Chanam Lee

Dual-frequency microstrip antenna with inserted strips

The authors introduce a novel dual-frequency microstrip antenna which is within a single structure and does not require vertical connections. The resonant frequencies can be varied over a wide range of frequency. The input impedances are matched at both resonant frequencies in a much easier manner than the available dual-band microstrip antennas. The fabrication process is relatively simple.<<ETX>>

Antenna Efficiency Measurements in a Reverberation Chamber Without the Need for a Reference Antenna

This letter proposes a reverberation chamber approach for antenna efficiency measurement that does not require a reference antenna, that allows the antenna efficiency to be determined over a potentially wide frequency, range and which is applicable to electrically large antennas, thus demonstrating clear advantages over currently employed techniques for antenna efficiency measurement. This letter outlines the proposed method and presents results for a monopole antenna that demonstrate the efficiency can be obtained with reasonable accuracy over a range of frequencies.

Dual-band microstrip antenna with an airgap

A novel dual-band microstrip antenna is demonstrated. The resonant frequencies can be varied over a wide frequency range and the input impedances are easily matched for both resonance frequencies. The radiation pattern is not affected by the modification for the dual-frequency operation. The design process is physically intuitive and relatively simple.<<ETX>>

Electrically small microstrip antenna with height discontinuity

With the proposed scheme, the size of a microstrip antenna can be reduced as much as desired. However the antenna efficiency as well as the bandwidth will be lowered because of the reduced aperture area, which will be communicated further in the future.

Radiation efficiency of a microstrip antenna with height discontinuity (MAHD)

Radiation efficiency of a microstrip antenna with a height discontinuity (MAHD) is evaluated based on a cavity model. The radiation efficiency of an MAHD is shown to be better than that of a comparable standard microstrip antenna. The field distributions are given to explain how such better efficiency is possible. The numerical results are relatively in good agreement with the simulation results of HFSS.

Beam-steerable flat-panel reflector antenna

Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-borne applications is an umbrella-type reflector antenna that can be folded while being lifted into Earth orbit. We propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the curved main reflector is replaced by a flat reconfigurable surface for easy packing and deployment in space. A number of waveguides are placed on the flat surface so that the effective surface impedances at the waveguide openings are configured to give a focused beam. The length of each waveguide is adjusted so that, after the incident wave is reflected from the back conducting plate, the reflected wave has a phase at the open waveguide end such that the beam is focused in the predetermined direction. In other words, the law of reflection does not apply at the reconfigured surface. Also, beam steering can be achieved by adjusting the waveguide heights. Since the height of each waveguide is always less than a half of a wavelength, all the waveguide plates are relatively short. If the waveguide heights are controlled by an electronic means, an electronically beam-steerable antenna results.