Tamotsu Nishino

Experiments on wireless power transfer with metamaterials

In this letter, we propose the use of metamaterials to enhance the evanescent wave coupling and improve the transfer efficiency of a wireless power transfer system based on coupled resonators. A magnetic metamaterial is designed and built for a wireless power transfer system. We show with measurement results that the power transfer efficiency of the system can be improved significantly by the metamaterial. We also show that the fabricated system can be used to transfer power wirelessly to a 40 W light bulb.

Wireless power transmission efficiency enhancement with metamaterials

In this paper, a wireless power transfer system with magnetically coupled resonators is studied. The idea to use metamaterials to enhance the coupling coefficient and the transfer efficiency is proposed and analyzed. With numerical calculations of a system with and without metamaterials, we show that the transfer efficiency can be improved with metamaterials.

Tunable MEMS hybrid coupler and L-band tunable filter

Simultaneous control of frequency and coupling coefficient of a directional coupler provides a wide band tunable hybrid coupler. This hybrid coupler is combined with identical two tunable band rejection filters (BRF), to achieve a small-size wide-band tunable band pass filter (BPF). The BPF is called a reflection-type BPF and has a feature of converting rejection frequency bands of the BRF to pass frequency bands.

Millimeter-wave plastic waveguide phased array antenna

Low cost and high performance millimeter-wave phased array antennas have been demanded in recent years due to increasing millimeter-wave applications in highspeed mobile communications, broadband wireless LAN/PAN (WLAN/WPAN), automotive collision avoidance radars, and so on. Several types of millimeter-wave antennas and components have been proposed for these systems. For example, plastic waveguide structures, which are composed of hollow liquid crystal polymer (LCP) and plated copper [1], [2], have been reported in order to reduce the cost for mass-production scheme. However, the phased array antennas are difficult to form their complex configurations and difficult to obtain low-loss characteristics as well. This paper presents millimeter-wave waveguide-type phased array antennas using low-loss engineering plastics not only to reduce cost but also to obtain high performances with complex configurations. That is a Cyclo-Olefin Polymer (COP) waveguide horn array antenna which is fabricated by injection molding process [3].

An Rfmems Switched Capacitor Array for a Tunable Band Pass Filter

In this paper, we present an RFMEMS switched capacitor array, which is proposed as a RF component to achieve various kinds of tunable RF filters. Our RFMEMS switched capacitor array consists of RFMEMS direct contact switches and metal-insulator-metal capacitors. In order to obtain reliable capacitors, the metal sacrificial layer for the RFMEMS switch fabrication is also applied to the capacitor implementation. We have achieved a C- to Ku-band tunable band pass filter by using the RFMEMS switched capacitor array. The capacitance of capacitor is designed corresponding to each tuning state of the band pass filter, which is selected by the RFMEMS switch operation. The insertion losses of the band pass filter were 7.1dB, 4.9 dB and 6.2 dB at 8 GHz, 12 GHz and 16 GHz, respectively.

A novel grounded coplanar waveguide with cavity structure

This paper presents a grounded coplanar waveguide (GCPW), which is useful in RF-MEMS devices in order to effectively reduce noise from neighboring transmission lines. The GCPW structures demonstrated here were fabricated by front-surface-only processes on a single silicon wafer. A silicon nitride membrane supports the coplanar waveguide, which is located above a ground plane formed on an etched silicon cavity We found that the insertion losses of the 50-/spl Omega/ GCPWs with a 26-/spl mu/m-wide signal line and a 6-/spl mu/m-deep cavity do not exceed 0.4 dB/mm up to 20 GHz, which agreed with the simulated loss. The demonstrated maximum depth of metallized cavity is 30 /spl mu/m, which enables the GCPWs loss to be as low as 0.08 dB/mm at 20 GHz.

A grounded co-planar waveguide MEMS switch

A grounded co-planar waveguide (GCPW) MEMS switch is presented. The proposed switch has a movable SiN membrane with a signal line and ground lines above a dielectric-air-metal (DAM) cavity on which a ground metal is patterned, resulting in a structure of GCPW transmission line. The electrostatic force makes an RF short path to the ground metal on the bottom of the DAM cavity with metal-to-metal contact. The ground metal which covers silicon substrate makes the switch to be on a low-resistivity silicon substrate. The measured results of the switch validate the proposed structure of the switches utilizing the DAM cavity.

Simultaneous implementation of various RF passives using a novel RF MEMS process module and metallized air cavity

We present a novel device structure applicable to various RF MEMS devices that consist of a dielectric membrane and metallized air cavity. RF MEMS device components are formed on the dielectric membrane, which is suspended above the metallized air cavity. The metallization of the bottom of the air cavity allows us to realize the ground plane. Moreover, by applying the air cavity, the influence of the substrate on the loss characteristics of the device can be minimized. In this paper, we also present a novel RF MEMS process module to realize our proposed device structure. By means of our RF MEMS process module, four RF passives could be successfully developed. The implementation of these passives could be achieved simultaneously on the same silicon substrate. Our fabricated passives are a grounded coplanar waveguide (GCPW), a 90° hybrid, an elliptic low pass filter (LPF) and an inductor. All of them are fabricated on a silicon nitride membrane suspended above the 30 µm deep metallized air cavity. They have been developed as components of a wireless communication transceiver module at 12 GHz. We performed characteristics measurement and obtained 2.03 dB and 2.18 dB as insertion losses, and 21.63 dB as the return loss for the 90° hybrid at 12 GHz. For the elliptic LPF and GCPW, we obtained the insertion losses at 12 GHz as 1.86 dB and 0.1 dB mm−1, respectively. The measurement results are also in agreement with the simulation results. Our proposed device structure and RF MEMS process module have the advantages in terms of loss characteristics, manufacturing cost and applicability.

A 12GHz lumped-element hybrid fabricated on a micromachined dielectric-air-metal (DAM) cavity

A novel lumped-element hybrid is presented. The hybrid is disposed on a newly developed dielectric-air-metal (DAM) cavity, which consists of an SiN membrane above a metallized 30-um-deep cavity made by a micromachining process. This process enables to make every component be worked from one-side of a silicon (Si) substrate, and to leave back-side as a part of a package. This is indispensable to realize a very thin MEMS-packaged-device consisting of two wafers bonded. Also, patterned metal grounds can provide all kinds of lumped elements. Among those, series inductors are investigated in detail. A hybrid with series inductors and shunt capacitors is fabricated. Good agreement between the measured and simulated results was obtained to validate this structure for fabrication of micro-size microwave components on an Si substrate.

A CPW hybrid coupler with an enhanced coupling microstructure

A new micromachined coplanar waveguide (CPW) 3-dB hybrid coupler has been demonstrated. A micromachined enhanced coupling structure at the middle of two coupled transmission lines is employed to obtain high directivity. The coupling structure is composed of alternately overlapping plated conductors employing micromachined air-gap structures. This structure relaxes the tolerance of the gap between the coupled transmission lines, and mitigates production error. Moreover, this coupling structure enhances the coupler directivity by equalizing phase velocities of both even- and odd modes. We fabricate the CPW hybrid coupler with the enhanced coupling structure on a silicon substrate to verify the performance. The results showed the return loss of better than 28 dB, the isolation of more than 25 dB over 11 to 15 GHz.