Takeshi Fukusako

Broadband Design of Circularly Polarized Microstrip Patch Antenna Using Artificial Ground Structure With Rectangular Unit Cells

This paper presents a broadband circularly polarized patch antenna using an artificial ground (AG) structure with rectangular unit cells as a reflector. The AG structure changes the reflection phase in accordance with the polarization state of the incident wave. By properly combining the transmitted wave from the antenna and the reflected wave from the AG structure, broadband circular polarization can be obtained. The AG structure and the antenna are simulated using a full-wave solver and the results show a 10 dB return loss bandwidth of 48.6% and a 3 dB axial ratio bandwidth of 20.4%. The measured results are in good agreement with the simulated results. The radiation characteristics of the antenna are almost the same as those for an antenna with a PEC reflector.

BANDWIDTH ENHANCEMENT OF CIRCULARLY POLARIZED SQUARE SLOT ANTENNA

Bandwidth enhancement technique of circularly polarized square slot antenna is presented in this paper. A square slot antenna with the components of L-probe separated could achieve an axial ratio (AR) bandwidth of 33.84%. Placing Stubs in the slot by studying the electric fleld behaviour could enhance the AR bandwidth by around 10%. Creating an L-shaped slot on the ground plane, where the electric fleld rotates in the desired clockwise direction, can further enhance the bandwidth by 7%. A < i10dB S11 bandwidth of 46.15% and < 3dB AR bandwidth of 50.35% could be achieved with the present design. Unidirectional patters are obtained by having a cavity at the wide slot of the antenna and shows a measured bandwidth of 41.79% in S11 and 44.97% in AR. Both antennas show a cross polarization discrimination of more than 15dB on a wide azimuth range. The measured results well comply with the simulated results.

Gain Enhancement of Low-Profile, Electrically Small Capacitive Feed Antennas Using Stacked Meander Lines

The present paper describes the gain enhancement of a small and low-profile linear antenna with capacitive feed (C-feed) using three metallic layers. The antenna has very small leakage current on the outer conductor of the coaxial cable and can easily control the imaginary part of the input impedance. The gain of the stacked three-layer meander line antenna, with the meander line in the middle layer being opposite to that of the other two layers, has increased by around 7 dB compared to the single layered C-feed antenna. The antenna gain is discussed based on simulated and measured results, which demonstrates that the antenna has successfully achieved the acceptable impedance and sufficient gain for mobile terminals and RFID tags.

Low-Profile and Electrically Small Meander-Line Antenna Using a Capacitive Feed Structure

An electrically small and low-profile meander-line antenna using a capacitive feed structure is presented. The meander line has a length of one quarter-wavelength with a shorted end, and the capacitive feed structure is installed at the other end. A back conductor, which works as a ground plane, is located at a distance of 0.01λ0 to the meander-line element forming in the area of 0.121λ0 × 0.075λ0, which satisfies the condition of electrically small antennas (ka = 0.435 <; 0.5, wavenumber k, radius a of a sphere surrounding the antenna, and wavelength λ0 at the resonance frequency). The fabricated antenna has successfully achieved a peak gain of 0.62 dBi and exhibits a higher radiation efficiency of more than 30% compared to an inverted-F antenna of the same dimension.

Design of broadband circularly polarized horn antenna using an L-shaped probe

This paper deals with a circular horn antenna fed by an L-shaped probe. The design process for broadband matching to a 50 Omega coaxial cable, and the antenna performance in axial ratio and gain are presented. The simulation results of this paper were obtained using Ansoft HFSS 9.2

Circularly polarized broadband antenna with circular slot on circular ground-plane

A novel circularly polarized antenna with a circular radi- ating aperture and circular ground plane for broadband characteristics is presented in this paper. The vertical and horizontal components of the L-shaped probe are separated and placed at the front and back sides of the substrate. The antenna is excited by a microstrip line which is connected to the vertical component of the L-shaped probe and electromagnetically couples the signal to the horizontal compo- nent of the L-shaped probe. The concept of placing an appropriate stub in the slot, by observing the electric fleld vector behaviour in the slot, is proposed to enhance the axial ratio (AR) bandwidth by around 15%. The fabricated antenna shows wideband impedance and circu- lar polarization characteristics of 48% along with a maximum gain of 6dBic. The measured and simulated antenna characteristics are in good agreement.

Circular slot antennas using L-shaped probe for broadband circular polarization

Novel circularly polarized antennas with a circular radiating aperture for broadband characteristics are presented in this paper. The vertical and horizontal components of the L-shaped probe are separated and placed at the front and back side of the substrate. The antennas are excited by a microstrip line which is connected to the vertical component of the L-shaped probe and electromagnetically couples the signal to the horizontal component of the L-shaped probe. A novel concept of placing stub in the slot of a planar antenna, by observing the electric fleld vector behaviour in the slot, is proposed to enhance the axial ratio (AR) bandwidth by around 10%. Unidirectional patterns can be obtained by having a cylindrical cavity of height ‚g=4 behind the antenna and is efiective when no stubs are placed in the slot. A < 3dB AR bandwidth of 39.5% with cavity and 41.18% without cavity but with stub in the slot is obtained in simulation and the results well match with the measurement.

Circularly polarized reconfigurable patch antenna using Y-branched feed circuit

This paper is devoted to a circularly polarized patch antenna with the Y-branch feeding structure for switching circular polarization (CP) between left-hand CP (LHCP) and right-hand CP (RHCP). In this structure, the feed circuit is installed behind the ground plane because the electromagnetic distribution on the feeding line has no effect on the radiation pattern. In addition, the slot coupled structure is adopted to avoid a complicated manufacturing process like via-hole structures resulting in ease of fabrication of multi-layered structure. This provides an interest for us in the effect of the slot structure on cross-polarization discrimination (XPD) because we need two adjacent slots in the present structure.

An interpretative study on circularly polarized patch antenna using artificial ground structure

This communication presents some interpretative studies on a circularly polarized broadband patch antenna using an artificial ground structure (AGS). This patch antenna has a broadband characteristics in both impedance and axial ratio, which are more than 20% and 40%, respectively. The principle to expand the 3-dB axial ratio characteristics is discussed using a combination of circularly polarized patch antenna and an AGS polarizer. Furthermore, a broadband matching method using an extended outer conductor of coaxial cable is discussed. The mechanism of the matching structure is also discussed.

Circularly Polarized Broadband Antenna With L-Shaped Probe and L-Shaped Wide-Slot

This paper deals with a novel type of circularly polarized broadband planar antenna with broadband characteristics in impedance matching and axial ratio. The proposed antenna consists of an L-shaped wide-slot and reshaped probe. Both the characteristics are discussed for simulated and measured 3 dB axial ratio over 40% at 6 GHz.