Vol. 38

Ultra wide band (UWB) impulse radio (IR) technology has different applications in different sectors such as short range radios and collision avoidance radar. A strong signal denoising method is needed for UWB-IR signal detection. One of the challenges of UWB-IR signal detection technique is the environmental interferences and noises. Wavelet Packet Transform (WPT) based multi-resolution analysis technique is suitable for this kind of signal denoising and detection. The paper describes a better method of denoising and detection technique of UWB-IR signal based on calculation of energies of the coefficients of each WPT terminal-node and by using an improved threshold calculation technique. The proposed technique is investigated through both simulation and experimentation.

A GPR object detection algorithm delivers a promising performance using the Hough transform through a high computational load. This paper presents a fast Hough-based algorithm. To reduce the parameter space of the Hough transform, first, two parameters for a reflection hyperbola were estimated using cross correlation between adjacent A-scans. Next, only a 1D Hough transform is necessary to detect an object compared with the 3D transform, which comprises the traditional Hough-based methods. Our method is compared with three other detection methods using field data. The results show that the proposed method has an encouraging detection ability and high computational efficiency.

Design of (2 x 2) E-shaped microstrip patch antenna array integrated with spiral ring resonators (SRRs) is introduced for the reduction of cross-polar (XP) radiation. The addition of SRRs in the array structure does not affect other characteristics of the array antenna. The array is designed to function in the 5.25 GHz which corresponds to IEEE 802.11a wireless LAN application. The characteristic analysis such as return loss (RL), bandwidth (BW), and radiation patterns of the antenna with and without SRRs have been investigated. The array offers a bandwidth of 405 MHz (For RL < -10 dB) covering frequencies ranges from 5.175 to 5.580 GHz and gain of 12.60 dBi has been achieved. The array has been studied both numerically and experimentally by introducing SRRs. The XP radiation has been reduced by 10.5 dB with two sets of SSRs of similar geometry placed in between the patch elements of the array structure. Prototype antennas with and without SRRs have been fabricated tested and a remarkable agreement is obtained between the measured and the simulated results.

A modified Schwarz-Christoffel transformation (SCT) is used to obtain guided- and radiated-wave characteristics of a singly-curved rectangular patch antenna. The method is to map a straight channel into an arbitrarily-curved channel. This simplifies the problem to that of a planar rectangular patch antenna. Applying conventional SCT to the problem confronts two difficulties: The region under investigation is elongated, and it has curved boundaries. Therefore, SCT is modified to handle the problem. Input impedance, VSWR and radiation patterns of a conformal patch antenna on a parabolic surface are obtained utilizing the proposed SCT and either numerical or analytical treatment of a planar patch antenna, and the results are verified. Effect of parabolic curvature on the above-mentioned characteristics is investigated.

The round-corner design of an all symmetric edge-coupled bandpass filter (BPF) is presented. The manufacturing tolerances and its effects of frequency shift on the design of the edge-coupled are investigated. Consequently, the round-ended design method is proposed in order to compensate the open-end effect in the half-wavelength resonator section with the round-ended corners rather than decrementing the lengths in a conventional way, and an experience formula and a corresponding procedure are devised for the design of such filters. The widths of all the half-wavelength resonators are set equal to avoid discontinuities in the interior of the filter. The filter is realized on a ceramic filled soft substrate with dielectric constant of 6.2. For obtaining the de-embedded measured results at the device plane an in-house customized through-reflect-line (TRL) calibration kit is produced. Three kinds of filters at different center frequencies are manufactured, and their measured results are in good agreement with the simulated ones after calibration.

This paper presents an approach to the design of novel diplexers with pairs of transmission zeros for each output port. A rotationally symmetric structure with shorted circuited stubs is proposed to achieve diplexer operation, and the diplexer exhibits a good filtering performance with a pair of transmission zeros allocated at two sides of the passbands as well. The analysis of the rotationally symmetric structure bandpass filter is also presented in this paper in detail. Moreover, the interdigital coupled-lines are introduced to improve the out-of-band performance of the proposed rotationally symmetric diplexer. In order to verify the proposed structure, first a diplexer with rotationally structure operating at 2.4/2.73 GHz with simulated insertion loss of 1.217/0.930 dB is designed and simulated, then a diplexer with interdigital coupled-lines operating at 5/5.8 GHz with measured insertion loss of 1.524/1.524 dB is designed, simulated and measured to improve the passband selectivity, and the measured results are in good agreement with simulated ones.

This paper presents an effective weighted-L₁-sparse representation of array covariance vectors (W-L₁-SRACV) algorithm which exploits compressed sensing theory for direction-of-arrival (DOA) estimation of multiple narrow-band sources impinging on the far field of a uniform linear array (ULA). Based on the sparse representation of array covariance vectors, a weighted L₁-norm minimization is applied to the data model, in which the weighted vector can be obtained by taking advantage of the orthogonality between the noise subspace and the signal subspace. By searching the sparsest coe±cients of the array covariance vectors simultaneously, DOAs can be effectively estimated. Compared with the previous works, the proposed method not only has a super-resolution but also improves the robustness in low SNR cases. Furthermore, it can effectively suppresses spurious peaks which will disturb the correct judgment of real signal peak in the signal recovery processing. Simulation results are shown to demonstrate the efficacy of the presented algorithm.

Conventional reflector based Impulse Radiating Antennas (IRA's) are designed with conical taper transmission line feed. A novel feed design approach is used to enhance gain of the IRA without increasing diameter of the reflector. This paper discuses conventional and new IRA designs of different input impedances. IRA with conventional feed and with new dipole feed is designed for both 200 Ω and 100 Ω input impedance category. The IRA with new feed design offers better gain compared to conventional IRA for both 200 Ω and 100 Ω input impedance category. These antenna designs are analyzed using the Finite Difference Time Domain (FDTD) method and the result obtained shows that IRAs with new dipole feed offers better gain than IRAs with conventional feed for respective input impedance category without any compromise in time domain characteristics. A half IRA with new feed with input impedance of nearly 50 Ω was realized and measured to establish the advantage of new dipole feed IRA.

A slim wideband patch antenna designed for the ultra-high frequency (UHF) band radio frequency identification (RFID) tag is presented in this paper, which can be mounted on flat or curved metallic surfaces directly. The presented antenna is fabricated on a very thin (only 0.5 mm) PET substrate (ε_r=3.8, tanδ=0.02). The proposed design consists of tow coplanar patches which are electrically connected to the metallic ground through two symmetrical shorting walls. Double symmetrical U-shaped slots are etched out to improve the antenna bandwidth. A perfect matching between antenna and tag chip can be obtained by varying the geometry parameters of the slots. The simulated bandwidth is about 97 MHz, which covers the Europe and North America UHF RFID frequency range. The measured maximum reading range of the proposed antenna can be up to 5 m when the tag is mounted on a metal plate whose size is 150×150×8 mm³.

This paper introduces a flexible antenna, printed on a low-cost Polyethylene Terephtalate (PET) substrate for UHF applications. The RF characteristics of the PET substrate are examined using a microstrip resonator to characterize the substrate's relative permittivity and the loss tangent at UHF band. The PET substrate is used to print an antenna designed to work in the 868 ISM-Band. The printing process described is carried out using a semi-industrial roll-to-roll (R2R) machine with mass production capability. The fabricated dipole antenna was mounted on cylindrical objects made from several materials such as paper and glass, and its RF characteristics were measured and discussed.

In this paper, reflectarrays mounted on or embedded in cylindrical and spherical surfaces are designed, analyzed, and simulated at 11.5 GHz for satellite applications. A unit cell consists of a square dielectric resonator antenna (DRA) mounted on or embedded in metallic conformal ground plane is investigated. The radiation characteristics of the designed reflectarrays are investigated and compared with that of planar reflectarray. A 13 x 13 planar reflectarray antenna on the x-y plane was designed. By varying the length of the DRA element between 2 mm and 6.2 mm a full range from 0° to 360° phase shift can be obtained. The size of each element is equivalent to a compensation phase shift. A maximum directivity of 24.3 dB was achieved while the side lobes were below -12.94 dB in E-plane and -15.79 dB in the H-plane for planar reflectarray. A Full-wave analysis using the finite integration technique (FIT) is applied. The results are validated by comparing with that calculated by transmission line method (TLM).

The improved configurations with dual-mode double-square-loop resonators (DMDSLR) for tri-band application are proposed in this paper. Two sets of loops including double-square-loop and G-shaped loop are involved in the resonators. The resonant frequency equations related to DMDSLR geometries are introduced for simply designing tri-band bandpass filter (BPF). Resonant frequencies and transmission zeroes can be controlled by tuning the perimeter ratio of the square rings and the couples. To obtain lower insertion loss, higher out-of-band rejection level, wider bandwidth of tri-band, and compact applications, the miniaturized DMDSLR structure is designed. The effective design procedure is provided. The proposed filter is successfully simulated and measured. It can be applied to WLAN (2.45, 5.20 and 5.80 GHz) and WiMAX (3.50 GHz) systems.

The wideband and omnidirectional performance of a printed dipole antenna with a novel coupling feed structure is presented. Besides using printed dipole for omnidirectional radiation patterns, the coupling feed structure, which includes the transmission line coupling to a slot line to effectively improve the impedance matching, can be used for bandwidth enhancement. A wideband impedance characteristic of about 45.6% for VSWR ≤2 ranging from 1.54 to 2.45 GHz is obtained. The omnidirectional radiation patterns in the whole operation bands are achieved which the un-roundness in H-plane is less than 1.6dB. It is sufficient for accommodating recent wireless communication services such as DCS1800, PCS1900, UMTS, IMT2000, Wibro, etc. Furthermore, the proposed antenna should be a good candidate as a unit of the omnidirectional array. A prototype has been fabricated and tested, and the experimental results validate the design procedure.

A substrate-integrated-waveguide (SIW) antenna with high directivity for data transmission between a missile and a control platform, usually an aircraft, is presented. By simply setting vias and loading parasitic elements to a rectangle patch on an FR4 substrate, good resonance with effective concentration of current was therefore achieved. For verification, constructed prototypes of both the proposed SIW antenna and the 2/3 scaled system of the designed SIW antenna mounted on the missile were simulated and measured. Good agreement between both has been obtained. The original SIW antenna working at C band has an operating bandwidth of 100 MHz (4.78-4.88 GHz ) and an average gain of about 5 dBi as well, whereas the scaled missile-mounted antenna system has an operating bandwidth of 160 MHz (7.15-7.31 GHz ) with a peak gain of 3.7 dBi at 7.24 GHz. Also, directive radiation patterns suitable for use on data transmission in a missileaircraft transceiver system have been measured for the both cases.

A novel dual-band annular ring slot antenna is investigated. The antenna consists of a center-fed circular microstrip patch antenna with a coupled annular ring. And it is shorted concentrically with a set of conductive vias. By adjusting the parameters of the antenna, the dual resonant frequencies for two modes (TM₀₁ and TM₀₂ modes) are achieved. The antenna is fabricated and tested. Results show that the proposed antenna with height of 0.0217λ₀ can provide gains of 3.01 dBi at 2.6 GHz (the receiving frequency) and 5.74 dBi at 2.95 GHz (the transmitting frequency). Good agreement between the measurement and simulation for the return loss and radiation patterns is achieved. The proposed antenna has dual-band characteristics, simple structure, low profile, and omni-directional azimuth radiation pattern. It is suitable for aircraft both receiving and transmitting signals and frequency division duplex (FDD) applications.

A compact waveguide(CPW)-fed dual-frequency planar monopole antenna is proposed, which can excite two modes.The antenna is composed of a epsilon negative (ENG) meta-structured transmission line (MTL) unit cell and a monopole. The first resonance is zeroth-order mode,which is described using dispersion relation of ENG MTL based on Bloch and Floquet and designed on a CPW single layer where vias are not required. And the second is electromagnetically coupled monopolar mode. The zeroth-order resonant phenomenon is employed to reduce the antenna size. To design and analyze the proposed antenna, the circuit simulation of the ENG MTL unit resonator is executed by the equivalent circuit, and the results are compared with those of full wave simulation and experiment. The results show that the presented antenna reasonable radiation characteristics of bandwidth gain and size, verified by a commercial EM simulation software HFSS11, and is suitable for compact dual-frequency antenna. Then the antenna is fabricated and measured. The realized antenna has a compact size of 0.288λ₀ x 0.199λ₀ x 0.011λ₀(25.1mm x 17.4 mm x 1 mm) at 2.43 GHz. Simulated and experimentally measured results show that the proposed antenna can operate at 2.41(2.43) GHz and 4.11(4.14) GHz bands, respectively. Good agreement between the simulated and measured results is obtained.

This paper deals with the dielectric loaded Exponentially Tapered Slot (ETS) antenna needed for ultra-high-speed, high-capacity wireless communication systems which work at 60 GHz and illustrates its specifications and requirements. The antenna in such system requires high gain, high-efficient and high performance design specifications. The ETS antenna and the loaded dielectric are integrated using the same single substrate resulting in easy fabrication and low cost. The ETS antenna with rectangular and elliptical shaped loaded dielectrics were designed and fabricated. These antennas have high gain and wider beamwidth in both E-plane and H-plane. The proposed antenna design is simulated using 3D electromagnetic software CST Microwave Studio and the comparison is made with Ansys HFSS to validate the design procedure. The results obtained from the simulations and the measurements are in good agreement.

A metamaterial based electronically controlled microstrip structure, performing as leaky wave (LW) antenna with beam steering capability was synthesized. The structure has the configuration of metamaterial transmission line(TL) composed of cascade composite right- /left-handed(CRLH) unit cells. The direction of maximum radiation is tuned via the variation of varactros' capacities incorporated to the structure. Theoretical analysis and synthesis, based on the metamaterial TL theory, was made and novel methods to realize some of the elements of the units cells are proposed. Results, received via simulation, demonstrate that the LW antenna has steering capability of the direction of maximum radiation in a range of 40°, gain changing a little, 6 dB to 7 dB, during the scanning, whereas small number of cells is enough to obtain this performance.

A printed Log-periodic dipole array (LPDA) is presented, operating over the C, X and Ku bands. The antenna feeding structure consists of two coaxial cables, in order to realize an infinite balun which provides the required broadband input matching. The second coaxial cable mirrors the first one, connected to the antenna input, and is capable of both stabilizing the antenna phase center and improving the radiation pattern. The antenna has been designed using CST Microwave Studio, with an useful frequency range of 4-18 GHz. Moreover, both simulated and measured results show that the proposed LPDA can be successfully used as an Ultra Wideband Antenna in the range 4.25-13.25 GHz, in which its phase center remains stable.

Square slot antennas with modified edges for broadband circular polarization are presented. Slots with only stubs or notches are studied and it is found that the axial ratio (AR) bandwidth is quite sensitive to the perturbations of the stubs and notches. To further enhance the AR bandwidth, slot antennas with combination of stubs and notches are proposed and wide 3-dB AR bandwidth of 15.5% (2.45-2.86 GHz) is obtained. By placing a conducting reflector at the rear of the slot, another modified square slot antenna is designed for practical applications, which achieves a 3-dB AR bandwidth of 6.5% (2.38-2.54 GHz) and peak gain of 8.7 dBic. Agreement between simulated and measured results is satisfactory.