Anastasis C. Polycarpou

Prof. Anastasis C. Polycarpou

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Research Focus & Metrics

Academic Career Length

33Years (1994-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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2 April 2012 in Earthquake Engineering & Structural Dynamics
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PPPanayiotis C. Polycarpou
Panayiotis C. Polycarpou
Petros KomodromosPetros Komodromos
Petros Komodromos
APAnastasis C. Polycarpou
Anastasis C. Polycarpou

1 January 2006 in Synthesis Lectures on Computational Electromagnetics
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APAnastasis C. Polycarpou
Anastasis C. Polycarpou
This series lecture is an introduction to the finite element method with applications in electromagnetics. The finite element method is a numerical method that is used to solve boundary-value problems characterized by a partial differential equation and a set of boundary conditions. The geometrical domain of a boundary-value problem is discretized using sub-domain elements, called the finite elements, and the differential equation is applied to a single element after it is brought to a “weak” integro-differential form. A set of shape functions is used to represent the primary unknown variable in the element domain. A set of linear equations is obtained for each element in the discretized domain. A global matrix system is formed after the assembly of all elements. This lecture is divided into two chapters. Chapter 1 describes one-dimensional boundary-value problems with applications to electrostatic problems described by the Poisson's equation. The accuracy of the finite element method is evaluate...

30 July 2014 in IEEE Transactions on Antennas and Propagation
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APAnastasis C. Polycarpou
Anastasis C. Polycarpou
MCMarios A. Christou
Marios A. Christou
NPNectarios C. Papanicolaou
Nectarios C. Papanicolaou
A nematic liquid crystal (N-LC) cell is used as a substrate to a microstrip patch antenna in order to control its resonant frequency through the use of a DC or low-frequency AC bias voltage. The dielectric tensor properties of the liquid crystal (LC) are dependent on the orientation of the LC molecules, called the directors. The directors' tilt angle is controlled by the amplitude of an externally applied electric field. A finite-difference (FD) scheme with relaxation is formulated in order to solve the highly nonlinear partial differential equation (PDE) that models the directors' tilt angle in the LC. The problem of solving for the directors' field is coupled to an electrostatic boundary value problem (BVP) in a nonhomogeneous anisotropic medium. The orientation of the directors determines the constitutive parameters of the material. The HFSS is then utilized to obtain the radiation characteristics of the antenna under various bias conditions. Comparisons with measurements are provided in order to validate the proposed numerical approach and illustrate the potential use of LC's as tunable materials in microwave and millimeter-wave frequencies.

1 January 1997 in IEEE Transactions on Microwave Theory and Techniques
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APAnastasis C. Polycarpou
Anastasis C. Polycarpou
PTP.A. Tirkas
P.A. Tirkas
CBC.A. Balanis
C.A. Balanis

1 January 1998 in IEEE Transactions on Antennas and Propagation
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APAnastasis C. Polycarpou
Anastasis C. Polycarpou
CBC.A. Balanis
C.A. Balanis
JAJ.T. Aberle
J.T. Aberle
CBC. Birtcher
C. Birtcher

1 May 2001 in IEEE Transactions on Antennas and Propagation
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APAnastasis C. Polycarpou
Anastasis C. Polycarpou
CBC.A. Balanis
C.A. Balanis
ASA. Stefanov
A. Stefanov
This paper investigates rotor modulation on the gain and input impedance of an antenna mounted on a helicopter's fuselage. The rotor blades, which are rotating about an axis with a given angular velocity, continuously modulate the signal transmitted by the antenna and adversely affect the established communication links. In this study, particular emphasis is placed on wire antennas operating within the HF and VHF bands. Specifically, the Doppler spectrum of the magnitude and phase of the radiated field from a vertical and a horizontal short dipole underneath the rotors is computed and analyzed. The variation of the corresponding antenna gain as a function of rotor angle and frequency is also investigated. The same type of analysis is then extended to a 14-ft towel-bar antenna mounted on the tail boom of a 10:1 scaled helicopter model. In addition to gain, the variation of input impedance versus angle and frequency is computed within the HF band. Finally, the bit error rate (BER) assuming a quadrature phase-shift keying (QPSK) modulation is evaluated assuming linearly and circularly polarized receiving antennas.