1、 Rep. ITU-R M.2081 1 REPORT ITU-R M.2081 Test results illustrating compatibility between representative radionavigation systems and radiolocation and EESS systems in the band 8.5-10 GHz (2006) 1 Background There is a need for contiguous spectrum in the bands around 9 GHz for the radiolocation servic
2、e, that is allocated on a primary basis worldwide, in order to provide adequate spectrum for new radar systems to function. Emerging requirements for increased image resolution and increased range accuracy necessitate wider contiguous emission bandwidths than are currently available. This fact was r
3、ecognized at WRC-03 and agenda item 1.3 was developed to consider the upgrade of the frequency allocations of the radiolocation service in the frequency range 9 000-9 200 MHz and 9 300-9 500 MHz to co-primary status with the radionavigation service in order for existing and planned radar systems to
4、satisfy their required missions. The band 9 500-9 800 MHz is allocated on a primary basis to the Earth exploration-satellite (EESS) (active), space research (active), radiolocation and radionavigation services, taking into account the constraints of footnote 5.476A (EESS must protect systems in radi
5、onavigation and radiolocation services). It is desirable to increase by up to 200 MHz the bandwidth available to the EESS (active) and the space research service (active) to satisfy global environmental monitoring requirements for improved resolution. There are plans to enhance spaceborne synthetic
6、aperture radars (SAR) that operate near 9.6 GHz to improve the spatial resolution to the order of 1 m, which would require up to 500 MHz bandwidth. This additional bandwidth would greatly improve the resolution of the features for global monitoring and for environmental and land-use purposes. To acc
7、ommodate this desire for additional bandwidth, consideration is being given to both the 9 300-9 500 MHz band, and the 9 800-10 000 MHz band. 2 Representative radionavigation and weather radar systems Five representative radionavigation systems operating in the 9 000-9 200 and 9 300-9 500 MHz bands w
8、ere identified to be tested to assess their compatibility with radiolocation and EESS systems. They are: marine radionavigation, precision approach (PAR), airborne weather, and airport surface detection equipment (ASDE) radars. A general description of these systems and how they are used are given i
9、n the following paragraphs. The exact technical characteristics of the radionavigation systems that will be tested are also included. 3 Objectives The objective of these measurements is to: a) Collect a parametric set of radar performance data that demonstrated the compatibility of maritime radionav
10、igation, aeronautical radionavigation, meteorological radars, and radiolocation services in the 8.5-10 GHz band. The compatibility of EESS systems with those representative radionavigation systems was also analysed through the testing. b) Verify that the radar performance degradation is a function o
11、f the interference-to-noise (I/N) ratio at the receiver IF output (detector input) as well as the undesired signal pulse 2 Rep. ITU-R M.2081 width and PRF (duty cycle), and perhaps modulation by observing the radar display for lost targets and/or an increase in false targets. Three types of radioloc
12、ation waveforms were used for these tests: chirped, phase coded, and un-modulated. Various subsets of each type of radiolocation waveform were tested. c) Collect a parametric set of radar performance data that can be used to assess the compatibility of pulsed and digital communications type modulati
13、ons with radionavigation systems operating in the 9 000-9 200 and 9 300-9-500 MHz bands. 4 Approach To show that the EESS can have an extension and radiolocation service can be upgraded to a primary allocation status without causing unwanted interference to systems already operating in the radionavi
14、gation service, the five representative radionavigation systems that operate in the 9 000-9 200 and 9 300-9 500 MHz bands were tested to show their compatibility with various radiolocation and EESS systems. Since the band contains many types of radiolocation systems mounted on land, ship, and aircra
15、ft platforms as shown in the draft new Recommendation entitled “Characteristics of and protection criteria for radars operating in the radiodetermination service in the frequency band 8.5-10.5 GHz”, it was impractical to make measurements using the actual radiolocation system themselves. Therefore,
16、the radionavigation systems were tested with simulated waveforms of representative radiolocation systems contained in the 8.5-10 GHz Recommendation and waveforms of representative EESS systems from other ITU-R documents. For the tests, the radiolocation and EESS waveforms were calibrated at the radi
17、olocation receivers IF to produce peak I/N values of I/N levels of 9, 6, 3, 0, 3, 6, 9, 12, 20, and 40 dB or greater. The waveforms of the radiolocation and EESS systems were generated and injected into the receiver of the radionavigation systems at the RF level for calibrated levels in the IF bandw
18、idth of the victim receiver, and their performance degradation, if any, was monitored and documented. This Report can be referenced in the WRC-07 Conference Preparatory working (CPM) text to support the upgrade and be available for all administrations for review. A similar method was used for the su
19、ccessful radiolocation upgrade in the 2.9-3.1 GHz band1for WRC-03. 5 Performance criteria The maritime, PAR, and ASDE radars are used to observe point targets in space at some distance from the radar itself. Pilots of aircrafts use the airborne weather radar while in flight, to observe distributed t
20、argets such as rain, hail, windshear, and other atmospheric conditions. Therefore, the performance criteria of the weather radar are very different than the criteria of the other radars. The performance criteria of the marine, PAR and ASDE radars and the meteorological radars are discussed in the fo
21、llowing paragraphs. 5.1 Maritime, PAR, and ASDE radars performance criteria The following radar performance criteria were monitored during the measurements to evaluate the effects of the radiolocation, and EESS, type of emissions on the maritime, PAR, and ASDE radars system performance. 1Report ITU-
22、R M.2032 Tests illustrating the compatibility between maritime radionavigation radars and emissions from radiolocation radars in the band 2 900-3 100 MHz. Rep. ITU-R M.2081 3 a) Loss of desired target. For the marine radar, the power level of the simulated target returns was set to obtain a probabil
23、ity of target detection of 90% without the undesired2signal being present, with the targets non-fluctuating3. This corresponds to a loss of one target per rotation. Twenty rotations were used to set the baseline probability of detection, Pd, without interference being present. With the undesired wav
24、eform being present, twenty rotations were also used for each data point with calibrated values of the radiolocation signal set to produce specific I/N levels in the IF of the radionavigation receiver. The number of lost targets per 20 rotations was counted and the Pdwas calculated based on 200 tota
25、l targets generated. b) False targets/strobes. For the ASDE-X and PAR radars, the display was observed for evidence of false indications and false targets resulting from injection of the undesired signals. This was reflected in the test logs and this Report. The target power for both radars was non-
26、fluctuating as in the case of the marine radar. Note that these criteria are not based on any particular decrement of Pd. They are based on the increase of signal power required to recover the overall performance of the radar (Pdfor a search radar, track precision for a track radar, image resolution
27、 for an imaging radar, rainfall rate and wind velocity accuracy for weather radars, etc.) to the values they would have in the absence of interference, regardless of the size of decrement in those measures of effectiveness that needs to be recovered. The increase of signal power could occur through
28、decrease in maximum free-space range, loss of coverage in regions to/from which propagation is less favourable, or expensive increase of the radars power-aperture product. We can show that irrespective of the more gradual falloff of Pdwith I/N (to a degree that depends on the particular radar being
29、tested) that attends fluctuating target return relative to steady target return. 5.2 Airborne weather radar performance criteria The following radar performance criteria will be monitored during the measurements to evaluate the effects of the radiolocation and EESS emissions on the airborne weather
30、radar system performance. ARINC has a performance standard identified as ARINC 7084for airborne weather radar systems. RTCA has also published a specification5for airborne weather radars. The RTCA requirement is that “Transmission from an identical-type radar, operating on an aircraft flying a paral
31、lel approach to an adjacent runway or following the equipped aircraft as closely as two nautical miles, shall not cause false alerts, missed detections or other observable interference”. The display of the weather radar was observed for effects due to the interference, such as strobes, abrupt colour
32、 changes and variations. 2The term undesired signals refers to both the radiolocation and EESS signals. 3The target power was held constant. 4Airborne Weather Radar with Forward Looking Windshear Detection Capability, ARINC Characteristic 708A-3, November 1999. 5RTCA/D0-220, Minimum Operational Perf
33、ormance Standard for Airborne Weather Radar with Forward-looking Windshear Capability. Section 2.2.2.15. September 1993. 4 Rep. ITU-R M.2081 6 Description of radionavigation radars 6.1 Maritime radionavigation radar The maritime radionavigation radar used for these tests nominally operates at 9 410
34、MHz and was introduced into service in 2000. This type of radar is regularly updated with improved software and hardware. It was designed for commercial applications and is an International Maritime Organization (IMO) category radar. Nominal values for the principal parameters of this radar were obt
35、ained from regulatory type-approval documents, sales brochures, and technical manuals. This radar is designed for Coastguard and Navy ships and therefore has features not normally available to commercial and recreational radionavigation radars. This includes constant false alarm rate (CFAR) processi
36、ng, synthetic/enhanced targets, and target tracking. Table 1 contains the pulse characteristics of the radar. The radar is an “upmast” design in that the transmitter and receiver are located directly below the antenna in a sealed housing. The plan position indicator (PPI) and associated radar contro
37、ls are located away from the housing and connected to it via cabling. TABLE 1 Marine radionavigation radar characteristics Frequency Short pulse 1 Short pulse 2 Medium pulse 1 Medium pulse 2 Long pulse 80 ns 200 ns 400 ns 700 ns 1.2 s Range 0.125-1.5 NM (2-8 km) 0.5-3 NM (0.9-5.6 km) 1.5-6 NM (2.8-1
38、1.2 km) 3-24 NM (5.6-44.4 km) 6-72 NM (11.2-133.3 km) Pulse repetition rate 9 410 MHz 2 200 Hz 1 000 Hz 600 Hz IF bandwidth 27 MHz 4.5 MHz 3 MHz The radar uses a summing multistage logarithmic amplifier with the IF bandwidths given in Table 1 for each pulse width and associated range. A test point w
39、as provided that is located at the output of the 3rd amplifier. A CW signal was swept in frequency to determine the response of the receiver and measure the IF bandwidth. The result is shown in Fig. 1. The 3 dB IF bandwidth of the radar when set to short pulse mode 1, which uses a pulse width of 200
40、 ns for a maximum range of three nautical miles, was measured to be about 6 MHz. This mode was used for all of the tests. Rep. ITU-R M.2081 5 FIGURE 1 Marine radar IF response curve 6.1.1 Marine radar video displays The marine radar has the ability to display various types of targets in different co
41、mbinations. The radar is able to display amorphous “blips” (known as image display and what people typically see when looking at a ppi display) and synthetic targets that are processed “blips”. For these types of targets, the radar itself has declared the “blips” as targets and they appear as an “o”
42、 on the PPI overlaid onto the “blip”. Targets that are tracked by the radar appear as an “x” on the PPI. The brightness of the video image targets corresponds to the level of the target return. Targets that have a brighter “blip” have a greater return echo. The synthetic targets required about 2-3 d
43、B of additional desired power than the video targets to obtain the same Pdwhen operating at MDS level, but do not change their brightness in correspondence to the reflected signal strength. That is to say that if the target power for the 90% Pdfor image or “blip” display was 90 dBm, then the power l
44、evel to achieve the Pdof 90% for the synthetic targets would be about 88 dBm. Adding signal power does not change the intensity of the display of the synthetic targets. For synthetic targets the radar has a built in target counter that counts the number of targets per scan and display that value on
45、the PPI. 6.1.2 Marine radar test target characteristics The targets for these tests were generated using a variety of test equipment including RF signal generators, arbitrary waveform generators, and pulse generators. Ten equally spaced targets at the same azimuth were generated for each scan6with t
46、he farthest target being located at the maximum range of 3-nmi. Each target was comprised of 18-19 pulses with the characteristics of the short pulse 2 mode setting. Each target on the radial had the same power level. That power level was held 6A scan is a 360 rotation of the antenna. 6 Rep. ITU-R M
47、.2081 constant. When the radiolocation and EESS signals were injected into the radar, they were at the same azimuth of the targets for a duration time equal to the antenna beam sweeping across a stationary object. A number of trials were performed to determine the target signal power that would resu
48、lt in a Pdof 90% without the radiolocation or EESS waveforms being present. This value was found to be about 70 dBm at the panel display of the target generator. The target power supplied to the low noise amplifier (LNA) input of the radar receiver due to RF losses from the test set-up was 88 dBm. T
49、he noise figure was measured to be about 9 dB. This results in a calculated noise power of about 97 dBm in the 6 MHz IF bandwidth of the radar receiver. Therefore, the signal-to-noise value to achieve the Pdof 90% was about 8-10 dB. Note that the accuracy of this measurement is probably within 2 dB. The receivers noise power measured at the IF test point using the spectrum analyser in zero span mode without any targets, radiolocation, or EESS waveforms present in the bandwidth was about 57 dBm. This shows a nominal gain of about 40-42 dB. The gain compression point7using an on
