A novel wideband unidirectional antenna composed of a planar electric dipole and a shorted patch antenna is presented. The antenna is excited by a Γ-shaped strip feed line. A wide impedance bandwidth of 43.8% (SWR≤1.5) from the frequency of 1.85 to 2.89 GHz is achieved. Stable radiation pattern with low cross- polarization, low backlobe radiation, nearly identical E-and H-plane patterns and an antenna gain of ~8dBi is found across the entire operating bandwidth.

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A New Wideband Unidirectional Antenna Element

A novel dual-polarized magneto-electric dipole antenna excited by two -shaped strips is presented. The antenna achieves a common impedance bandwidth of 65.9% (SWR < 2) at both input ports. The antenna has excellent performance in isolation, which is more than 36 dB between the two input ports, and the gain of the antenna is about 9.5 dBi. The radiation pattern and bandwidth over the operating frequency band are very stable.

A Broadband Dual-Polarized Magneto-Electric Dipole Antenna With Simple Feeds

In this paper, stringent requirements imposed on the design of base station antennas for mobile communications are summarized. Conventional techniques for implementing base station antennas are reviewed. The complementary antenna concept of combining an electric dipole with a magnetic dipole is reconsidered. Recently, this kind of antenna has been commonly called a “Huygen's source.” The purpose is to develop wideband unidirectional antennas with stable frequency characteristics and low back radiation. Based on this concept, the magnetoelectric dipole was invented by integrating an electric dipole with an -probe fed shorted quarter-wave patch antenna. A number of magnetoelectric dipoles with different radiation patterns and different polarizations have been developed in recent years. An overview of the characteristics of this new class of complementary antennas is presented. Major design challenges are explained. Finally, a new magnetoelectric dipole that is low in profile and robust in structure is presented. The magnetic dipole part of this antenna is realized by a triangular-shaped loop antenna. The antenna is inherently direct current (dc) grounded, which satisfies the requirement for outdoor applications.

The Magnetoelectric Dipole—A Wideband Antenna for Base Stations in Mobile Communications

A planar array antenna having radiating elements characterized by dual simultaneous polarization states and having substantially rotationally symmetric radiation patterns. A distribution network, which is connected to each dual polarized radiator, communicates the electromagnetic signals from and to each radiating element. A ground plane is positioned generally parallel to and spaced apart from the radiating elements by a predetermined distance. The conductive surface of the ground plane operates to image the radiating elements over a wide coverage area, thereby enabling a radiation pattern within an azimuth plane of the antenna to be independent of any quantity of radiating elements. Side walls, placed on each side of the array of radiators, can operate in tandem with the ground plane, to reduce the half-power beamwidth in the azimuth plane for a selected radiator design. A central polarization control network (PCN), which is connected to the distribution network, can control the polarization states of the received signals distributed via the distribution network by the radiating elements.

Dual polarized array antenna

A new low-profile magneto-electric dipole antenna composed of a horizontal planar dipole and a vertically oriented folded shorted patch antenna is presented. The antenna is simply excited by a coaxial feed without the need of an additional balun. A rectangular cavity-shaped reflector is introduced for enhancing the stability in radiation pattern over the operating frequencies. A parametric study is performed for providing practical design guidelines. A prototype with a thickness of 0.173λ was designed, fabricated and measured. Results show that an impedance bandwidth of 54.8% for SWR ≤ 1.5 from 1.88 to 3.3 GHz was achieved. Stable radiation pattern with low cross polarization, low back radiation and an antenna gain of 8.6 ± 0.8 dBi was found over the operating frequencies. In addition, the antenna is d.c. grounded, which satisfies the requirement of many outdoor antennas.

A Low-Profile Magneto-Electric Dipole Antenna

An antenna element consisting of a slot plus two parasitically excited wires has been found to exhibit many properties useful in array applications. The introduction of the wires provides a means of controlling both the E - and H -plane element radiation patterns. Specifically, the principal plane radiation patterns can be equalized and the directivity increased. If desired, the element pattern can closely approximate a cos \theta pattern in both planes. A 14-dB reduction in interelement mutual coupling is also achievable with this source as compared to a slot alone. A comparison of the characteristics of a four-quadrant 60-slot monopulse array with and without the wire elements indicates a 0.6-dB increase in gain and a significant reduction in back radiation for the former.

F. Kilburg

Papers

An improved element for use in array antennas