Yu-Ming Wu

A Uniplanar Triple-Band Dipole Antenna Using Complementary Capacitively Loaded Loop

A uniplanar compact metamaterial-inspired triple-band dipole antenna is designed and proposed for wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. By introducing two pairs of complementary capacitively loaded loop (CCLL) slots into a uniplanar bow-tie antenna, two notched bands can be generated to form a triple-band operation. The antenna is directly fed by a 50- Ω microstrip line and a microstrip-to-coplanar-stripline (CPS) transition as a wideband balun. Antenna parameters, including voltage standing-wave ratio (VSWR), radiation patterns, and gain, are obtained by numerical simulations and experimental measurements. The results show that the proposed antenna can provide triple-band operation at 2.21-2.77, 3.33-3.95, and 5.04-6 GHz with the VSWR less than 2 to achieve 2.4/5.2/5.8-GHz WLAN and 2.5/3.5/5.5-GHz WiMAX applications.

Millimeterwave and Terahertz Waveguide-Fed Circularly Polarized Antipodal Curvedly Tapered Slot Antennas

Antipodal curvedly tapered slot antennas (ACTSAs) with different slot profiles are investigated to achieve the optimum circular polarization performance. The profiles of the tapered slots can be determined by different curves, such as linear, exponential, and logarithmic curves. Therefore, the corresponding waveguide-fed circularly polarized (CP) antipodal linear, exponential, exponential-logarithmic tapered slot antennas (AL-, E-, EL-TSA) are designed, fabricated, and measured at Ka-band for a comprehensive study. The optimized AELTSA provides good impedance matching, gain above 10.3 dBi, sidelobe lower than -15 dB, low cross-polarization, and left-hand circularly polarized (LHCP) axial ratio (AR) lower than 3 dB, from 28 to 40 GHz. Moreover, a waveguide-fed LHCP antipodal exponential-exponential tapered slot antenna (AEETSA) is designed at 500 GHz and fabricated by silicon micromachining. The radiation characteristics are examined by measurement results of symmetric beams and ARs lower than 1.5 dB, from 490 to 510 GHz.

A Ka band circularly polarized corrugated antipodal tapered slot antenna

A waveguide-fed circularly polarized corrugated antipodal tapered slot antenna (ATSA) working in the Ka band (26.5~40 GHz) is proposed in this paper. The exponential tapering shape is adopted to maintain the consistency of the antennas beam-width. In addition, the corrugation structure along the edges of ATSA is particularly designed to improve the axial ratio and cross polarization properties of the antenna. Our simulation results indicate that such corrugated ATSA is able to provide the good antenna radiation performances.

Dual-band bandpass filter using composite metamaterial resonator

A dual-band bandpass filter at X-band is proposed using composite metamaterial resonator consisting of an outer square closed-ring resonator (SCRR) and two inner electric inductance–capacitance (ELC) resonators. Numerical simulation and microwave measurement reveal that the filter exhibits two passbands centered at 8.76 GHz and 11.04 GHz, with 3 dB bandwidths of 130 MHz and 290 MHz, respectively. The complex dispersion relation of the filter is further derived based on the effective medium theory, where two balanced composite right-/left-handed bands are found, i.e. lines exhibiting two left-handed and two right-handed bands alternating. The proposed filter may find useful in dual-band or multi-band wireless communication systems.

Polarization-Independent and Angle-Insensitive Metamaterial Absorber Using 90-Degree-Rotated Split-Ring Resonators

We present the design, simulation, and measurement of a polarization-independent and angle-insensitive metamaterial absorber (MA) in X-band. Since the unit cell of the MA consists of four subwavelength split-ring resonators with 4-fold symmetric rotation, the MA is insensitive to the variation of both polarization and incident angle of the planar electromagnetic wave. The electromagnetic performances of the MA are studied by full-wave simulations based on finite-element method and the Naval Research Laboratory arch experimental measurements. The electric field distributions are numerically investigated, which confirm the polarization-insensitive property of the MA, as expected from the symmetric nature of the structure. When the incident angles vary from 0 to 45 degrees, the MA remains at full width at half maximum of 0.4 GHz (0.5 GHz) with peak absorptions of 99.9% (95.2%) at 10.27 GHz (10.3 GHz) by simulations (measurements).

Recent investigation of wideband millimeter-wave dielectric reflectarray in Beijing Institute of Technology

Several wideband millimeter-wave dielectric reflectarray antennas are discussed in this paper. Different phase distributions are realized by changing the shape or material of the array element. Three dielectric reflectarray of 20×20 elements operating at 100GHz are compared. The 1dB gain bandwidths of the dielectric reflectarray are larger than 10% and up to 40%. As compared to the microstrip reflectarray, the dielectric reflectarray can reduce the metal losses and effectively improve the gain bandwidth.

Noncoplanar optical bow-tie shaped nanoantenna and array for near-field enhancement

In this paper, a new form of noncoplanar optical bow-tie shaped nanoantenna structure is proposed, analyzed, and further arranged in array to investigate their near-field enhancement properties. The noncoplanar design not only improves the near-field electric field enhancement performance by 33% compared with that of the coplanar form, but also achieves better compatibility with subsequent conversion circuit by providing appropriate process tolerance. In particular, the array is designed by collecting the convergence of enhanced near-field from each unit to a fixed point for observation conveniently. By adopting the 16-element array composed of noncoplanar configuration, the strongest electric field strength can reach as high as 210 V/m, while that is 33.6 V/m for the conventional bow-tie shaped nanoantenna. Moreover, the field enhancement bandwidth has been broadened.

Front end design of 8mm polarimetric microwave radiometer

A front end of 8mm polarimetric microwave radiometer is presented in this paper. Simulations and measurements have shown that it has a good performance. The actual measured results show that it has an impedance bandwidth of VSWR<;1.25 over 35GHz-39GHz, within which the two ports isolation is lower than -39dB, the gain of it is larger than 21.6dBi and the sidelobe level is less than -20dB. For the advantages mentioned above, it could be used in measuring the sea surface wind vector. As an important aspect, the methods to design ortho-mode transducer (OMT) and multimode horn (MMH) are discussed in this paper.

Design of a Terahertz circularly polarized planar corrugated horn antenna

This paper proposes a design for low profile, compact, circularly polarized double-layer horn antenna integrated with the planar corrugated polarizer with high gain and low cross polarization for THz applications. In particular, the novel polarizer with the planar corrugates is introduced to make the horn antenna circularly polarized. Based on such corrugates, the antenna gained better performance at 420 GHz to 480 GHz. Due to the proper designing and optimization, an excellent axial ratio of -1.5 dB has been achieved at the center frequency of 450 GHz. Moreover, the low cross-polarization of rotationally symmetrical radiation pattern is observed profile without any obvious side lodes. It possesses good impedance matching showing VSWR<;2 in the frequency range ~60 GHz. The silicon MEMS technology makes the design possible and meets the reliability and consistency requirements.

Design of a wide bandwidth monopole antenna with graded multi-layer metal slabs

As the simple structure, Monopole antenna has been widely used in various communication systems. However, the narrow bandwidth of the monopole antenna always restricted their applications. The article presents a method to improve the bandwidth of the monopole antenna with graded multi-layer metal slabs. The measured results of the proposed monopole antenna show wide bandwidth between 2.9GHz and 3.4GHz for standing wave ratio of less than 1.5, omnidirectional characteristic in the H-plane and shape of a figure “ 8 ” in the E-plane.