1、Rec. ITU-R M.1462 1 RECOMMENDATION ITU-R M. 1462 CHARACTERISTICS OF AND PROTECTION CRITERIA FOR RADARS OPERATING IN THE RADIOLOCATION SERVICE IN THE FREQUENCY RANGE 420-450 MHz (Question ITU-R 226/8) (2000) The ITU Radiocommunication Assembly, considering a achieve their functions are optimum in cer
2、tain frequency bands; that antenna, signal propagation, target detection and large necessary bandwidth characteristics of radar to b) mission of the system and vary widely even within a band; that the technical characteristics of radars operating in the radiodetermination service are determined by t
3、he c been removed or downgraded since WARC-79; that considerable radiolocation and radionavigation spectrum allocations (amounting to about 1 GHz) have 4 that some ITU-R technical groups are considering the potential for the introduction of new types of systems (e.g. fixed wireless access and high d
4、ensity fixed and mobile systems) or services in bands between 420 MHz and 34 GHz used by radars in the radiodetermination service; e radiodetermination service are required to determine the feasibility of introducing new types of systems; that representative technical and operational characteristics
5、 of systems operating in bands allocated to the I) radiodetermination service and systems in other services; that procedures and methodologies are needed to analyse compatibility between radars operating in the s that propagation and target detection characteristics to achieve these functions are op
6、timum in certain frequency bands, and that 420-450 MHz is particularly useful for very long range (e.g. space) object identification, tracking, and cataloguing by terrestrial radars; h) primary basis and to the radiolocation service on a secondary basis; that the frequency bands 420-430 MHz and 440-
7、450 MHz are allocated to the fiied and mobile services on a j that the frequency 430-440 MHz is allocated to the radiolocation service on a primary basis, and to the amateur service on a primary basis in Region 1 and in those Region 2 countries listed in RR No. S5.278 and on a secondary basis in Reg
8、ions 2 (except for countries listed in RR No. S5.278) and 3; k) frequency range 420-450 MHz, with respect to the fixed, mobile, radiolocation and amateur services, that there are many alternative and additional allocations, and different categories of service throughout the 2 recommends Rec. ITU-R M
9、.1462 1 considered representative of those operating in the frequency range 420-450 MHz; that the technical and operational characteristics of the radiolocation systems described in Annex 1 be 2 operating in the radiodetermination service with systems in other services; that Recommendation ITU-R M.
10、1461 be used as a guideline in analysing compatibility between radars 3 that an interfering signal power to radar receiver noise power level, ZlN, ratio of -6 dl3 be used as the required protection level for the radiolocation systems, and that this represents the net protection level if multiple int
11、erferers are present (see Note 1). NOTE 1 - The protection criterion given in recommends 3 should not be applied to the space object tracking radars described in Annex 1; these are highly sensitive radars that cannot tolerate the resulting 6% degradation in detection range (corresponding to a 19% lo
12、ss of surveillance volume). Specialized studies of compatibility with these radars are required. NOTE 2 - This Recommendation will be revised as more detailed information becomes available. ANNEX 1 Technical and operational characteristics of radiolocation systems operating in the frequency range 42
13、0-450 MHz 1 Introduction High power airborne, shipborne and ground radars operate in the frequency range 420-450 MHz. Their operational and technical characteristics are described in the following paragraphs. 2 Characteristics of radars in the 420-450 MHz range Representative characteristics of radi
14、olocation systems in the band 420-450 MHz are provided in the following paragraphs. The information presented in this Annex is sufficient for general calculations to assess the compatibility between these radars and other systems. 2.1 Ground radars The frequency band 420-450 MHz provides unique char
15、acteristics that are ideal for very long range detection, identification, and tracking of objects. Space object tracking and cataloguing are accomplished in this frequency band using very high power (up to 5 MW) transmitter powers and high antenna gains. The radars operate continuously; around the c
16、lock and year round. They scan from a surveillance “fence“ from around 3“ up to 60“ in elevation, in 120“ sectors in azimuth. The radar receivers are very sensitive in order to detect returns from exo-atmospheric and space objects. Because of their specialized function and requisite design character
17、istics (e.g. very large antenna arrays) these particular ground radars are not numerous, but because of their sensitivity and function they deserve special recognition and protection. Table 1 gives the characteristics of the radars, and Table 2 gives the identified locations for such radars. Rec. IT
18、U-R M.1462 Tuning type; range Peak RF output power (MW) 3 Frequency agile; 420-450 MHz 1-5 TABLE 1 Characteristics of ground radars in the 420-450 MHz range Polarization Pulse duration (ms) Value I Parameter Circular 0.25, 0.5, 1, 2,4, 8, 16 Duty cycle (average) (%) Pulse frequency modulation (linea
19、r chirp) 25 Search: 100-350 kHz chirp track: 1 or 5 MHz chirp Receiver noise temperature (K) Receiver bandwidth (MHz) up to 41 I Pulse repetition rate (Hz) 450 1 or 5 (see chirp width) Planar array; 22+ metre diameter I Antenna type Radar Location 38.5 I Antenna gain (dBi) Latitude Longitude Antenna
20、 scan Massachusetts (United States of America) Texas (United States of America) 3-85 elevation; f60“ azimuth per each of 2 planar arrays for total 240“ azimuth scan 41.8“ N 70.5“ W 31.0“ N 100.6“W Antenna beamwidth (degrees) California (United States of America) Georgia (United States of America) 2.
21、2 elevation 2.2 azimuth 39.1“ N 121.5“W 32.6“ N 83.6“ W Florida (United States of America) N. Dakota (United States of America) TABLE 2 Location of space object tracking radars operating in the 420-450 MHz range 30.6“ N 86.2“ W 48.7“ N 97.9“ w Pirinclik (Turkey) 37.9“ N 40.0“ E 149.2“W I 64.3“ N I A
22、laska (United States of America) 68.3“ W I 76.6“ N I Thule (Greenland) 4.0“ W I 54.5“ N I Fylingdales Moor (United Kingdom) Rec. ITU-R M.1462 Parameter Tuning type; range 4 2.2 Value Fixed frequency or frequency agile; 420-450 MHz Airborne radars Peak RF output power (MW) Polarization Three lower ra
23、diolocation bands (420-450 MHz, 1 215-1 400 MHz and 3 100-3 700 MHz) have been and will continue to be essential for the development and operation of airborne radar surveillance systems. These systems operate worldwide, for extended periods (hours to days) once in their intended areas of operation.
24、Long range object detection, acquisition, and tracking are essential functions to sense and control air traffic. Ground-based radars are extremely limited by the radar horizon, and the employment of long range radars on airborne platforms is an excellent way to extend an individual radars capability
25、. Similar to ground air surveillance radars, airborne radars employ rotating scans in azimuth and scan over a specified range in elevation either by electronically scanning in elevation or by using a relatively wide elevation beamwidth. The radar will be operating during aircraft ascent and descent
26、as well as at operating altitudes; aircraft ceiling altitude is around 9 km. Table 3 gives the characteristics of a representative airborne radar system operating in the frequency band 420-450 MHz. 2 Horizontal TABLE 3 Characteristics of airborne radars operating in the 420-450 MHz range Antenna typ
27、e Antenna gain (dBi) Yagi element array or planar array 22 Antenna scan Antenna beamwidth I 1,2,4, 8 I I Pulse duration (p) f60“ elevation (mechanically positioned or electronically scanned); 360“ azimuth at 3-7 rpm 6-20 elevation (depending upon scan type); 6“ azimuth I Unmodulated pulses I I Pulse
28、 modulation Receiver noise figure (dB) Receiver IF bandwidth (MHz) I o. 1-2 I I Pulse repetition rate (kHz) 5 1 2.3 Shipborne radars Shipborne surveillance radars are also operated in the frequency range 420-450 MHz. They normally operate at sea, though operations in coastal waters as well in naval
29、ports should be expected. As is typical with surveillance radars, the system scans 360“ in azimuth, and operations are on a continuous basis. Table4 gives the characteristics of a representative shipborne radar in the band 420-450 MHz. Rec. ITU-R M.1462 TABLE 4 Characteristics of shipborne radars op
30、erating in the 420-450 MHz range Parameter 5 Value Receiver IF selectivity Receiver noise level (dBW) Fixed frequencies; 420-450 MHz I I Tuning type; range -3 dB 2 MHz -103dB 20MHz -136 I Peak RF output power (MW) I 2 Antenna type Unmodulated pulses I I Pulse modulation Parabolic reflector Antenna g
31、ain (dBi) 30 (mainbeam) O (median sidelobe) Transmitter RF emission curve -3 dB 2 MHz -20 dB 3 MHz -70dB 20MHz 3 Protection criteria The desensitizing effect on radiodetermination radars from other services of a continuous-wave or noise-like type modulation is predictably related to its intensity. I
32、n any azimuth sectors in which such interference arrives, its power spectral density can, to within a reasonable approximation, simply be added to the power spectral density of the radar receiver thermal noise. If power spectral density of radar-receiver noise in the absence of interference is denot
33、ed by NO and that of noise-like interference by ZO, the resultant effective noise power spectral density becomes simply ZO +NO. An increase of about 1 dl3 would constitute significant degradation, equivalent to a detection-range reduction of about 6%. Such an increase corresponds to an (Z + MIN rati
34、o of 1.26, or an ZIN ratio of about -6 dl3. This represents the aggregate effect of multiple interferers, when present; the tolerable ZIN ratio for an individual interferer depends on the number of interferers and their geometry, and needs to be assessed in the course of analysis of a given scenario
35、. If continuous-wave interference were received from most azimuth directions. a lower ZIN ratio would need to be maintained. The aggregation factor can be very substantial in the case of certain communication systems in which a great number of stations can be deployed. The effect of pulsed interfere
36、nce is more difficult to quantify and is strongly dependent on receiversIprocessor design and mode of operation. In particular, the differential processing gains for valid-target return, which is synchronously pulsed, and interference pulses, which are usually asynchronous, often have important effe
37、cts on the impact of given levels of pulsed interference. Several different forms of performance degradation can be inflicted by such desensitization. Assessing it will be an objective for analyses of interactions between specific radar types. In general, numerous features of radiodetermination rada
38、rs can be expected to help suppress low-duty cycle pulsed interference, especially from a few isolated sources. Techniques for suppression of low-duty cycle pulsed interference are contained in Recommen- dation ITU-R M. 1372 - Efficient use of the radio spectrum by radar stations in the radiodetermination service.
