Mikko Keskilammi

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.

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.

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.

Performance issues on the wireless 2.4 GHz ISM band in a multisystem environment

Adoption of wireless systems in consumer electronics products is increasing rapidly. The 2.4 GHz industrial scientific and medical (ISM) band offers an attractive platform for the implementation of different mass products due to worldwide appearance and existing standards, like the most well-known, Bluetooth, wireless LAN and HomeRF. Popularity and multiple standards present also a threat to the usability of this popular band, and it is essential to understand how the different systems affect each other. This paper presents both the theoretical background of these systems and measured results.

Different kinds of walls and their effect on the attenuation of radiowaves indoors

This paper describes a study of how different walls and wall materials affect the attenuation of electromagnetic waves with frequencies 433MHz, 868MHz, 2.4GHz, and 5.0GHz. The attenuation of the transmitted signals has been studied by creating propagation models using an advanced computer tool. Concrete, wood, and plaster board are the studied wall materials. Furthermore, different wall thicknesses (0.15m, 0.20m, 0.25m, 0.30m, 0.40m) have been used. The long term goal of the research is to compile an easy-to-understand manual containing information on what kind of an effect do walls that differ by material and thickness have on the attenuation of electromagnetic waves. Thus, the simulation construction has been left fairly simple on purpose. Finally, an example of how the information can be used in practice is shown.

A novel Bluetooth antenna on flexible substrate for smart clothing

The development of wearable computer systems and smart clothing has been rapid. They are becoming more and more lightweight and soon we should see a wide range of unobtrusive wearable and ubiquitous computing equipment integrated into everyday wear. Rapid progress in wireless communication promises to replace wired-communication networks, in which antennas play a more important role. This paper presents an antenna design for wearable applications. Due to wearable system demands this paper discusses mainly physically small planar antennas. A design example is given in which a flexible PIFA (FlexPIFA) structure for single and dual-band operation is introduced into smart clothing in Bluetooth and UMTS fields. To our knowledge this is first time a thin and flexible antenna has been designed for commercial smart clothing. Measured results are compared with simulations and good agreement was observed. In addition the effect of the human body on antenna performance is discussed.

An intelligent 2.45 GHz beam-scanning array for modern RFID reader

As part of the general identification procedure, radiofrequency identification (RFID) is an essential field of research in the modern industrial automation. Radio frequency identification is among the most technically advanced methods of collecting data automatically. This paper presents an intelligent 2.45 GHz beam-scanning array for a RFID reader. The design is based on the paper industrys needs but is still applicable to other fields of industry. A new current amplitude distribution is applied to feed the array elements. With this amplitude current distribution the -37.5 dB sidelobe level is achieved while maintaining the half power beamwidth at the same level as the Dolph-Chebyshev current amplitude distribution with a sidelobe level of -30 dB. Thus, the new distribution is a compromise of binomial and Dolph-Chebyshev. The system level description of the intelligent beam-scanning array is also discussed.

Textile antennas: Effect of antenna bending on radiation pattern and efficiency

In this paper the radiation characteristics of three different textile antennas, namely, a conventional patch antenna, a dual-band antenna, and an EBG antenna is focused. The results show that antenna bending has remarkable effect on radiation characteristics, i.e., radiation pattern shape, gain, and radiation efficiency. It is intuitively clear that antenna bending broaden the radiation pattern in the bending plane, which results a drop of gain. In addition, it was also noticed that radiation efficiency slightly reduces due to the antenna bending. These results again show that EBG antenna performs better compared to the conventional antenna.

Indoor propagation comparison between 2.45 GHz and 433 MHz transmissions

This paper describes a study of how 2.45 GHz electromagnetic waves propagate indoors. 2.45 GHz is a typical Bluetooth frequency. Propagation models with both one and several transmitters have been made using an advanced computer program. Furthermore, a model of the propagation of 433 MHz radio waves has been made and used as a standard point of comparison. To make sure that such models are reliable, the study was renewed using a real 2.45 GHz transmitter and receiver and then comparing the results to those given by one of the propagation models. Finally, the suitability of Bluetooth for indoor use is discussed.

Dual-band and wide-band PIFA with U- and meanderline-shaped slots

This paper describes a novel dual-band planar inverted-F antenna (PIFA) for which the impedance bandwidth can be remarkably improved. The proposed PIFA uses a single feed only. Two top plate geometries, a U-shaped and a novel meanderline-shaped slot, are discussed. An example is given for frequency bands of 2.4 GHz and 5.2 GHz. Simulation based upon the method of moments is used to model the performance of the antennas. Comparisons with measured results on fabricated antenna structures are provided for simulations validation.