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Radio Physics and Radio Astronomy

ISSN Imprimir: 2152-274X
ISSN On-line: 2152-2758

Archives: Volume 1, 2010 to Volume 3, 2012

Radio Physics and Radio Astronomy

DOI: 10.1615/RadioPhysicsRadioAstronomy.v2.i2.30
pages 105-113

A SUPER-WIDEBAND BASIC ELEMENT FOR LOW-FREQUENCY ANTENNAS OF RADIO TELESCOPES: PART 1. PRINCIPLES OF REALIZATION

Alexandr A. Konovalenko
Institute of Radio Astronomy of the National Academy of Sciences of Ukraine
I. N. Zhouck
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, Kharkiv, Ukraine
A. A. Gridin
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 4, Chervonopraporna St., Kharkiv 61002, Ukraine
V. P. Bovkoon
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
I. N. Boobnov
Institute of Radio Astronomy, National Academy of Sciences of Ukraine

RESUMO

Discussed in the paper are requirements to the super-wideband basic element of the radio telescope antenna operating below 200 MHz, as well as the principles underlying realization of such passive, short, symmetric, horizontally oriented dipole and possibilities for its matching with the high frequency (h.f.) feed of the telescope’s antenna array. It is shown that, despite the sharp variations of the dipole’s input impedance, it proves possible to obtain, taken the high effective temperature of the celestial sphere, a degree of matching characterized by a SWR lower than 3 over the frequency band 12.5 to 60 MHz. Within this band the antenna sensitivity is not reduced by more than 0.5 dB relative to the value for a fully matched lossless half-wave antenna. The effect is achieved by means of connecting an additional attenuator in series with the input impedance of the antenna’s basic element. As a result, the ohmic component of the input impedance is leveled through the band of 12.5 to 60 MHz. Coaxial line sections with a common central conductor are used as arms of the antenna basic element, which provides for a 0.8 to 1.0 coupling between the line sections (i.e. aperiodic circuits), and a substantially depressed reactive component of the element’s input impedance.


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