1、Rec. ITU-R M.1466 1 RECOMMENDATION ITU-R M. 1466 CHARACTERISTICS OF, AND PROTECTION CRITERIA FOR RADARS OPERATING IN THE RADIONAVIGATION SERVICE IN THE FREQUENCY BAND 31.8-33.4 GHz (Question ITU-R 226/8) (2000) The ITU Radiocommunication Assembly, considering that antenna, signal propagation, target
2、 detection, and large necessary bandwidth characteristics of radar to a achieve their functions are optimum in certain frequency bands; 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
3、 by the c cannot be accepted; 4 been removed or downgraded since WARC-79; e 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 density fixed and mobile systems) or services in bands between 420 MHz and 34
4、GHz used by radars in the radiodetermination service; I) radiodetermination service are required to determine the feasibility of introducing new types of systems; s radiodetermination service and systems in other services; that the radionavigation service is a safety service as specified by RR No. S
5、4.10 and harmful interference to it that considerable radiolocation and radionavigation spectrum allocations (amounting to about 1 GHz) have that representative technical and operational characteristics of systems operating in bands allocated to the that procedures and methodologies are needed to an
6、alyse compatibility between radars operating in the h) that WRC-97 requested that the ITU-R conduct studies to determine what criteria would be necessary forsharing between stations in the fiied service and stations in the other services to which the frequency band 3 1.8-33.4 GHz is allocated; j tha
7、t the frequency band 3 1.8-33.4 GHz is allocated on a primary basis to the fiied and radionavigation services and that portions of the band are allocated on a primary basis to the space research (deep space) and intersatellite services, recommends 1 in Annex 1 be considered representative of those o
8、perating in the frequency band 3 1.8-33.4 GHz; 2 operating in the radiodetermination service with systems in other services; 3 that the criterion of interfering signal power to radar receiver noise power level, I/N, of -6 dB be used as the required protection level for the radionavigation radars, an
9、d that this represents the net protection level if multiple interferers are present. NOTE 1 - This Recommendation will be revised as more detailed information becomes available. that the technical and operational characteristics of the radars operating in the radionavigation service described that R
10、ecommendation ITU-R M.1461 be used as a guideline in analysing compatibility between radars 2 Parameter Rec. ITU-R M.1466 RadarNo. 1 Radar No. 2 ANNEX 1 Fixed frequency Tunes continuously across 31.8-33.4 GHz Technical and operational characteristics of radars operating in the radionavigation servic
11、e in the frequency band 31.8-33.4 GHz Fixed frequency or frequency hopping Operates in either mode on one of 9 discrete channels spaced 100 MHz apart (32.2-33 GHz) 1 Introduction Emission type RF emission bandwidth (MHz) The radionavigation service operates worldwide on a primary basis in the freque
12、ncy band 31.8-33.4 GHz. This Annex presents the technical and operational characteristics of representative radars operating in the radionavigation service in this frequency band. Unmodulated pulses 37 17 (instantaneous) 117 (hopping) 2 Technical characteristics of radionavigation systems in the 31.
13、8-33.4 GHz frequency band Receiver IF bandwidth (-20 dB) (MHz) Receiver noise figure (dB) The technical parameters of two radionavigation radars operating in the band 31.8-33.4 GHz are presented in Table 1. Both systems are operated worldwide aboard aircraft. The radars are used for ground mapping,
14、weather avoidance, and to calibrate aircraft on-board navigation systems for accurate aerial delivery in adverse weather conditions. 40 17 11 TABLE 1 Antenna type Antenna main beam gain (dBi) Antenna scan Radionavigation radar characteristics in the band 31.8-33.4 GHz Parabolic reflector 44 41.1 Ele
15、vation: -30“ to +lo“, manual azimuth: 360“ at 7, 12, or 21 rpm Elevation: -30“ to +lo“, manual azimuth: 360“ at 12 or 45 rpm Tuning type I 0.2 I I Pulse duration (p) I I Pulse repetition frequency (pps) I 2000 I 1600 I 6o I 39 I I Peak transmitter power (kW) Rec. ITU-R M.1466 3 3 Operational charact
16、eristics of radionavigation systems in the 31.8-33.4 GHz frequency band Aircraft radionavigation radars in the band 3 1.8-33.4 GHz operate continuously during flight. This encompasses an altitude range of from just off the ground to approximately 30 O00 feet (9 O00 m). Flight times can be up to six
17、hours, and typically the majority of the time is spent en route, but some linger time at either the departure or destination points is expected. Up to 18 aircraft operating these radionavigation radars can be active in a small geographic area (Le., separated by less than a kilometre from each other)
18、, though most often only 1-3 aircraft will be operating simultaneously together. 4 Protection criteria The desensitizing effect on radars from other services of a continuous-wave or noise-like type modulation is predictably related to its intensity. In any azimuth sectors in which such interference
19、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 denoted by NO and that of noise-like interference by Z
20、O, 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 ratio of 1.26, or an ZIN ratio of about -6 dl3. This
21、 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. If continuous-wave interference were received
22、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 interference is more difficult to quantify and is strongl
23、y 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 effects on the impact of given levels of pulsed inte
24、rference. 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 radars 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.
