Abstract.
For
cylindrical multi-beam lens antennas, a method for the formation of frequency-independent
radiation characteristics in a wide frequency band is proposed. The method is
based on the choice of the aperture configuration, forming the decreasing
amplitude distribution of an equivalent linear radiator and introducing an
additional frequency-dependent quadratic phase aperture distribution, formed by
defocusing the lens. In this case, the decrease in the width of the pattern
with increasing frequency is compensated by an increase in the dephasing of the
aperture. The electrodynamic simulation confirmed the possibility of
stabilizing the width of the partial patterns of the lens antenna in the
frequency range with overlap of 2.25: 1. The prototype
of the lens antenna is made of polystyrene and includes seven sectorial horns
irradiators. Amplitude excitation in the aperture of the lens, given by the
horns, is practically uniform. Using an absorbing
diaphragm of a special shape mounted on the illuminated side of the lens, an
amplitude distribution of an equivalent linear radiator of the form
"cosine in square" with a pedestal Δ
= 0.2 is formed in its aperture. The prototype of a multibeam lens antenna,
forming seven beams in the sector ± 18º, was tested. The experimental values
of the width of the partial-beam patterns in the frequency band are 5.45°
with a maximum deviation of ± 0.85°, while maintaining a stable level of
intersection of the partial patterns and the steepness of the direction-finding
characteristics. The relative level of intersection of partial patterns is 3 ±
1 dB. The proposed method for constructing broadband multi-beam lens antennas
with frequency-independent radiation characteristics can be used in the
development of antenna systems for various purposes.
Key words:
lens
antenna, amplitude-phase distribution, radiation pattern.
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