It is commonly believed that improved interaction between humans and electronic device, it is effective to draw the viewer's attention to a particular object. Augmented reality (AR) applications can call attention to real objects by overlaying highlight effects or visual stimuli (such as arrows) on a physical scene. Sometimes, more subtle effects would be desirable, in which case it would be necessary to smoothly and naturally guide the user's gaze without external stimuli. Here, a novel image modification method is proposed for directing a viewer's gaze to specific regions of interest. The proposed method uses saliency analysis and color modulation to create modified images in which the region of interest is the most salient region in the entire image. The proposed saliency map model that is used during saliency analysis reduces computational costs and improves the naturalness of the image using the LAB color space and simplified normalization. During color modulation, the modulation value of each LAB component is determined in order to consider the relationship between the LAB components and the saliency value. With the image obtained in this manner, the viewer's attention is smoothly attracted to a specific region very naturally. Gaze measurements as well as a subjective experiments were conducted to prove the effectiveness of the proposed method. These results show that a viewer's visual attention is indeed attracted toward the specified region without any sense of discomfort or disruption when the proposed method is used.

Recently, a multi-way TE10 mode power divider based on the TE10-TEp0 mode transducers consisting of a linearly arranged single-mode waveguide (SMWG) and an over-moded waveguide (OMWG) has been reported. However, the multi-way power divider based on the present mode transducer results in poor isolation and output matching characteristics. In this paper, an improvement of the isolation and the output matching characteristics is attempted by inserting the resistive sheets in the OMWG. It is shown that the isolation characteristics of about 20 dB are achieved by adjusting the dimensions of the resistive sheets. The validity of the design results is confirmed by an experiment.

This paper proposes a new type of compact waveguide directional coupler, which is constructed from two crossed E-plane rectangular waveguide with two metallic posts in the square junction and one metallic post at each port. The metallic posts in the square junction are set symmetrically along a diagonal line to obtain the directivity properties. The metallic post inserted at each input/output waveguide port can realize a matched state. Tight-coupling properties 0.79-6 dB are realized by optimizing the dimension of the junction and the positions/radii of the posts. The design results are verified by an em-simulator (Ansoft HFSS) and experiments.

This paper proposes a novel waveguide intersection separating two H-plane waveguide systems from each other. If a four-port network in a four-fold rotational symmetry is completely matched, it has necessarily intersection properties. The proposed waveguide intersection consists of a square H-plane waveguide planar circuit connected four input/output waveguide ports in a four-fold rotational symmetry, and several metallic posts inserted at the junction without destroying the symmetry to realize a perfect matching. By optimizing the circuit parameters, high isolation properties are obtained in a relatively wide frequency band of about 8.6% for return loss and isolation better than 20 and 30 dB, respectively, for a circuit designed at 10 GHz. The proposed waveguide intersection can be analyzed by H-plane planar circuit approach, and possess advantages of compactness, simplicity, and high-power handling capability. Furthermore, an SIW intersection is designed by applying H-plane planar circuit approach to a waveguide circuit filled with dielectric material, and high isolation properties similar to H-plane waveguide intersection can be realized. The validity of these design concepts is confirmed by em-simulations and experiments.

We attempt to design and fabricate of a 4×4 Butler matrix for short-millimeter-wave frequencies by using the microfabrication process for a polytetrafluoroethylene (PTFE) substrate-integrated waveguide (SIW) by the synchrotron radiation (SR) direct etching of PTFE and the addition of a metal film by sputter deposition. First, the dimensions of the PTFE SIW using rectangular through-holes for G-band (140-220 GHz) operation are determined, and a cruciform 90 ° hybrid coupler and an intersection circuit are connected by the PTFE SIW to design the Butler matrix. Then, a trial fabrication is performed. Finally, the validity of the design result and the fabrication process is verified by measuring the radiation pattern.

The microfabrication technique based on synchrotron radiation (SR) direct etching process has recently been applied to construct PTFE microstructures. This paper proposes a PTFE substrate integrated waveguide (PTFE SIW). It is expected that the PTFE SIW contributes to the improvement of the structural strength. A rectangular through-hole is introduced taking the advantage of the SR direct etching process. First, a PTFE SIW for the Q-band is designed. Then, a cruciform 3-dB directional coupler consisting of the PTFE SIW is designed and fabricated by the SR direct etching process. The validity of the PTFE SIW coupler is confirmed by measuring the frequency characteristics of the S-parameters. The mechanical strength of the PTFE SIW and the peeling strength of its Au film are also additionally investigated.

It has been reported that a left-handed waveguide can be constituted using cutoff TE10 mode of rectangular waveguide. Because the cutoff TE10 mode shows effectively negative permittivity, the left-handed mode propagates by adding series capacitance in the form of short- or open-stubs. This paper suggests a constitution method of left-handed waveguides using cutoff TM mode. In this case, the cutoff TM mode shows effectively negative permeability. Therefore, a left-handed waveguide can be constituted by adding parallel inductance. In this paper, two types of the left-handed waveguides are designed using circular TM01 mode and rectangular TM11 mode, and the dispersion characteristics are numerically investigated. The validity of the constituting principle is confirmed by an experiment.

The microfabrication technique based on SR (Synchrotron Radiation) direct etching process has recently been applied to construct PTFE microstructures. This paper attempts to fabricate an integrated PTFE-filled waveguide Butler matrix for short millimeter-wave by SR direct etching. First, a cruciform 3-dB directional coupler and an intersection circuit (0-dB coupler) are designed at 180 GHz. Then, a 4×4 Butler matrix with horn antennas is designed and fabricated. Finally, the measured radiation patterns of the Butler matrix are shown.

The present paper treats the analysis and design method of the (H)NRD guide and E-plane rectangular waveguide integrated structures on the basis of the transverse resonance technique. The analysis is made by assuming a resonant cavity short-circuited at appropriate reference planes and considering the cavity as a waveguide discontinuity problem in the transverse direction. The resonant lengths are determined from the transverse equivalent circuit, and the scattering parameters are calculated from the lengths. We analyze (H)NRD discontinuities and design two types of HNRD guide to E-plane waveguide transitions and a directional coupler composed of HNRD and E-plane waveguide. The theoretical results are in good agreement with results calculated by an EM-simulator.

A broadband cruciform substrate integrated waveguide coupler is designed based on the planar circuit approach. The broadband property is obtained by widening the crossed region in the same way as rectangular waveguide cruciform couplers. As a result, a 3 dB coupler with fractional bandwidth of 30% is realized at 24 GHz.

This paper treats multi-way microstrip power dividers composed of multi-step, multi-furcation, and corners. Since the design procedure is founded on the planar circuit approach in combination with the segmentation method, optimization of the circuit configuration can be performed in a reasonable short computation time when applying the Powell's optimization algorithm. Actually, broadband 3- and 4-way power dividers with mitered bends are designed, and fractional bandwidths of about 90% and 100% are realized for the power-split imbalance less than 0.2 dB and the return loss better than -20 dB, respectively. The validity of the design results is confirmed by an EM-simulator (HFSS) and experiments.

The metallic waveguide is one of many effective media for millimeter- and submillimeter-waves because of the advantage of its low-loss nature. This paper describes the fabrication method of PTFE-filled waveguide components with the use of the SR (synchrotron radiation) direct etching process of PTFE, sputter deposition of metal, and electroplating. PTFE is known as a difficult material to process with high precision. However, it has been reported that PTFE microstructures can be fabricated by the direct exposure to SR. First, an iris-coupled waveguide BPF with 5-stage Chebyshev response is designed and fabricated for the Q-band. It is demonstrated that the present process is applicable for the fabrication of the practical components inclusive of narrow patterns. Then, a cruciform 3 dB coupler with air-filled posts is designed and fabricated for the Q-band. Directivity and matched state of the coupler can be realized by “holes” in the dielectric material. The measurement results are also shown.

A composite right/left-handed transmission line (CRLH-TL) using substrate integrated waveguide (SIW) with floating-conductor (SIW-type CRLH-TL) for microwave and millimeter wave frequencies has been proposed by the authors. This paper proposes a new configuration that is shield type of the SIW-type CRLH-TL, which can suppress the radiation from the exposed floating-conductors, and shows that even if the shielded structure is used, the SIW-type CRLH-TL supports the LH mode as well as the prototype. Proposed CRLH-TL consists of a SIW with slot apertures (part 1), a dielectric film with floating-conductors (part 2) and a SIW without lower conductor (part 3). A shielded SIW-type CRLH-TL for X--K band (with wide LH mode bandwidth of 6 GHz and transition frequency of 16 GHz) that satisfies the balance condition is designed. Dispersion diagram and S-parameters are derived numerically, and typical field distributions of RH and LH transmission and the zeroth-order resonance are shown. Measured result agrees well with theoretical result, by considering the accuracy performance and loss factors of the fabricated CRLH-TL. Proposed CRLH-TL has advantage of simple manufacturing, because the parts 1--3 are composed of simple planar periodic structure. It is expected to be one of the basic structure of CRLH-TL or components such as LH coupler above 10 GHz or millimeter wave frequency.

In this paper, we suggest a method of analyzing the post-wall waveguide (PWW) or the substrate integrated waveguide (SIW) by applying the analytical technique of the H-plane waveguide discontinuities based on the planar circuit approach. The analytical procedure consists of the derivation of the mode impedance matrices for regular-shaped circuits and the short-circuiting operation on fictitious ports arranged at the peripheries of the metallic posts. First, a straight section of the PWW is treated as an example and the analytical method for the calculation of the S-parameters is described in detail. Then the attenuation and phase constants of the PWW are computed with the aid of the Thru-Reflect Line (TRL) calibration technique. Next, the analytical method is applied to the design of two types of right-angled corners. The analysis and the design results are verified using an em-simulator (HFSS).

This paper presents a design method of multi-stage, multi-way microstrip power dividers with the aim of constructing a compact low-loss power divider with numbers of outputs. First, an integration design technique of power dividers composed of multi-step, multi-furcation and mitered bends is described. Since the analytical technique is founded on the planar circuit approach combined with the segmentation method, the optimization of the circuit patterns can be performed in a reasonable short computation time. Next, the present method is applied to the design of broadband Nn-way power dividers such as 32-way power divider consisting of 3-way dividers in two-stage structures, respectively. In addition, a 12-way power divider constructed from a series connection of a 3-way and three 4-way dividers is designed. The dividers equivalently contain a 3-section Chebyshev transformer to realize broadband properties. As a result, the fractional bandwidths of nearly 85% and 66.7% for the power-split imbalance less than 0.2 dB and the return loss better than -20 dB are obtained for the 9- and 12-way power dividers, respectively. The validity of these design results is confirmed by a commercial em-simulator (Ansoft HFSS) and experiments.

It is estimated that 80% of the information entering the human brain is obtained through the eyes. Therefore, it is commonly believed that drawing human attention to particular objects is effective in assisting human activities. In this paper, we propose a novel image modification method for guiding user attention to specific regions of interest by using a novel saliency map model based on spatial frequency components. We modify the frequency components on the basis of the obtained saliency map to decrease the visual saliency outside the specified region. By applying our modification method to an image, human attention can be guided to the specified region because the saliency inside the region is higher than that outside the region. Using gaze measurements, we show that the proposed saliency map matches well with the distribution of actual human attention. Moreover, we evaluate the effectiveness of the proposed modification method by using an eye tracking system.

Directional couplers with flat coupling are designed by using an asymmetrical coupled-HNRD-guide consisting of two HNRD guides of different cross sections arranged closely. First, propagation characteristics of the asymmetrical coupled-HNRD-guide are analyzed by the transverse resonance technique. Next, the whole directional couplers including tapered sections are designed from the S-parameters of the coupled HNRD guides derived from a superposition of the even-like and odd-like modes. Finally, the validity of the design procedure is confirmed by an em-simulator (HFSS).

This paper suggests a new type of 180-degree 3 dB hybrid, which consists of a cylindrical cavity and four E-plane rectangular waveguides radially coupled with it, and shows that good hybrid properties are realized by modifying the positions of the four input/output waveguides and the radius of the cylindrical cavity that are determined by the field distribution of the TE111 resonant mode. Moreover, a method of broadening the bandwidth with additional impedance steps is described. The present hybrid is marked by simple structure, and hence is useful for applications at millimeter wave frequencies and to high-power microwave systems. Experimental verification is additionally shown.