Geri Dön

Kablo TV sistemi koaksiyonel dağıtım elemanlarında işaret seviyelerinin bulunması

Başlık çevirisi mevcut değil.

  1. Tez No: 75503
  2. Yazar: AYTEN KARAHAN
  3. Danışmanlar: Belirtilmemiş.
  4. Tez Türü: Yüksek Lisans
  5. Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Elektronik ve Haberleşme Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Elektronik ve Haberleşme Mühendisliği Bilim Dalı
  13. Sayfa Sayısı: 68

Özet

ÖZET Kablo-TV sistemleri başlangıçta havadan yapılan TV yayınlarının sorunlarını ortadan kaldırmak ve uzak mesafelere bu yayınları iletmek amacıyla geliştirilmiştir. Bu sistemin sunduğu olanaklardan verimli şekilde yararlanabilmek için iletim ortamı çok iyi seçilmelidir. Bu ortam önceleri bakır teller iken daha sonra koaksiyel kabloların kullanımıyla daha yüksek frekanslı işaretleri taşımak mümkün olabilmiştir. Fiber optik teknolojisi ile beraber uzak mesafelere kaliteli yayın yapma imkanı doğmuştur. Bu çalışmada Kablo-TV sistemleri genel olarak incelendi. Bölüm 2'de Kablo-TV sistemi iletim kademeleri hakkında bilgi verilmiştir. Bölüm 3, fiber- koaksiyel karma sistemleri hakkında bilgi içermektedir. Bölüm 4te Kablo-TV lokal dağıtım sistemi ve elemanları incelenmiştir. Bölüm 5te ise programın kullanılması ve çalışması hakkında bilgi verilmiştir. Programı test etmek amacıyla kullanılan örnek devre Ek A'da verilmiştir. vııı

Özet (Çeviri)

SUMMARY CALCULATION OF THE VALUES OF CABLE-TV LOCAL DISTRIBUTION SYSTEMS ELEMENTS A cable television system is simply a means of delivering television signals to at home television set via a cable instead of the usual rooftop antenna. These systems were known as Community Antenna Television (CATV) because the cable system was used for those communities that could not get a signal or a quality signal. When the television broadcast industry developed to the point that rural or suburban areas desired service, more sophisticated rooftop antennas, antenna rotation schemes, and antenna amplifiers were employed by residents as their homes became more distant from the television transmitting antenna. Of course, as the distance from the transmitting antenna and the receiving antennas increased, the signal level decreased to unusable values. In mountainous country, people living in the valleys could not get sufficient signal level and often received the same signal twice, once directly and once reflected off some object. This is known as multipath reception. Some of the problems with television reception are shown in Figure 1. Path3 Wfeiter i tank W Patfi2X V Horaeb Home a Figure 1 The problems of receiving TV signalOne other cause of poor television reception is called co-channel, in which the television receiver receives two television stations on the same channel. From a general point of view, there are three networks related to video transmission: 1. The contribution network, to support exchange of video between television studios. 2. The primary distribution network, to support the transfer of video information from the transmitting TV studio and the cable distribution center. 3. The secondary distribution network, to support the transport of the video signal from the headend to the viewer Early attemps to solve the difficult receiving problems in distant communities involved several schemes to obtain high-quality television signals at some good location. This receiving location was and to this day is known as the head-end. A cable headend is the central point at which TV signals, downlinked from a satellite or received from a terrestrial microwawe system using the equipment of the locaşl cable TV company, are multiplexed with signals provided by local stations and then are multiplexed onto the cable for local distribution. Hence, the headend receives, processes organizes, and distributes video signals. The headend may also have automatic commercial insertion equipment that triggers on tones tape or optical drive for injection of local advertisements. The headend converts the received video signals which might be in various formats, processes them as needed, modulates them over a radio frequency (RF) carrier at the appropriate frequency, and finally combines them in a frequency division multiplexing (FDM) manner, through a combiner. As noted, a headend can inject local programming such as local commercials, public service programming, and other programming of particular relevance. There could also be more than one headend belonging to a cable company in a large metropolitan area. Many cable TV networks also employ subsidiary facilities called hubs; a hub is a signal reception and retransmission facility supporting a range of functionality, including optical to electrical conversion, or processing and control functions similar to those of the headend but on a smaller scale. A traditional cable TV network is optimized for one-way transmission of a common set of video signals. In such a cable system, the distribution networkconsists of a trunk line, connected to a trunk-bridger amplifier (TA-BA), connected to a feeder line, (optionally) connected to a line extender amplifier (LEA), connected over a tap to a drop line, and finally connected to the residence's TV and/or setup box. Larger trunk cables carry signals from the headend to the various neighborhoods around town; this main section of the network is called the trunk network (in telephony, this would be called the feeder network). Figure 2 depicts a traditional coax-based tree-and-branch (also referred to as trunk-and-branch) system. Every couple of hundred metres, the main cable is tapped to carry off the signal for local distribution within a certain area of a given neighborhood. Trunk amplifiers Distribution plant Headend op table Figure 2 Traditional coax distribution system This bus-based cable TV distribution network contains trunk amplifiers, and taps; line extender amplifiers may also be used for longer runs. The demarcation point between the trunk network and the local distribution network (which in the cable TV industry is called the feeder network or, for short, the feeder) is realized in a bridger amplifier. In any bus network, the signal intended for any recipient on the network passes by all the other network ports that are on that bus branch of the tree-and-branch network. In the traditional tree-and-branch cable network, a common set of outbound signals is distributed to every home (port) on the network; inbound signals flowing from a single port toward the headend pass by all the other XIupstream ports on the segment of distribution cable that serves that cluster of homes. The reach of the cable system (with amplification) is typically 15 to 20 miles, at which point the signal-to-noise ratio is in the -40dB range. Amplifiers are used every app. 600 metres to boost the signal that has experienced attenuation along the way. Some of the factors leading to signal degradation in a traditional coaxial system include attenuation (already discussed), noise along the distribution path, nonlinear distortion introduced by amplifiers, noise ingress at the home, and reflections. These impairments manifest themselves as picture degradation (noise), interference patterns, and poor audio. These factors not only limit the number of cascaded amplifiers but also negatively impact the usable bandwidth in the system and the use of the upstream channel. Cable attenuation increased sharply as the television carrier frequency increased. Some cables either do not support the higher bandwidths, or the attenuation is simply too high, which implies that a cable plant based on these cables would have to be replaced if the operator wanted to deliver more channels. In cable TV applications, coaxial cables are used from the headend or from the fiber termination node into the varous neigborhoods. The required distribution cables are available in a number of sizes, depending on the amount of signal loss that is tolerable, a larger diameter cable (as measured by the inner diameter of the outer conductor) has a lower attenuation. These cables are designed to have a life approaching 30 years. The drop cable connects a customer to the tap. It has different transmission requirements than the distribution cable. Because of the high loss in coax cable, a different transmission system was needed. With the fiber-optic technology, some important developments have been occured. Many traditional cable TV networks are now migrating to HFC (hybrid fiber-coax) networks. Reliability is an important factor in relation to cable networks. Traditional cable TV networks, being bus- and amplifier-based, are subject to failure. It is estimated that 50 percent of all network outages are caused by power surges and power failures. Studies show that replacing the traditional cable plant with an HFC xusystem can reduce outages from about 2 to 3 h Per year (for a well-maintained plant) to 0.5 to 1 h Per year. Security (specifically called interdiction) is an important factor in cable TV systems. Currently, the following techniques are used: 1. Negative trap: A filter is added on the drop wire or tap of the house in question. 2. Positive trap: The signal contains a jamming frequency; a notch filter must be inserted at the drop wire, tap, or setup box to remove the interfering signal. 3. Addressable setup boxes are to enable the signal to be transferred or descrambled. The cable system design begins with the mapping procedure. The area to be designed, such as a neighborhood, a town, or a city, must be studied from a demographic standpoint as well as by a survey of the methods available to install the cable plant. Maps of the area will show the road layout and where the residential buildings are situated. In this study, Section 2 contains a general overview of the Cable-TV systems and its subsections such as Control Center, Fiber-Optic Cable Network, Coax Cable Network. In Section 3, some comprehensive information can be found about the Hybrid fiber-coax networks. Section 4 includes some information about equipment that are used in Cable-TV local distribution systems. Section 5 contains the information about the program in question.. xm

Benzer Tezler

  1. Tez No

    126988

    HFC altyapısındaki kabloTV sistemlerinde dağıtım ve iki-yönlü iletişim

    Distribution and two-way transmission in HFC architectured cable TV systems

    ELİF AYDIN

    Yüksek Lisans

    Türkçe

    Türkçe

    2002

    Elektrik ve Elektronik Mühendisliğiİstanbul Teknik Üniversitesi

    Elektrik ve Elektronik Mühendisliği Ana Bilim Dalı

    PROF. DR. OSMAN PALAMUTÇUOĞLU

  2. Tez No

    100996

    Karma fiber koaksiyel yapısındaki sayısal kablo TV sistemlerinde tasarım ve ölçüm teknikleri

    Design and measurement techniques of hybrid fiber coax architectured digital cable TV systems

    YEŞİM POYRAZ

    Yüksek Lisans

    Türkçe

    Türkçe

    2000

    Elektrik ve Elektronik Mühendisliğiİstanbul Teknik Üniversitesi

    PROF.DR. OSMAN PALAMUTÇUOĞULLARI

  3. Tez No

    34178

    Fiber optik alıcı-verici sistem tasarımı

    Başlık çevirisi yok

    ŞERMİN ÇİFTLİKLİ

    Yüksek Lisans

    Türkçe

    Türkçe

    1994

    Elektrik ve Elektronik MühendisliğiErciyes Üniversitesi

    Elektronik Ana Bilim Dalı

    YRD. DOÇ. DR. CEBRAİL ÇİFTLİKLİ

  4. Tez No

    86992

    Kablo televizyon yayıncılığı

    Cable television broadcasting

    HÜSEYİN SELAMİ ÇELEBİOĞLU

    Yüksek Lisans

    Türkçe

    Türkçe

    1999

    Radyo-TelevizyonMarmara Üniversitesi

    Radyo Televizyon ve Sinema Ana Bilim Dalı

    DOÇ. DR. AHMET ŞAHİNKAYA

  5. Tez No

    845844

    Smart gain slope management system

    Akıllı kazanç eğimi yönetim sistemi

    BURHAN AKÇİL

    Yüksek Lisans

    İngilizce

    İngilizce

    2023

    Elektrik ve Elektronik MühendisliğiYeditepe Üniversitesi

    Elektrik ve Elektronik Mühendisliği Ana Bilim Dalı

    PROF. DR. SERKAN TOPALOĞLU

Geri Dön