1、 Recommendation ITU-R M.1461-2 (01/2018) Procedures for determining the potential for interference between radars operating in the radiodetermination service and systems in other services M Series Mobile, radiodetermination, amateur and related satellite services ii Rec. ITU-R M.1461-2 Foreword The
2、role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are
3、adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Pat
4、ent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent
5、Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadca
6、sting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing an
7、d coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution
8、ITU-R 1. Electronic Publication Geneva, 2018 ITU 2018 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R M.1461-2 1 RECOMMENDATION ITU-R M.1461-2* Procedures for determining the potential for interference between
9、 radars operating in the radiodetermination service and systems in other services (Question ITU-R 226/5) (2000-2003-2018) Scope This Recommendation provides guidance and procedures for determining the potential for interference between radars operating in the radiodetermination service and systems i
10、n other services. Keywords Radar, procedure, interference, protection criteria Abbreviations/Glossary BPSK: Binary phase shift keying CW: Continuous-wave FDR: Frequency dependent rejection LNA: Low noise amplifier OFR: Off-frequency rejection OTR: On-tune rejection QPSK: Quadrature phase shift keyin
11、g The ITU Radiocommunication Assembly, considering a) that antenna, signal propagation, target detection, and large necessary bandwidth characteristics of radar to achieve their functions are optimum in certain frequency bands; b) that the technical characteristics of radars operating in the radiode
12、termination service are determined by the mission of the system and vary widely even within a frequency band; c) that the radionavigation service is a safety service as specified by the Radio Regulations (RR) No. 4.10 and harmful interference to it cannot be accepted; d) that some ITU-R technical gr
13、oups are considering the potential for the introduction of new types of systems (e.g. fixed wireless access and high-density fixed and mobile systems) or services in frequency bands between 420 MHz and 34 GHz used by radars in the radiodetermination service; e) that representative technical and oper
14、ational characteristics of systems operating in frequency bands allocated to the radiodetermination service are required to determine the feasibility of introducing new types of systems; * This Recommendation should be brought to the attention of the International Maritime Organization (IMO), the In
15、ternational Civil Aviation Organization (ICAO), the International Maritime Radio Committee (CIRM) and the World Meteorological Organization (WMO). 2 Rec. ITU-R M.1461-2 f) that procedures and methodologies are needed to analyse compatibility between radars operating in the radiodetermination service
16、 and systems in other services, recommends 1 that the procedures in Annex 1 should be used to provide guidance for determining the potential for interference between radars operating in the radiodetermination service and systems in other services; 2 that those radar characteristics contained in appr
17、opriate ITU-R Recommendations should be used for the frequency band under study. Annex 1 Procedures for determining the potential for interference between radars operating in the radiodetermination service and systems in other services 1 Introduction Analysis procedures have been developed. Because
18、of the high transmitter output power (50 kW to several MW) and antenna gain (30 to 45 dBi) of radars operating in the radiodetermination service (hereafter simply referred to as radars), compatibility between radars and systems in other services is largely determined by analysing the effects of the
19、emissions from radars on receiving functions of other services. Therefore, this analysis procedure primarily addresses the methods to assess the potential for interference from radars. In addition, potential desensitization of radar receivers by emissions from modulated continuous-wave (CW) systems
20、in other services is briefly discussed. By the nature of the missions of radars, many are mobile and cannot be constrained to prescribed areas of operation. Also, the mission of radars often requires frequency agility and utilize the entire allocated band. But when radars are anticipated to operate
21、in certain areas in proximity to other systems, the potential for interference can be assessed using the procedures contained in this Recommendation. 2 Interference from radars to systems of other services Investigations of several interference cases have identified two primary electro-magnetic inte
22、rference coupling mechanisms between high power radar systems and other services. These interference coupling mechanisms are receiver front-end overload and radar transmitter emissions coupled through the receiver IF passband. Discussion of the interference mechanisms are provided below. 2.1 Receive
23、r front-end overload This interference mechanism occurs when energy from the fundamental frequency (necessary emissions) of an undesired signal saturates the victim receiver front-end (low noise amplifier (LNA) in some systems), resulting in gain compression of the desired signal sufficient to degra
24、de receiver performance. Receiver front-end overload is typically a result of inadequate RF selectivity in the front-end of the victim receiver. Rec. ITU-R M.1461-2 3 2.1.1 Assessing the potential for receiver front-end overload The input threshold at which receiver front-end overload occurs is a fu
25、nction of the 1 dB gain compression (saturation) level and the gain of the receiver front-end or LNA. Specifically: T C G (1) where: T : input threshold at which receiver front-end overload occurs (dBm) C : output 1 dB gain compression (saturation) level of the receiver front-end or LNA (dBm) G : ga
26、in of the receiver front-end or LNA at the radar fundamental frequency (dB). For example, if the receivers use LNAs with gains of 50 to 65 dB and they have an output 1 dB compression level of 10 dBm, the range of values for T is 55 dBm to 40 dBm, depending on the gain of the LNA. A potential for int
27、erference from receiver front-end overload will exist whenever: RFT FDRTI (2) where: IT : peak radar signal level at the antenna output or receiver input that causes receiver front-end overload (dBm) T : input threshold at which receiver front-end overload occurs (dBm) FDRRF : frequency dependent re
28、jection (FDR) of the radar fundamental from any RF selectivity that may be ahead of the receiver RF amplifier (LNA) or that may be inherent in the RF amplifier (LNA) itself. Equation (3) can be used to determine whether receiver front-end overload is likely when radars operate within a particular di
29、stance of other stations and are separated in frequency by certain amounts: (3) where: I : peak power of radar pulses, at the radars fundamental frequency, at the receiving antenna output or receiver input (dBm) PT : peak power of the radar transmitter (dBm) GT : main beam antenna gain of the radar
30、(see Note 1) (dBi) GR : receiver antenna gain in the direction of the radar station under analysis (dBi) LT : insertion loss in the radar station transmitter (dB) (2 dB assumed) LR : insertion loss in the victim receiver (dB) LP : propagation path loss between transmitting and receiving antennas (dB
31、). In determining the propagation path loss, appropriate propagation models and possible indirect coupling should be used taking into consideration antenna heights and terrain when appropriate. If the calculated peak power of the radar pulses, at the fundamental frequency, I, exceed the threshold at
32、 which receiver front-end overload occurs, IT, necessary steps to ensure compatibility need to be taken. NOTE 1 Interference cases of radar transmitter emissions causing receiver front-end overload for radar mainbeam coupling have been documented. Therefore, it is recommended that the radar mainbeam
33、 gain be used in assessing the maximum potential for interference caused by receiver front-end overload. PRTRTT LLLGGPI 4 Rec. ITU-R M.1461-2 2.2 Radar transmitter emission coupling This interference mechanism occurs when energy emitted from the radar transmitter falls within the IF passband of the
34、receiver. This energy then passes through the receiver chain with little or no attenuation. When the radar emission levels in the receiver passband are high relative to the desired signal level, performance degradation to the receiver can occur. 2.2.1 Assessing the potential for radar transmitter em
35、ission interference The initial step in assessing compatibility is the determination of the signal level at which the receiver performance starts to degrade, IT. IT I/N N (4) where: I/N : interference-to-noise ratio at the detector input (IF output) necessary to maintain acceptable performance crite
36、ria (dB) N : receiver inherent noise level (dBm) (N 144 dBm 10 log BIF (kHz) NF or N 168.6 dBm 10 log BIF (kHz) 10 log T) where: BIF : receiver IF bandwidth (kHz) NF : receiver noise figure (dB) T : system noise temperature (K). Also, the signal level at which a receiver starts to degrade, IT, can b
37、e calculated using equation (5): IT C (C/I) (5) where: C : desired carrier signal level at the antenna output (receiver input) (dBm) C/I : carrier-to-interference ratio at the predetector input (IF output) necessary to maintain acceptable performance criteria (dB). Equation (6) can be used to determ
38、ine whether radar transmitter emission interference is likely when radars operate within particular distances of other stations and are separated in frequency by certain amounts. I PT GT GR LT LR LP FDRIF (6) where: I : peak power of the radar pulses at the receiver (dBm) PT : peak power of the rada
39、r transmitter under analysis (dBm) GT : main beam antenna gain of the radar under analysis (see Note 2) (dBi) GR : receiver antenna gain in the direction of the radar station under analysis (dBi) LT : insertion loss in the radar station transmitter (dB) LR : insertion loss in the victim receiver (dB
40、) LP : propagation path loss between transmitting and receiving antennas (dB) FDRIF : frequency-dependent rejection produced by the receiver IF selectivity curve on an unwanted transmitter emission spectra (dB). Rec. ITU-R M.1461-2 5 NOTE 2 Interference cases of radar transmitter emissions causing r
41、eceiver degradation for radar mainbeam coupling have been documented. Therefore, it is recommended that the radar mainbeam gain be used in assessing the maximum potential for interference caused by radar transmitter emissions in the receiver IF passband. The FDR value to be used in equation (6) can
42、be determined from Recommendation ITU-R SM.337. The FDR can be divided into two terms, the on-tune rejection (OTR) and the off-frequency rejection (OFR), the additional rejection which results from off-tuning the radar and the receiver. )()( fO F RO TRfF D R IF (7) For CW and phase-coded pulsed sign
43、als, the OTR factor is given by: OTR 0 for BR BT (8) OTR 20 log (BT / BR) for BR BT (9) where: BR : receiver 3 dB bandwidth (Hz) BT : transmitter 3 dB bandwidth (Hz). For chirped pulsed signals, the OTR factor is given by: OTR 0 for BC / (BR2 T) 1 (10) OTR 10 log (BC / (BR2 T) for BC / (BR2 T) 1 (11
44、) where: T : chirped pulse width (s) BC : transmitter chirped bandwidth during the pulsewidth, T (Hz). Calculation of the OFR requires the IF response and the emission spectrum characteristics of the radar transmitter. The ITU-R has provided methods for calculating the emission spectrum characterist
45、ics of CW pulsed and chirped pulsed radars. If information is not available for radar transmitter rise and fall time characteristics, the radar emission envelops should be calculated for nominal rise and fall times of 0.1 s. The spurious emission levels from radar transmitters are a function of the
46、transmitter output device. Representative spurious emission levels for various radar output devices are contained in Recommendation ITU-R M.1314. Since many radars have high transmitter power and antenna gains, large frequency separations, guard bands, may be required to ensure compatibility. In det
47、ermining the propagation path loss, appropriate propagation models and possible indirect coupling should be used taking into consideration antenna heights and terrain when appropriate. If the calculated peak power of the radar pulses, at the receiver input, I, exceed the threshold at which receiver
48、performance degrades, IT, necessary steps to ensure compatibility need to be taken. 3 Interference to radars from systems in other services Introduction Two primary electromagnetic interference coupling mechanisms between the radar system and interfering signals from other services exist. The first
49、mechanism is caused by front-end overload causing saturation, and the generation of intermodulation products. The second is interfering emissions within the receiver IF passband leading to desensitization and degradation of performance resulting in an overall lowered quality radar data output. 6 Rec. ITU-R M.1461-2 3.1 Receiver front-end overload 3.1.1 Front-end saturation This interference mechanism occurs when energy from an undesired signal saturates the LNA of the radar receiver front-end resulting in gain
