Simple Feeding Structure Research Articles

Low-Profile PIFA Array Antennas for UHF Band RFID Tags Mountable on Metallic Objects

Two PIFA array antennas, designed for UHF band RFID tags mountable on metallic objects, are presented in this paper. The proposed array antennas are fabricated on a very thin substrate with a thickness of 0.8 mm. The first array that has shorting pins placed at the outer edges of PIFAs is fed by two quarter-wavelength microstrip lines. This array has a simple feeding structure, which is its main advantage. Meanwhile, the second array has shorting pins located at the inner edges of PIFAs, and incorporating additional matching stubs into the quarter-wavelength microstrip lines is needed to achieve complex impedance matching, which can offer a broad bandwidth. By properly selecting the spacing between the PIFAs, an enhanced antenna gain and a good reading-range performance can be obtained for both array antennas. In addition, the two array antennas proposed are studied mounted on differently sized metallic plates. It is found that there is a negligible influence of the metal-plate size on the reading range is found for the second array antenna, which is superior to the first one.

Analysis and Design of Tapered Slot Antenna for Ultra-Wideband Applications

The tapered slot antenna, such as Vivaldi, has been widely used due to its ultra-wideband, high gain, simple feed structure, and easy fabrication. However, there is no rigorous analytical theory for this type of antenna. This paper analyzed the metal parts of a tapered slot antenna in a conical coordinate system with the medium analyzed in rectangular coordinates. This mixed mode gave an approximate analytical form for the tapered slot antenna with the field distribution and radiation characteristics. A planar tapered slot antenna was proposed according to the results of the analysis methods. Measured and simulated results demonstrate the antenna performance. The antenna shows good impedance matching over a wide bandwidth of 9 GHz, from 2 GHz to 11 GHz, and good radiation patterns. It is suitable for ultra-wideband applications.

A Novel Shorted Rectangular-Loop Antenna for Circularly Polarized Wave Operations

A shorted rectangular-loop antenna is presented for circular polarization applications. The proposed antenna is connected to feeding pin in one end of rectangular-loop metal and shorted to ground in the other end of rectangular-loop metal. It can own wide impedance bandwidth, wide AR bandwidth, and high gain performances in the low profile configuration, especially, without a balanced feeding structure. It is well-known situation of open-loop antenna with circular polarization. The proposed antenna in this paper is interesting for shorted-end of loop antenna, and then, it still has the similar antenna performances as open-loop antenna. An example of WLAN 2.4 GHz application is given. The antenna height is adjusted to fit the required AR bandwidth. The measured impedance's center frequency and bandwidth are 2.56 GHz and 17.5%, respectively. Also, the AR's center frequency and bandwidth are 2.44 GHz and 4.1%, respectively. Both impedance and AR bandwidths satisfy the specification of WLAN 2.4 GHz applications. Besides, radiation patterns are broadside radiation and antenna gain in the operating band is about 8 dBic. The proposed shorted rectangular-loop antenna can be applied to high gain antenna or become the elements of higher gain antenna by its good performances and simple feeding structure in a low profile configuration.

A small RFID tag antenna with bandwidth‐enhanced characteristics and a simple feeding structure

AbstractA small RFID tag antenna in a UHF band is proposed in this article. Using dual resonance, the antenna has bandwidth‐enhanced characteristics without an additional matching circuit. The meander shape of the proposed antenna helps to reduce the antenna size. The bandwidth of the antenna is enhanced by two radiators that create dual resonance in adjacent frequencies. When the length and location of each radiator are adjusted, the antenna can make dual resonance at an arbitrary impedance point, thereby enabling the antenna to match an RFID tag chip in a wide frequency range. According to the simulated and measured results, the proposed antenna has almost double the bandwidth of a regular antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2027–2031, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23576