Peng Yang

DOA Estimation with Sub-Array Divided Technique and Interporlated ESPRIT Algorithm on a Cylindrical Conformal Array Antenna

A novel DOA flnding method for conformal array applications is proposed. By using sub-array divided and interpolation technique, ESPRIT-based algorithms can be used on conformal arrays for 1-D and 2-D DOA estimation. In this paper, the circular array mounted on a metallic cylindrical platform is divided to several sub- arrays, and each sub-array is transformed to virtual uniform linear array or virtual uniform planar array through interpolation technique. 1-D and 2-D direction of arrivals can be estimated accurately and quickly by using LS-ESPRIT and 2-D DFT-ESPRIT algorithms, respectively. This method can be applied not only to cylindrical conformal array but also to any other arbitrary curved conformal arrays. Validity of this method is proved by simulation results.

Compact Metallic RFID Tag Antennas With a Loop-Fed Method

Several compact, low profile and metal-attachable RFID tag antennas with a loop-fed method are proposed for UHF RFID systems. The structure of the proposed antennas comprise of two parts: (1) The radiator part consists of two shorted patches, which can be treated as two quarter-wave patch antennas or a cavity. (2) A small loop printed on the paper serves as the feeding structure. The small loop provides the needed inductance for the tag and is connected to the RFID chip. The input impedance of the antenna can be easily adjusted by changing loop dimensions. The antenna has the compact size of 80 mm × 25 mm × 3.5 mm, and the realized gain about dB. The measured results show that these antennas have good performance when attached onto metallic surfaces.

Low-Cost Wideband and High-Gain Slotted Cavity Antenna Using High-Order Modes for Millimeter-Wave Application

A novel single-fed low-cost wideband and high-gain slotted cavity antenna based on substrate integrated waveguide (SIW) technology using high-order cavity modes is demonstrated in this paper. High-order resonant modes (TE130, TE310, TE330) inside the cavity are simply excited by a coaxial probe which is located at the center of the antenna. Energy is coupled out of the cavity by a 3 × 3 slot array etched on the top surface of the cavity. Two antennas with different polarizations are designed and tested. Measured results show that the linearly polarized prototype achieves an impedance bandwidth (|S11| <; -10 dB) of > 26% (28 to 36.6 GHz), and a 1-dB gain bandwidth of 14.1% (30.3 to 34.9 GHz). In addition, a measured maximum gain of 13.8 dBi and radiation efficiency of 92% are obtained. To generate circularly polarized radiation, a rotated dipole array is placed in front of the proposed linearly polarized antenna. Measured results show that the circularly polarized antenna exhibits a common bandwidth (10-dB return loss bandwidth, 3-dB axial ratio bandwidth, and 1-dB gain bandwidth) of 11%.

ROBUST ADAPTIVE BEAMFORMER USING INTERPOLATION TECHNIQUE FOR CONFORMAL ANTENNA ARRAY

A novel robust adaptive beamforming method for conformal array is proposed. By using interpolation technique, the cylindrical conformal array with directional antenna elements is transformed to a virtual uniform linear array with omni-directional elements. This method can compensate the amplitude and mutual coupling errors as well as desired signal point errors of the conformal array e-ciently. It is a universal method and can be applied to other curved conformal arrays. After the transformation, most of the existing adaptive beamforming algorithms can be applied to conformal array directly. The e-ciency of the proposed scheme is assessed through numerical simulations.

Microstrip Phased-Array In-Band RCS Reduction With a Random Element Rotation Technique

The techniques of random antenna element distribution and rotation have been proposed to design a low sidelobe and low crosspolarization phased array or reflect array for a long time. In this communication, we demonstrate that the use of randomly rotated (RR) elements can provide random scattering phases and phase center distributions, which can lead to an in-band radar cross section (RCS) reduction for the array. To illustrate the effectiveness of the proposed method, three 8 × 8 circularly polarized (CP) microstrip arrays, 1) the uniform array without rotation; 2) sequentially rotated (SR) array; and 3) RR array, are compared and analyzed. Results indicate that the RCS of the RR array can be reduced significantly, even in the main beam region, while maintaining its high radiation performance.

Robust Beamformer Using Manifold Separation Technique for Semispherical Conformal Array

Conventional beamformers suffer from problems of finite samples, desired signal pointing errors, as well as imperfect array. A simple and robust beamformer based on the manifold separation technique (MST) is proposed in this letter to alleviate these problems. Using MST, the steering vector of an arbitrary array can be modeled as the product of an array sampling matrix and a vector with a Vandermonde structure. Robust characteristics are found by using this transformation. The analysis is verified via simulations based on a real-world semispherical conformal antenna array.

Low-Profile Microstrip Antenna with Bandwidth Enhancement for Radio Frequency Identification Applications

Abstract Two low-profile microstrip antennas, which can be mounted on metallic objects for radio frequency identification applications, are proposed. By using a single-layer FR4 as the substrate, the thickness of the antennas is only 1.6 mm (about 1% dielectric wavelength at 900 MHz). In order to broaden the bandwidth, slots are added on the surface of the patch to excite two different modes. Compared to conventional microstrip antennas, the impedance bandwidth (voltage standing wave ratio < 3) of the design can reach 100 MHz, and the 3-dB gain bandwidth is about 50 MHz, which can satisfy most applications for UHF radio frequency identification systems. The size of the compact design is only 84 mm × 26 mm. Prototypes were fabricated and measured. The read range of the designed antennas can reach 4 m when mounted on metallic plates.

Separated Fractal Antennas For Improved Emission Performance Of Terahertz Radiations

Abstract We investigate the emission of terahertz (THz) radiation from two kinds of recently reported fractal photoconductive antennas by the method of separating antennas from transmission lines. A model for analyzing the separation design is presented. From the numerical simulations, the radiation power and center frequency of Sierpinski fractal photoconductive antenna are increased by ∼ 120% and ∼ 25%, respectively. Meanwhile, the first peak frequency emission intensity of H-fractal photoconductive antenna is increased by ∼ 70%. Because of the stronger resonant effect of the emitting antenna, this method shows high potential applications to various photoconductive antennas.

FAST 2-D DOA AND POLARIZATION ESTIMATION USING ARBITRARY CONFORMAL ANTENNA ARRAY

A fast and simple parameter estimation algorithm, joint azimuth angles, elevation angles and polarization parameters of incident sources for an arbitrary conformal array is proposed. Based on 2-D Discrete Fourier Transform (2-D DFT), the computational complexity can be reduced signiflcantly compared with traditional 2- D space-search MUSIC or polynomial rooting (search-free) methods. The antenna elements can be mounted on arbitrary curved surfaces or platforms. Conformal array characteristics, such as directional radiation patterns of the elements and polarization are taken into consideration. Numerical simulations based on real-world conformal arrays are provided to demonstrate the performance of the proposed method.

Enhanced Center Frequency of Terahertz Pulse Emission from Photoconductive Antenna

The center frequency of terahertz (THz) pulse radiated from photoconductive antenna is located at the low-frequency range of THz band. None of the antenna designs have been done to enhance the center frequency without decreasing antennas dimension, which would largely decrease the radiation power. We introduce here the idea of separating antennas from the transmission lines to reduce the current distribution on them, showing superior performance for both the center frequency (∼ 90% increased) and the radiation power from the simulations of the dipole antennas.