Y. F. Cao

A Multiband Slot Antenna for GPS/WiMAX/WLAN Systems

The design of a four-band slot antenna for the global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) is presented. The antenna consists of a rectangular slot with an area of 0.37λg × 0.14λg = 48 × 18 mm2 (where λg is the guide wavelength), a T-shaped feed patch, an inverted T-shaped stub, and two E-shaped stubs to generate four frequency bands. The radiating portion and total size of the antenna are less than those of the tri-band antennas studied in literature. Parametric study on the parameters for setting the four frequency bands is presented and hence the methodology of using the design for other frequency bands is proposed. The multiband slot antenna is studied and designed using computer simulation. For verification of simulation results, the antenna is fabricated and measured. The simulated and measured return losses, radiation patterns, realized peak gains, and efficiencies of the antenna are presented. Measured results show that the antenna can be designed to cover the frequency bands from 1.575 to 1.665 GHz for the GPS system, 2.4-2.545 GHz for the IEEE 802.11b&g WLAN systems, 3.27- 3.97 GHz for the WiMAX system, and 5.17-5.93 GHz for the IEEE 802.11a WLAN system. The effects of the feeding cable used in measurement and of the cover are also investigated.

A Simple Planar Polarization Reconfigurable Monopole Antenna for GNSS/PCS

The design of a simple planar polarization reconfigurable monopole antenna for the Global Navigation Satellite System (GNSS) and Personal Communications System (PCS) is presented. The antenna consists of two meandered monopoles, a feeding network using the Wilkinson power divider, two switchable 90 0-phase shifters implemented using λ/4-microstrip lines and a defected ground structure (DGS). The meandered monopoles resonating at about 1.55 GHz are placed perpendicular to each other. The input signal is divided into two signals with equal amplitude and phase by the power divider and fed to the meandered monopoles via the phase shifters. The two signals arriving at the two monopoles have a phase difference of 90 0, -900 or 0 0, depending on the phase shifters controlled using six PIN-diode switches, hence generating a right/left-handed circularly polarized (CP) or linearly polarized (LP) signal. We propose a novel biasing technique to control the six PIN diodes using five voltages. Measurement results show that the antenna in CP has an impedance bandwidth of 1.06-1.64 GHz and an axial-ratio bandwidth of 1.43-1.84 GHz, and in LP has an impedance bandwidth of 1.63-1.88 GHz. Simulated and measured results on S11, AR, radiation pattern, and gains show good agreements.

Dual-Cap Mushroom-Like Metasurface Used in CP Reconfigurable Monopole Antenna for Performance Enhancement

A dual-cap mushroom-like metasurface (MS) is proposed. The proposed MS is called dual-cap mushroom-like MS because each unit cell has a simple patch with a centered via on one side of the substrate and a meandered slot on the other side, while conventional mushroom-like MS has one side of the substrate being a plain conducting plate. The meandered slot on the other side of the substrate introduces inductive effects to lower down the operating frequency and increases the operating bandwidth of the unit cells. Comparison is made with other unit cells. The proposed MS is then used as a reflector in the design of a planar circular-polarization reconfigurable (CPR) monopole antenna for the global navigation satellite system (GNSS). Simulation results show that, by placing at only 0.0λ90 from the antenna, the MS can increase the boresight gain and the operating bandwidth from 0.4 to 6.6 dBi, and 1.46-1.79 GHz to 1.42-1.88 GHz, respectively.

Circularly polarized monopole antenna using CRLH TL feed network

A circularly polarized (CP) monopole antenna with the feed network designed based on using composite right/left-handed transmission line (CRLH TL) is proposed. The CP antenna consists of two monopole elements, a 90°-phase shifter implemented using a CRLH TL unit cell and a Wilkinson power divider. The two monopole elements are designed to operate at a frequency of about 2.3 GHz and placed in perpendicular to each other to generate two orthogonal-electric fields. The power divider divides the input signal into two signals with equal amplitude and phase. One of the signals is fed to a monopole element via the phase shifter, while the other signal is fed directly to the other monopole element. The two signals at the corresponding monopole elements are therefore in phase quadrature, hence generating a CP signal. Simulation results show that the antenna has an impedance bandwidth (S11 <; -10 dB) of 1.89-3.20 GHz and a wide axial-ratio bandwidth (AR <; 3 dB) of 2.08-2.36 GHz.