Takashi Yamagajo

Low correlation antenna design for diversity handset applications

The design of compact diversity antenna for wireless handset applications has been presented. The results obtained demonstrate high potential of such a design for the handset antenna systems realizing various diversity techniques, such as switched diversity, maximal ratio combining and selection diversity. This antenna structure can also be utilized in a MIMO system, where the low mutual coupling between the antenna elements is required. It has been confirmed that the antenna radiation characteristics (radiation gain, directivity and total efficiency) satisfy the specification parameters being demanded for wireless handset applications.

A circulary polarized planar antenna for near field and far filed communication systems

A novel planar antenna design is proposed. The antenna generates uniform electromagnetic field in the near field and radiates circularly polarized wave in the far field. Communication area can be easily controlled by changing the antenna size. The antenna is composed of the open ended micro strip line (MSL) and the multiple pairs of the folded dipole antenna (FDA) placed in close proximity to the MSL. Adjusting the position of the FDAs properly, they couple electromagnetically to the MSL and radiate circularly polarized wave. This antenna is suitable for near field and far field communication systems.

Planar CP RFID R/W antennas based on EM Coupling

This paper presents the new approach to design planar circularly polarized (CP) antennas for RFID read/write (R/W) applications in UHF band. The objective of this work has been to design an RFID R/W antenna having simple unobstructed layout and single feeding port yet demonstrating good CP performance. Two RHCP antennas utilizing the principle of EM coupling from dipole element to the parasitic structure have been realized. The first design is the loop coupled dipole antenna (LCDA) where the pair of rectangular loops is placed in close vicinity of a dipole element. The second one is the dipole coupled dipole antenna (DCDA) which includes a pair of parasitic strips coupled to a dipole element. The operational principle of producing the CP radiation has been analyzed and illustrated in the detail. Both simulations and prototype measurements data demonstrating the required impedance characteristics and CP axial ratio have been obtained.

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.