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Analiza pełnofalowa anteny skanującej na podłożu ferroelekrycznym

Jaszczyszyn E.

Kwartalnik Elektroniki i Telekomunikacji

2004

Vol. 50, z. 2

287-311

W pracy przedstawiono koncepcję i opracowano nowy rodzaj skanującej anteny paskowej na podłożu ferroelektrycznym bez konieczności wykorzystania przesuwników fazy. Ponadto opracowano uogólnioną metodę analizy elektrodynamicznej rozpatrywanej struktury promieniującej wraz z metodą analizy numerycznej. Wyniki badań anteny skanującej wskazują na możliwość szerokiego jej zastosowania, a przedstawiona metoda analizy pełnofalowej do projektowania struktur promieniujących.

Electronically scanned microwave antennas is accomplished by electronically altering the phase across the antenna radiating aperture (by means of discrete phase shifting elements or by changing frequency). This conventional inertialess scanning techniques in the microwave region are not cheap. A new scan antenna concept that realizable design using low-cost fabrication processes is presented. This concept is based on the first higher order mode on a microstrip line, which substrate is made using ceramic-polymer composite with modified ferroelectric powder Ba0,65Sr0,35TiO3 and appropriate polymer (grains of the powder have been sprayed into polymer with specific method). This ceramic-polymer composite was designed to change permittivity in response to an applied electric control field. The property of ferroelectric materials having a dielectric constant which can be modulated at high frequencies is very attractive. The feasibility of dielectric scanning (changing the direction of the beam by varying the relative permittivity of the electrically controlled ceramic-polymer composite) has been investigated. The radiation characteristics of such antenna have been accurate evaluated. Both longitudinal and transverse currents are treated. The method of solution used is an extension of the Fourier integral method which is used in conjunction with the method of moments (Galerkin solution). The propagation constant kx for higher order modes in open microstrip were calculated. In the present structure the complex propagation constant can be changed by changing the frequency or by changing the dielectric constant of the substrate (E2) as in the case of electrically controlled ferroelectric ceramic-polymer composite. In general, the direction of the radiated beam is given by Om = sin-1 (B), where kx (E2) = B(E2) = j * A(E2). For frequencies not far above the cut-off frequency, that means for B/k 0 < 1 (B in phase constant of the first higher order mode), the fields of the first higher order mode on the microstrip line are coupled to the line very loosely resulting in a considerable radiation.