The 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 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 Patent 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 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)
Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1.
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU.
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)
Rec. ITU-R M.1466
This Recommendation specifies the characteristics of and protection criteria for radars operating in the radionavigation service in the frequency band 31.8 33.4 GHz. These technical and operational characteristics are to be used as a guideline in analyzing compatibility between radars operating in the radiodetermination service with systems in other services.
The ITU Radiocommunication Assembly,
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 radiodetermination service are determined by the mission of the system and vary widely even within a band;
c) that the radionavigation service is a safety service as specified by RR No. 4.10 and harmful interference to it cannot be accepted;
d) that considerable radiolocation and radionavigation spectrum allocations (amounting to about 1 GHz) have 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 GHz used by radars in the radiodetermination service;
f) that representative technical and operational characteristics of systems operating in bands allocated to the radiodetermination service are required to determine the feasibility of introducing new types of systems;
g) that procedures and methodologies are needed to analyse compatibility between radars operating in the radiodetermination service and systems in other services;
h) that WRC-97 requested that the ITU-R conduct studies to determine what criteria would be necessary for sharing between stations in the fixed service and stations in the other services to which the frequency band 31.8 33.4 GHz is allocated;
j) that the frequency band 31.8-33.4 GHz is allocated on a primary basis to the fixed and radionavigation services and that portions of the band are allocated on a primary basis to the space research (deep space) and intersatellite services,
1 that the technical and operational characteristics of the radars operating in the radionavigation service described in Annex 1 be considered representative of those operating in the frequency band 31.8 33.4 GHz;
2 that Recommendation ITU-R M.1461 be used as a guideline in analysing compatibility between radars 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, and 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.
Technical and operational characteristics of radars
operating in the radionavigation service
in the frequency band 31.8-33.4 GHz
The radionavigation service operates worldwide on a primary basis in the frequency 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.
2 Technical characteristics of radionavigation systems in the frequency band 31.8 33.4 GHz
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, weather avoidance, and to calibrate aircraft on-board navigation systems for accurate aerial delivery in adverse weather conditions.
Radionavigation radar characteristics in the band 31.8-33.4 GHz
Radar No. 1
Radar No. 2
Tunes continuously across 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)
RF emission bandwidth (MHz)
Pulse duration (s)
Pulse repetition frequency (pps)
Peak transmitter power (kW)
Receiver IF bandwidth (–20 dB) (MHz)
Receiver noise figure (dB)
Antenna main beam gain (dBi)
Elevation: –30 to 10, manual
azimuth: 360 at 7, 12, or 21 rpm
Elevation: –30 to 10, manual
azimuth: 360 at 12 or 45 rpm
3 Operational characteristics of radionavigation systems in the frequency band 31.8 33.4 GHz
Aircraft radionavigation radars in the band 31.8-33.4 GHz operate continuously during flight. This encompasses an altitude range of from just off the ground to approximately 30 000 feet (9 000 m). Flight times can be up to six 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 (i.e., separated by less than a kilometre from each other), 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 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 N0 and that of noise-like interference by I0, the resultant effective noise power spectral density becomes simply I0 N0. An increase of about 1 dB would constitute significant degradation, equivalent to a detection-range reduction of about 6%. Such an increase corresponds to an (I N)/N ratio of 1.26, or an I/N ratio of about – 6 dB. This represents the aggregate effect of multiple interferers, when present; the tolerable I/N 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 from most azimuth directions, a lower I/N 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 strongly dependent on receivers/processor 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 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 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 Recommendation ITU R M.1372.
* Radiocommunication Study Group 5 made editorial amendments to this Recommendation in 2008 in accordance with Resolution ITU-R 44.