Kwok Kan So

60 GHz Plated Through Hole Printed Magneto-Electric Dipole Antenna

A wideband unidirectional antenna, which is composed of a planar electric dipole and a magnetic dipole formed by a vertically-oriented shorted patch antenna, is presented for millimeter wave applications. The antenna is realized by a plated through hole printed technique with the use of a microwave substrate and is excited by a T-shaped coupled strip feed. An impedance bandwidth of 33% (S11 ≤-15 dB) from 50 to 70 GHz is achieved. Stable radiation patterns with low cross polarizations and a stable antenna gain of ~7.5 dBi are achieved across the entire operating bandwidth. This single antenna element yields advantages of wideband, good directional radiation pattern and low fabrication cost.

Small Antennas in Wireless Communications

The objective of this paper is to provide the context, physical insight, and perspective on antennas in wireless communications. Although it does not mean to be comprehensive, the four key technologies related to small antenna designs to be reviewed and discussed, including multiband planar inverted-F antennas, broadband folded patch antennas, compact differentially fed antennas, and miniature circularly polarized patch antennas, would cover a wide range of topical interests and practical applications. A brief overview of computer software for analyzing these antennas is also provided. Hopefully, this paper will be beneficial for the diverse engineering readership of the IEEE.

Virtually Shorted Patch Antenna for Circular Polarization

This letter presents a new circularly polarized patch antenna with loaded shorting elements to achieve symmetric broadside radiation and size reduction. The loaded elements are parasitic to the driven patch, but are shorted to the ground plane. Conventionally, shorting pins or walls are a common technique for reducing the size of the antenna. However, deterioration in broadside radiation with high cross-polar level occurs. The proposed shorting elements provide a solution for size reduction of the radiating patch while maintaining good broadside radiation pattern. Since the radiating patch is effectively shorted to the ground at the operating frequency, it is designated as a virtually shorted patch antenna (VSPA).

Bandwidth enhancement and frequency tuning of the dielectric resonator antenna using a parasitic slot in the ground plane

The slot-fed hemispherical dielectric resonator antenna (DRA) with a parasitic rectangular slot in the ground plane is studied in this paper. It is found that the length and position of the parasitic slot can be used to widen the DRA bandwidth or to tune the DRA frequency. The exact DRA Greens function is used in the formulation, and the unknown slot currents are solved using the method of moments. Measurements were carried out to verify the calculations, and good agreement between theory and experiment is obtained.

Rectangular waveguide excitation of dielectric resonator antenna

In this communication, the waveguide-fed dielectric resonator antenna (DRA) is proposed and investigated. The waveguide is terminated by a baffle ground plane in which a coupling slot is cut, and the DRA resides above the coupling slot. To enhance the coupling, a second DR is placed on the other side of the slot inside the waveguide. The measured return loss, radiation patterns, and antenna gain of this novel configuration are discussed in this paper.

A circularly polarized dielectric resonator antenna excited by an asymmetrical U-slot with a backing cavity

A cavity-backed circularly polarized dielectric resonator antenna (DRA) excited by an asymmetrical U-slot is investigated theoretically and experimentally. The finite-difference time-domain method using nonuniform orthogonal grids is employed to study the new configuration, with the excitation modeled by an independent resistive voltage source. The return loss, input impedance, axial ratio, and radiation pattern of the antenna are studied. Reasonable agreement between theory and experiment is obtained.

Frequency-tunable designs of the linearly and circularly polarized dielectric resonator antennas using a parasitic slot

A method for tuning the operation frequency of a dielectric resonator antenna (DRA) in the design stage is proposed. The method employs a parasitic annular slot, which can be applied to both the linearly-polarized (LP) and circularly-polarized (CP) DRAs. To demonstrate the former, an annular-slot-excited hemispherical DRA is used. By changing the radius of the parasitic slot, the operating frequency of the antenna can be adjusted while maintaining good impedance match and stable radiation patterns. For the CP case, a CP DRA excited by a shorted annular slot is used for the demonstration of this idea. It is found that good impedance matches and axial ratios can be obtained across the tunable frequency range. The radiation patterns are, again, stable across the frequency range. The problems are formulated using the Greens function approach, with the unknown slot currents solved using the method of moments. Measurements were carried out to verify the theory, and reasonable agreement between them is obtained.

Theory and Experiment of the Wideband Two-Layer Hemispherical Dielectric Resonator Antenna

The two-layer hemispherical dielectric resonator antenna (DRA) excited by an annular slot is investigated. The slot excitation can be placed in the inner or outer dielectric layer, and the two configurations are studied and compared in this paper. Both problems were solved rigorously using the Greens function approach and the method of moments. The maximum impedance bandwidth and a new bandwidth that considers the field pattern are investigated. Good agreement between the calculations, measurements, and HFSS simulations is obtained.

Bandwidth Enhancement of a Monopolar Patch Antenna With V-Shaped Slot for Car-to-Car and WLAN Communications

A monopolar patch antenna with a V-shaped slot for car-to-car (C2C) and wireless local area network (WLAN) communications is presented in this paper. To widen the impedance bandwidth of the antenna, techniques for adding a shorting pin and a V-shaped slot are applied to an equilateral triangular patch. By properly placing the shorting pins on an equilateral triangular patch, two operating modes, i.e., TM10 and TM20, are obtained. The presence of the V-shaped slot can generate an additional TM11 mode. These three resonances found in the operating frequency bandwidth resulted in a wideband characteristic. The proposed antenna can operate from 4.82 to 6.67 GHz for the reflection coefficient ≤ -10 dB with the gain of around 5.0 dBi. In addition, an omnidirectional radiation pattern is yielded by a coaxial center-fed probe excitation. The antenna has a thickness of 0.09λg (at the center frequency of 5.5 GHz), which is easily hidden on the roof of a vehicle for C2C communication. This proposed design can also be used as indoor base-station antennas for WLAN communication.

Miniaturized Circularly Polarized Patch Antenna With Low Back Radiation for GPS Satellite Communications

A new size-reduction technique for circularly polarized (CP) patch antenna with the use of parasitic shorting strips is presented. The operating frequency of the CP patch antenna can be controlled by those parasitic shorting strips. Rectangular, U-shaped, and meandering shorting strips are studied. It is found that the size and the back radiation of the patch antenna can be reduced simultaneously. Good impedance matching and CP radiation characteristics can be achieved with different shapes of the shorting strips. The proposed antenna with meandering shorting strip is measured. Good agreement between analytical and experimental results is obtained.