This paper presents a design for the perpendicular-corporate feed in a four-layer circularly-polarized parallel-plate slot array antenna. We place a dielectric layer with adequate permittivity in the region between the coupling-aperture and the radiating-slot layers to remove x-shaped cavity walls completely in the radiating part of a conventional planar corporate-feed waveguide slot array antenna. To address fabrication constraints, the dielectric layer consists of PTFE and air. It excites a strong standing wave in the region and so provides 2×2-element subarrays with uniform excitation. None of the slot layers are in electrical contact due to air gaps between the slot layers. The four-layer structure with apertures for circular polarization contributes to wideband design for axial ratios because of the eigenmodes in the desired band. We realize an 11.9% bandwidth for axial ratios of less than 3.0dB as confirmed by measurements in the 60GHz band. At the design frequency, the measured realized gain is 32.7dBi with an antenna efficiency of 75.5%.

This paper details the design of a plate that controls the beam direction in an aperture array excited by a waveguide 2-plane hybrid coupler. The beam direction can be controlled in the range of ±15-32deg. in the quasi H-plane, and ±26-54deg. in the quasi E-plane at the design frequency of 66.425GHz. Inductive irises are introduced into tapered waveguides in the plate and the reflection is suppressed by narrow apertures. A plate that has a larger tilt angle in the quasi E-plane and another plate with conventional rectangular waveguide ports as a reference are fabricated and measured. The measured values agree well with the simulation results.

A PCB-integratable metal cap slot antenna is developed for the 60-GHz band. The antenna is composed of two slots and a T-junction and is fed by a post-wall waveguide on a substrate. The dimensions of the designed antenna are 8.0×4.5×2.5mm3. The designed antenna is insensitive with a metal block behind the antenna. The designed antenna is fabricated by machining a brass block and evaluated by measurement. The measurement shows reflection less than -10.0dB, gain larger than 7.8dBi and beamwidth between 54°-65° over the 60-GHz band with endfire radiation. The antenna showed high gain together with short length of half wavelength in the radiation direction. This antenna also can be integrated with printed circuit board (PCB) and is suitable for mobile terminals such as smart phones and tablets.

This paper presents the mode matching (MM)/finite element method (FEM) hybrid analysis for a short-slot 2-plane coupler, and an optimization process for a wideband design based on a genetic algorithm (GA). The method of the analysis combines a fast modal analysis of the MM which reduces the computation time, with the flexibility of an FEM which can be used with an arbitrary cross-section. In the analysis, the model is reduced into the one-eighth model by using the three-dimensional structural symmetry. The computed results agree well with those by the simulation and the computation time is reduced. The bandwidth is improved by the optimization based on the GA from 2.4% to 6.9% for the 2-plane hybrid coupler and from 5.4% to 7.5% for the 2-plane cross coupler. The measured results confirm the wideband design.

The sidelobe level at tilts around 30-40 degrees in both the E and H planes due to a tapered excitation of units of 2×2 radiation slots is suppressed by introducing slit layers over a corporate-feed waveguide slot array antenna. The slit layers act as averaging the excitation of the adjacent radiating slots for sidelobe suppression in both planes. A 16×16-element array in the 70GHz band is fabricated. At the design frequency, the sidelobe levels at tilts around 30-40 degrees are suppressed from -25.4dB to -31.3dB in the E-plane and from -27.1dB to -38.9dB in the H-plane simultaneously as confirmed by measurements. They are suppressed over the desired range of 71.0-76.0GHz frequencies, compared to the conventional antenna.

This paper presents a 120-GHz-band split ring resonator (SRR) bandstop filter whose insertion loss can be controlled by coupling another lattice pattern substrate. The SRR bandstop filter and lattice pattern substrate is composed of 200-µm-thick quartz substrate and 5-µm-thick gold patterns. S21 of the SRR bandstop filter is -37.8 dB, and its -10-dB bandwidth is 115-130 GHz. S21 of the SRR bandstop filter changes to -4.1 dB at 125 GHz by arranging the lattice pattern substrate in close proximity to the SRR stopband filter, because coupling between the SRR and the lattice pattern occurs when the SRR and lattice pattern are opposed in close proximity. It was found that 10 Gbit/s data transmission can be achieved by setting the lattice pattern substrate just above the SRR bandstop filter with a spacer thickness of 50 µm, even though data transmission is impossible when only the SRR bandstop filter is inserted between the transmitter and the receiver.

In this paper, we present the transmission characteristics control of a 125 GHz-band split-ring resonator (SRR) bandstop filter by coupling an alignment-free lattice pattern. We demonstrate that the transmission characteristics of the SRR filter can be controlled by coupling the lattice pattern; however, the required accuracy of alignment between the SRR filter and lattice pattern was below 200 µm. Therefore, we designed an alignment-free lattice pattern whose unit cell size is different from that of the SRR unit cell. S21 of the SRR bandstop filter changes from -38.7 to -4.0 dB at 125 GHz by arranging the alignment-free lattice pattern in close proximity to the SRR stopband filter without alignment. A 10 Gbit/s data transmission can be achieved over a 125 GHz-band wireless link by setting the alignment-free lattice pattern substrate just above the SRR bandstop filter.

Intersymbol interference (ISI) is a significant source of degradation in many digital communication systems including our proposed non-far region communication system using large array antennas in the millimeter-wave band in which the main cause of ISI can be attributed to the path delay differences among the elements of an array antenna. This paper proposes a quantitative method to evaluate the ISI estimated from the measured near-field distribution of the array antenna. The influence of the uniformity in the aperture field distribution in ISI is discussed and compared with an ideally uniform excitation. The reliability of the proposed method is verified through a comparison with another method based on direct measurements of the transmission between the actual antennas. Finally, the signal to noise plus interference is evaluated based on the estimated ISI results and ISI is shown to be the dominant cause of the degradation in the reception zone of the system.

A waveguide 2-plane hybrid coupler with two operating bands is proposed. The cross-sectional shape of the coupled region inside the proposed coupler is designed with a two-dimensional arbitrary geometry sorting method. Simulations of the proposed hybrid coupler has a fractional bandwidth (FBW) of 2.17% at the center of 24.99GHz, and at the center of 28.28GHz an FBW of 6.13%. The proposed coupler is analyzed by the mode-matching finite-element hybrid method, and the final result is obtained using a genetic algorithm. The analyzed result of the coupling for the main modes in the coupled region is presented. The design result is confirmed by measurements.

Shaped beam reflector antennas are widely used because they can achieve a shaped beam even with a single primary feed. Because coverage shapes depend on service areas, optimum primary radiators and reflector shapes are determined by the service areas. In this paper, we propose a simultaneous optimal design method of the primary radiator and reflector for the shaped beam antenna. Particle swarm optimization and the conjugate gradient method are adopted to optimize the primary radiator and reflector. The design method is applied to Japan coverage to verify its effectiveness.

This paper presents the excitation coefficient optimization of slot array antennas for increasing channel capacity in 2×2-mode two-dimensional ROM (rectangular coordinate orthogonal) transmission. Because the ROM transmission is for non-far region communication, the transmission between Tx (transmission) and Rx (reception) antennas increases when the antennas radiate beams inwardly. At first, we design the excitation coefficients of the slot arrays in order to enhance the transmission rate for a given transmission distance. Then, we fabricate monopulse corporate-feed waveguide slot array antennas that have the designed excitation amplitude and phase in the 60-GHz band for the 2×2-mode two-dimensional ROM transmission. The measured transmission between the fabricated Tx and Rx antennas increases at the given propagation distance and agrees with the simulation.

A 16×16-element corporate-feed waveguide slot array antenna in the 60-GHz band is designed to achieve broadband reflection and high antenna efficiency. The sub-arrays consisting of 2×2-elements are designed to improve the reflection bandwidth by implementing lower Q and triple resonance. The designed antenna is fabricated by diffusion bonding of thin copper plates. A wide reflection bandwidth with VSWR less than 2.0 is obtained over 21.5%, 13.2GHz (54.7-67.8GHz). The measured gain is 32.6dBi and the corresponding antenna efficiency is 76.5%. The broad bandwidth of more than 31.5-dBi gain is realized over 19.2%, 11.9GHz (56.1-68.0GHz). The gain in bandwidth covers the whole of the license-free 60-GHz band (57-66GHz).