Phased Arrays in Radar and Communication Systems. Pattern Characteristics and Synthesis of Linear and Planar Arrays. Patterns of Nonplanar Arrays. Elements, Transmission Lines, and Feed Architectures for Phased Arrays. Summary of Element Pattern and Mutual Impedance Effects. Array Error Effects. Special Array Feeds for Limited Field of View and Wideband Arrays.

Phased Array Antenna Handbook

Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency patch antennas is presented, and future perspectives are outlined. Geometries are discussed in particular.

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Dual-frequency patch antennas

The electromagnetic properties of electrically thick rectangular microstrip antennas were investigated experimentally. Antennas were fabricated with different patch sizes and with electrical thicknesses ranging from 0.03 to 0.23 wavelengths in the dielectric substrate. The resonant frequencies were measured and compared to existing formulas. The bandwidth was calculated as a function of electrical thickness and the antenna radiation patterns were measured.

An experimental investigation of electrically thick rectangular microstrip antennas

Experimental results of a dual-frequency microstrip antenna consisting of two stacked annular rings of outer radii 5 cm and inner radii 2.5 cm are presented. Fabricated on a Duroid substrate with relative permittivity 2.32 and thickness 0.159 cm, the separations of the two resonant frequencies range from 6.30-9.36 percent for the first three modes. The frequency separations can be altered by means of an adjustable air gap between the lower ring and the upper substrate.

Dual-frequency stacked annular-ring microstrip antenna

A single-feed low-profile and easy to fabricate circularly polarized microstrip patch antenna has been developed for GPS applications. For dual frequency operation, four slots are etched near edges of the patch and a crossed slot etched in the center for generating circular polarization. In order to reducing the frequency ratio of two frequency bands of the antenna, the patch is loaded by four short circuit microstrip stubs. The paper reports several simulation results that confirm the desired characteristics of the antenna. Using stub loading, the frequency ratio of two bands of the antenna can be, even, reduced to 1.1.

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A Dual-Band Circularly Polarized Stub Loaded Microstrip Patch Antenna for GPS Applications

A previously derived theory is applied to a microstrip antenna with a reactive load to produce a dual-band radiator. A model consisting of a rectangular patch radiator loaded with a variable length short-circuited coaxial stub was investigated experimentally. Comparisons of theoretical predictions and experimental data are made for the impedance and resonant frequencies as a function of the position of the load, the length of the stub, and the characteristic impedance of the stub.

Dual-band reactively loaded microstrip antenna

The design and experimental measurement of a dual-band, monolithic microstrip antenna is presented. The structure utilises a short-circuited length of microstrip transmission line to provide reactive loading and, thereby, retains the low-profile characteristic of a normal microstrip patch radiator.

Dual-band microstrip antennas with monolithic reactive loading

Design To most simply model the previously investigated coaxially loaded antennas one can straightforwardly substitute a short-circuited microstrip line attached to the edge of a rectangular patch element. Use of a coaxial load was considerably more flexible, however, since the separation between resonances as well as the resonant frequencies themselves could also be adjusted by moving the load position away from the edge. To emulate this variation the microstrip line has also been designed with a specified "inset" dimension as shown in figure 1. Unfortunately positioning the load in the interior of the patch results in yet another parameter, g, the gap spacing between the line and the radiator. This parameter seems to have little effect on the upper resonance but tends to reduce the lower resonant frequency as the gap spacing is

http://ieeexplore.ieee.org/iel6/8257/25863/01149499.pdf

S. Davidson

Papers

Dual-band reactively loaded microstrip antenna

Dual-band microstrip antennas with monolithic reactive loading

Monolithic design of dual-band microstrip antennas using reactive loading