An optimization approach is presented for the problem of constructing the time-dependent voltage waveform at the input terminals of a dipole antenna such that the radiated electric field waveform at the far zone is equal to a predetermined function of time. This problem is treated as an optimal control problem where the control is the voltage at the input terminals of the dipole antenna and the functional to be minimized is a suitable norm of the difference of the required and calculated far zone electric field amplitudes. The feed voltage and the current induced on the antenna are related by Pocklington's integro-differential equation, which will be called the state equation throughout this paper. In addition, the current induced on the antenna is related to the far zone electric field by an integral expression. The problem is formulated as a constrained optimization problem where the constraint is Pocklington's equation. Using the method of Lagrange multipliers we obtain the augmented functional, and the problem is reduced to finding the stationary points of the augmented functional. A variational approach is used to find the conditions for optimality, yielding the costate equation which is the adjoint of Pocklington's integro-differential equation. The problem is solved by the steepest descent method where the state and costate equations are solved by the time domain finite element method at each iteration step. The one-dimensional search at each step is carried out in the direction of the negative gradient with respect to the input voltage. A suitable stopping criterion is chosen to terminate the iterations. Numerical results show a close match between required and calculated waveforms.


Adaptive control of DC link current in current source converter based STATCOM for improving its power losses
Karaduman, Ferdi; Ermiş, Muammer; Bilgin, Hazım Faruk; Department of Electrical and Electronics Engineering (2012)
In conventional three-phase PWM (Pulse Width Modulation) current source converter based STATCOM (Static Synchronous Compensator) applications, DC link current is kept constant at a predefined value and the reactive power of STATCOM is controlled by varying modulation index. This control strategy causes unnecessary power losses especially when the reactive power of STATCOM is low. For this purpose, in order to reduce the active power drawn by STATCOM, the modulation index can be maximized by adjusting DC lin...
Correlations of the thermodynamic quantities with the frequency shifts of a lattice mode close to the I-II transition in NH4Br
Yurtseven, Hasan Hamit (Elsevier BV, 2010-06-01)
We correlate here the specific heat C-p with the frequency shifts (1/V) (partial derivative V/partial derivative T) and the thermal expansivity alpha(p) with the (1/v) (partial derivative V/partial derivative P)(T) close to the I-II transition in NH4Br. This correlation is performed for the Raman mode of vs (140 cm(-1)) using the molar volume data for NH4Br. It is shown here that spectroscopic modifications of the Pippard relations are applied satisfactorily to the I-II phase transition by using a lattice m...
Closed-form Green's functions for finite grounded dielectric substrate
Öğücü, Gölge; ALATAN, LALE; Aydın Çivi, Hatice Özlem (Informa UK Limited, 2005-02-01)
The approximate closed-form Green's functions of the vector and scalar potentials in the spatial domain are derived for a horizontal electric dipole placed over a finite grounded dielectric medium. The effects of the discontinuity at the edges are considered by including the surface wave reflections from the edges, which are obtained as a function of the incident angle by using the edge admittance concept. The closed-form expressions of the reflection coefficients are then derived by means of the generalize...
Optimal Power Allocation for Average Detection Probability Criterion Over Flat Fading Channels
Sarıtaş, Serkan; Sezer, Ahmet Dundar; Gezici, Sinan; Yuksel, Serdar (2017-03-01)
In this paper, the problem of optimal power allocation over flat fading additive white Gaussian noise channels is considered for maximizing the average detection probability of a signal emitted from a power constrained transmitter in the Neyman-Pearson framework. It is assumed that the transmitter can perform power adaptation under peak and average power constraints based on the channel state information fed back by the receiver. Using results from measure theory and convex analysis, it is shown that this o...
Transformation Electromagnetics Based Analysis of Waveguides With Random Rough or Periodic Grooved Surfaces
Ozgun, Ozlem; Kuzuoğlu, Mustafa (Institute of Electrical and Electronics Engineers (IEEE), 2013-02-01)
A computational model is introduced which employs transformation-based media to increase the computational performance of finite methods (such as finite element or finite difference methods) for analyzing waveguides with grooves or rough surfaces. Random behavior of the roughness is taken into account by utilizing the Monte Carlo technique, which is based on a set of random rough surfaces generated from Gaussian distribution. The main objective of the proposed approach is to create a single mesh, and to ana...
Citation Formats
M. ONDER and M. Kuzuoğlu, “OPTIMAL-CONTROL OF THE FEED VOLTAGE OF A DIPOLE ANTENNA,” IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, pp. 414–421, 1992, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/43087.