Xianling Liang

Compact Elliptical Monopole Antenna With Impedance Bandwidth in Excess of 21:1

A compact CPW-fed monopole antenna composed of an elliptical monopole patch and a coplanar trapeziform ground plane is introduced. The simulated and experimental results demonstrate that this antenna achieves a ratio impedance bandwidth of 21.6:1 for VSWR les 2, and exhibits a nearly omnidirectional radiation pattern, while its area is only about 0.19 lambda1 times 0.16 lambda1 where lambda1 is the wavelength of the lowest operating frequency. By comparing with various designs, it is shown that its bandwidth broadening comes from three factors: the optimum elliptical monopole shape, a trapeziform ground plane and a tapered CPW feeder.

H-Shaped Dielectric Resonator Antenna for Wideband Applications

A novel dielectric resonator antenna design is presented for wideband applications in this letter. By using a dielectric resonator with an optimized H-shaped across section and an optimized trapezoidal patch adhered on the concave surface of the resonator as a feeding mechanism, an impedance bandwidth of about 62% (for VSWR les 2) , covering the frequency range of 3.6-6.85 GHz, is achieved. The measured results in terms of bandwidth and radiation pattern agree well with the simulated ones, confirming the theoretical design.

A broadband slotted ridge waveguide antenna array

A longitudinally-slotted ridge waveguide antenna array with a compact transverse dimension is presented. To broaden the bandwidth of the array, it is separated into two subarrays fed by a novel compact convex waveguide divider. A 16-element uniform linear array at X-band was fabricated and measured to verify the validity of the design. The measured bandwidth of S11les-15 dB is 14.9% and the measured cross- polarization level is less than -36 dB over the entire bandwidth. This array can be combined with the edge-slotted waveguide array to build a two-dimensional dual-polarization antenna array for the synthetic aperture radar (SAR) application

Wideband L-Shaped Dielectric Resonator Antenna With a Conformal Inverted-Trapezoidal Patch Feed

In this paper, a new dielectric resonator antenna (DRA) is introduced for wideband applications, where a simple L-shaped dielectric resonator (DR) is excited by a conformal inverted-trapezoidal patch connected to a microstrip line. It is observed that the impedance bandwidth can be expanded by using an inserted intermediate substrate, an L-shaped DR, and an inverted-trapezoidal patch feed mechanism. The experimental and numerical results were carried out and compared, showing a good agreement. The measured results demonstrate that the proposed DRA achieves an impedance bandwidth of about 71.4% for VSWR les 2, covering the frequency range from 3.87 to 8.17 GHz. Furthermore, this antenna provides a stable broadside radiation pattern across the operating bandwidth.

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.

Numerical Study of the Near-Field and Far-Field Properties of Active Open Cylindrical Coated Nanoparticle Antennas

A very electrically small, active open cylindrical coated nanoparticle model is constructed, and its electromagnetic properties are investigated in the visible frequency band. Its optical response under both planewave and electric dipole antenna excitations shows very strong dipole behavior at its lowest resonance frequency. The scattering cross section at that dipole resonance frequency is increased by more than +50 dBsm for the planewave excitation. When the open structure is excited by a small current (I0 = 1 ×10-3A) driven dipole antenna, the maximum radiated power of the composite nanoantenna can be increased by +83.35 dB over its value obtained when the dipole antenna radiates alone in free space. The behaviors under various locations and orientations of the dipole are explored. Dipole orientations along the cylinder axis and symmetric locations of the dipole produced the largest radiated power enhancements.

Printed Binomial-Curved Slot Antennas for Various Wideband Applications

This paper presents a new design of wide slot antenna for various wideband applications. The proposed printed antenna consists of a slot and a turning stub, both formed by a binomial curve function; thus, various bandwidths (BWs) can be obtained based on the structure with different binomial curves. Some key parameters affecting the antenna performance have been analyzed and discussed in detail as an antenna design guideline. To validate the theoretical design, six prototypes of various binomial-curved slot antennas were designed, fabricated, and measured. Good agreement between the simulated results and the measured ones is observed. The results demonstrate that the proposed type of antenna can obtain a BW range from 9.8% to 99.7% for VSWR ≤ 2 by selecting various binomial-curved slots, which may provide a convenience for various wideband antenna designs. Moreover, the proposed type of antenna owns a simple structure and a stable gain of about 3-5.5 dBi, which is very suitable for wideband wireless system applications.

High-Gain Planar Antenna Arrays for Mobile Satellite Communications [Antenna Applications Corner]

Two large and low-profile panel antenna arrays, used as receiving and transmitting antennas for mobile satellite communications, are described. The receiving and transmitting arrays have overall dimensions of 120 cm × 20.7 cm × 1.3cm and 107.5 cm × 20.4 cm × 1.7 cm, respectively. They exhibit high gains and adequate efficiencies, due to integrated array designs. For the receiving panel array, a method using a number of high-efficiency subarrays, combined with a novel active integrated global feed network, is proposed. For the transmitting panel array, a number of high-efficiency subarrays, together with a novel compact waveguide feed network, is employed. Based on the above techniques, two large panel antenna arrays were successfully developed. We present the detailed designs of the subarrays, the passive and active feed networks, and the vertical transitions. Simulated and experimental results showed that the designed receiving and transmitting panel arrays achieved measured gains and efficiencies of 34.1 dBi and 48.2%, and 33.5 dBi and 36.3%, respectively, in each band. This indicated that the proposed antenna panels are good candidates for future satellite communications applications.

A Three-Way Reconfigurable Power Divider/Combiner

In this paper, a three-way reconfigurable power divider/combiner is proposed based on novel switch element with matching network (SEMN) and reconfigurable impedance transformer network (RITN). A good matching performance and a high isolation of the SEMN with one p-i-n diode can be obtained by the parasitic inductance and reverse capacitance of the p-i-n diode involved in matching circuits. With different parameters of one p-i-n diode under forward bias and reverse bias, the reconfigurable impedance matching can be obtained by the RITN with a simple structure. By using four RITNs and nine SEMNs, the three-way reconfigurable power divider/combiner can provide seven different states in the three-path mode, the two-path mode, and the single-path mode. For verification, a 5-GHz three-way reconfigurable power divider/combiner is designed and fabricated. In the three-path mode, measured insertion losses from port 1 to transmission ports (port 2, port 3, and port 4) are less than 0.74 dB and the isolations between transmission ports are higher than 32.1 dB. In the two-path mode with three states, the measured insertion losses are less than 0.93 dB; the isolations between transmission ports, transmission ports and isolation ports, and port 1 and isolation ports are higher than 27.5, 35.1, and 30.5 dB, respectively. In the single-path mode with three states, the measured insertion losses are less than 1.13 dB; the measured isolations between transmission ports and isolation ports are higher than 28.8 dB, and the isolations between port 1 and isolation ports are higher than 28.2 dB at the design frequency.

Direction Finding by Time-Modulated Array With Harmonic Characteristic Analysis

A novel direction-finding method by the time-modulated array (TMA) is proposed through analyzing the harmonic characteristic of received signal, which requires only two antenna elements and a single RF channel. The signal processing of the proposed method is concise, and its calculation amount concentrates on a two-point discrete Fourier transform (DFT). Numeric simulations are provided to examine the performance of the proposed method, and a simple S band two-element TMA is constructed and tested to verify its effectiveness.