Pasif radar alıcılarında kullanılan anten dizilerinin ön bilgiye dayalı hedef kestirimine etkisi

Abstract

Radar sistemleri genel olarak neşrettikleri elektromanyetik enerjinin yayılımı ve bir cisme çarpması sonucunda uzaydaki nesneleri tespit amacıyla kullanılmaktadır. Aktif radar sistemlerinin kullanımı esnasında kullanım alanlarına göre bazı dezavantajları ortaya çıkmaktadır. Bu tez kapsamında kendisine ait bir elektromanyetik enerji üretme ihtiyacı olmayan, çevresinde bulunan fırsat aydınlatıcılarını kaynak olarak kullanan pasif radarlardan bahsedilmiştir.Pasif radar teknolojisi günümüzde özellikle ülkelerin hava sahalarının gözetlenmesi, müteakiben tespit, teşhis ve takip basamaklarını gerçekleştirirken çevresindeki tüm olanaklardan istifade etmesi ve kendisini en iyi şekilde gizlemesi açısından büyük önem kazanmaktadır. Bu önemin farkına varan ülkeler günümüze kadar çeşitli çalışmalar yapmış ancak bir çoğunu açık kaynak olarak dünya ile paylaşmamışlardır. Pasif radar uygulamaları sadece askeri alanla sınırlı değil özellikle sivil hava trafiği gözlemlenmesi ve atmosferik olayların incelenmesi gibi amaçlarlada kullanılmaktadır.Pasif radarlar çalışma prensibi olarak yön ölçen, Doppler kayması ölçen yada her ikisinide beraber ölçen karma sistemler olarak hedefin konumu ve hızı hakkında bilgiler vermektedir. Bununla beraber kullanılan fırsat aydınlatıcısı sayısı veya alıcı sayısına göre çeşitlilikler göstermektedir. Bu uygulamaların çoğunda dikkati çeken bir husus ise tespit edilecek hedefin konum ve hız gibi parametrelerinin doğru olarak belirlenebilmesi için alıcı bölümlerinde anten tipi olarak dizi anten kullanılmasının neredeyse zorunlu olduğu görülmüştür. Dizi anten kullanımı özellikle anten gücünün yönlendirilebilmesi açısından öneme sahip olup özellikle hedefin uçuş rotası biliniyorsa yada tahmini mümkün ise büyük avantaj sağlamaktadır.Tezin gelişiminde pasif radar ihtiyacının ortaya çıkmasındaki nedenlerden bahsedilmiş, çeşitlerinden, aktif radarlara göre avantaj ve dezavantajlarından bahsedilerek günümüzde ve günümüze kadar dünya literatüründeki pasif radar uygulamaları hakkında bilgi verilmiştir.Son olarak ise uygulama kısmında, muhtemel yada zorunlu uçuş rotası bilinen veya tahmin edilebilen bir jet motorlu savaş uçağının dört faklı uçuş rotasında uçuş yaparken, konumu sabit bir FM verici istasyonunu fırsat aydınlatıcısı olarak kullanarak, yine konumu sabit olan ve farklı faz dizili antenlere sahip olabileceği MATLAB ortamında ortaya konulan alıcı istasyonunu kullanarak hedefin tespit edilebileceği maksimum mesafeler üzerine uygulamalar yapılmıştır. Hedefin uçuş rotasının hedefin tespit edilebilirliğine etkisinin yanında, farklı tip dizi alıcı anten uygulamanında hedefin tespit edilebilirliğine etkisi gösterilmiştir. Özellikle faz dizili antenler sinyalin ışıma hüzmesini belirli bir bölgede yoğunlaştırabilme veya yöneltebilme kabiliyetine sahip oldukları için özellikle uçuş rotası bilinen yada tahmin edilebilen sektörlerde omni ışıma yapan alıcılara göre daha iyi tespit mesafeleri verebildikleri uygulamalar sonucunda ortaya konulmuştur.

The reflection quality of electromagnetic energy prompts scientists and raddars are produced using this quality. In fact radars that are used extensively in military meaning are composed from a receiver antenna which pick ups electromagnetic energy. This energy that is composed via receiver antenna is evaluated using some signal algorithm and various information about materials that cause reflection is obtained. Radars that expands electromagnetic energy to athmosphere with its own transmitter are regarded as active radars.When active radars are regarded with their current situations, it is viewed that their ranges are remote enough, they have enough clearness and correctness in terms of detection and the ability of tracking, they use technology that is mature and proving itself. However, on the other hand, this mentioned radar has some important sensitivity towards jammer, anti radiation arms, using chaff, invisible technology and negative air conditions.There are a lot of energy resources such as; television, radio, satellite and mobile phone in the world. This electromagnetic energy that is expanded from these resources progresses in athmosphere, crashes to some substance like plane and ship and reflects from this substances. Also, various means like plane, ship spread electromagnetic energy. This electromagnetic energy that reflects and spreads from the resource directly is gathered with a reciever antenna, is evaluated through some signal algorithm and is obtained many information about materials that have resources.In this thesis, it is mentioned about passive radars that don't need its own electromagnetic energy production and use non-cooperative sources of illumination in the environment as resource. Passive radar hasn't got its own active transmitter encompass objects by processing reflections from non-cooperative sources of illumination in the environment as transmitter. It is a passive system that has one or more alternatives as receiver. Passive radars generally benefit from non-cooperative illuminations, analog tv and signals from radio, digital tv and signals from radio, signals from GSM or GPS, IFF, TDL, ATDL, GCA and TACAN that are released from air vehicles and other active radar signals.Passive radar receivers regard signals that are spreaded by non-cooperative illuminations as echo that is reflected from target and directly. As a result of evaluation of this signal, at first the detection of target and then its speed, accelaration and direction is controlled.The technology of passive radar has very big importance in terms of especially monitoring countries' air zones, using every possibilities in the environment when to realize detection, recognation and tracking and hiding itself in the best way. Countries which notice this importance have done various workings till this time but, don't share many of them with the world as an open source. Passive radar isn't just limited with military term but especially is related with monitoring civil air traffic and investigating athmospheric events.Passive radars that measure direction, Doppler shifting or both of them give information about the speed and location of the target as mixed systems. Moreover, they range from the number of non-cooperative illumination to the number of receiver. One particular point pays attention to the fact that it is compulsory to use array anttenna as the type of antenna in the parts of receiver to specify parameters such as the location and speed of the target correctly. Using array antenna is especially important in terms of to be able to be directed the power of antenna and has big advantage if it is known or it is possible to guess the flight direction of target.Passive radars are classified two as their types of illumination; passive broadcast perception and complex passive perception. The broadcast of radar and radio of different objects and vehicles such as plane, ship, IFF and data link signals that has knowledge about the object using their own electromagnetic energies and using this information with the aim of radar is called as perception of passive broadcast. Complex passive perception is bistatic or multistatic radar that uses radar which diffuses signals to environment for different aims or receivers which broadcast with the aim of trade like tv, radio, satellite and mobile phone. The reason of using the word of 'complex' in tecnical meaning is to evaluate both amplitude and phase information.Electromagnetic energy no matter in which form certainly reflects when it crashes to an object that reflects. However, this reflection may have different characteristics. Signals that are designed with the aim of radar and have a special form have a specific characteristic. To transact in the signal that occurs in receiver antenna according to this known characteristic is enough to detect an object. But, in complex passive perceptive systems, it is necessary to transact on many signals. Since every signal has its own form and frequency, it reflects in different characteristic way. Thus, this needs complex transacting signal process that begins with the presumption about how the reflection has what kind of characteristic. In the implementation part, possible route while flying in four different route of a fighter aircraft known, using the FM transmitter station the non-cooperative sources of illumination, The maximum distance can be determined in different phased array receiving antenna having the antenna side modeled in MATLAB. The flight route of target has an effect on detection of target but also different kind of array antenna receiver application has an effect on the detection of target. Especially, because phase array antenna has the ability of intensification in a specific area of signal beam or the ability of shiftingFinally, it is thought that passive radar systems have many advantages in terms of their using area. In the future, the application of passive radar will have much more importance and it will be common with the developing technology. Because of this reason, it is thought that there should be more research on passive radar systems and different alternative scenarios can be modelled since it is useful for our national benefits.