Xiulong Bao

Dual-Frequency Circularly-Polarized Patch Antenna With Compact Size and Small Frequency Ratio

A novel probe-fed single-layer annular-ring patch antenna for dual-frequency circular polarization is evaluated numerically and experimentally verified. The proposed antenna consists of a small circular patch surrounded by two concentric annular-rings, which is loaded by an unequal lateral cross-slot ground plane. The circularly-polarized frequency ratio of the two resonant modes is tunable to a small value, suitable for wireless communications systems. The patch size of the proposed antenna is reduced by about 53% compared to the conventional circular patch at a given frequency. The radiation characteristics of the novel antenna are also presented.

Dual-Frequency Dual-Sense Circularly-Polarized Slot Antenna Fed by Microstrip Line

A new design of a dual-frequency dual circularly-polarized slot antenna is presented. The dual-frequency is achieved using a single-layer microstrip-fed configuration coupled to a modified annular-slot antenna. The dual sense circular-polarization is obtained by four unequal linear slots which augment the annular slot. Experimental results show the proposed antenna has good circular polarization characteristics for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). The 10 dB return loss impedance bandwidths for the lower (RHCP) and higher (LHCP) bands are 26.7% and 11.3%, respectively. The 3 dB axial-ratio bandwidths are 6.1% and 6.0% with respect to 1.5 GHz (RHCP) and 2.6 GHz (LHCP), respectively.

A Novel GPS Patch Antenna on a Fractal Hi-Impedance Surface Substrate

A compact high-performance circularly-polarized microstrip antenna for the global positioning system application is proposed. It comprises a fractal hi-impedance surface electromagnetic bandgap (EBG) structure printed on a high permittivity substrate. Measurements and simulation of return loss and axial ratio are in good agreement. It is shown that the proposed Global Positioning System antenna has good axial ratio performance in the upper half-plane, an improvement in gain and a significantly wider axial ratio bandwidth when compared to the same antenna without EBG

Compact Patch Antenna for Electromagnetic Interaction With Human Tissue at 434 MHz

Single element loop, dipole and conventional square patch antennas have been used as hyperthermia applicators in the treatment of cancerous human cells at superficial depths inside the body. A smaller novel patch antenna in very close proximity to a phantom tissue model produces an enhanced specific absorption rate pattern without significant frequency detuning or impedance mismatch. The new patch increases its coupling aperture by supporting a combination of resonances that are also typical for loop, dipole and square patch antennas. For computation efficiency and clarity in the synthesized hyperthermia treatment conditions, simplified planar tri-layered tissue models interfaced with a water-bolus are used to study the permittivity loading on the antennas and the resultant specific absorption rates.

Printed Band-Rejection UWB Antenna with H-shaped Slot

The development of the high data rate wireless communication systems, has placed significant demands on antenna designers, in particular, the requirement for smaller elements with broader bandwidths. In this paper, a novel UWB antenna with notch-band frequency is studied. Effects of the various parameters for antenna performances are also discussed. An optimized compact UWB antenna with notch-frequency function is fabricated and experimentally examined. The measured results show the proposed UWB antenna can achieve a return loss greater than 10 db over an ultrawide bandwidth, of 9.8 GHz, from 2.97 GHz to 12.77 GHz with a tunable notch-frequency band of 5.15 GHz to 5.825 GHz

Dual Circularly-Polarized Patch Antenna Using Even and Odd Feed-Line Modes

This communication proposes a new patch antenna with dual circularly polarized capability at 2.575 GHz. The design exploits the even and odd modes in a coplanar waveguide transmission line and enables simultaneous right- and left-handed circular polarization, with two individual excitation ports. A patch antenna is fed by multimode transmission line and the advantages and disadvantages are discussed. A prototyped antenna realized up to 20 dB isolation between ports with S21 <; -10 dB bandwidth of 87 MHz. Realized gains for the two modes of operation are 5.77 and 7.23 dBic. The proposed structure is compact and easy to manufacture.

Circularly Polarized Antenna With Steerable Dipole-Like Radiation Pattern

An omnidirectional circularly polarized antenna with a rotatable dipole-shaped radiation pattern is proposed. The antenna is realized using a back-to-back coupled microstrip patch arrangement. The pattern is rotated by means of a phase shift, enabling reception (or transmission) of signals from all angles around a sphere. The method enables continuous pattern steering without the need for semiconductor or MEMS components integrated into the antenna. It also allows the use of more than one radiation pattern simultaneously, potentially providing coverage for any spherical angle. The theory is supported by simulation and measurement of four typical antenna configurations. The maximum gains are between 1.9 and 4 dBic and average axial-ratio varies between 2.5 and 3.65 dB at 2.47 GHz. The impedance bandwidth is from 2.4 to 2.51 GHz and the reconfigurable circular polarization is achieved from 2.464 to 2.484 GHz.

Wideband Dual-Frequency Dual-Polarized Dipole-Like Antenna

A wideband dual-frequency dual-polarized printed antenna is proposed for LTE, WLAN, and UWB systems. The dual-band antenna provides wide impedance bandwidths of 74% with respect to the center frequency of 2.725 GHz, and 39% with respect to the center frequency of 7.15 GHz. An open slot in the ground plane between the feed arms provides an orthogonal path to realize an embedded circularly polarized band at 2.35 GHz with an axial-ratio bandwidth of 16%. Dual-band characteristics are achieved by an asymmetrical dipole-like element and the coupling configuration between the T-shaped feed line and the wide ground-plane slot.

A Printed Triangular Monopole With Wideband Circular Polarization

A printed triangular monopole antenna with wideband circular polarization is presented. The wideband circular polarization is achieved by asymmetrical excitation of a triangular ground plane and planar triangular monopole. The combined radiation provides a wide axial-ratio bandwidth spanning from 1.42 to 2.7 GHz (62%). A parametric study of key geometric parameters is given for clear understanding of the radiation mechanism.

Bidirectional circularly polarized microstrip antenna for GPS applications

A bidirectional circularly polarised (CP) antenna for 1.575 GHz GPS L1 band is presented. The antenna consists of two back-to-back coupled patches and is fed directly by 50Ω Coplanar Waveguide (CPW). It is compact and relatively easy to manufacture compared to other antennas with similar properties. The bidirectional CP pattern is achieved by proper adjustment of patch dimensions as well as feed parameters. A study of the key parameter is provided.