CST – Computer Simulation Technology

Low-Loss Wideband Multimodal Interferometric Antenna for DOA in Azimuth and Elevation

Title:
Low-Loss Wideband Multimodal Interferometric Antenna for DOA in Azimuth and Elevation
Author(s):
Jacob Remez, Erez Ben-Ari
Source:
IEEE Antennas and Wireless Propagation Letters
Vol./Issue/Date:
Volume: 8, 2009
Year:
2009
Page(s):
898 - 902
Keywords:
Circular phase modes, direction-finding (DF) antennas, direction-of-arrival (DOA) estimation, interferometry, multimodal antennas
Abstract:
A novel direction-finding (DF) antenna is presented. The antenna uses interferometry with the three low-order circular phase-modes (CPMs) ( -1, 0, +1) to estimate the direction-of-arrival (DOA) of a received microwave signal. The antenna system consists of two antennas positioned one above the other. The omnidirectional n=0 mode created by a top biconical dipole antenna serves as the phase reference for the other +/- 1 modes. The second antenna consists of a novel two-port waveguide feed creating left- and right-hand circularly polarized (CP) fields inside a thick coax that opens gradually to a radial waveguide and a biconical horn antenna. Each CP-field propagates between the circular parallel plates in a spiral path (a TE 10 radial line mode) creating a linear phase field in the aperture. The amplitude of the resulting radiation field is uniform in azimuth, with a continuous linear phase in azimuth. Thus, in transmit mode, one port creates a positive phase slope (+1 port) and the other creates a negative phase slope ( -1 port). In the operating receive mode, the linearly polarized TE11 mode of the thick coax is resolved into right- and left-hand CP TE11 modes. The DOA information is obtained by measuring the phase differences between the CP modes and the reference n=0 mode. The two phase differences, when processed, yield azimuth and elevation DOAs of the received signal. The suggested antenna is simpler in its structure, smaller in size, and light compared with a previous multiport biconical antenna. It is also more wideband and less lossy, and it is capable of detecting the elevation DOA of the received signal.
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