Kwang Seon Kim

Multiplexed Cassegrain Reflector Antenna for Simultaneous Generation of Three Orbital Angular Momentum (OAM) Modes

A multiplexed Cassegrain reflector antenna with a 2u2009×u20092 open-ended rectangular waveguide (OERW) matrix feed and an orbital angular momentum (OAM) mode mux is proposed for the simultaneous generation of three OAM modes (lu2009=u20090, ±1). The OAM mode mux (OMM) was designed using sequential combinations of quadrature hybrids, crossovers, and phase shifters to multiplex and demultiplex three OAM modes at the same time. The 2u2009×u20092u2009OERW matrix feed and the OMM were separately measured and their performances were verified according to proposed theories. A near-field antenna measurement for a multiplexed Cassegrain reflector antenna was conducted to obtain the far-field magnitude and phase patterns around polar elevation angle θ and azimuthal angle ϕ, thus confirming that our antenna can produce three OAM modes simultaneously. We also measured the communication link characteristics of two identical multiplexed antennas. The measurement results show that the channel isolation of three OAM modes is more than 12.7u2009[dB] and 17u2009[dB] for fixed and compensated receiver positions, respectively, indicating that the proposed antenna system can be used for independent communication links with the same frequency and polarisation.

Design of a novel switched four beam array antenna for millimeter wave

Phased array system is used to scan an antenna beam to given angles in space. It consists of multiple stationary antenna elements, which are fed coherently, and uses variable phase shifter at each element. The phase shifter is one of the main parts of phased array antennas but it causes loss and complexity is making it. Inevitably, recent demands for highly flexible array control have highlighted the feed network offered by digital control such as, butler matrix for less complexity and loss. The butler matrix makes the orthogonal sets of beams with uniform aperture illumination using switches. But it needs four 90deg hybrids and two crossovers to make a four beam array antenna. These 90deg hybrids and crossovers worsen not only the antenna phase characteristics and operating bandwidth but also the system complexity. We propose a simple feed network for a four beam array antenna with just one 90deg hybrid, two switches, and delay lines. The merit of the proposed antenna is less complexity, in comparison with four beam butler matrix and easy fabrication due to planar structure.