Progress in energy harvesting technology and the increasing need for the energy efficient and environmentally friendly applications have called for reconsideration of communication systems. This reconsideration results in new problem formulations regarding the recent developments on energy harvesting systems. Recently, optimal strategies for various types of energy harvesting networks have been developed based on different harvesting models. This thesis reports the results of our research to develop the optimal scheduling structures on an energy harvesting broadcast and fading channels, and to devise online implementable algorithms for a point-to-point communication system. Particularly, structural properties of an optimal offline schedule in, (1) an energy harvesting broadcast channel with one transmitter two receivers, (2) a single user communication system under fading conditions, are investigated. Moreover, an online algorithm is proposed for a single-user energy harvesting communication system considering the physical constraints and necessities regarding implementation. The proposed scheme is implemented through GNU Radio framework on a USRP device.

Spectrum has been a scarce commodity in RF communication. Acoustic data communication is an alternative to RF communication where data is transmitted through sound waves. In this thesis, several different aspects of acoustic data communication are investigated. A physical test setup is built where the data communication spectrum extends up to 40 kHz. Impulse response of the acoustic channel is considered in a laboratory environment. Acoustic spectrum beyond the hearing limit between 25 kHz to 35 kHz is found as a suitable band for the developed setup. Distance and multipath components are important factors, determining the communication accuracy. The physical layer for the communication system is built by taking RF Pager system as a reference. This system is also modified to improve the performance. Dierent modulation techniques are used in order to evaluate their performances for acoustic channels. BFSK, BPSK, QPSK, GMSK, OFDM, DSSS and FHSS techniques are implemented for comparison. Total and effective bit rate are considered for the overall performance evaluation of differentt modulation techniques. Several experiments are done in laboratory environment where there are several multipath components. As the distance between the transmitter and receiver is increased, path loss and multipath increases. It is shown that certain modulation techniques are more robust to multipath and are better candidates for acoustic communication. While acoustic environment is inefficient in terms of power, it is still a good candidate for communication in short distances.

RF/Microwave switches are widely used in microwave measurement systems, telecommunication and radar applications. The main purposes of RF switches are Tx-Rx switching, band select and switching the signal between different paths. Thus, they are key circuits especially in T/R modules. Wideband operation is an important criterion in EW applications. High power handling is also a key feature especially for radars detecting long range. In this study, different types of high power solid state switches operating at X-Band are designed, fabricated and measured. The main objectives are small size and high power handling while keeping good return loss and low insertion loss. The related studies are investigated and analyzed. Solutions for increasing the power handling are investigated, related calculations are done. Better bias conditions are also analyzed. The measurement results are compared with simulations and analysis. Circuit designs and simulations are performed using AWR&reg / and CST&reg / .

In passive target localization, source position is estimated by only using the source signal. In this thesis, position of a stationary target is estimated by using the data collected by a moving platform. Since the focus of the thesis is the location estimation, the parameters used for localization such as angle-of-arrival (AOA), time-difference-of-arrival (TDOA), Doppler frequency shift are assumed to be known. Different emitter localization methods are implemented in this thesis. Some of these methods are known in the literature and some are the modified or hybrid versions of these algorithms. Orthogonal Vector Estimator (OVE), Pseudolinear Estimator (PLE), Weighted Instrumental Variables Estimator (WIVE) and Maximum Likelihood Estimator (MLE) use only the AOA information. In MLE, Gauss Newton (GN) search algorithm is used to realize the search process effectively. AOA localization methods are also implemented together with the extended Kalman filter (EKF) realization. Doppler Shifted Frequency (DSF) based Least Squares (LS) and MLE are implemented which use Doppler frequency shift only. AOA-DSF combined hybrid algorithm is shown to perform better. LS and Maximum Likelihood (ML) TDOA localization methods are also implemented. AOA-DSF-TDOA combined hybrid algorithm is shown to perform better than the algorithms which use one type of parameter and AOA-DSF hybrid algorithm. Estimator performances are analyzed in this thesis. Error ellipsoid is a useful tool to evaluate an estimator

In this thesis, Inverse Synthtetic Aperture Radar image reconstruction techniques, named as Range Doppler, Back Projection, Polar Formatting, Multiple Signal Classification (MUSIC) and Time Frequency techniques are analysed and compared using simulations. Time Frequency techniques investigated in this thesis are Short Time Fourier Transform, Wigner-Ville Distribution, Smoothed Wigner-Ville Distribution and Choi-Williams Distribution. First, some fundamental concepts of ISAR, such as resolution, range profile, time dependent Doppler frequency are given. A data simulator is designed and implemented for the purpose of providing configurable input to ISAR signal processing algorithms for a given ISAR target geometry. Estimation of target rotational velocity is explained with the help of three methods, namely Grid Search, WVD Slope and Radon Wigner-Hough Transform. Then, theoretical background of image formation algorithms is discussed. MATLAB simulations for each algorithm are implemented with several configurations in order to visualize and analyse the results. Finally, processing algorithms are compared to discuss the advantages and disadvantages.

A novel topology is developed and used to design a switched multiplexer. In the new topology there are two noncontiguous switched multiplexer modules containing the channels 2-4 GHz, 6-8 GHz, 10-12 GHz and 14-16 GHz named as odd channels and 4-6 GHz, 8-10 GHz, 12-14 GHz and 16-18 GHz, named as even channels to improve isolation between adjacent channels. The input signal is split at input into the two multiplexer and the outputs of the multiplexers are combined by 2-18 GHz power dividers. The input and output multiplexers are combined through switch + Low Noise Amplifier + attenuator blocks which are also used for amplitude equalization. The input/output multiplexers are designed using a novel technique that transforms a contiguous manifold multiplexer into non-contiguous multiplexers with 2 GHz bandwidth to form guard bands between channels to improve isolation. The HP outputs of the channels are split by LP-HP diplexers with corner frequencies at the centers of the channels. Then only the LP outputs of these diplexers are fed to the output to form a non-contiguous multiplexers. The HP outputs of LP-HP diplexers are terminated in 50 ohms. The incorporation of LP-HP diplexer to form noncontiguous channels is a novel approach which avoids interaction of channels. The diplexers forming the switched multiplexer are designed using a novel approach which incorporate open circuited parallel coupled line as diplexing element. This structure acts as an integral part of the diplexer and contributes its performance. The LP-HP diplexers are designed and fabricated successfully in suspended stripline. The implemented LP-HP diplexers are then combined to form the even and odd channel multiplexers. The measured results of the individual diplexers are then combined with attenuator+Amplifier blocks to form the circuit model of the targeted switched multiplexer yielding successful performance. Thus, the design is complete and ready for the realization of a switched multiplexer.

Ground Moving Target Indication (GMTI) operation relies on clutter suppression techniques for the detection of slow moving ground targets in the presence of strong radar returns from the ground. Space Time Adaptive Processing (STAP) techniques provide a means to achieve this goal by adaptively forming the clutter suppression filter, whose parameters are obtained using an estimated covariance matrix of the clutter data. Therefore, the performance of the GMTI operation is directly aected by the performance of the estimation process mentioned above. Knowledge based techniques are applicable in applications such as the parametric estimation of the clutter covariance matrix and the estimation of the clutter covariance matrix in a nonhomogeneous clutter environment. In this study, a knowledge based approach which makes use of both a priori and instantaneous data is proposed for the mentioned estimation process. The proposed approach makes use of Shuttle Radar Topography Mission (SRTM) data as well as instantaneous platform ownship data in order to determine distributed homogeneous regions present in the region of interest / and afterwards employs Doppler Beam Sharpening (DBS) maps along with the colored loading technique for the blending process of the a priori data and the instantaneous data corresponding to the obtained homogeneous regions. A nonhomogeneity detector (NHD) is also implemented for the elimination of discrete clutter and target-like signals which may contaminate the STAP training data. Simulation results are presented for both the knowledge aided and the traditional cases. Finally, the performance of the STAP algorithm will be evaluated and compared for both cases. Results indicate that by using the developed processing approach, detection of previously undetectable targets become possible, and the overall number of false alarms is reduced.

The transmission rate and reliability are the most crucial elements of a communication system on sea platforms. In this thesis, the performance of a high speed and reliable communication system that can be used on ship to ship sea platforms will be evaluated. The two ray channel model is used in order to characterize the channel considering the refraction and reflection. Using the channel model, the path loss and the Shannon channel capacities are obtained for different systems. In order to increase the system performance, frequency diversity technique is used and a detailed comparison of diversity combining techniques is provided. As an alternative to Shannon channel capacity, cut off rate analysis is considered to get more realistic results about the rate of the communication system in that it takes modulation into account and the results are compared with the channel capacity. Block fading model and jamming effects on the achievable rate of the system is considered for different linear modulation techniques. Finally, an OFDM system design is given as an example using the tools obtained in this work.

The Decision Feedback Equalizer (DFE) is a known method of channel equalization which has performance superiority over linear equalizer. The best performance of DFE is obtained, commonly, with training period which is used for initial acquisiton of channel or recovering changes in the channel. The training period requires a training sequence which reduces the bit transmission rate or is not possible to send in most of the situations. So, it is desirable to skip the training period. The Unsupervised (Blind) DFE (UDFE) is such a DFE scheme which has no training period. The UDFE has two modes of operation. In one mode, the UDFE uses Constant Modulus Algorithm (CMA) to perform channel acquisition, blindly. The other mode is the same as classical decision-directed DFE. This thesis compares the performances of the classical trained DFE method and the UDFE. The performance comparison is done in some channel environments with the problem of timing error present in the received data bearing signal. The computer aided simulations are done for two stationary channels, a time-varying channel and a frequency selective Rayleigh fading channel to test the performance of the relevant equalizers. The test results are evaluted according to mean square error (MSE), bit-error rate (BER), residual intersymbol interference (RISI) performances and equalizer output diagrams. The test results show that the UDFE has an equal or, sometimes, better performance compared to the trained DFE methods. The two modes of UDFE enable it to solve the absence of training sequence.

This thesis presents various studies on energy efficient design of wireless networks. It starts with a survey on recent shortest path based energy efficient routing algorithms developed for ad hoc and sensor networks, making a comprehensive classification for these algorithms. In addition to energy efficient design, sustainable and environmentally friendly deployment of wireless networks demands increased use of renewable energy. However, this calls for novel design principles to efficiently utilize the variation in the availability of the energy. The thesis continues with an investigation of state-of-the-art resource management and scheduling algorithms developed for energy harvesting wireless sensor networks. Building on the stateof- the-art, the main contribution of this thesis is to formulate and solve a utility maximizing scheduling problem in a multiuser broadcast channel with an energy harvesting transmitter. The goal is to determine the optimal power and time allocations to users between energy arrivals. The structural properties of the problem are analyzed, and its biconvexity is proved. A Block Coordinate Descent (BCD) based algorithm is developed to obtain the optimal solution. Two simple and computationally scalable heuristics, PTF and ProNTO, which mimic the characteristics of the optimal policy, are proposed. Finally, an online algorithm, PTF-On,that will bypass the need for offline knowledge about the energy harvesting statistics, is developed. PTF-On uses a Kalman filter based energy harvesting prediction algorithm, developed in this thesis, to predict the energy that will arrive in the future.