1、 STD-CEPT ERC REPORT 37-ENGL 1995 m 2326414 OOL5YBL 341 D ERC REPORT 37 i European Radiocommunications Committee (ERC) x;. -_,I k. . v within the European Conference of Postai and Telecommunications Administrations (CEPT) b-.%.- SHARING THE BAND 11.7 GHz - 12.5 GHz BETWEEN ENG/OB AND DIRECT-TO-HOME
2、TV BROADCASTING SATELLITES Chester, October 1995 STD-CEPT ERC REPORT 37-ENGL 1775 = 2326414 0015482 286 Copyright 1995 the European Conference of Postai and Telecommunications Administrations (CEPT) STDmCEPT ERC REPORT 37-ENGL 1995 W 2326414 0015483 134 m ERC REPORT 37 Page 1 SHARING THE BAND 11.7 G
3、Hz - 12.5 GHz BETWEEN ENG/OB AND DIRECT-TO-HOME TV BROADCASTING SATELLITES 1. INTRODUCTION At WARC-77, the bad 11.7 GHz to 12.5 GHz was allocated, in Region 1, to Broadcasting Satellite. The band also contained a primary allocation to Fixed and a secondary allocation to Mobile (excluding aeronautica
4、l mobile). A foonote to the allocation gave the Broadcasting Satellite Service protection from harmful interference from the other services. In the UK and throughout Europe, ENG/OB video links operated in the band. It was understood by ENG/OB operators that the use of this band would be progressivel
5、y restricted as the Broadcasting Satellite Service was introduced. In a later EC directive, the Broadcasting Satellite Service was limited to the use of the MAC format. This decision was unpopdar with the BSS developers who in some cases launched services using conventional PAL in the band 10.7 GHz
6、to 11.7 GHz, contrary to the allocation table in the Radio Regulations. Many of these services are still operated in this band. As a consequence the 11.7 GHz to 12.5 GHz band remains under used and ENG/OB use continues. The restrictions on Broadcasting Satellite usage of 11.7 GHz to 12.5 GIIZ are cu
7、rrently being reviewed and it is understood that new analogue and digital television services will occupy the band. This paper presents a study which examines the potential for sharing the band 11.7 GHz to 12.5 GHz, assuming that new services are to be introduced. 2. ENGIOB OPERATIONS FOR CONSIDERAT
8、ION The Band 11.75 GHz to 12.5 GHz is used by the broadcasters and programme makers for temporary point-bpoint fixed video links and also for cordless camera links. Fixed links will generally use an e.r.p. of 40 dB (Watt) operating with 0.6 or 1.2m diameter parabolic dishes at both transmit and rece
9、ive terminals. Cordless cameras are much lower power systems and typically transmit less than O dB (Watt) e.r.p Transmitting antennas are either omni-directional or directional with some form of beam tracking. Receive antennas are normally small (circa. 0.5m diameter) parabolic dishes. The current g
10、eneration of cordless camera systems use an array of antennas which are electronically switched to provide the optimum received signal. In order that the cameraman is aware of the technical quality of his pictures, it is common practice nowadays to use a second radio channel to transmit the video ba
11、ck from the receiving site to the cameraman, to be displayed in his viewfinder. This enables the cameraman to adjust his position slightly to avoid locations produhg local nulls at the receiving site. The return link uses a transmit power of around 20 dB (Watt) and uses a diplexer to employ the same
12、 0.5m diameter parabolic dish for both receiving and transmitting. It is important that this type of equipment is considered in sharing studies as both the outgoing and return video links may cause interference and may be subject to interference. ERC REPORT 37 Page 2 3. 3.1. INTERFERENCE ANALYSIS In
13、terference into both Domestic Receiving Installations and ENG/OB receivers is calculated for -channel operation. The interference scenarios for consideration are shown in Figures 1, 2 and 3. For simplicity, the transmitted power bandwidth and the receiver bandwidth of all systems is assumed to be th
14、e same. A vaiue of 20 MHz is used which is representative of all systems. Interference into a Domestic Satellite Receiving Installation from ENG/OB operations The maximum permissible level of interference at the domestic satellite receiver is derived from noise considerations. Values for the antenna
15、 gain and off axis discrimhation are taken from Appendix 30 of the Radio Regulations. A value for Co-ordination distance is then derived using procedures outlined in Appendix 28 of the Radio Regulations (Appendix 28 concerns earth station cc+ordination and considers the case of a terrestrial station
16、 interfering with a earth station receiver). For scenarios where Appendix 28 produces Co-ordination distances below its minimum value, free space propagation incorporating a site shielding factor is applied. The noise power in the receiver bandwidth of 20 MHz is kTB where k, Boltzmanns constant = -2
17、28.6 dB (Watt)/HdK T, effective noise temperature = 20 dl3k (effective antenna temperature 20 K with 1 .O dB noise figure receiver) B, Bandwidth = 20 MHz = 73 dB HZ So noise power = -136 dl3 (Watt) If the limit for unacceptable interference is a 0.5 dB decrease in Carrier to Noise + Interference mar
18、gin, the maximum permissible interference becomes -146 dB (Watt). Appendix 28 of the Radio Regulations uses the concept of a minimum permissible transmission loss, based on the premise that the attenuation of an unwanted signal is a monotonically increasing function of distance. From Appendix 28 the
19、 transmission loss is calculated as: Transmission loss = A, + (S x co-ord dist) + A, where A, = 120 + 20 log f (in GHz) dB = 141.6 dB at 12 GHz Ah is the horizon angle correction which may be taken as O dB . includes tem for attenuation due to water vapour, oxygen and other effects. For a path consi
20、shg entirely of land, at 12 GHz, = 0.232 dB/km So equating the path loss to the required transmission loss, x co-ord dist + 141.6 = Transmitter E.I.R.P. + Receiver antenna gain - Permissible Interfering Power This is significantly better than the figure shown in Appendix 30 of the Radio Regulations
21、but reflects ment performance 232b4L4 E.I.RP. of ENG/OB Transmitter dB Watt 40 0015485 T? CMIdkltiOIl Distance km 213 ERC REPORT 37 Page 3 From Appendix 30, receiver antenna gain is 38 dBi and antenna discrimination to signals arriving beyond 10“ from boresight is 33 dB. (por terrestrial transmissio
22、ns interfering with a sateilite receiving instailation the fuli discrimination is apprqriate for most of Europe). Appendix 28 states that the value for gain of the receiving antenna is the actual gab in the direction of the interferer, whereas the E.I.RP. of the transmitter is taben to be the maximU
23、mvalue. so, substituting figures from above? B x mord dist + 141.6 =Transmitter E.I.R.P. + (38 - 33) - (-146) x co-ord dist = Transmitter E.I.R.P. + 5 + 146 - 141.6 x mord dist = Transmitter E.I.R.P. + 9.4 Cead dist = Transmitter E.I.R.P. + 9.4 Using this expression, table 1 shows the coordination d
24、istance for ENGIOB Operations with E.I.RP.s of 40 dB (Watt) down to O dB (Watt). The value of 40 dB (Watt) relates to an ENG/OB fixed link transmitter, the vaiue of 20 dE3 (Watt) to the return link to a cordiess camera Unit and the value of O dl3 (Watt) to the low pow outgoing link -cm a cordless ca
25、mera Table 1: &ordination distances for ENG/OB It is clear that ENG/OB temparary point-tepoht links using the higher vaiue of E.LRP. and the retuni link to cordless camera units using an E.LRP. of 20 dE! (watt) offer little hope for cwxdhation. Below au E.I.R.P. of 15 dl3 (Watt) the wordhation disia
26、nces calculated are less than the minhum value shown in Appendix 28, in which case accordllig to Appendix 28, the minimum vaiue of lkm should be used. Obviously, this is not realistic for low power cordless cameras and it is probably true that Appendix 28 was never intended to cover such operations.
27、 In practice, cordless cameras wiU be operated in football grounds, sports sadiums etc. these are genaaily enclosed areas and some degree of site shielding may be taken into account. If this site shielding is incorpoI.ated in the E.I.R.P. of the cordless camerq a free space path loss may then be app
28、iied to determine the interfering distance. Using the parameters shown above for the domestic satellite receiving antenna, Gain 10“ off axis = (38 -33) = 5 dBi which equates to an effective area of -38 dB (m) The maximum permissible interfering PPD is, -146 + 38 = -108 dB (WatVrn) ERC REPORT 37 Page
29、 4 Site Shielding Table 2 shows the interfexing distance for a cordes camera Operation using an E.I.RP. of O dB (Watt) and aiiowing O dB, 10 dB and 20 dB of site shielding. _ Effective E.I.R.P. Free Space Interferhg Distance (lan) OdB 10 dB 20 dB O dB (Watt) 71 -10 dB (Watt) 22 -20 dB (Watt) 7 Table
30、 2: Hee Space Interfering distances for ENG/OB Whilst the density of domlestic receiving installations in the iocatity of the cordless camera site remains low, co-existeaice between them and the low power outgoing link h the camera, may be considered possible. 3.2. Interference to ENG/OB from Broadc
31、asting Satellite Emissions The maximum level of inthne at the ENG/OB receiver is derived using the same method as above. The noise power in the receiver baudwidth of 20 MHz is kTB where k, Boltzmanns constaut = -228.6 dB (Watt)HzK T, effective noise temperatut (effective antenna tanperature 290 K wi
32、th 7 dB noise figue receiver) = 32 dBk B, Bandwidth = 20m =73 dB Hz So noise power = -123.6 dB (Watt) If the limit for unacceptable interference is a 0.5 dB deaease in Canier to Noise + Interference mark the maximum permissible interfaence becanes -134 dB (Watt). The IFRB notificaticm documws show t
33、hat within the sateate sexvice area, a PFD of arcund -107 dB (Watt/m? is prrxiuced and this is shown to be similar for both the anaiogue and digital rrruiSmissiom. Pirstiy considering the case where a simple cordless camera transmitter is received by a 0.5 m diameter parabolic antenna. On axis, a 0.
34、5 m antenna has an effective area of -7 dB (m). For Compatibility, the off axis discrimination of the antenna must be better than: 134 - 107 -7 = 20 dB This may be achieved if the pointing of the receiving antenna is restricte to angla of greater than about 20“ relative to the interfering satellite
35、orbital ldon, or general gmtaticnaxy orbit avoidance. Fracticaliy this means ensuring that the area of opei-dtion of the cordless camera is to the north of the receiving instaliation. Note. If the potentlay high outgoing interfemm from tempomry point-to-point link transmitters does not exclude their
36、 use, their receivers may be protected by using the same orbit avoidance techniques as outiined above. STD CEPT ERC REPORT 37-ENGL 1995 m 232b4L4 0015487 8bT m ERC REPORT 37 Page 5 Secondly, Consider the cordless camera system of the type currently used. This requks a rem signai from the receiving i
37、nstallation to the radio camera for both the viewfinder and also for its antenna selection control systems. To protect the link. radicamera to rever, it is necessary that the above criterion is met i.e. avoidance of orbit. However, the rehm link back to rad.iwamer% must also be protected. The receiv
38、ing antaina on the radio-camera may be pointing directly towards the interfering signal, but has a much low gain (der aperture). A realistic gain value for the radio camera antenna is 6 &i. on axis, this equates to an effective mea of -37 dB (m). If this antulna points directly at the satellite, the
39、 resulting power from the antenna is: -107 - 37 dB (Watt) = -143 dB (Watt) This is less than the permissible interference limit of -134 dB (Watt). 4. CONCLUSIONS Depending on geographic separation, ENG/OB video links in the band 11.7 GHz-12.5 GHz may interfere with domestic satellite receiving insta
40、llations. Low powex operations such as simple uni-dirdonai mdiess camaas have significantly less potential to cause interference and whilst the densiy of domestic receiving installations in the locality of the cordless camera site remains low, their mexistence may be casidered pible. Interference to
41、 ENG/OB operations from the Brdcasting Satellite will occur within the Service area of the satellite but may be reduced to tolerable levels if the ENG/OB receiving terminal is able to apply geostationary miit avoidance. This may be possible at Certain ENG/OB locations. As for the ment type of bi-dir
42、ectionai ENG/OB cordless camera systems, providing a live viewnder image, the situation is more complex. Although the rem link to the ouneraman is not subject to interference from the satellite, it has the potential to cause significant interference to a doniestic satellite receiver. The practicai v
43、alue of these operations along with the strategy behind technical impl-tation must be the subject of a more &taed study. STDaCEPT ERC REPORT 37-ENGL 1995 232b4L4 0015488 7Tb m ERC REPORT 37 Page 6 Figure 1 : ENGIOB Interfering with a Domestic Broadcasting Satellite Receiver ERC REPORT 37 Page 7 Figure 2 : Broadcasting Satellite Interfering with a simple Cordless Camera System STD-CEPT ERC REPORT 37-ENGL 3995 9 232b4L4 0035490 354 ERC REPORT 37 Page 8 Figure 3 : Broadcasting Satellite Interfering with a complex Cordless Camera System using a Return Link
