In this paper, we propose a direction-of-arrival (DOA) estimation algorithm under unknown mutual coupling with a sparselinear array (SLA). We employ an SLA composed of two uniform linear arrays (ULA), and the element spacing of one of the subarrays is large enough to neglect the effect of the mutual coupling (MC). The forth-order-cumulants (FOCs) of the received data from partial elements of the first subarray and all elements of the second subarrayare exploitedto construct an extended FOC matrix. Then, the DOAs of incident signals are estimated by dealing with the FOC matrix. The array aperture is extended greatly due to the sparsestructure. Hence, the proposed method shows much better performance than some classical blind DOA estimation methods in accuracy and resolution. We also proposed some simulation results to prove the effectiveness of our method.
In the field of radar target detection, vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has drawn great attention in recent years because of its prospect to improve the capacity of information acquisition. As a typical vortex EM wave, the high-order Bessel vortex beam (HOBVB) has the properties of non-diffraction propagation, small central spot diameter, good direction, and long propagation distance. This study investigates the scattering of non-diffracting HOBVB by radar targets. The mathematical description of the electromagnetic field components of the arbitrarily incident HOBVB are given. The surface integral equations for solving the scattering problems involving typical radar targets are established. The effects by OAM intrinsic mode characteristics on the radar scattering cross section are simulated. This investigation is expected to provide useful guidance for revealing EM scattering mechanism in the OAM domain.
In this paper, a parallel Higher-order FDTD (HO-FDTD) algorithm is described. Moreover, a novel implementation of convolution PML (CPML) is presented for the HO-FDTD method. A printed microstrip patch antenna is designed to analyze the feasibility of the parallel algorithm and the absorbing performance of the CPML. Moreover, the proposed algorithm is used to deal with the large-scale computational model of the vaulted tunnel. The simulation results show that the adopted parallel strategy is feasible. and the CPML performs well in the HO-FDTD scheme.
This paper presents the design and analysis of a planar pattern reconfigurable antenna for WLAN applications. The proposed design makes use of four Vee dipoles placed around a center input probe. The directional beam generated can be reconfigured to any one of the four directions in the azimuth plane. The antenna pattern can be controlled by means of switches provided to connect the Vee dipoles to the input port. The design and analysis of the parameters show the scalability of the design to adapt to any frequency of choice. To validate the concept, an antenna is designed for the WLAN frequency of 5.3 GHz， and a prototype is fabricated. The measured results match closely to that of simulated results. The gain provided by the antenna is noted as 7.5 dBi. The planar structure and simple design of the antenna enable this antenna to be useful for modern pattern reconfigurable communication systems.
A novel design of frequency reconfigurable Fabry-Pérot cavity antenna is presented. The superstrate of the antenna is a reconfigurable partially reflecting surface with PIN diodes on it. A dual-band patch antenna is used as the radiator of the antenna. Through changing the states of diodes, the partially reflecting surface can present different reflection phases, so the working frequency of the antenna can be tuned. The operation of frequency reconfiguration and the design method of the antenna are described exhaustively. A prototype antenna is fabricated and measured. The measured results show that the antenna can realize 13.1 dB gain at 4.6 GHz and 17.1 dB gain at 5.5 GHz with impedance bandwidths of 3.3% and 4.7%, respectively. Good agreement between the simulated and measured results is achieved, which proves the correctness of the design method. Besides, this method can also be used to design Fabry-Pérot cavity antenna working at other frequencies.
A miniaturized monopole-like slot antenna with improved un-roundness of H-plane radiation patterns at higher frequency response for ultra-wideband application is presented and discussed. With the monopole-like slot antenna structure, wide working band (3.21-16.3 GHz) is obtained within a limited physical size (21×21.5×1.6 mm3). By modifying the structure of the proposed antenna, such as etching a quarter of a circular slot at the corner of the ground plane and a trapezoidal slot in the radiating patch, the un-roundness of H-plane radiation patterns is reduced by 5 dB in high-frequency band. Measured results show that it has a bandwidth from 3.2 GHz to 17.52 GHz, which are in good agreement with simulations.
This paper presents an electrically small, low-profile and ultra-wideband antenna with monopole-like radiation type. The antenna is composed of a top-loading hat and two tapered radiation patches on the crossed substrates shorted to the ground. Introducing two tapered radiation patches with the meander loop traces allows for achieving ultra-wideband operation and very low profile simultaneously. In addition, two columns of metal via-holes nested in the crossed substrates can broaden the bandwidth further. The proposed antenna is simulated, fabricated and measured. The measured and simulated results show good agreement and indicate that a measured VSWR lower than 2.0 over 632-3907 MHz (a 144% relative bandwidth) can be accomplished. The antenna has a low profile (0.053 λmin) in height and occupies a small circle of radius 0.078 λmin, where λmin is the free-space wavelength at the lowest frequency. The antenna has a kmin a = 0.59, where kmin is the wavenumber at the lowest frequency of operation. The frequency band covers LTE (0.7 GHz), BDS (1.268 GHz), GPS (1.575 GHz), WIFI (2.5 GHz) and WIMAX (3.5 GHz).
A miniaturized dual-band microstrip antenna has been designed and analyzed for Wireless LAN application. The proposed antenna comprises a 29 × 29mm2 radiating patch, fed by a microstrip line on a 1.6mm thick FR4 dielectric material substrate. The antenna measurement illustrates impedance bandwidth of around 10% at 2.4GHz resonance and 6% at 5.5GHz resonance. The measured stable return loss and radiation patterns are presented for the proposed dual-band electrically small microstrip antenna for wireless applications.
The terahertz (THz) compact antenna test range (CATR) detection technology is the foundation of terahertz target recognition technology. It provides an excellent plane wave area which can well meet the far-field condition of antenna pattern and RCS test. Based on the microwave single reflector CATR system that we have designed before, this paper mainly aims at designing a 0.3 THz CATR system and then gives the simulation model of the system errors. After the preparation of the above work, we begin to detect its 0.3 THz band plane wave field, and the final test results can be used for further application.
This paper presents a compact diplexer with high selectivity. The proposed diplexer employs two sets of triple-mode bandpass lters. Using this approach, the pair of even-mode resonant frequencies can be flexibly controlled by adjusting the characteristic impedance or electrical lengths of the two open-circuited stubs while the odd-mode resonant frequency remains at the fundamental resonant frequency. For a demonstration, a diplexer with two passbands centred at 1.50 and 1.70 GHz and the transmission zeros are created close to the passband edges which extremely improve the skirt selectivity. As a result, the proposed diplexer occupies an extremely small area, i.e., approximately 0.30λg x 0.35λg. The measured results are in good agreement with the simulated predictions.
Comb generator has been an indispensable tool in the electromagnetic compatibility (EMC) testing field. It is used for calibration and self checking of the test systems. This paper presents a rarely explored yet promising radiated comb generator that makes use of a single-ended PECL D Flip-Flop as the pulse forming component. Measurements show that the generated pulses typically possess fall time and rise time of 330 ps and 410 ps, respectively. Its frequency accuracy is offset by +24 ppm, which is common for crystal oscillators. When being connected to a monopole rod antenna, the comb generator is able to generate radiated emissions that have smooth envelope profile up to 1000 MHz frequency range.
A broadband ultra-high-frequency (UHF) Radio Frequency Identification (RFID) antenna using double-tuned impedance matching theory is proposed. This paper presents a proximity coupled vertical meandered strip feed technique based on double-tuned impedance match which results in a wide bandwidth. This antenna mainly consists of a rectangular ground plane, a U-shaped radiation patch, and a suspended vertical meandered strip (VMS) by mesas of rotated г-shaped strip. The U-shaped radiation patch is fed by the VMS. The simulated and measured results show that the antenna has a very wide impedance matching bandwidth of 150MHz (820-970 MHz) or 16.8% with the voltage standing wave ration (VSWR) less than 1.5 and achieves a high gain level about 8.5 dBi. Therefore, the proposed antenna can cover the entire UHF band of 840-960 MHz and is a good candidate for universal UHF RFID applications.
This paper presents design and analysis of six different configurations of Coplanar Waveguide Band Reject Filters (CPW-BRF) using Rectangular Dumbbell Electromagnetic Band Gap (RDEBG) cell structures. The performance in terms of rejection bandwidth, attenuation, cutoff characteristics of the proposed design are found superior to the earlier reported CPW-BRF. Using cascading of six RDEBG cells, rejection bandwidth has been improved up to 2.8 GHz with attenuation of -38.8 dB and filter selectivity of 26.9 dB/GHz. In addition, the radiation losses have also been analyzed by extracting equivalent R, L and C values from electromagnetic (EM) simulation results. Fabricated CPW-BRF using four RDEBG cells has been analyzed. For the fabricated CPW-BRF simulated and measured results are found in good agreement.
Two compact dual-band bandpass filters (BPFs) with closely spaced passbands are presented in this paper. Each of the filters consists of a stub loaded resonator, to which shorted lines are coupled. The ratio of the center frequencies of two passbands can be easily adjusted from 1.2 to 1.1 by changing the gap of the coupled line. In addition, seven transmission zeros (TZs) can be yielded to obtain high passband selectivity and enhance the out of band performances. As an example, two filters are designed, fabricated and measured. Both filters exhibit the merits of high passband selectivity, very low center frequency ratio, and wide stopband suppression.
In this paper, a multi-frequency broadband planar reconfigurable antenna is designed for smart mobile phone applications. The antenna comprises two monopole strips and a parasitic shorting strip, and generates several independent resonant modes through this kind of stub loading. The miniaturization and broadbandization of the antenna is achieved by bending the strip line and using coupling feed. In addition, loading the matching circuit at the feeding point, the bandwidth can completely cover 824-960 and 1710-2690 MHz. In order to cover a lower band LTE band 20 (800 MHz), a RF switch at shorting point is used to switch low frequency to 791 MHz. So the proposed antenna can work at GSM850,900; DCS1800; PCS1900; WCDMA bands 1, 2, 4, 5, 8; TD-SCDMA bands A, F; CDMA BC0,BC1 and LTE bands 1, 3, 5, 7,8, 20, 38, 39, 40, 41. Also, the total size of the antenna is 15 mm×30 mm×0.8 mm, which is very suitable for 4G slim smart mobile phone applications.
This paper presents a novel miniaturized dual-band fractal antenna for WLAN/WiMAX applications. The miniaturization of the proposed antenna is achieved by inserting, in the center ground of the antenna, square slots to excite two resonant modes simultaneously, leading to dual-band operation. The novelty of the proposed antenna is miniaturized size and ability to support multiband operations, which can be integrated in many electronic applications and wireless communication. This antenna has a compact size of only 25×25 mm2 and fed by a 50 Ω-microstrip feed line. To validate the design approach, an experimental prototype is fabricated and measured. The simulation and measurement results show that the antenna provides dual-band operation at 2.4 and 3.75 GHz with omnidirectional radiation pattern.
Two opposite uni-directional radiation bands with good circular polarization (CP) characteristics are achieved in an Archimedean Spiral Antenna (ASA). A sandwich configuration is formed by utilizing two resonance based reflectors (RBRs) at the bottom and top sides of the ASA. Owing to the resonance characteristic, the RBRs do not act as reflectors at the other operational band, then, opposite uni-directional radiations are obtained, and the two uni-directional bands can be tuned independently. The proposed ASA with two uni-directional bands (ASA-TUB) has a wide impedance bandwidth about 4.4:1 (1.8-8 GHz), while its front-fire band (FFB) ranges from 1.8 GHz to 2.2 GHz (20.0%), and its back-fire band (BFB) is 4.4-7.1 GHz (46.9%) for front-to-back ratio (FBR) larger than 5 dB. The maximal FBRs for the FFB and BFB are 11.3 dB and 20 dB, respectively. Moreover, good CP performances are also obtained for the FFB and BFB. Besides, the whole profile of the proposed antenna is only 0.16 λ at the lowest operational frequency. The proposed antenna has the properties of dual opposite uni-directional radiation bands, low profile, good FBR and CP.
A compact stacked Yagi antenna is proposed with bandwidth enhancement in this paper. To reduce the size of the antenna and simultaneously improve the front-to-back ratio (FTBR), a reflector, modified with six slots, two λ0/4 meanderline-shaped slots and four straight short slots, is employed. Furthermore, a ladder-like director is designed to overcome the mismatch loss caused by the diminution of the height between the reflector and driven dipole. As shown in both simulation and measurement, the proposed compact Yagi antenna can achieve a compact size of 0.55λ0×0.55λ0×0.08λ0, |S11| ≤ -10 dB bandwidth of 17.2% and an FTBR of 22dB at 2.2GHz. The acceptable results make the proposed Yagi antenna a good candidate for applications where compact size and wide bandwidth are needed.
In this paper, a novel monopole printed fork-shaped antenna for ultra-wideband (UWB) applications with triple band-notched characteristics is presented. The proposed antenna, with compact size of 42×24×1.6 mm3, yields an impedance bandwidth of 3.1-11 GHz for S11 < -10dB, except on the notched bands which are obtained by introducing three different types of slots. A U-shaped and two extended U-shaped defected ground structure (DGS) slots give respectively two notched bands， 3.3 to 3.7 GHz for WiMAX and 7.1 to 7.76 GHz for downlink X-band satellite communication systems. Therefore, a semi arc-shaped slot is etched on the radiating patch to notch the band from 5.15 to 5.825 GHz for WLAN applications. The proposed antenna is fabricated and measured.
We present an angular stable dual-band frequency selective surface (FSS) in this paper. By placing anchor-shaped elements with different structural parameters along x-axis alternately within hexagonal wire grid, the proposed FSS can provide two closely spaced passbands. And the resonant frequency ratios are only 1.16 and 1.19 for TE and TM polarizations, respectively. In addition, the proposed FSS has stable frequency response under oblique incidence, and resonant frequency deviation is below 0.5% within 60° incident angle. An FSS prototype is fabricated and measured for further verification, and good agreements between the simulated and measured results can be observed.