Markku Kivikoski

Single-feed dual-band planar inverted-F antenna with U-shaped slot

The development of small integrated antennas plays a significant role in the progress of rapidly expanding wireless communication applications. This paper describes a novel dual-band planar inverted-F antenna (PIFA) for wireless local area network applications. The proposed PIFA uses single feed only. A novel top-plate geometry, a U-shaped slot, is discussed. An example is given for this novel slot shape for frequency bands of 2.4 and 5.2 GHz. Simulation based upon the method of moments (MoM) is used to model the performance of the antenna. Comparisons with results measured on fabricated antenna structures are provided for simulations validation.

Effects of metallic plate size on the performance of microstrip patch-type tag antennas for passive RFID

Metallic objects are challenging for passive ultra high frequency (UHF) spectrum radio frequency identification (RFID) systems due to the effects of conductive materials on tag antenna performance. In this letter, we analyze the effects of metallic plate size on the performance of microstrip patch-type tag antennas. Microstrip patch antennas with regular ground plane and electromagnetic band gap (EBG) ground plane are studied attached to two differently sized metallic plates. Analysis is based on finite element method (FEM) simulations and practical read-range measurements.

A small planar inverted-F antenna for wearable applications

Small printed antennas will replace the commonly used normal-mode helical antennas of mobile handsets and systems in the future. This paper presents a novel small planar inverted-F antenna (PIFA) which is a common PIFA in which a U-shaped slot is etched to form a dual band operation for wearable and ubiquitous computing equipment. Health issues are considered in selecting suitable antenna topology and the placement of the antenna. Various applications are presented while the paper mainly discusses about the GSM applications.

Chip Impedance Matching for UHF RFID Tag Antenna Design

Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance match between the antenna and the chip is crucial in RFID tag design. It directly influences RFID system performance characteristics such as the range of a tag. It is known that an RFID microchip is a nonlinear load whose complex impedance in each state varies with the frequency and the input power. This paper illustrates a proper calculation of the tag power reflection coefficient for maximum power transfer by taking into account of the changing chip impedance versus frequency.

Wearable antennas in the vicinity of human body

A wearable antenna can be defined as an antenna which is designed and meant for part of clothing. In this paper, we address the following issues: (i) textile antenna input-match performance in the vicinity of the human body; (ii) textile antenna radiation characteristics; (iii) power absorbed in the human body; and (iv) peak and averaged SAR over 1 g tissue at the 2.4 GHz ISM band. To our best knowledge, this paper presents the first in-depth results concerning the textile antenna performance in the vicinity of the human body. Numerical results with and without the presence of the human body are discussed in detail.

Dual-band wearable textile antenna

Future utilization of smart clothing will necessitate applications of multi-function and multifrequency wearable antennas. This work addresses the development of a dual-band textile antenna for wearable applications. The antenna is for GSM operation in the 1900 MHz band and for WLAN operation in the 2.4 GHz band. The proposed antenna has a U-shaped slot-structure mounted on the surface of fleece fabric. The proposed antenna structure is easy to attach to clothing and the structure does not limit the possible antenna placements. Details of the proposed antenna design are described, and the experimental results of a prototype are presented.

A novel dual-frequency circularly polarized rectenna

A novel dual-frequency circularly polarized shorted ring-slot rectenna (rectifying antenna) for wireless power transmission at 2.45 and 5.8 GHz is proposed. The rectenna is composed of two nested microstrip-fed shorted annular ring-slot antennas and two rectifier circuits. Output DC voltage of over 2 V at the lower frequency band and over 1 V at the higher frequency band is achieved at a transmission distance of 2 m.

Folded dipole antenna near metal plate

The paper presents the effects on antenna parameters when an antenna is placed horizontally near a metal plate. The plate has finite size and rectangular shape. A folded dipole antenna is used and it is placed symmetrically above the plate. The FEM (finite element method) is used to simulate the dependency of antenna parameters on the size of the plate and the distance between the plate and the antenna. The presence of the metal plate, even a small one if it is at the right distance, causes very big changes in the behaviour of the antenna. The bigger the plate, especially in width, the sharper and narrower are the lobes of the radiation pattern. The antenna height defines how many lobes the radiation pattern has. A number of the antenna parameters, including impedance, directivity and front-to-back ratio, change periodically as the antenna height is increased. The resonant frequency of the antenna also changes under the influence of the metal plate.

Effect of conductive material on wearable antenna performance: a case study of WLAN antennas

This work focused on studying the effects of different materials on textile WLAN antenna performance. The results of this study can be used to improve the already introduced textile antennas. The results with different conductive element materials show that textile antennas can be fabricated using both conductive tape and fabrics without affecting the antenna performance. Discontinuations that are perpendicular to current flow need to be avoided and fabrics need to be densely knitted and use sufficiently conductive material. Eventually, textile antennas can replace the printed circuit board antennas in wearable applications.

Effect of textile materials on wearable antenna performance: a case study of GPS antennas

Recently, textile antennas have been presented in international conferences. These studies have demonstrated that fabrics are suitable for microstrip antenna substrates. In this paper, our study focuses on the characterization of different synthetic fabrics suitable for circular polarized micro-strip antennas. Special attention is paid to GPS antennas. Five different synthetic textile materials are chosen for the comparison. The word textile is typically used for antenna class and fabric to describe a particular material. However, in many cases these words are interchangeable.