improve RA resilience to energy outside of the band.To further support the development of a robust next
45、generation of RAs,CTIA commissioned laboratory testing and designed proof-of-concept bandpass filters to reject energy outside of the RA band.The first step in formulating an engineering solution is to define the existing landscape.Section 3 provides an overview of the commercial RAs manufactured an
46、d flown today,along with their technical specifications.Section 4 derives specifications for bandpass filters capable of providing significant protection from energy outside of the RA band,with special consideration given to the design constraints of size,weight,and performance.Section 5 explains CT
47、IAs laboratory test setup and inputs.Section 6 summarizes the fundamental emissions test results.Section 7 summarizes the spurious emissions test results.8 3.Radio Altimeter Specifications Five RA manufacturers are currently producing eleven products flown by civil aviation today.Key specifications
48、are summarized in Table 3-1 below,sourced from publicly available manufacturer manuals,web sites,and FCC equipment authorization documentation.Table 3-1:Civilian RAs Currently Produced and FlownTable 3-1:Civilian RAs Currently Produced and Flown1616 RA design characteristics that impact performance
49、include transmit power,RF filter roll off,and the RA antenna pattern.17 The role of transmit power in improving RA performance is evident in FreeFlights product evolution.Early aviation testing highlighted some potential weaknesses in the legacy RA-4000/4500 model.Following the release of the RTCA R
50、eport,FreeFlight developed a new RA that is marketed as resilient to C-Band 5G signals,the RA-5500/6500.18 This model received FCC and FAA approval in 2022 and is currently in production,along with a variant model that is a form and fit replacement for the RA-4000/4500 labeled the RA-4500 Mk II.19 O
51、ne of the design changes in the RA-5500/6500 was to increase the RA transmitter power by 6.4 dB.20 A higher transmitter power level increases the desired signal level at the receiver,directly improving the RA 16 The table identifies RAs flown in Commercial/Transport(C/T),Business Aviation(BA)and Gen
52、eral Aviation(GA)based on descriptions of their intended installation on the RA manufacturer web sites.17 The RA antenna pattern is not included in lab testing;the antenna rejection of energy outside of the RA band should be reflected separately in coexistence analyses.18 See FreeFlight RA-5500TM Te
53、rrain Series Radar Altimeter,https:/ See RA-4500TM MK II Terrain Series Radar Altimeter,https:/ From Table 3-1,26.3 19.9=6.4 dB.Source:FCC equipment authorization test reports.Radio Altimeter ManufacturerCountry of OriginRadio Altimeter ModelFCC EA YearAviation CategoryOperating Bandwidth(MHz)Transm
54、it Power(dBm)Frequency Range(MHz)SourceALT-1000/40001995C/T,BA,GA10026.54250-4350 Operations manualLRA-21002010C/T15025.44225-4375 FCC test reportLRA-9001994C/T11027.84245-4355 FCC equipment authorizationRA-4000/45002009BA,GA10419.94256-4360 FCC test reportRA-5500/65002022BA,GA102.326.34249-4351 FCC
55、 test reportGarminUSAGRA 55/55002013BA,GA101.930.54249-4351 FCC test reportALA-52B2008C/T12827.94235-4365 FCC test reportKRA 405B1996C/T,BA,GA10022.04235-4365 Installation manualRT-3001970sBA,GA10102320Zulu-8-42-2102Victor-38-54-2423India-31-28-12-101918Alpha-12-1310102223Zulu-21-17-10-10117Victor-5
56、0-35-10-104025India-29-23-602323Alpha-18-174-22215Zulu-19-16-3-51611Victor-71-57-22-184939RA Model RA Model TestedTestedTest Height Test Height(ft)(ft)20020002000Without FilterWith FilterImprovementWithout FilterWith FilterImprovement20 7.Spurious Emissions Test Results CTIAs spurious emi
57、ssions test results are provided in Table 7-1 for the three test heights.The power levels are in dBm per 1 MHz measurement bandwidth.Table 7-1:CTIA Spurious Emissions Test Results Table 7-1:CTIA Spurious Emissions Test Results Table 7-1s worst-performing RA,India,was subject to some recent redesign
58、work by the manufacturer.The other RAs performed considerably better.The CTIA test results generally compare favorably to the draft DO-399 guidance:36 Table 7-2:Draft DO-399 Spurious Emissions Test Results Table 7-2:Draft DO-399 Spurious Emissions Test Results 36 The draft DO-399 results have been c
59、onverted to the power level at the RA receiver port using the process explained previously for receiver blocking.RA Model Tested200 ft1000 ft2000 ftRA Model Tested200 ft1000 ft2000 ftIndia-94-91-86Alpha-66-66-75Zulu-77-86-82Victor-78-90-99DO-399 ModelDO-399 ModelSpurious ThresholdSpurious Threshold(
60、dBm/MHz)(dBm/MHz)Mike-78.5Papa-82.1Tango-53.4Whiskey 1-88.0Whiskey 2-80.021 8.Conclusions CTIAs testing of BA/GA RA models confirmed that some RAs deliver excellent performance in the presence of strong adjacent band signals,without modification.Moreover,the few RA models that were consistent outlie
61、rs in testing were further evaluated with a custom bandpass filter,and those RAs exhibited excellent rejection of energy outside of the RA band,even with a modest 20 MHz of frequency separation.The RTCA/EUROCAE committee working on the next generation MOPS for RAs are evaluating the performance impr
62、ovements which may be achieved with enhanced RA antenna design,improved receiver selectivity,higher transmitter power levels,and improved bandpass filter design.The CTIA tests evaluated the efficacy of custom-designed filters and demonstrated that the filters significantly improved RA tolerance of h
63、igh-power services in adjacent spectrum.The FreeFlight product evolution suggests that increasing transmitter power is an important step in improving RA performance in-band,and RA tolerance to signals outside of the band.Further improvements to RA tolerance can be realized by encouraging a minimum RA transmit power of close to 30 dBm,investigating RA antenna improvements,and ensuring a robust receiver design.