1、 Rec. ITU-R M.1227-2 1 RECOMMENDATION ITU-R M.1227-2 Technical and operational characteristics of wind profiler radars in bands in the vicinity of 1 000 MHz (1997-2000-2001) The ITU Radiocommunication Assembly, considering a) Recommendation 621 of the World Administrative Radio Conference for Dealin
2、g with Frequency Allocations in Certain Parts of the Spectrum (Malaga-Torremolinos, 1992) (WARC-1992); b) that wind profiler radars (WPRs) are important meteorological systems used to measure wind direction and speed as a function of altitude; c) that many administrations plan to deploy WPRs in oper
3、ational networks in order to improve meteorological predictions and warnings, and support studies of the climate and increase the safety of navigation; d) the need for frequency bands in the vicinity of 50 MHz, 400 MHz and 1 000 MHz to permit the full performance capability of WPR operations, as req
4、uested by the World Meteorological Organization (WMO); e) that wind profilers operating near 1 000 MHz may be installed at fixed locations or may be transportable, to support a variety of requirements including environmental emergencies, pollution monitoring, etc.; f) that Resolution 217 (WRC-97) id
5、entified the frequency bands 904-928 MHz (Region 2), 1 270-1 295 MHz and 1 300-1 375 MHz for WPRs having due regard to the potential for incompatibility with other services; g) that selection of a proper frequency band for a WPR depends upon height coverage user needs, local climate and interference
6、 conditions, but performance of WPRs decreases as frequency increases; h) that, once designed and built, the WPRs could operate on centre frequencies over a range of 1%; j) that WPRs may have to share spectrum with other systems both current and future; k) that it would be desirable to have a limite
7、d number of frequencies authorized worldwide, in order to minimize research and development investment in the design of components; l) that technical standards would enhance compatibility with other systems within the same band, recommends 1 that minimum requirements on system performance, as in Ann
8、ex 1, should be adopted by administrations desiring to construct or operate WPRs in the bands near 1 000 MHz; 2 Rec. ITU-R M.1227-2 2 that the transmitter power should be limited to that necessary to obtain data at the maximum altitude for which the profiler was designed; 3 that the occupied bandwid
9、th (see Note 1) should be as close to the necessary bandwidth (see Note 2) as is technically and economically feasible to provide the required range resolution, noting that reduced values of resolution are generally acceptable at higher altitudes. Values are given in Annex 1. NOTE 1 Occupied bandwid
10、th: the width of a frequency band such that, below the lower and above the upper frequency limits, the mean powers emitted are each equal to 0.5% of the total mean power of the given emission. NOTE 2 Necessary bandwidth: for a given class of emission, the width of the frequency band which is just su
11、fficient to ensure the transmission of information at the rate and with the quality required under specific conditions; 4 that the unwanted emissions from WPRs should be reduced as much as technically and economically feasible. Values are given in Annex 1; 5 that the antenna radiation pattern should
12、 minimize the levels of the side lobes, especially those at or near the horizon. Representative values which have been achieved in one case of side-lobe gain and field strength are given in Annex 1; 6 that administrations may develop appropriate sharing criteria, such as frequency-distance (FD) sepa
13、rations in accordance with Recommendation ITU-R SM.337, for specific WPR designs sharing with other systems; 7 that the selection of WPR locations should take advantage of terrain and siting configuration to minimize the possibility of interaction with other systems; additional enhancements (e.g. fe
14、nces, barns) and antenna orientation may improve compatibility; 8 that the frequency bands 904-928 MHz (Region 2), 1 270-1 295 MHz and 1 300-1 375 MHz should be chosen when compatibility is possible taking due account of the frequency dependence of performance over this frequency range. ANNEX 1 Repr
15、esentative values and minimum requirements on system performance for WPRs in bands near 1 000 MHz 1 Introduction The values given below are based on current knowledge and field measurements on pulse modulated systems. Rec. ITU-R M.1227-2 3 2 Representative values for operational WPRs in bands near 1
16、 000 MHz TABLE 1 3 Minimum requirements on system performance 3.1 Emission bandwidth TABLE 2 System parameter Range of representative values(1)Pulse peak power (kW) 0.5-5 Maximum transmitter average power (W) 50-500 Duty cycle (%) 0.5-10 Pulse repetition frequency (kHz) 1-50 Main beam antenna gain (
17、dBi) 25-32 Beamwidth (degrees) 4-12 Tilt angle (degrees) 12-25 Antenna size (m2) 3-15 Height range(2)(km) 0.05-3 Height resolution (m) 50-500 (1)Users of this table should exercise caution in using combinations of these values to represent a “typical” or “worst” case profiler. For example, a profile
18、r operating with an average power of 500 W while using short pulses to yield a height resolution of 50 m would be an unusual system. (2)The maximum operating height for a given range resolution depends upon the product: (mean power) (antenna gain). Pulse width (s) Necessary bandwidth (MHz) Occupied/
19、necessary bandwidth ratio 0.3-3 0.7-7.3 2.5(1)(1)Values down to 1.5 can be obtained at the expense of higher cost and somewhat inferior performance resulting from pulse shaping. The limit applies to the power and pulse width combination producing the highest power density in the signal sidebands.4 R
20、ec. ITU-R M.1227-2 3.2 Spurious emissions Spurious emission levels should be measured at antenna input using the bandwidth values given below: IF bandwidth: 1/T for fixed-frequency, non-phase-coded pulsed radars, where T = pulse length. (E.g. if radar pulse length is 1 s, then the measurement IF ban
21、dwidth should be 1/1 s = 1 MHz) 1/t for fixed-frequency, phase-coded pulsed radars, where t = phase-chip length. (E.g. if radar transmits 26 s pulses, each pulse consisting of 13 phase coded chips that are 2 s in length, then the measurement IF bandwidth should be 1/2 s = 500 kHz) Video bandwidth: Measurement system IF bandwidth Suppression of spurious emission: 55 dB. 3.3 Antenna side-lobe suppression for specified angles above the horizon TABLE 3 Angle above the horizon (degrees) Antenna side-lobe suppression (dB) Median Minimum 0-5 5-45 45 40 25 20 28 18 13
