Search

Frequency-based localization methods are widely used to find emitter locations. Several techniques are described in the literature for emitter localization based on Doppler frequency shifts. These techniques can be used efficiently for emitter localization by using narrowband signals. Although these methods are simple and efficient, the application to the radar systems for target localization is very limited. In this paper, a new low-complexity target localization method, Target Localization via Doppler Frequencies (TLDF), for Doppler-only Multi-Input, Multi-Output (MIMO) radar with widely separated stations is described. By using widely separated MIMO radars with unmodulated continuous wave signals, the received frequencies and the Doppler shifts can be estimated efficiently. The position and the velocity of the target can be found from these estimated frequencies by a search in the position space. As the Doppler frequency is estimated efficiently, not only the target velocity but also the direction of the target is estimated accurately with the TLDF method. The Cramer-Rao Bounds (CRB) are calculated for the target velocity and the target position estimations in two-dimensional space. In simulations, the proposed method is compared with the iso-Doppler curves-based traditional method and with the CRB for different geometries. The performance of the proposed method is not affected from the target amplitude fluctuations because of its frequency-based nature. Finally, the comparison between the frequency-only MIMO radar and the pulsed monostatic radar is investigated, and the simplicity and the efficiency of the proposed method are demonstrated.

In this paper, we derive the Cramer-Rao Bounds (CRBs) for the 2-dimensional (2D) target localization and velocity estimations for widely separated Multiple-Input Multiple-Output (MIMO) radar. The transmitters emit signals with different frequencies and the receivers receive these signals with amplitude fluctuations and with Doppler shifts due to the target motion. The received signal model is constructed using the Swerling target fluctuations to take into account the undesired effects of target amplitude and phase fluctuations. Moreover, the time delays and the Doppler frequencies are included in the signal model to get a more realistic model. Then, the Cramer-Rao Bounds are derived for the proposed signal model for the target position and velocity estimations. Contrary to known models of CRBs, we derived the CRBs jointly and using the Swerling target fluctuations.

Bu tezde, sadece frekans bilgisi kullanan, antenleri geniş alana yayılmış, çoklu-giriş, çoklu-çıkış (ÇGÇÇ) radar sistemleri için yeni hedef konumlama ve hız kestirim yöntemlerinin geliştirilmesi üzerinde durulmuştur. Eğer yayımlanan sinyallerin frekans çözünürlüğü yeteri kadar iyi ise, hedefin konumunu bulabilmek için sadece alınan frekanslar ve Doppler kayması kullanılabilir.Hedefin konumunun ve hızının kestirilebilmesi için birçok çoklustatik radar veya radar ağları, hedeften gelen, varış-zamanı, varış-açısı ve varış-frekansı gibi çoklu, bağımsız ölçümleri kullanırlar. Frekans temelli sistemlerin bir çok avantajına rağmen, frekans temelli hedef konumlama yöntemlerinin, çözümlerinde hayli doğrusal olmayan denklemler içermelerinden dolayı literatürdeki uygulamaları oldukça kısıtlıdır. Bu tezde, sadece-frekans bilgisi kullanan sistemler için, daha az karmaşık, alternatif hedef konumlama ve hız kestirim yöntemleri önerilmiştir.Önerilen yöntemlerden biri, hedefin konumunu ve hedefin hızını Doppler frekansları temeline dayanan ölçümlerden kestirebilmektedir. Bunun yanında, hedefin hareket yönü de etkin bir şekilde kestirilebilmektedir. Bu yöntem `Doppler Frekansları yoluyla Hedef Konumlama - DFHK` olarak isimlendirilmiştir ve sadece radarlarda değil, sonar ve kablosuz sensör ağları gibi frekans temelli tüm hedef konumlama sistemlerinde de kullanılabilir.DFHK yönteminin yanında, alternatif iki yöntem daha önerilmiştir. Bu yöntemler de Doppler frekansı temelinde çalışır ancak hedefin hız vektörüne de ihtiyaç duyarlar. Bu yöntemler, `Doppler Frekansları ve Hedef Hızı yoluyla Hedef Konumlama - D&HHK` yöntemleri olarak isimlendirilmiştir ve iki alt gruba ayrılabilir. Bunlardan birincisi Doppler frekansının türevine dayandığı için `Türevlenmiş Doppler, D&HHK-TD yöntemi` olarak isimlendirilir. İkinci yöntem ise en yüksek olabilirlik ilkesi ve ızgara arama yöntemine dayandığı için `D&HHK-subML yöntemi` olarak isimlendirilmiştir.Yerde konuşlu ve geniş olarak dağıtılmış ÇGÇÇ radarlar için, Swerling hedef dalgalanmalarını ve Doppler frekanslarını da içeren daha gerçekçi bir sinyal modeli yapılandırıldı. Bu sinyal modeli için, hedef hız ve hedef konum kestirimi Cramer-Rao Sınırları (CRS) türetildi. Alınan sinyal yapılandırıldıktan sonra, Doppler frekansları DFT temelli periodogram frekans kestirimci ile kestirildi. Daha sonra, kestirilen Doppler frekansları hedefi konumlayabilmek için bir merkezi birleştirme biriminde toplandı.Son olarak, sadece frekans bilgisini kullanan ÇGÇÇ radar için çoklu hedef konumlama problemi ele alındı ve yeni bir veri ilişkilendirme yöntemi önerildi. DFHK yöntemi kullanılarak, önerilen yöntemin geçerliliği sadece doğrusal hareket eden hedef için değil, aynı zamanda manevra yapan hedef için de gösterildi.Önerilen yöntemler, eş-Doppler eğrilerinin kullanıldığı geleneksel yönteme göre daha az hatayla hedef konumlayabilmekte ve hedefin hızını kestirebilmektedir. Ayrıca bu yöntemler hesaplama karmaşıklığı olarak da geleneksel yöntemden daha üstündür. MATLAB programı kullanılarak yapılan benzetimlerle, önerilen yöntemlerin geleneksel yönteme göre üstünlüğü gösterildi. This dissertation is focused on developing the new target localization and the target velocity estimation methods for frequency-only multi-input, multi-output (MIMO) radar systems with widely separated antennas. If the frequency resolutions of the transmitted signals are enough, only the received frequencies and the Doppler shifts can be used to find the position of the target.In order to estimate the position and the velocity of the target, most multistatic radars or radar networks use multiple independent measurements from the target such as time-of-arrival (TOA), angle-of-arrival (AOA) and frequency-of-arrival (FOA). Although, frequency based systems have many advantages, frequency based target localization methods are very limited in literature because of the fact that highly non-linear equations are involved in solutions. In this thesis, alternative target localization and the target velocity estimation methods are proposed for frequency-only systems with low complexity.One of the proposed methods is able to estimate the target position and the target velocity based on the measurements of the Doppler frequencies. Moreover, the target movement direction can be estimated efficiently. This method is referred to as `Target Localization via Doppler Frequencies - TLDF` and it can be used for not only radar but also all frequency-based localization systems such as Sonar or Wireless Sensor Networks.Besides the TLDF method, two alternative target position estimation methods are proposed as well. These methods are based on the Doppler frequencies, but they requires the target velocity vector to be known. These methods are referred to as `Target Localization via Doppler Frequencies and Target Velocity - TLD&V methods` and can be divided two sub-methods. One of them is based on the derivatives of the Doppler Frequencies and hence it is called as `Derivated Doppler - TLD&V-DD method`. The second method uses the Maximum Likelihood (ML) principle with grid search, hence it is referred to as `Sub-ML, TLD&V-subML method`.The more realistic signal model for ground based, widely separated MIMO radar is formed as including Swerling target fluctuations and the Doppler frequencies. The Cramer-Rao Bounds (CRB) are derived for the target position and the target velocity estimations for this signal model. After the received signal is constructed, the Doppler frequencies are estimated by using the DFT based periodogram spectral estimator. Then, the estimated Doppler frequencies are collected in a fusion center to localize the target.Finally, the multiple targets localization problem is investigated for frequency-only MIMO radar and a new data association method is proposed. By using the TLDF method, the validity of the method is simulated not only for the targets which are moving linearly but also for the maneuvering targets.The proposed methods can localize the target and estimate the velocity of the target with less error according to the traditional isodoppler based method. Moreover, these methods are superior than the traditional method with respect to the computational complexity. By using the simulations with MATLAB, the superiorities of the proposed methods to the traditional method are shown. 139

A new method for target localization in MIMO radar is proposed. Localization of a moving, non-maneuvering target is possible by using Doppler-shift measurements and angle information in MIMO radar systems. This is a nonlinear problem and it must be solved for a grid search strategy. If the received frequencies and the angels between the target and the transmitter and the target and the receiver are known, we can search space grid by grid for desired (x, y) coordinates to find the position of the target in 2D space.