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By transmitting some sound through the earshell, an active-sound transmission ear protector is more comfortable than a passive design. The authors explain how careful attention to sound control can improve comfort levels further.

This letter describes an accurate two-dimensional (2-D) hard-source model for finite-difference time-domain (FDTD). The proposed model allows accurate control over the effective radius of a 2-D hard source. In addition, the TM version of the source model is directly applicable as a very accurate 2-D thin-wire model. The proposed model is verified in 2-D for both TM and TE case using a recently introduced method for finding the effective radius of a filamentary 2-D hard source.

The difference equations arising from a Yee discretization of Maxwell's equations produce numerical dispersion artifacts whose effects are widely known. Reduction of these effects is important for accurate modelling over a large number of time steps. Conventional methods for tackling this problem include the usage of higher order differencing schemes and denser sampling rates, both approaches resulting in many cases in comparable additional computational burden. In this work, it is suggested to adopt a radically different approach, i.e., construct a family of new difference equations that are not direct discretizations of the continuous equations, but have solutions that are discretized versions of the continuous solutions, and tend to the continuous limit as Deltaz rarr 0 and Deltat rarr 0. The rationale behind these new equations is described. The first formulation involves a narrowband modified difference equation, for which it is shown that a total elimination of numerical dispersion is achieved for a single frequency, with useful results obtained over a certain frequency band. This formulation can be generalized to multiple frequency equations with higher bandwidths

This paper presents measurement-based calculations for actual aggregate and link throughputs of Bluetooth system. The co-interference between fully loaded piconets formed in a 10*10 sq. meter room is inspected. The results show that the maximum aggregate throughput is gained with 45 active piconets. When comparing the ideal performance with the one based on measured results best overall performance over a distance of 10 meters can be achieved using DM5, DM3 and DH1 packets for data transfer. When the distance is less than 3 meters the use of only DH packets gives the best results.

The FDTD method is used to model microstrip structures fabricated using a 0.35 /spl mu/m CMOS process. Modeling thin metal and oxide layers of 1 /spl mu/m thickness results in a very small vertical cell size. As a consequence, a very short time step is required to ensure stability. This in turn results in difficulties in obtaining simulation data below 20 GHz without resorting to all excessive number of time steps. In this paper, we investigate microstrip structures fabricated on a thin oxide layer from the computational point of view. The problem is to obtain accurate low-frequency data while (i) using a small cell size to accurately model the layer structure resulting in a short time step, and (ii) using a limited number of time steps to reduce the simulation time. To accomplish this, the simulation is excited using a resistive source resulting in fast decay of the incident field. To excite TEM mode in the microstrip, a model to connect the source across multiple cells "in parallel" is presented. Finally, the frequency resolution is improved by using the frequency-shifting technique. The results are validated by comparison to experimental data at 0.5-20 GHz measured using an on-wafer probe station.

Wearable computing and ubiquitous computing are the latest solutions in mobile virtual reality. These technologies together with wireless data transmission enable both augmented reality and multimedia in mobile environments. Wearable and ubiquitous computing are energetically finding their position in the future information society. This paper describes the main requirements of modern mobile VR systems and also highlights the problems of the present systems. The approach is to focus on state-of-the-art mobile VR by describing three implementation cases from Finnish industry as examples of how to use these novel concepts as building blocks for a new economy. Future expectations and development in the field are discussed.

A dual-band circularly polarized (CP) microstrip-fed shorted ring-slot rectenna (rectifying antenna) was designed and its reception performance from both broadside directions was measured and compared at 2.45 GHz and 5.8 GHz ISM bands. CP performance at the lower frequency band was very similar for both directions of reception whereas considerable deviation was detected at the higher frequency band.

This paper is an investigation about the performance of the three Bluetooth low power modes (i.e. hold, sniff and park). The performance metrics of interest were response times from master to slave, from slave to master, and the current consumptions in each mode. From these low power modes the sniff mode offers generally the best response times whereas parked devices have the smallest current consumption. Since the characteristics of each mode offer different functions to the Bluetooth system itself, the final usage defines which mode should be selected.

A secure infrared remote control system is presented. Offering flexible programmability, the presented system matches several data encoding methods and carrier modulation techniques. Arbitrary long data codes can be transmitted within the capacity of the system memory. The low cost of the implementation is due to commercial components and a minimum number of circuits on the small sized printed circuit board. Powered by a battery energy source, the presented system is suitable for electronic door locking purposes for domestic and automotive applications. An example application for a car security access control is presented. The system has been tested under variable environment conditions and found to be very reliable and robust.

We investigated coarseness error related to the finite difference time-domain (FDTD) thin-wire models. We showed that due to coarseness error wires appear longer than the nominal length, and that this error can be considerably larger than that caused by numerical dispersion. Finally, we showed that coarseness error primarily depends on the ratio of wire radius and transverse cell size.

The subject of this paper is a dual frequency microstrip patch antenna operating at 2.45 GHz and 5.2 GHz ISM (industrial, scientific and medical) band. The IEEE 802.11b WLAN (wireless local area network) and Bluetooth standards utilise the 2.45 GHz band and 5.2 GHz is specified as an operating frequency in HIPERLAN (High PErformance Radio Local Area Network) standard. Antenna design was based on the previously developed dual frequency microstrip patch antenna. Adjustment for the desired frequencies, 2.45 GHz and 5.2 GHz, was achieved by using two different multiplying factors and setting the gaps between the two patches so that the return loss would be under 40 dB. Although the antenna was fabricated of a high-loss FR4 substrate material, it performed well having a matching of 32 dB for the lower and 13 dB for the upper resonant frequency. The bandwidth was over 100 MHz for both of these frequencies. FR4 was chosen as a substrate material for cost savings.

A new model for coupling a coaxial cable modeled as a one-dimensional transmission line to an FDTD grid is proposed. The TEM mode is not assumed at the intersection of the coaxial cable and FDTD grid. Instead, at the intersection the transverse electric field components around the center probe need not to be symmetrical and the longitudinal magnetic field component is not assumed zero. For unsymmetrical structures the proposed model describes the problem more accurately compared to a model where the TEM mode is assumed.

Three planar rectennas (rectifying antennas) on different PCB materials have been designed. Patch antennas were designed with a MoM (method of moments)-based simulator while in RF-to-DC conversion circuits microstrip and discrete rectifier diode models were utilized in circuit simulations. The goal was to achieve maximum antenna and conversion efficiency at the desired reception power level. 80% antenna efficiency and 70% conversion efficiency was achieved in simulations. The terms for achieving a sufficient reception power level were considered and compared to the performance of the designed antennas. The accuracy requirements for the realization of these rectenna structures were also defined with the aid of both simulation and measurement results.

As part of the general identification procedure, radio frequency 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 multidimensional beam-scanning array for an RFID reader. The design is based on the paper industry needs but is still applicable to other fields of industry. New current amplitude distribution is applied to feed the array elements. With this amplitude current distribution the -37.5 dB side lobe level is achieved while maintaining the half power beam width at the same as Dolph-Chebyshev current amplitude distribution with the side lobe 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.

In some in-beam experiments, an adjustment of the time structure of the cyclotron ion beam guided to the desired research target by a beamline is sometimes needed. This situation occurs if, for example, the decay times of the reaction products are too short compared to the period corresponding to the beam frequency. In the accelerator laboratory of the University of Jyvaskyla the frequency of the ion pulses hitting the research target is 10–21 MHz depending on the frequency of the acceleration voltage. A RF deflector system was constructed to adjust the ion beam pulse frequency according to the respective requirements. A desired portion of the ion pulses are deflected by feeding a high-amplitude RF-signal between deflecting plates located into the beam line. The specified deflecting voltage amplitude of 10–15 kV is achieved with 1 kW of RF power.

The effect of antenna bending on return loss, impedance bandwidth, and radiation pattern is studied, taking four antennas as examples. These include a patch, slot, inverted-F, and dipole antenna. Some of them exhibit circular polarization and one is broadband. Impedance is seen to be fairly constant regardless of bending, though if circular polarization is excited by careful antenna shaping, the circular polarization and corresponding resonance are easily lost. The axial ratios of all examined antennas degrade quickly with decreasing bend radius. Linearly polarized antennas are more tolerant to bending effects, though their polarization may twist and main lobe direction change.

Due to conversion losses, free-space attenuation, and limited transmitted power only a small amount of DC power can be received from a rectifying antenna (rectenna). In addition to optimisation of the rectenna efficiency, other methods for increasing the applicability of wireless power transmission (WPT) are also needed. The utilisation of circular polarisation and operation in two frequency bands in order to enhance the performance of WPT are demonstrated in this paper. The design and performance of a CP (circularly polarised) annular ring-slot antenna and microwave rectifier circuit operating at 2.45 GHz and 5.8 GHz ISM (Industrial, Scientific and Medical) bands are represented. The effect of a simple electromagnetic band-gap (EBG) structure on the antenna performance is also demonstrated and discussed.