ITU-R SA 1805-2007 Technical and operational characteristics of space-to-space telecommunication systems operating around 354 THz and 366 THz 《运行在354 THz和366 THz范围内空对空电信系统的技术和运行特性》.pdf
《ITU-R SA 1805-2007 Technical and operational characteristics of space-to-space telecommunication systems operating around 354 THz and 366 THz 《运行在354 THz和366 THz范围内空对空电信系统的技术和运行特性》.pdf》由会员分享,可在线阅读,更多相关《ITU-R SA 1805-2007 Technical and operational characteristics of space-to-space telecommunication systems operating around 354 THz and 366 THz 《运行在354 THz和366 THz范围内空对空电信系统的技术和运行特性》.pdf(8页珍藏版)》请在麦多课文档分享上搜索。
1、 Rec. ITU-R SA.1805 1 RECOMMENDATION ITU-R SA.1805 Technical and operational characteristics of space-to-space telecommunication systems operating around 354 THz*and 366 THz*(Question ITU-R 235/7) (2007) Scope This Recommendation specifies technical parameters (frequencies, link direction, signal an
2、d data characteristics, antenna parameters, etc.) and operational characteristics of telecommunication systems operating in the space-to-space direction around 354 THz and 366 THz, which could be used in sharing studies. The ITU Radiocommunication Assembly, considering a) that telecommunication link
3、s are planned for use on some satellite systems for inter-orbit telecommunication at frequencies in the region of 354 THz and 366 THz; b) that using recent technological developments, astronomers are making a concerted effort to build telescopes and make observation in this segment of the spectrum;
4、c) that this segment of the spectrum is also being used for other terrestrial and space services; d) that this segment of the spectrum is also being used for scientific and industrial purposes other than telecommunication, recommends 1 that sharing studies considering space research satellites opera
5、ting in the space-to-space direction around 354 THz and 366 THz should take into account the technical and operational parameters presented in Annex 1. Annex 1 1 Introduction Due to increased pressure for use of the electromagnetic spectrum and the advancement of technology, there is more attention
6、being given to the use of frequencies above 3 000 GHz for free-space telecommunications. Free-space telecommunication at frequencies above 3 000 GHz has the ability to support higher data rates with less mass than traditional RF systems as well as meet gain and directivity requirements of beams used
7、 for space-to-space applications. *1 THz = 1 000 GHz. *This Recommendation should be brought to the attention of Radiocommunication Study Group 1. 2 Rec. ITU-R SA.1805 1.1 Frequency considerations Currently, most of the interest in free-space telecommunications links above 3 000 GHz is focused aroun
8、d the frequencies 200, 283, 311 and 353 THz, whose corresponding wavelengths are approximately 1.5, 1.06, 0.965 and 0.850 m. These frequencies are the same as those most widely used for telecommunications in optical fibres. For inter-orbit telecommunication, attention is being focused on the use of
9、high power semiconductor lasers operating around 0.850 m or the use of a semiconductor laser beam amplified by an Erbium-doped (Er) fibre-optical amplifier (EDFA) at the wavelength of 1.5 m. The system with semiconductor lasers operating around 0.85 m is superior to that with EDFA in reliability and
10、 power consumption for relatively low data-rate applications which do not require high transmitter power. 1.2 Generic mission parameters Technical parameters suitable for interference analyses should be based on generic inter-orbit telecommunication links near the Earth. Therefore, link distances wi
11、ll be between a few to several hundred thousand km. A summary of the fundamental technical parameters around 354 THz and 366 THz near-Earth inter-orbit telecommunication link is provided in Table 1. TABLE 1 Technical parameters of a reference inter-orbit telecommunication system operating around 354
12、 THz and 366 THz in the space-to-space direction Parameter Forward link Return link Transmitter power (mW) 10 40 Transmitter aperture (cm) 25 26 Transmitter frequency (wavelength) (THz) Comm: 366 (0.819 m) Beacon: 374 (0.801 m) 354 (0.847 m) Modulation 2PPM NRZ Pointing accuracy (rad) 2.6 (3) Range
13、in free space (km) up to 40 000 Data rate (Mbit/s) 2.048 49.3724 Receiver aperture (cm) 26 25 Detector type APD detector APD detector APD: avalanche plid-o-diode NRZ: non-return to zero PPM: parts per million 2 Link considerations Inter-orbit links are established between a goesynchronous Earth orbi
14、t (GEO) satellite and a low-Earth orbit (LEO) satellite in the space-to-space direction, operating around 366 THz for the Rec. ITU-R SA.1805 3 forward link and 354 THz for the return link. A beacon signal at 374 THz is emitted to assist with telescope pointing and tracking. 2.1 Link performance Like
15、 a space-to-space system operating in the traditional RF spectrum, performance of a link operating around 354 THz and 366 THz is measured in terms of data rate andBER. Performance is calculated as a function of power, telescope quality, propagation considerations, noise and receiver sensitivity. Eac
16、h of these parameters is a function of additional variables. 2.1.1 BER Frames of data must have a BER of less than 106after error correction in order to be retained. A link must retain 99% of data frames. 2.1.2 Margin requirement The typical margin requirement of an inter-satellite link operating ar
17、ound 354 THz and 366 THz is on the order of 1 to 3 dB. 2.2 Modulation The return link operating around 354 THz utilizes NRZ. The forward link operating around 366 THz utilizes 2PPM. This modulation technique allows for direct detection by the receiver rather than implementing coherent receivers. 2.3
18、 Received signal The general method for calculating the signal level around 354 THz and 366 THz received by the space-to-space station is the same as that used with traditional RF systems. SprtrttSLLLLGGPP += dBW (1) where: PS: received signal power (dBW) Pt: average laser output power (dBW) Gt: tra
19、nsmitter antenna gain (dBi) Gr: receiving antenna gain (dBi) Lt: transmitter losses (dB) Lr: receiver losses (dB) Lp: pointing losses (dB) Ls: free-space loss (dB). 2.4 Link losses Ltincludes the effects of absorption, scattering and reflection losses in the optical system of the transmitter; Lrincl
20、udes the effects of absorption, scattering, and reflection losses in the optical train of the receiver; Lpincludes the effects of antenna or satellite jitter and mispointing of the transmitting antenna; Lsis due to the physical separation between the transmitter and receiver. 4 Rec. ITU-R SA.1805 Va
21、lues of each source of loss vary with hardware design, hardware age, mission requirements and the phase of the mission. Suggested values of losses to be used in generic interference analyses are provided in Table 2. TABLE 2 Link losses of a reference inter-orbit telecommunication system operating ar
22、ound 354 THz and 366 THz in the space-to-space direction Mechanism of loss Typical value Transmitter losses, Lt0.63 (= 2 dB) Receiver losses, Lr0.5 (= 3 dB) Pointing losses, Lp0.5 (= 3 dB) Free-space loss, Ls, is calculated around 354 THz and 366 THz in the same manner as with traditional radio-freq
23、uency systems. 2244=fRcRLs(2) where: R: distance between the transmitter and receiver (m) : wavelength (m) f: optical frequency (Hz) c: speed of light (m/s). 2.5 Transmit/receive telescope parameters Telecommunication links operating around 354 THz and 366 THz utilize telescopes as transmitting and
24、receiving antennas. The transmitter and receiver antenna patterns are also different since the transmitter optics are usually fed by a Gaussian distributed beam while the receiver optics use a planar detector. For an envelope of the antenna gain patterns of transmitting and receiving antennae operat
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