This paper presents a planar monopole antenna with slits and a stub for multi-band operation in vehicles. The proposed antenna is at least 55% smaller than the regular rectangular monopole antenna and covers eight wireless application bands. Slits cut into the rectangular monopole alter the surface current paths so that the band coverage is expanded. A long bent-stub is also added to cover the lowest service band.

The ability of a modified bow-tie dipole antenna, which has an asymmetric-feed structure to operate at UHF-band (470-862 MHz) and dual ISM-band (2.4 GHz and 5.8 GHz) is demonstrated. Experimental results indicate that the VSWR 2:1 bandwidths achieved were 125.7%, 8.2% and 23.6% at 660 MHz, 2.45 GHz and 5.5 GHz. The proposed modified bow-tie dipole exhibits a nearly omni-directional radiation pattern with very easy to fabricate structure, and so is suitable for various commercial wideband applications.

Radiation of a Hertzian dipole placed within a cylindrical cavity with narrow slots is investigated. Narrow axial and transverse slots are considered. Scattered fields are expanded in terms of eigenfunctions and boundary conditions are enforced to obtain a set of simultaneous equations. Computations are performed to check the validity of the formulation.

A new elliptic-function bandpass filter (BPF) is proposed, which utilizes an inter-digital coupled line (IDCPL) as a left-handed transmission line. The IDCPL is employed in order to realize a negative coupling between non-adjacent resonators in a wideband BPF. As the authors' knowledge, the left-handed operations of the IDCPL has rarely utilized before, although the IDCPL itself has been widely used in many microwave circuits without being paid attention to the left-handed operations. Measured characteristics of two BPFs are presented in this paper, one is targeted for 3-4 GHz WiMAX systems, and the other is for 3-5 GHz ultra wideband communication systems (UWB).

New structure of broadband planar antenna, combining monopole elements with electromagnetic bandgap (EBG) structures, is proposed. The antenna has a simple single layer structure and unique beam pattern. Antenna is fabricated on a surface of a single layer dielectric substrate and back side of the substrate is covered with metal layer. At the center of the substrate, an inverted L monopole strip is fabricated and on both sides of this monopole, EBG unit cells are placed. By tuning monopole length and EBG bandgap frequency, the monopole resonates even if metal layer exists close to the monopole radiator. Three types of EBG, one dimensional (1D), square two dimensional (2D) and hexagonal 2D, are tested. By combining monopole strip with hexagonal 2D-EBG, the bandwidth of prototype antenna, whose return loss is less than 10 dB, is 840 MHz in 5 GHz band. To control beam patterns of antenna, parasitic elements are placed close to the monopole radiator and EBGs. These parasitic elements work as directors of quasi Yagi-Uda antenna and radiation gain at lower tilt angles is improved.

This paper investigates the performance of multiple monopole antennas mounted on a card-type terminal, which is expected to be used in the systems beyond 3 G, based on the calculated and measured radiation patterns for the 2.0 GHz. We characterize the feasible performance of quarter-wavelength monopole antennas mounted on a card-type terminal in a multiple antenna configuration with narrow element spacing of less than a half-wavelength assuming that the antennas used must satisfy the space restrictions of the mobile terminal. Performance figures of merit for the multiple antenna performance include the beamforming gain, correlation coefficient, and MIMO channel capacity. Furthermore, we investigate the influence of a finite ground plane on the characteristics of multiple monopole antennas using a typical antenna configuration comprising a simple finite ground plane and multiple monopole antennas to discuss the fundamental characteristics.

A compact built-in handset antenna for multiple-input multiple-output (MIMO) system at 2 GHz, comprising two elements array of newly proposed L-shaped folded monopole antenna (LFMA), is evaluated under the multipath radio wave propagation environments. By analyzing the fundamental characteristics, mean effective gain (MEG), correlation, and channel capacity, the significant enhancement in the capability, as a handset MIMO antenna under practical use conditions, was confirmed. The performances were also compared to those of an array antenna comprising two planar inversed-F antenna (PIFA) elements in order to verify the effectiveness of the proposed antenna. The results show that the equivalent or improved performances can be realized, by using the proposed LFMA array with a compact size, taking only the volume of 44% of a PIFA array. The LFMA array provides almost the same bandwidth and enhanced isolation compared with a PIFA array, and the sufficiently low correlation and acceptable effective gain are obtained under the multipath radio wave propagation environments. In addition, a greater channel capacity than a PIFA array is achieved especially when the proposed LFMA array is inclined for the display-viewing mode, and moreover, an almost doubled increase in the channel capacity is obtained by using MIMO transmission compared with single-input single-output (SISO). This study also show that the MEG has much effects on the channel capacity, rather than the correlations, for the proposed antenna.

A multiband T-shaped monopole antenna for WLAN/WiMAX applications is presented. The T-shaped monopole is comprised of two horizontal arms of different lengths, which generate two separate resonant modes for 2.5/5.5 GHz WLAN/WiMAX bands, and with a shortened parasitic element, which generates a middle resonant mode for 3.5 GHz WiMAX band, for seamless wireless network access applications. The proposed antenna has been successfully simulated and implemented. Both results of simulation and measurement show good agreement. For the lower band from 2.3 to 2.7 GHz, the gain varies in the range of 2.5-3.3 dB, while the radiation efficiency is from 72% to 85% over the band. As for the middle band from 3.3 to 3.7 GHz, the gain varies from 1.5 to 2.0 dB, and the radiation efficiency is from 62% to 70%. As for the upper band from 5.2 to 5.8 GHz, the antenna gain varies from 5.4 to 5.9 dB, and the radiation efficiency is from 63% to 66%.

A novel helix-monopole antenna is proposed which combines the helix and monopole together to form improved current distribution. The current magnitudes are computed with Moment Method (MM) and results show the current difference between helix-monopole and helix antenna. Two antennas are fabricated for comparison and measured on the same two-way portable radio with frequency band from 400-420 MHz. Measurements prove that the proposed antenna offers a significant improvement in gain.

In this letter, we present a modified printed folded λ/2 dipole antenna design for Digital Video Broadcasting (DVB) applications in UHF band (470-862 MHz). The arms of dipole are meandered to yield an asymmetrical structure. Wideband operation is obtained by increasing dipole-area. The impedance matching of the dipole structure is obtained by inserting some slots on the dipole-arms. This antenna combines omni-directional radiation pattern and wide bandwidth in an easy-to-fabricate structure. The experimental results of the constructed prototype are presented.

A comparison among the possible nonlinear photonic interactions for scalable nanometer networks and quantum gates as well as for coherence retention in solids is made theoretically, and then numerical plottings are given, on the basis of the dipole length estimated from our µ-PL (microphotoluminescence) spectra of GaAs/AlGaAs coupled quantum dots (QDs) having a pair of 0.3 meV splittings. Furthermore, prospective device concepts based on these nonlinear multipolar interactions are given.

In this paper, we report the detailed investigation of novel printed disc monopole antennas for ultra-wideband (UWB) applications focusing on miniaturization of the disc radiator. First, the basic property was examined for the case of a circular disc with diameter of 50 mm, and it was found that the VSWR is less than 2 in the UWB band of 3.1-10.6 GHz when the feed gap length is between about -0.1 and 0.2 mm. Next, in order to reduce the size of the disc radiator, various dimensions of elliptical discs were investigated. It is shown that if the dimensions of the elliptical disc are chosen appropriately, a smaller disc size antenna can be achieved. To decrease the antenna size further, a triangular notch and an exponentially curved notch on the ground plane of the antenna were examined. It is observed that the use of the notched ground is very effective and that the diameter of the circular radiator can be reduced to 17 mm. The proposed antenna has an omnidirectional pattern in the x-y plane. The influence of the notch on the radiation pattern is very small. Details of the simulation results using the FDTD method and experimental results for the proposed antenna are presented and analyzed. These features are very attractive for UWB applications.

The electric fields inside and outside a car must be carefully determined when designing a wireless communication system to be employed in the car. This paper introduces an effective simulation method and a precise measurement method of electric field distributions in a cabin of a simplified scale car model. A 1/3 car model is employed for ease of measurement. The scaled frequency of 2859 MHz, 3 times 953 MHz, is employed. The use of a moment method simulator utilizing the multilevel fast multipole method allows calculations to be performed on a personal computer. In order to judge the accuracy of simulation results, convergence of simulation output in accordance with segment size (triangle edge length) changes is ensured. Simulation loads in the case of metallic body only and a metallic body with window glass are also shown. In the measurements, an optical electric field probe is employed so as to minimize the disturbances that would otherwise be caused by metallic feed cable; precise measurement results are obtained. Comparisons of measured and simulated results demonstrate very good agreement which confirms the accuracy of the calculated results. 3-dimensional electric field distributions in the car model are shown and 3-dimensional standing wave shapes are clarified. Moreover, calculated and measured radiation patterns of the car model are shown so the total electric field distributions around a car are clarified.

In order to support driving safety, TPMS (Tire Pressure Monitoring System) has been introduced in U.S.A. and Europe. In Japan, the AIRwatch system has been developed and commercialized. Some studies were made to clarify the electric field environment of this system. However, no detailed calculation of the electric field between the transmitter in the tire and the receiving antenna has been published. This paper clarifies the electric field environment of the Japanese system through electromagnetic simulations by a high performance MoM simulator that utilizes the MLFMM scheme. First of all, electric wave emissions from an antenna mounted in a tire are shown to be larger than that of the same antenna in free space. The tire rubber effects are also investigated. Next, electric field distributions on the windshield holding the receiving antenna are calculated. By comparing calculated electric field levels with those in the free space condition, car body interruptions are clarified. Because car body interruptions are not so severe, it is shown that the free space electric field levels can be used as rough design parameters. Moreover, electric field changes due to tire rotation are also clarified. Calculation accuracy is confirmed by the good agreement with measured data collected from a 1/5 scale car model. To permit estimations to be made in actual situations, the effects of the ground are also investigated. This simulation study introduces a lot of important data useful in TPMS system design.

This paper presents an ultra-wideband (UWB) bandpass filter using a combination of broadside-coupled structure and lumped-capacitor-loaded shunt stub resonator. The broadside-coupled microstrip-to-coplanar waveguide structure provides an ultra-wide bandpass filtering operation and keeps a good stopband at lower frequencies from DC at the same time. The lumped-capacitor-loaded shunt stub resonator creates two transmission zeros (attenuation poles which can be located at the outsides of the two bandedges of the UWB bandpass filter to improve the out-band performance by selecting a suitable combination of the length of the shunt stubs and the capacitance of the loaded chip capacitors. The filter was designed based on electromagnetic simulation for broadside-coupled structure, microwave circuit simulation and experiments for determining the transmission zeros. The filter was fabricated on a one-layer dielectric substrate. The measured results demonstrated that the developed UWB bandpass filter has good performance: low insertion loss about 0.46 dB and low group delay about 0.26 ns at the center of the passband and very flat over the whole passband, and less than -10 dB reflection over the passband. The implemented transmission zeros, particularly at the low frequency end, dramatically improved the out-band performance, leading the filter satisfy the FCC's spectrum mask not only for indoor but also for outdoor applications. These poles improved also the skirt performance at both bandedges of the filter. A lowpass filter has been also introduced and integrated with the proposed bandpass filter to have a further improvement of the out-band performance at the high frequency end. The filters integrated with lowpass section exhibit excellent filter performance: almost satisfying the FCC's spectrum mask from DC to 18 GHz. The developed UWB bandpass filter has a compact size of 4 cm1.5 cm, or 4.8 cm1.5 cm with lowpass section implemented.

Pole-tip-driven structure, which is composed of a coil wounded at the main pole tip, is favorable for obtaining a sharp and strong head field as a single-pole-type head. Three kinds of pole-tip-driven-type heads with different yoke and coil structures are investigated in terms of magnetomotive force dependence of head field and effect of coil recession. Field calculation by finite-element method (FEM) showed that the three heads exhibited the same field sensitivity in spite of the difference in distribution of coil exciting field and magnetization of the main pole. In a lower range of magnetomotive force the heads showed different dependence of field sensitivity on the coil recession. However, there was not much difference in degradation of sensitivity in a region near the saturation of field. Thus, the importance of reducing coil recession was confirmed as reported earlier.

Popcorn noise is a large transient noise spike at the reader shortly after writing due to unstable domains in writer yoke. The popcorn noise was found to dependent on write frequency. It is firstly reported that the popcorn noise occurred by the write instability of shielded-single-pole head (SSPH) can be captured in row-bar level QST which is experimentally confirmed. Thus, a PMR head can be rejected by the row-bar level QST. In addition, the writing stress traced by the MR transfer curve can possibly accelerate the head degradation.

3-D sound using head-related transfer functions (HRTFs) is applicable to embedded systems such as portable devices, since it can create spatial sound effect without multichannel transducers. Low-order modeling of HRTF with an IIR filter is effective for the reduction of the computational load required in embedded applications. Although modeling of HRTFs with IIR filters has been studied earnestly, little attention has been paid to sound movement with IIR filters, which is important for practical applications of 3-D sound. In this paper, a practical method for sound movement is proposed, which utilizes time-varying IIR filters and variable delay filters. The computational cost for sound movement is reduced by about 50% with the proposed method, compared to conventional low-order FIR implementation. In order to facilitate efficient implementation of 3-D sound movement, tradeoffs between the subjective quality of the output sound and implementation parameters such as the size of filter coefficient database and the update period of filter coefficients are also discussed.

In this research, a sub-array preconditioner is applied to improve the convergence of conjugate gradient (CG) iterative solver in the fast multipole method and fast Fourier transform (FMM-FFT) implementation on a large-scale finite periodic array antenna with arbitrary geometry elements. The performance of the sub-array preconditioner is compared with the near-group preconditioner in the array antenna analysis. It is found that the near-group preconditioner achieves a little better convergence, while the sub-array preconditioner can be easily constructed and programmed with less CPU-time. The efficiency of the CG-FMM-FFT with high efficient preconditioner has been demonstrated in numerical analysis of a finite periodic array antenna.

The computational error of the multilevel fast multipole algorithm is studied. The error convergence rate, achievable minimum error, and error bound are investigated for various element distributions. We will discuss the boundary between the large and small buffer cases in terms of machine precision. The needed buffer size to reach double precision accuracy will be clarified.