Correlation Effects on the MIMO Capacity for Conformal Antennas on a Paraboloid

The use of conformal antennas in a MIMO link scenario is investigated. Conformal slot antennas are considered both in the transmitter and the receiver. First, a new modified correlation coefficient is derived that goes beyond the Clarke coefficient and takes into account the element radiation pattern. Secondly, a hybrid formulation that accounts for the impact of the mutual coupling and the pattern dependent correlation on the capacity is presented. The mutual coupling for slots placed circumferentially on a paraboloid substrate is derived using a rigorous approach based on Uniform Theory of Diffraction (UTD). The capacity is evaluated for the case of Rayleigh fading channel considering the new pattern dependent correlation coefficient and the conformal antenna mutual coupling. The planar case is included as a limiting case. It is shown that for conformal antennas on a paraboloid the capacity degradation compared to the planar case is up to 0.5 bps/Hz due to coupling and correlation.Grant numbers : The authors acknowledge EU COST Action IC1301 Wireless Power Transmission for Sustainable Electronics

An Iterative Technique for the Synthesis of Active Antenna Oscillator Arrays

A design procedure for the synthesis of a coupled active antenna oscillator array is presented. Such an array is synthesized by deriving two sets of parameters: the radiators' positions and the oscillators' outputs. The outputs are used to excite the radiators. Minimization of the mean square error between the desired pattern and the resulting one is made. Synthesis starts from an initial array, which is perturbed iteratively by varying simultaneously the element excitations and positions. In the iteration, the first variation of the cost function is set equal to zero. The final array results from the last iteration, where the stopping criteria are met. The procedure designs simultaneously both the antenna and the attached coupled oscillator array providing viable solutions. The second by properly configuring the tuning parameters through the use of closed-form formulas. The resulting arrays are shown to comply with the desired pattern and the nonlinear dynamics thus proving the validity of our method

Procjena smjera dolaska vala primjenom neuralnih mreža za sustave D-CDMA s preklapanjem snopa

A Neural Network (NN) methodology is presented for the Direction of Arrival (DoA) estimation of the desired mobile user, namely the Signal of Interest (SoI), in the asynchronous Direct Sequence Code Division Multiple Access (DS-CDMA) scheme. In DS-CDMA the SoI DoA should be estimated in the presence of a group of interfering users that constitute the Multiple Access Interference (MAI). In this paper a NN algorithm follows the MAI suppression done by the code-matched filters, to achieve the DoA finding goal for a Switched-Beam System (SBS). The proposed method is developed, while DoA estimation simulation tests show accurate results for a varying number of mobile users.Prikazana je metodologija procjene smjera dolaska signala željenog pokretnog korisnika uz primjenu neuralnih mreža za sustave s višestrukim pristupom po kodnoj osnovi s asinkronom izravnom sekvencijom (DS-CDMA). U sustavima DS-CDMA, valja procijeniti smjer dolaska signala željenog korisnika u nazočnosti više korisnika koji stvaraju interferencije (smetnje) što vodi do interferencije višestrukog pristupa. U ovom se radu rabi algoritam neuralnih mreža za potiskivanje interferencije uz primjenu kodno prilagodenih filtara kako bi se mogao odrediti smjer dolaska signala u sustavu s preklapanjem antenskog snopa. Razvijena je predložena metoda, a simulacijski pokusi s procjenom smjera dolaska signala pokazali su točne rezultate za različit broj pokretnih korisnika

An Iterative Technique for the Synthesis of Active Antenna Oscillator Arrays

A design procedure for the synthesis of a coupled active antenna oscillator array is presented. Such an array is synthesized by deriving two sets of parameters: the radiators' positions and the oscillators' outputs. The outputs are used to excite the radiators. Minimization of the mean square error between the desired pattern and the resulting one is made. Synthesis starts from an initial array, which is perturbed iteratively by varying simultaneously the element excitations and positions. In the iteration, the first variation of the cost function is set equal to zero. The final array results from the last iteration, where the stopping criteria are met. The procedure designs simultaneously both the antenna and the attached coupled oscillator array providing viable solutions. The second by properly configuring the tuning parameters through the use of closed-form formulas. The resulting arrays are shown to comply with the desired pattern and the nonlinear dynamics thus proving the validity of our method