Young Seung Lee

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

A multiplexed Cassegrain reflector antenna with a 2 × 2 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 (l = 0, ±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 2 × 2 OERW 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 12.7 [dB] and 17 [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.

A Validation Model for the Statistical Power Balance Method Using a Reverberation Chamber

This paper proposes a validation model using a reverberation chamber for verification of the effectiveness and accuracy of the statistical power balance (PWB) method. The PWB method treats electromagnetic (EM) field distributions in certain environments as a representative value of an “ensemble” average, so a reverberation chamber is utilized as a testing apparatus to experimentally simulate the sets of measurement field “ensemble” inside a complex environment. Measurements are performed with various test conditions for environmental loss using flat absorbers, and front and side doors of the chamber. Comparison between the PWB analysis and the measurement results shows good agreement, indicating the usefulness of this statistical analysis method for stating the electromagnetic field inside the EM zone

Static Field by an Infinitely Long Cylinder Penetrating a Circular Aperture

Absract An electrostatic problem of a long conducting cylinder penetrating a circular aperture on a conducting plane is solved in this study. The Weber transform and mode matching are utilized to determine the electrostatic potential. The boundary conditions are enforced to obtain series equations for the discrete modal coefficients. Computations are carried out to illustrate the static fields, surface charge densities, and capacitance changes for various geometries.

Extension of a Plane Wave Integral Representation for Fields in Lossy Reverberation Chambers

Abstract This article develops a theoretical extension of a plane wave integral representation to account for fields inside a reverberation chamber with an arbitrary lossy configuration. It is shown that the presented development can explain a general over-moded reverberation chamber with the anisotropy condition; i.e., each of the six complex field components possesses non-zero mean values and different variances from one another. It is found that the ensemble average of the absolute square of the total field can satisfy the homogeneity property (i.e., being independent of position), despite the correlation between the angular spectrum components of the received field. To the of the best authors knowledge, a detailed physical explanation of a high-loss reverberation chamber based on this extended plane wave integral formulation is not currently available due to the difficulty finding a homogeneity property. The theoretical expressions and physical explanations can not only provide fresh insights into the understanding of a lossy reverberation chamber, but they can also be extended to other non-ideal lossy environments and statistical methods. The measured mean power densities inside a reverberation chamber with a variety of lossy configurations are compared with the values obtained from the power balance method, showing the importance of this theoretical development and several future directions for research.

Electrostatic solution for 3-port pyramidal cell

The electrostatic potential in the 3-port pyramidal cell is investigated by solving Laplace’s equation. Potentials are expressed in eigenfunctions in spherical coordinates. The mode-matching method is applied with the orthogonality of sinusoidal function to obtain simultaneous series equations. Numerical computations are carried out to illustrate the behavior of potential and electric field.

Effect of Eccentricity on the Charge Distribution by a Cylinder-Penetrated Circular Aperture

This letter considers the effect of the eccentricity on the static field and charge distribution for a circular aperture pierced by a long cylinder. The conformal mapping method is used to convert the problem of an eccentric aperture into that of a concentric aperture. The Weber transform, superposition principle, and mode matching are employed to calculate the static potential for this concentric problem. Numerical computations illustrate the behavior of potential distribution, surface charge density, and partial charges on the plane for various aperture eccentricities.

Reactive near-field to near-/far-field transformation in semi-anechoic chamber

In this paper, the technique of the reactive near-field to near-/far-field transformation has been proposed. The different thing compared with the previous work is that the environment of the semi-anechoic chamber with the ground plane was assumed during the transformation. The sources of electronic device are reconstructed from the detected reactive near-field. And then, the composite array source using the image theory is built, and then the transformation from the composite source to the near-/far-field are performed. For the verification, the simulated results have been utilized, and their results show small errors. Therefore, the proposed technique in this paper could be applied to predict the radiated field at 3 m or 10 m without the expensive large semi-anechoic chamber.