Eisuke Nishiyama

Stacked microstrip antenna with wide bandwidth and high gain

A stacked microstrip antenna with two parasitic elements, one of which increases the impedance bandwidth and the other which enhances the gain, has been investigated experimentally. The effects of each parasitic element have been clarified as well as the characteristics of the stacked three-element antenna and the design procedure for the stacked microstrip antenna have been described.

Stacked microstrip antenna with wide band and high gain

A microstrip antenna composed of radiating, matching, and director elements is presented. The director element increases the gain of the antenna, while the matching element widens the frequency bandwidth of the input impedance. By adjusting the distance between the matching element and the radiating element by varying the height of the former element, the input impedance of the antenna is matched to the output impedance of the feed line. The proposed antenna, therefore, has wider impedance bandwidth and higher gain than the single-patch antenna. Since this antenna can be directly fed from the back of the ground plane, the feed circuit is simpler than that of the planar array antenna. For mobile communications, the stacked microstrip antenna array is useful when a gain of about 8 approximately 12 dBi is required.<<ETX>>

Three-element stacked microstrip antenna with wide-band and high-gain performances

In this paper, the three-element stacked microstrip antenna which is composed of a fed element and two parasitic elements is proposed. It has a wide bandwidth and a high gain. The stacked microstrip antenna is precisely analyzed using the FDTD method, in order to investigate the characteristics and the behavior mechanism of the stacked antenna.

5.8-GHz Series/Parallel Connected Rectenna Array Using Expandable Differential Rectenna Units

This communication demonstrates series and/or parallel connection of the differential rectenna units. The differential rectenna unit provides high expandability of rectenna arrays due to its balanced structure. The proposed rectenna array produces higher voltage and/or more current by the series and/or parallel connection of the rectenna units. In the measurement, 30% RF-DC conversion efficiency at the power density of 0.03 W/m2 was achieved in all the case of series and/or parallel four-units connected rectenna array. The maximum conversion efficiency was about 38% in the case of the series-parallel connection. As the proposed rectenna arrays can be easily expanded to large scale integrated rectenna arrays, it will be practically attractive for wireless power transmission.

5.8-GHz Integrated Differential Rectenna Unit Using Both-Sided MIC Technology With Design Flexibility

A 5.8-GHz integrated differential rectifying antenna (rectenna) unit with design flexibility is proposed, and its performance is confirmed experimentally. It positively uses both-sided microwave integrated circuit (MIC) technology, and its antenna feed circuit includes filters which suppress 2nd harmonic. This proposed rectenna unit is a very simple, compact and novel configuration. It operates in a differential mode, and effectively integrates an antenna array with a rectifying circuit. Its configuration provides the pragmatically advantages such as antenna array design flexibility and rectenna unit extensibility. Herein, the behavior of the rectenna unit was successfully confirmed under low radio frequency (RF) power density. Maximum RF-DC conversion efficiency at 5.8 GHz of Industry-Science-Medical (ISM) band was approximately 27% with the load resistance of 390 Ω when the received power density (PD) was 0.031 W/m2.

Gain enhanced linear polarization switchable microstrip array antenna

Recently the planner antenna technology is emerging due to the interesting demands for wireless communication of the ubiquitous society. The advantages of planner antenna over the other antenna types such as dipole, loop etc. are that, it is low cost, low profile and easily integrated with active components [1]. However the conventional microstrip antennas have some drawbacks such as narrow bandwidth, low gain etc. Several works have been done for increasing the gain of the antenna such as using the array technology. In this paper, a novel single fed orthogonal linear polarization switchable microstrip array antenna with enhanced gain is proposed. The structure based on the parasitic array technology [2] is used for the gain enhancement. The antenna consists of a fed patch and four parasitic patches. Four switching diodes are loaded on the corners of the fed patch to control the surface current. The proposed array antenna can switch the polarization axis to ±45deg. by controlling the surface current. The orthogonal transmission and reception function of conventional antenna is generally fixed, because of the absence of the switching function. If the switching function is possible, the design flexibility of the radio system will be much more expanded [3]. In order to realize ±45deg. orthogonal linear polarization controllable microstrip array antenna; four switching diodes are mounted on the corners of the fed patch. The FDTD method introduced by Yee [4] is used to simulate the antenna which is followed by the experimental investigation.

Wide-band and high-gain microstrip antenna with thick parasitic patch substrate

A stacked microstrip antenna which is composed, of a fed patch, a parasitic patch and a thick parasitic patch substrate, is proposed. Its characteristics have been investigated in detail using the FDTD method. The behavior mechanism for the high gain performances of the stacked microstrip antenna is explained clearly for the first time. The characteristics of the stacked antenna depend on the patch separation distance, that is, the thickness of the parasitic patch substrate. When the patch distance is approximately half a wavelength in the dielectric, an electric standing wave contributing to the radiation exists in the cavity between patches, and the amplitude of the electric fields becomes large. Because the thick dielectric is inserted in the space between the fed and the parasitic patches, the height of this stacked antenna becomes low. By adjusting the patch distance, the patch size and the feed point, the stacked microstrip antenna which has both wide bandwidth and high gain is successfully realized.

5.8-GHz Stacked Differential Rectenna Suitable for Large-Scale Rectenna Arrays With DC Connection

In this communication, a novel stacked differential rectenna is proposed and its characteristics are experimentally investigated. The proposed rectenna can effectively convert RF power to dc due to its differential operation. The conversion efficiency of 44.1% was obtained when the received power density was as low as 0.041 W/m2. The proposed rectenna can easily achieve large-scale rectenna arrays effectively using its simple structure. The rectenna array with DC connection provides almost the same conversion efficiency and incident angle characteristics in comparison with a single rectenna.

Linear polarization switchable slot ring array antenna with SPDT switch circuit

In this paper, a linear polarization switchable slot array antenna is proposed. A novel SPDT switch circuit is used in the proposed slot array antenna for polarization switching function. By using the SPDT switch circuit feed the RF signal to the array antenna, the antenna allowing switching orthogonal linear polarization is demonstrated. The excellent design flexibility of the “Both-Sided MIC technology” [1] is effectively employed in forming this type of antenna. The characteristics of this functional antenna are discussed by using simulated results. Consequently, it is verified that the linear polarization of the proposed antenna can be successfully controlled.

Wide band switchable circularly polarized microstrip antenna using double-balanced multiplier

In this paper, the reconfigurable antenna which excites orthogonal a circular polarization is proposed and the behavior and the characteristics of the antenna are experimentaly investigated. The proposed antenna has the cross slot at the center of the patch, and four diodes are embedded in a star form across the slot. A circular polarization is excited though in a wide band due to the nonlinearity of the diodes. When the bias voltage Vc superimposed on the RF signal is a slighty positive near 0 V, a LHCP is achieved. On the other hand, when Vc is a slightly negative near 0 V, a RHCP is achieved. Therefore, it is easily possible to switch the phase difference of plusmn90 degrees by a bias voltage Vc for those diodes in a wide band. As a result, switchable circular polarization antennas can be achieved in a wide frequency band. The proposed antennas are practically attractive for the wireless communications as a circularly polarized active antenna.