ITU-R REPORT M 2076-2006 Factors that mitigate interference from radiolocation and Earth exploration-satellite service space research service (active) radars to maritime and aeronaand .pdf
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1、 Rep. ITU-R M.2076 1 REPORT ITU-R M.2076 Factors that mitigate interference from radiolocation and Earth exploration-satellite service/space research service (active) radars to maritime and aeronautical radionavigation radars in the 9.0-9.2 and 9.3-9.5 GHz bands and between Earth exploration-satelli
2、te service/ space research service (active) radars and radiolocation radars in the 9.3-9.5 and 9.8-10.0 GHz bands (2006) 1 Introduction Question ITU-R 234/8 calls for study of technical characteristics, performance criteria, and other factors of radiolocation and radionavigation systems in the bands
3、 9 000-9 200 MHz and 9 300-9 500 MHz and of the interference criteria for those systems. In addition, Resolution 747 (WRC-03) has established Agenda item 1.3 for WRC-07 to consider upgrading the allocations to the radiolocation service in the 9 000-9 200 and 9 300-9 500 MHz bands to co-primary and t
4、o consider extending the primary allocation to the Earth exploration-satellite (EES) (active) service and space research (SR) (active) service in the band 9 500-9 800 MHz band contiguously by 200 MHz. Characteristics of representative terrestrial radars in the 8 500 MHz-10.5 GHz band are contained i
5、n Recommendation ITU-R M.1796. This Report is a further contribution to the studies required by Question ITU-R 234/8 and Resolution 747 (WRC-03). Recommendation ITU-R M.1372-1 Efficient use of the radio spectrum by radar stations in the radiodetermination service, describes some of the most importan
6、t interference suppression techniques that are used in radars generally. The emphasis in that Recommendation is on post-detection processing, although one of the techniques described there can be implemented prior to detection. The factors discussed herein include some of those covered in Recommenda
7、tion ITU-R M.1372 as well as some that complement those. 1.1 Summary of findings The main form of interference degradation that pulsed interference is likely to cause is an increase of the rate of false alarms. This is naturally mitigated by some common characteristics of radars, including low anten
8、na sidelobes and asynchronous pulsing. Responses to individual pulses, including fast time constant, matched filtering effects, and other pulse-shortening effects, are beneficial. The form of coupling of most concern is sidelobe-to-main-beam coupling. Prudent radar design can mitigate pulsed interfe
9、rence in numerous ways. These include: multiple-pulse techniques, including M-out-of-N processing; deliberate removal of individual asynchronous pulses; sensing of asynchronous-pulse effects in post-processing review of Doppler-filter outputs; nonlinear and time-varying processes such as limiting an
10、d sensitivity time control; scan-to-scan correlation. 2 Rep. ITU-R M.2076 2 Types of radars in the bands Several types of radionavigation radars operate in the 9 000-9 200 and 9 300-9 500 MHz bands. Ground-based aeronautical radionavigation radars operate in the 9 000-9 200 MHz band; they include pr
11、ecision-approach radars (PARs) and airport surface detection equipment (ASDE) radars. These are discrete-target surveillance radars. The 9 300-9 500 MHz band is used by a large number of maritime radionavigation radars, the great majority of them being aboard ships, and by airborne weather-avoidance
12、 radars. The maritime systems are discrete-target radars while the airborne systems are distributed-target radars. The radiolocation service operates on a secondary allocation basis in the 9 000-9 200 and 9 300-9 500 MHz bands. Land-based weather radiolocation radars operating in the 9 300-9 500 MHz
13、 band are privileged with respect to other radiolocation radars (Radio Regulations (RR) No. 5.475). Radiolocation radars also operate in the 9 500-9 800 MHz and 9 800 MHz-10.0 GHz bands on a primary-allocation basis. Spaceborne synthetic-aperture radars (SARs) in the EES/SR (active) services current
14、ly operate in the 9.5-9.8 GHz band on a co-primary allocation basis. The proposal to extend that allocation by 200 MHz is driven by a desire to enhance the range resolution of the SARs. 3 Types of potential interference effects The two most prominent types of performance degradation that radiolocati
15、on or EES/SR (active) radars could inflict on discrete-target surveillance radars such as PARs, ASDEs, or maritime navigation radars fall into the categories of: missed target detections; generation of false target detections or “false alarms” and false target tracks. These two effects can be though
16、t of as a decrease in probability of detection and an increase in probability of false alarm, respectively. Although radiolocation or EES/SR (active) radars could conceivably inflict some degree of desensitization (missed target detections, etc.), that effect is expected to be minor, as has been dem
17、onstrated in several measurement programs, so attention will focus on the generation of false targets. Pulsed signals from other radars create a potential for generation of false target detections even when a well-designed “constant-false-alarm-rate” (CFAR) operation is provided in the terrestrial r
18、adar. However, the remainder of this Report shows that these effects can largely be avoided by good design. Discrete-target radars, including target-dedicated tracking radars, are also subject to aggravation of position-estimation errors and target-classification errors due to unwanted signals. Howe
19、ver, these effects are more likely to be inflicted by continuous, noise-like interference than by pulsed interference from other radars. Performance degradation that radiolocation and EESS radars could inflict on distributed-target radars, including weather-avoidance radars or weather surveillance r
20、adars, consists of discrete (e.g. single-pixel) false alarms (referred to in the weather-radar community as speckle) and introduction of inaccuracy into derived measures of weather phenomena. The degradation that interference of any kind can inflict on synthetic-aperture imaging radars is being expr
21、essed by the space-science community as an increase of the variance of processor output power in any pixel1. 1Recommendation ITU-R RS.1166 Performance and interference criteria for spaceborne active sensors. Rep. ITU-R M.2076 3 These effects are in contrast to the effect of continuous noise-like int
22、erference on discrete-target radar that has effective control over its false-alarm rate. In that case, the probability of false alarm tends to remain unchanged, but the curve of probability of detection as a function of target range or radar cross section (RCS) inexorably suffers a shift to shorter
23、range or higher RCS as the undesired signal becomes stronger. This is generalized desensitization, predominately affecting targets that are small, distant, or poorly illuminated due to adverse propagation conditions such as multipath propagation or adverse ducting. It also degrades other functions s
24、uch as tracking precision. However, continuous noise-like interference is outside the purposes of this Report. 4 Interference-mitigating characteristics commonly found in radars Interference can be mitigated by weak or transient power coupling, certain receiver nonlinearities, time-varying gain, sig
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