This paper presents dual bands and dual polarization reflectarrays for 5G millimeter wave applications. The frequency bands of 28GHz and 39GHz are allocated for 5G to realize high speed data transmission. However, these high frequency bands create coverage holes in which no link between base station and receivers is possible. Reflectarray has gained attention for reducing the size and number of coverage holes. This paper proposes a unit cell with swastika and the patch structure to construct the dual bands reflectrray operating at 28GHz and 39GHz by supercell. This paper also presents the detailed design procedure of the dual-bands reflectarray by supercell. The reflectarray is experimentally validated by a bistatic radar cross section measurement system. The experimental results are compared with simulation and reflection angle agreement is observed.

We present a novel circularly polarized ring microstrip antenna and its design. The shorting pins discretely disposed on the inner edge of the ring microstrip antenna are introduced as a new degree of freedom for improving the resonance frequency control. The number and diameter of the shorting pins control the resonance frequency; the resonance frequency can be almost constant with respect to the inner/outer diameter ratio, which expands the use of the ring microstrip antenna. The dual-band antenna where the proposed antenna includes another ring microstrip antenna is designed and measured, and simulated results agree well with the measured one.

In December 2018, satellite broadcasting for 4K/8K ultra-high-definition television (UHDTV) will begin in Japan. It will be provided in the 12-GHz (11.7 to 12.75GHz) band with right- and left-hand circular polarizations. BSAT-4a, a satellite used for broadcasting UHDTV, was successfully launched in September 2017. This satellite has not only 12-GHz-band right- and left-hand circular polarization transponders but also a 21-GHz-band experimental transponder. The 21-GHz (21.4 to 22.0GHz) band has been allocated as the downlink for broadcasting satellite service in ITU-R Regions 1 (Europe, Africa) and 3 (Asia Pacific). To receive services provided over these two frequency bands and with dual-polarization, we implement and evaluated a dual-band and dual-circularly polarized parabolic reflector antenna fed by 12- and 21-GHz-band microstrip antenna arrays with a multilayer structure. The antenna is used to receive 12- and 21-GHz-band signals from in-orbit satellites. The measured and experimental results prove that the proposed antenna performs as a dual-polarized antenna in those two frequency bands and has sufficient performance to receive satellite broadcasts.

A class-F high efficiency GaN power amplifier (PA) for dual band operation at 2.14 GHz and 2.35 GHz is proposed. A novel dual band harmonic-rejection load network, which controls the terminating impedances of the second and third harmonics, and contributes greatly to efficiency improvement of PA, is described. In addition, a matching network which guarantees the high efficiency and gain of PA for the desired dual bands is designed. The proposed load network has the harmonic rejection of more than 24 dB which is sufficient for rejecting harmonics, and an insertion loss of less than 0.11 dB. The dual band matching network for the maximum output power results in the measured highest output power for each operating frequency. The fabricated class-F GaN PA has 43 dBm-65.4% and 43 dBm-63.9% of output power - efficiency at the desired dual frequencies.

Many researchers have recently studied various applications such as Inter-Vehicle Communications (IVC) and Road-to-Vehicle Communications (RVC) for Intelligent Transport Systems (ITS). RVC is a key technology that can connect vehicles with the internet through Road Side Units (RSUs). Relative positions between vehicles vary within short periods of time. Neighboring vehicles and barriers cause shadowing that blocks communication for extended periods of time between RSUs and vehicles. We propose a fast scheme of Mobile IPv6 handover using dual-band communications in RVC. This scheme uses ISM and UHF dual bands. It switches to the UHF band during handover or in the shadowing period. We demonstrate that the proposed scheme can establish continuous communications through computer simulations.

In this paper, a novel feeding technique is proposed to feed a printed rectangular ring patch antenna that attains high gain in two bands simultaneously. The prototype antenna exhibits good impedance bandwidths satisfying ISM 2.45/5.8 GHz achieving maximum gain of 9.56 and 10.17 dBi, respectively, with a stable radiation pattern.

A stacked rectangular microstrip antenna with a shorting plate is proposed as a car antenna for dual band (VICS and ETC) operation in the ITS. The proposed antenna has the proper radiation patterns for the VICS and ETC. The antenna is small in size and effective in dual band operation.

This paper presents a novel dual-band comb-line filter using a pair of hybrid resonators. The resonator consists of a half-wavelength stripline resonator short-circuited at both ends and a quarter-wavelength resonator of coplanar waveguide that is nested in the half-wavelength resonator. Numerical calculations by an electromagnetic simulator clarify the characteristics of dual-frequency resonance of the hybrid resonator when the structural parameters are changed. The surface current density on the resonator is also investigated at the resonant frequencies. A typical model of the resonator is fabricated and its resonance frequency characteristics are measured.

This paper presents a design procedure of multilayer single-input/single-output dual-band filters of small size fabricated in high-permittivity LTCC (Low Temperature Co-fired Ceramic) substrates. The present dual-band filter, with pass bands of 950 MHz and 1.9 GHz, consists of two single-band filters each one of which has a matching circuit for controlling the input impedance in the pass band of the counterpart. Discussed first in this paper is a dual-band filter that has the matching circuit connected to the single-band filters externally. Then, a dual-band filter with the matching circuit embedded in its body is investigated together with metallization patterns of the matching elements. Presented finally is a very small single-input/single-output dual-band filter suitable for dual-band wireless communication systems.

A 2.4/5.2 GHz CMOS dual band driver stages with integrated 5.2 GHz power amplifier is presented in this work. For more accurate simulation of high power CMOS amplifier, a re-optimized macro NMOS model is used, whose nonlinear model accuracy is enhanced and its validity is proved by comparing load pull simulation with measurement. In order to achieve band selection, it has switched matching circuits at the first stage and SPDT path switch following them. At 2.4 GHz and 5.2 GHz bands, the achieved values of Psat of the switched amplifier are 9.7 dBm and 19.5 dBm, respectively. The achieved PAE is 15.3% at 5.2 GHz.

Research on the propagation characteristics in the microwave band aiming at broadband mobile services is attracting much attention. Typical examples are the Unlicensed-NII (U-NII) band in the U.S. and HIPER-LAN band in Europe, i.e. 5.2 GHz. An efficient approach to revealing the propagation characteristics in the 5-GHz band is to utilize the existing propagation data accumulated by many researchers on the 2-GHz band. This paper presents the differences in path loss between the 5.2-GHz and 2.2-GHz bands in a residential area by using a 5.2-GHz/2.2-GHz dual band antenna. This antenna enables a direct comparison of 5.2 GHz and 2.2 GHz in terms of the propagation characteristics. We found that the difference in path loss between the 2.2-GHz and 5.2-GHz bands depends on only the base/mobile station antenna height. Based on this, we formulate the relationship between the heights of the base/mobile station antennas and the difference in path loss between the 2.2-GHz and 5.2-GHz bands.