Yohei Koga

Frequency reconfigurable antenna with MEMS switches for mobile terminals

A new antenna for mobile terminals is proposed to cover all frequency bands between 640 MHz and 5.85 GHz. The antenna consists of a wide band antenna and a frequency reconfigurable circuit that includes micro electro mechanical system (MEMS) switches. The reconfigurable circuit is used to improve matching at frequency bands which cannot be covered by the wideband antenna alone. The favorable performance of the proposed antenna was confirmed by simulation and measurement.

A small tunable multiband antenna with parasitic elements for mobile applications

We propose a novel tunable multiband antenna with parasitic elements for mobile applications. The proposed antenna covers LTE/WWAN (703-960 MHz, 1447-1510MHz, 1710-2170 MHz, and 2496-2690 MHz) with a small size of 60 mm × 8 mm × 2.3 mm Our proposed antennas configuration consists of two branched 1/4λ monopoles, a parasitic 1/4λ monopole, a parasitic 1/2λ dipole, a dielectric material (ε r = 5.4), and a tunable capacitor. This parasitic 1/2λ dipole technique is a particularly effective method that can increase the bands without reducing the efficiency of the other antenna elements. Also, it does not need a large ground plane compared with the monopole. Because the low band (703-960 MHz) is wideband, the tunable capacitor is used to change the resonance frequency and total efficiency at the low band. The simulated and measured results show a total efficiency more than -3dB in the operation frequencies. The proposed antenna will be a good candidate for mobile applications with the LTE/WWAN operation.

Design of a low SAR multiband antenna for mobile applications

We propose a novel low specific absorption rate (SAR) multiband antenna for mobile applications. Our proposed antennas configuration consists of an antenna ground slit and branched elements to obtain multiband characteristics and low SAR. The proposed antenna covers Long Term Evolution and Wireless Wide Area Networks (703 - 960 MHz, 1447 - 1510 MHz, 1710 - 2170 MHz, and 2496 - 2690 MHz) and can reduce the SAR by at most 45 % compared with a traditional inverted-L antenna. The measured total efficiency of our proposed antenna has been found to vary between -5 dB and -1 dB for target band frequencies. The proposed antenna will be a good candidate for mobile applications with the LTE/WWAN operation.

Low-SAR multiband antenna with ground slit and parasitic elements for tablet computers

We propose a low specific absorption rate (SAR) multiband antenna for tablet computers. The proposed antenna has a ground between it and the body phantom to maintain low SAR. To achieve the multiband characteristics, the antenna has a ground slit and parasitic elements. It covers Long Term Evolution and Wireless Wide Area Networks (703 - 960, 1447 - 1510, 1710 - 2170, and 2496 - 2690 MHz) and is small; 60 × 10 × mm3 and can reduce the SAR by at most 39% (below the limit of 1.6 W/kg) compared with a traditional inverted-L antenna. In this paper, we argue that the proposed antenna is capable of exhibiting multiband and low SAR characteristics.

Metal frame multiband MIMO antenna for smartphones

In this study we present a new MIMO antenna which utilizes the metal frame of a smartphone. This antenna contributes to high mechanical strength which can help prevent the display from cracking when the smartphone is dropped. The antenna can generate multi resonant mode at about 0.9 GHz band as well as at 1.5 to 2.2 GHz bands. The operating mode at 0.9 GHz and 2.0 MHz is a loop antenna. At 1.5 GHz the operating mode is a slot antenna. Furthermore, to realize 2×2 MIMO, the proposed antenna is mounted on the top and bottom sides of the smartphone. The effects of some important parameters (loading capacitor and users hand) are discussed in this paper. The proposed MIMO antenna can successfully achieve high mechanical strength and multiband characteristics for smartphones that have a metal frame.

A new design system for low profile inverted L antenna including a matching circuit

A new design system for a low profile inverted L antenna including a matching circuit is developed to design IoT terminal antennas. By using this system, the length of the antenna element placed at the corner of the finite size ground plane can be optimized so as to maximize the product of the bandwidth and efficiency. The number of optimization trials is less than ten. This is quite low compared to other optimization methods.

Planer frequency reconfigurable antenna for mobile terminals

We propose a novel design of a frequency reconfigurable antenna. The electrical length and return loss of the antenna are reconfigured by RF-MEMS switches. The area of the antenna element is 15 × 50 mm2. The measured total efficiency of the antenna is higher than -3 dB at almost all frequencies between 0.78 GHz and 5.85 GHz. This antenna is suitable for future mobile terminals, which include many radio systems.