Fook-ong Lo

Circularly Polarized Elliptical Microstrip Patch Reflectarray

A double-layered elliptical microstrip patch element is proposed for designing a broadband circularly polarized (CP) reflectarray for the first time. The proposed reflectarray element is composed of two elliptical patches stacked on the top and middle surfaces of two substrates, and reflection phase range is generated by varying the major axes of the elliptical patches. Floquet method is employed for simulating the element, and it is found to be able to generate circular polarization (CP) with a broad reflection phase range of 550° with only two layers. With the use of the element, a CP

Reconfigurable Stepped-Impedance Slotline Power Dividers

11\times11

DRA REFLECTARRAY UNIT ELEMENTS WITH THIN UNDER-LOADING PARALLEL SLOTS

full-fledged reflectarray has been designed and fabricated. The reflectarray is fed by a linearly polarized horn. Measurement shows that the proposed CP elliptical microstrip patch reflectarray is able to achieve an antenna gain of 20.38 dBic and a 1-dB gain bandwidth of 11.6%. It also has a broad 3-dB axial ratio bandwidth of 12.47%.

Double-Layered Circular Microstrip Reflectarray Element with Broad Phase Range

For the first time, the higher-ordered modes of a stepped-impedance slotline resonator are closely combined for designing the broadband in-phase and out-of-phase power dividers. It was found that the output phases of the two modes can be easily reversed at the same time by changing the direction of their feeding currents. For this configuration, interestingly, a multifunctional power divider which is reconfigurable to produce either in-phase or out-of-phase signals can be easily designed from its passive counterparts by incorporating multiple RF diodes into the output feedlines, leading to significant cost saving and high compactness. The design procedure and equations of the power-dividing structures are discussed.

Study of Cross-Slotted Circular Microstrip for Reflectarray Design

This paper presents three dielectric resonator (DR) unit elements loaded with one, two, and three narrow slots underneath for designing re∞ectarrays. The slots are aligned in parallel, and the lengths are varied to function as phase shifter for changing re∞ection phase. It is found that the dominant TE mode of the square DR element can be easily excited by placing multiple parallel slots beneath a DR element. Study shows that the number and width of the slots can be used as additional design parameters for tuning the re∞ection loss and phase range of the re∞ectarray. Rectangular waveguide method has been deployed, showing reasonable agreement between simulation and measurement. It is found that a reasonable re∞ection phase range of 313 - with slow slope is obtainable when the DRA is loaded with two slots beneath, which can be used for designing a small-size re∞ectarray. The re∞ection characteristics of the unit elements are studied, along with a complete parametric analysis.

CIRCULARLY POLARIZED YAGI-UDA-LIKE TRANSMITARRAY

In this paper, a double-layered microstrip re∞ectarray element is studied. The unit element consists of a circular patch sandwiched between two substrates and a cross-slotted circular patch placed on the top-most surface. The radii of the two circular patches as well as the cross-slot lengths are varied simultaneously for controlling the phase range and the gradient of the re∞ection phase angle. Study shows that the sensitivity of the re∞ection phase angle can be made slower by utilizing substrates with lower dielectric constants. The component performance is studied using a rectangular waveguide and good agreement is found between the simulation and experiment. A wide re∞ection phase range of 681.82 - with loss magnitude less than i1dB is achievable in the re∞ection phase angle. A complete parametric analysis has been conducted to study the re∞ection characteristics of the proposed re∞ectarray unit element.

Compact Folded Dipole With Embedded Matching Loop for Universal Tag Applications

In this paper, a circular microstrip patch centrally etched with a cross slot is studied. The slot dimensions are varied for controlling the re∞ection loss and the phase range of a re∞ectarray. It is found that the dominant TM mode of the slotted circular patch can be easily excited, and the slot length can be varied to function as a phase-changing parameter. Cross slots with equal and unequal arms are investigated. Study shows that the slope of the S curve can be made slow-changing by increasing the slot widths simultaneously. A maximum re∞ection phase range of 328.68 - is achievable in the S curve. Rectangular waveguide method has been deployed for simulating and verifying the design idea. Reasonable agreement is found between the measurement and simulation.

Transparent Dielectric Resonator Reflectarray with Bottom-Loading Strip

A novel Yagi-Uda-like transmitarray is proposed for circularly polarized (CP) operation. The element consists of multiple strips stacked in parallel for achieving broad transmission phase range. By employing the design concept for the Yagi-Uda director, the transmitarray elements are made to provide the functions of phase shifter and director simultaneously. By introducing rotational offset into the stacking strips, the element is found to be able to generate circular polarization. To demonstrate the working principle, an 8-layer unit element is simulated using the Floquet method to provide a transmission phase range of 412◦. The proposed 5× 5 full-fledged CP transmitarray is able to produce an antenna gain of 16.2 dBi, a −1-dB bandwidth of 4%, an axial-ratio bandwidth of 7%, and an aperture efficiency of 40.4%. A simple curve-fitted design equation is also given.

Flexible Folded-Patch Antenna with Serrated Edges for Metal-Mountable UHF RFID Tag

A coin-shaped folded dipole is proposed for designing a UHF tag that can be placed in free space and on metal. The proposed tag antenna is compact (

Compact Orientation Insensitive Dipolar Patch for Metal-Mountable UHF RFID Tag Design

0.095\lambda )