Vahakn Nalbandian

Planar dual-band microstrip antenna

A novel dual-band microstrip antenna is introduced. The entire structure is planar and can be easily mass-produced by using printed-circuit technology. The antenna consists of multiple layers with metallic strips placed at one of the dielectric interfaces under the radiating patch. The resonant frequencies can be selected over a wide frequency range, and the impedance matching at those two frequencies is relatively simple. The physically intuitive cavity model is used for the analysis. A relatively simple design scheme is included. >

Planar circularly polarized microstrip antenna with a single feed

A novel circularly polarized (CP) microstrip antenna is introduced. The antenna is fed with a single coaxial probe and the structure is planar. The CP bandwidth is much larger than available single-probe microstrip antennas and the CP radiation quality is excellent over the entire upper hemisphere.

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>>

Planar, single-feed, circularly polarized microstrip antenna with enhanced bandwidth

The most common circularly polarized (CP) microstrip antennas are made by using a splitting network that feeds the two adjacent sides of a square patch with signals of equal magnitude and 90/spl deg/ phase difference. This splitting network becomes cumbersome especially in large arrays. Single-feed CP microstrip antennas have been investigated by a number of authors eliminating the need for a complex splitting network. Unfortunately these antennas have very narrow CP bandwidth. In the proposed antenna, a double layer microstrip is used. The two orthogonal modes occupy different cavities and the 90/spl deg/ phase difference between the modes is achieved by coupling holes between the two resonant cavities. The coupling hole concept was first introduced by Bethe (1944), and further refined by Collins (1966). In an earlier paper by Lee et al. (1996) each cavity had two side walls in order to suppress any unwanted modes. Unfortunately, side walls make fabrication difficult, especially in array structures. In this paper the side walls are eliminated and the CP bandwidth is substantially increased. In addition, the CP axial ratio does not degrade near the horizon.

Circularly polarized microstrip antenna with a single feed

A novel circularly polarized (CP) microstrip antenna with a single coaxial feed is introduced. The antenna consists of two layers, each radiating fields which at the zenith are perpendicular to each other with 90/spl deg/ phase difference. The CP bandwidth is substantially higher than that of the previously reported CP microstrip antennas with two nearly degenerate modes. In principle, a perfect CP radiation is feasible without the input impedance mismatch. The CP design procedure is independent of the feed location.

Planar double-layer leaky-wave microstrip antenna

This paper presents a double-layer leaky-wave microstrip antenna that is entirely planar for easy fabrication. The cavity model and the full-wave spectral domain method are used to analyze the proposed structure. The results from these two approaches agree well with experimental data. The planar structure makes the leaky-wave antenna convenient for implementation in a monolithic microwave integrated circuit (MMIC) environment. Also, due to the flexibility of the microstrip structure, the geometrical shape can be modified for other desirable radiation patterns.

Impedance matching of a dual-frequency microstrip antenna with an air gap

A microstrip antenna has been proposed to operate at dual frequencies. The microstrip is a single layer patch with nonradiating edges closed with a conducting foil. Resonant frequencies are altered by varying the air gap under the patch. The separation of the resonant frequencies can be nearly zero and has no upper limit in principle. The input impedance is easily matched by shifting the air gap. The radiation patterns are not affected by modification for dual-frequency operation. >

Tapered leaky-wave ultrawide-band microstrip antenna

Previous wideband or ultrawideband antennas have been bulky such as horn, helical and log periodic antennas. Conventional microstrip antennas are planar, conformal and inexpensive but have narrow frequency bandwidths. It is extremely desirable to have antennas with all the advantages of microstrip antennas and large bandwidths. The proposed wideband planar leaky-wave microstrip antenna provides such a need.

Gain enhancement of a thick microstrip antenna by suppressing surface waves

The most detrimental aspect of microstrip antennas for more widespread usage is their inherent narrow bandwidth. One simple way to increase the bandwidth is to use a thick substrate. As the layer thickness increases, the surface waves become highly excited. The surface waves are eventually dissipated at the substrate edges. This unwanted radiation reduces the antenna gain. In addition the radiation is uncontrollable and usually interferes with the main beam destructively to degrade the radiation quality. The purpose of this paper is to introduce a new device to reduce the surface wave excitation. The reduction of the surface waves is achieved by using parasitic elements next to the radiation edges of regular microstrip antennas. Such parasitic elements are usually used for increasing the bandwidth. These patches are placed on a surface coplanar to the main radiation patch. In the proposed antenna, the parasitic elements are between the top radiation surface and the ground plane. The surface waves reflected from the parasitic elements feed back to the microstrip cavity, thus enhancing the radiation efficiency. A simple cavity model is used for the analysis.<<ETX>>

Multi-layer dual-band microstrip antenna

Microstrip antennas have many advantages over the conventional antennas except their inherent narrow bandwidth. In many applications, only distinct frequency bands may be needed instead of a continuous operating frequency range. Dual-band microstrip antennas have been suggested to cover two narrow frequency bands while retaining their advantages as microstrip antennas. A new dual-band microstrip antenna is introduced. The advantage of the proposed antenna over other available dual-band microstrip antennas is its easy fabrication. The antenna consists of multiple layers and is planar without any structure perpendicular to the ground plane. Those vertical features are difficult to fabricate and are common in other dual-band microstrip antennas. The planar structure of the multi-layer microstrip antenna is attractive from a manufacturing point of view, especially for mass production using printed-circuit technology.<<ETX>>