Xudong Bai

A Broadband Dual Circularly Polarized Patch Antenna With Wide Beamwidth

A broadband dual circularly polarized patch antenna with wide beamwidth is presented. The patch is excited by four cross slots via a microstrip line with multiple matching segments underneath the ground plane. The four cross slots and the multiple matching segments are optimized simultaneously to obtain the best performance. Measurements show that the antenna has 10-dB return-loss bandwidth of 24%, 10-dB isolation bandwidth of 19%, 3-dB axial-ratio bandwidth of 16%, and beamwidth of 110 °. Moreover, the single feed makes it a good candidate for array design.

Generation of OAM Radio Waves with Three Polarizations Using Circular Horn Antenna Array

An effective solution of generating OAM-carrying radio beams with three polarizations is provided. Through the reasonable configuration of phased antenna array using elements with three polarizations, the OAM radio waves with three polarizations for different states can be generated. The vectors of electric fields with different OAM states for linear, as well as left or right circular polarizations are presented and analyzed in detail.

Dual-Circularly Polarized Conical-Beam Microstrip Antenna

A dual-circularly polarized (CP) microstrip antenna with conical-beam radiation is presented in this letter. The antenna is excited at the second-order mode to generate the conical radiation pattern and is fed by a hybrid coupler to obtain the dual-CP operation, which shows a stable performance with varisized metal reflectors. The measured results are consistent with the simulated ones in terms of good dual-CP conical patterns, which verified the effectiveness of the proposed design. All these features make the proposed antenna very suitable for vehicle-mounted satellite communication applications.

An Omnidirectional Circularly Polarized Slot Array Antenna With High Gain in a Wide Bandwidth

In this letter, a novel omnidirectional circularly polarized (CP) slot array antenna with high gain is proposed. The array is based on the coaxial cylinder structure. The omnidirectional radiation is realized by four perpendicular slot pairs surrounding the axis of coaxial cylinder in the outer conductor, which can be seen as a basic omnidirectional CP element. With four of these basic elements along the axis of the coaxial cylinder, the radiation slot array is constructed with desired omnidirectional CP property and particularly stable high gain in a wide bandwidth. To match the antenna, three cascade coaxial lines with the same outer radius but different characteristic impedance are connected to its input. Measured results show that the proposed antenna performs a -10 dB impedance bandwidth (S11<;-10 dB) of 16.4% ranging from 5.05 to 5.95 GHz and a 3-dB axial-ratio (AR) bandwidth of 14.5% ranging from 5.1 to 5.9 GHz. Within the common band ranging from 5.1 to 5.9 GHz, the measured gain in the omnidirectional plane (xy-plane) is stable and higher than 5 dBic.

Compact Design of Triple-Band Circularly Polarized Quadrifilar Helix Antennas

This letter introduces the compact design of triple-band circularly polarized quadrifilar helix antennas (QHAs) possessing the characteristics of wide beam, high gain at the low elevation, and high stability of the phase center. The available triple-band operation is achieved through the incorporation of a UHF-band QHA and an L/S-band QHA, which are assembled in a “piggyback” fashion. The UHF-band QHA is fed by a compact microstrip feed network, while the L/S-band QHA is fed by a split coax balun. The measured results coincide well with the simulated ones, which verified the effectiveness of the proposed compact design .

Rotman Lens-Based Circular Array for Generating Five-mode OAM Radio Beams

Recently, vortex beam carrying orbital angular momentum (OAM) for radio communications has attracted much attention for its potential of transmitting multiple signals simultaneously at the same frequency, which can be used to increase the channel capacity. However, most of the methods for getting multi-mode OAM radio beams remain up to now mainly at simulation level, since their implementations are of complicated structure and very high cost. This paper provides an effective design of generating five-mode OAM radio beams by using the Rotman lens-fed antenna array. The Rotman lens is a viable beamforming approach instead of electronically scanned arrays for its low cost and the ease of implementation. The lens-fed array employs a two-layer structure for size reduction, and the lens body and the antenna array are segregated by a common ground plane to eliminate spurious radiation and thus improve the performance of the OAM beams. The measured results coincide with the simulated ones, which verified the effectiveness of the proposed design for generating multi-mode OAM beams.

Perforated dielectric antenna reflectarray for OAM generation

A new type of perforated dielectric flat reflectarray for the generation of OAM-carrying radio waves is presented. The reflectarray is introduced to transform the spherical wave emanating from the feed into a vortex beam after reflection through the azimuthal variation of the effective dielectric permittivity. Through perforating the substrate with holes of various diameters, an azimuthal variation of the permittivity is obtained and the corresponding azimuthal phase-compensation creates a vortex, thus an OAM wave is generated. The reflectarray antenna works in the millimeter frequency band, and can be used to generate the OAM states of ℓ =+1.

Design of a horn lens antenna for OAM generation

A horn lens antenna designed for the generation of OAM-carrying radio waves is presented. The conventional horn antenna is integrated with a single-layer perforated planar dielectric lens by covering its aperture. Through varying the diameter of holes, an azimuthal variation of the permittivity is obtained and the corresponding azimuthal phase delay creates a vortex, thus an OAM wave is generated. The lens antenna works in the millimeter frequency band, and can be used to generate the OAM states of ℓ =+1 or -1.

A novel compact circularly polarized horn antenna

A novel circularly polarized horn antenna with wide bandwidth and compact size is presented. The antenna is composed of an ellipse-aperture horn antenna, circular-to-square transition and novel circularly polarizer. The polarizer consists of five-step septum in a square waveguide, coaxial-waveguide converter and reflecting back-cavity. The antenna achieves an impedance bandwidth (S11<;-10dB) of 22.1% and a 3-dB AR (Axial Ratio) bandwidth of 18.3%, with the 3dB-AR beam width of about 138°, and the antenna gain is over 10.5dBi in the operation band.

Experimental Array for Generating Dual Circularly-Polarized Dual-Mode OAM Radio Beams

Recently, vortex beam carrying orbital angular momentum (OAM) for radio communications has attracted much attention for its potential of transmitting multiple signals simultaneously at the same frequency, which can be used to increase the channel capacity. However, most of the methods for getting multi-mode OAM radio beams are of complicated structure and very high cost. This paper provides an effective solution of generating dual circularly-polarized (CP) dual-mode OAM beams. The antenna consists of four dual-CP elements which are sequentially rotated 90 degrees in the clockwise direction. Different from all previous published research relating to OAM generation by phased arrays, the four elements are fed with the same phase for both left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The dual-mode operation for OAM is achieved through the opposite phase differences generated for LHCP and RHCP, when the dual-CP elements are sequentially rotated in the clockwise direction. The measured results coincide well with the simulated ones, which verified the effectiveness of the proposed design.