In this study, we present an implementation of Ultra wide band (UWB) Koch Snowflake antenna for Radio Frequency Identification (RFID) applications. The compact antenna, based on the Koch Snowflake shape, is fed by coplanar waveguide (CPW) and microstrip line with an overall size of 31x27x1.6 mm3. The simulation analysis is performed by CST Microwave Studio and compared with HFSS software. The antenna design exhibits a very wide operating bandwidth of 13 GHz (3.4-16.4 GHz) and 11 GHz (3.5-14.577 GHz) with return loss better than 10 dB for microstrip line antenna and CPW antenna respectively. A prototype of CPW and microstrip antenna was fabricated on an FR4 substrate and measured. Simulated and measured results are in close agreement. The small size of the antenna and the obtained results show that the proposed antenna is an excellent candidate for UWB-RFID localization system applications.
A novel family of fractal curves is proposed which provides the designer a systematic way of miniaturizing the microwave components with the freedom of choosing among form factor, design complexity and achieved miniaturization. The proposed fractal curve is characterized by two integer values m and n. The m value determines the form factor of the fractal while n value governs the iteration number. The equations governing the geometry of fractals are also presented. The proposed fractal is characterized for miniaturization by designing a printed monopole antenna for various values of m and n. The results from the full wave simulations and experiments are analysed and explained. The effect of fractal on reducing the resonant frequency is quantified by an equation based on its physical interpretation. Based on this analysis, saturation point for miniaturization is established. The curves being symmetric around a straight line, distortionless radiation patterns are seen.
Development of new network standards leads to the use of bulky base station antennas. Their wide surfaces are not compatible with integration constraints in urban areas. As the antenna is composed of a high number of radiating elements, reducing the surface of each element is a way to reduce the antenna surface. Compact radiating element would allow integration of several antennas on the initial surface. In this paper, a new compact antenna is designed in order to obtain up to four antennas at the place of one. The antenna gain and horizontal Half Power Beamwidth (HPBW) should be maintained. The size reduction is obtained by dielectric embedding. In order to determine the dielectric characteristics in which the antenna must be immersed, a theoretical model is proposed in this paper. Simulations and measurements are provided to show the evolution of the antenna's performances in order to achieve manufacturer's specifications.
We investigate the efficiency of a metasurface supporting spoof plasmons to control the electro-magnetic emission of a radiating element. The three-dimensional metasurface is made of an array of metallic grounded rods, and it is used as the substrate of a printed antenna. Such a substrate provides a transmission band at low frequencies, corresponding to spoof plasmon propagation, and a total electromagnetic band gap above the cut-off frequency. We show how an efficient and directive emission with low side-lobe levels and backward radiation can be obtained when the operating frequency of the antenna is considered in the band gap. The role of the spoof plasmons is further demonstrated by tuning the transmission band at the operating frequency. The proposed meta-substrate is an original and efficient alternative to reshape the emission of electromagnetic sources.
A compact Ultra Wideband (UWB) antenna with Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN) with dual band-notched characteristics is presented in this article. The antenna design parameters have been optimized by the High Frequency Structural Simulator (HFSS) and CST Microwave Studio to be in contact with biological breast tissues over 3-13 GHz frequency range with dual band-notched characteristics. The proposed antenna is a polygon printed on a low dielectric FR4 substrate fed by a 50-Ω feed line and a partial ground plane in other side. The results exhibit that the proposed antenna shows a wide bandwidth covering from 3 GHz to at least 13 GHz with VSWR<2 and observing band elimination of WiMAX and WLAN bands. The proposed UWB antenna has omnidirectional radiation patterns with a gain variation of 0.5 dBi to 5.2 dBi and low distortion group delay less than 1 ns over the operating frequency range. The simulation and the measurement results show a good agreement. And good ultra-wideband linear transmission performance has been achieved in time domain with a compact dimension of 28×20 mm2.
Magnetically coupled resonant wireless power transfer (WPT) has been employed in many applications, including wireless charging of portable electronic devices, electric vehicles， etc. However, the power transfer efficiency (PTE) decreases sharply due to divergence of magnetic field. Electromagnetic (EM) metamaterial (MM) can control the direction of magnetic fields due to its nega-tive effective permeability. In this paper, MMs with negative effective permeability at radio frequencies (RF) are applied to a WPT system operating at around 16.30 MHz for improvement of PTE. This ul-tra-thin and assembled planar MM structure consists of a single-sided periodic array of the capaci-tively loaded split ring resonators (CLSRRs). Both simulation and experiment are performed to cha-racterize the WPT system with and without MMs. The results indicate that the contribution of high PTE is due to the property of negative effective permeability. By integrating MM in the WPT system, the experimental results verify that the measured PTE with one and two MM slabs have respectively 10% and 17% improvement compared to the case without MM. The measured PTEs of the system at different transmission distances are also investigated. Finally, the proposed MM slabs are applied in a more practical WPT system (with a light bulb load) to reveal its effects. The results verify the efficiency improvement by the realized power received the load.
This paper presents a new implementation of a millimeter wave heterodyne receiver based on six-port technology. The six-port circuit is designed using three hybrid couplers H-90º and a new ring power divider. For the characterization of the circuit, several six-port two-port measurement configurations were designed and fabricated on the same wafer along with calibration standards. The new six-port architecture evaluation based on qi points location demonstrates wideband performances and high coupled-port phase and amplitude balance in the 57-65 GHz frequency band. The six-port model based on S-parameter measurements is then implemented in ADS software, for realistic advanced simulation systems of a short-range 60 GHz wireless link. The millimeter wave frequency conversion is performed using a six-port down-converter. The second frequency conversion uses conventional means due to the low IF frequency value. The demodulation results of a V-band QPSK signal for high data rate from 100 to 1000 MBits/s are presented and discussed. The results of the Bit Error Rate (BER) analysis demonstrate that the proposed architecture can be successfully used for high speed wireless link transmission at 60 GHz.
A small-size ultra-thin and narrow frame antenna with a switchable matching network to achieve LTE dual-wide band operation in the 700-980 and 1710-2500 MHz bands is presented for mobile phone applications. The highlight of the antenna is that it has a low profile of only 2 mm and occupies a small ground clearance of 45 × 4.5 mm2, which are very attractive for ultra-thin mobile antenna applications. A folded monopole is used as a radiator fed via a switchable two-state matching circuit controlled by a PIN diode. The PIN type switchable matching network is mainly designed to tune the low band (700-980 MHz). By combining the two working states of the PIN diode, the proposed antenna can cover GSM850/GSM900/DCS1800/PCS1900/UMTS2100 and two LTE bands, LTE700/LTE2300. Details of the antenna are described in this study.
A coplanar waveguide-fed circularly polarized square slot antenna with the feasibility of obtaining a wider bandwidth and a relatively smaller size is proposed and demonstrated. The proposed antenna, consisting of a stepped feeding strip, a modified grounded L-shaped radiating patch, an inverted-L grounded strip and an asymmetric ground with an L-shaped slot as well as two horizontal slots, is designed, analyzed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide an impedance bandwidth of 106.3% (2.3-7.52 GHz) and a 3-dB axial ratio (AR) bandwidth of 90.2% (2.25-5.95 GHz). Additionally, within the effective circular polarization (CP) bandwidth of 88.5% (2.3-5.95 GHz), the proposed antenna has gains from 1.9 dBic to 5.2 dBic with an average gain of 3.9 dBic.
A novel fork monopole antenna is presented using metamaterial structures. The prototype monopole antenna consists of split-ring-resonators (SRR) as an electric-LC resonator and small ground. To prove the concept, the prototype antenna is designed and fabricated for wireless communication systems. The monopole structure makes UWB impedance bandwidth condition for 2-12 GHz. On the other hand, the prototype antenna shows dual notch band characteristics at 3.5-4.5 GHz and 5.3-6 GHz for WiMAX and WLAN rejection. The prototype antenna radiates omnidirectionally and has a gain altered between -4.5 and 6.2 dBi in 2.5-12 GHz, with an average gain of 4.2 dBi. The metamaterial model is suggested for the CRLH (ELC) resonator, and in addition, the parametric study for CRLH (ELC) resonator is presented for clarification of its manner on resonance controlling. Here, the final model antenna is fabricated on an FR-4, and experimental results are compared with simulations.
Based on space-time duality and through the use of temporal dispersive delay lines, this paper presents a demonstration of temporal cloaking/uncloaking at microwave frequencies. Numerical simulations of pulse generation, continuous wave signal recovery and data recovery are discussed in relation to the proposed system architecture. This paper also suggests a practical means for implementation of real time dual temporal cloaking/uncloaking. Compared to traditional signal processing systems, since the recovered data emerges with a reversed form in time domain before its final decoding, an extra operation named time-reversal is needed to obtain the correct data, which could help protect the significant signals better with the proposed temporal cloaking/uncloaking system. The proposed method and achieved results indicate potential application in secure communications and data multiplexing subject to channel bandwidth requirements.
In this paper we report on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. However, this is not always the case, and a cable with multiple shields may perform similar to or worse than a cable with a single shield. We want to shed more light on these situations, which represent the main focus of this paper.
In this paper, dual-chirped arbitrary microwave waveform has been generated through photonics, incorporated with single dual parallel mach-zehnder modulator (DPMZM) inbuilt mach zehnder interferometer (MZI) structure. We have taken two cases of chirping i.e. linear and nonlinear chirps. A case of linear chirping has been explored previously. However, to the best of the authors' knowledge effect of nonlinear chirping in this paper is evaluated for the first time. Other photonics approaches are also available, such as spectra shaping and wavelength to time mapping. But due to fixed spectral response of spectral shaper, center frequency of linear chirp generated waveform is fixed. To get the large center frequency again we have to use large number of spectral shapers which will increase the system complexity. DPMZM avoids such difficulties. These MZMs are biased at the minimum transmission point to get carrier suppressed modulation. Product modulator (PM) is cascaded to the lower arm of DPMZM. Here by using DPMZM we get two advantages. First we have two complimentarily chirped microwave waveforms and second up conversion of the frequency of microwave carrier. A dual-chirped microwave waveform with centre frequency 6 GHz with bandwidth 200 MHz and 2 GHz is generated. The paper gives specific details about various performance parameters such as input signal frequency and power, output signal parameters viz output frequency, chirp rate, chirp bandwidth, time bandwidth product (TBW), etc. The overall model and its performance parameters are computed through MATLAB simulation.
In this paper, three different frequency reconfigurable multiple-input-multiple output (MIMO) antennas are characterized in terms of their channel capacity performance in an indoor environment. Two 2×2 and one 4×4 MIMO antenna configurations are investigated. A complete MIMO system is implemented using software defined radio (SDR) platform. The antenna under test can be used at either transmitter or receiver ends. The channel capacity of the system is evaluated by computing the channel coefficient matrix. The measurements are performed at 2.45 GHz for line of sight (LOS) and non-line of sight (NLOS) scenarios. A comparison of the antennas is performed with an ideal system scenario with totally uncorrelated channels as well as an array of standard monopoles which are half-wavelength apart. The effects of antenna element efficiencies, radiation patterns and spacings on the channel capacity are discussed.
This paper investigates the design of a small antenna on a silicon substrate. The antenna on silicon substrate will be used for integration in a silicon-based GaN TR module. This Co-Planar Waveguide (CPW)-fed antenna has been successfully miniaturized up to λ/4 about 20% reductions by adding a slot to the patch antenna. Promising results are obtained from the antenna simulation and measurement. From the measurement result, the antenna bandwidth is 45% (4.8 GHz-7.5 GHz) with measured gain about 2.5 dBi over frequency range of 5 GHz-7.4 GHz.
An algorithm of solving phase ambiguity of multi-baseline direction finding system based on sparse uniform circular array is proposed in this paper. This sparse uniform circular array whose inter-element spacing is larger than half-wavelength distance suffers from cyclic phase ambiguities, which may cause estimation errors. In order to solve the above phase ambiguities, the corresponding virtual short baselines are acquired by transforming the array element phases that meet with the contraction relationship. The obtained short baselines are used to solve the phase ambiguities according to the virtual baseline and stagger baseline theory. Highly accurate estimates of direction of arrival are herein acquired. Furthermore, the direction of arrival and polarization parameter estimates are automatically matched with no additional processing. The array arrangement problem in high frequency scenario is solved. The estimation accuracy of angle of arrival is improved by means of the phase ambiguity resolution. Simulation results verify the effectiveness of this algorithm.
In this work, an anisotropic zero index material is designed for use in Vivaldi antennas. The metasurface structures are placed within the aperture of a Vivaldi antenna to improve the directivity and gain of the emitted radiation. The range of operation is in the ultrahigh frequency (UHF) range, between 300 MHz and 3 GHz. Two approaches are presented: a type of resonant metallic metamaterial that belongs to the larger class of anisotropic zero index metamaterials and a non-resonant material. A technique for lowering the dimensions of the resonant metamaterial unit cell is presented and applied. The work presented consists of simulation results obtained with HFSS modelling software from ANSYS.
In this paper, the slot-shape and slot-size introduced on the radiating surface of a microstrip antenna as well as the inserted air-gap between the substrate sheet and ground plane are predicted, simultaneously. This synthesizing-prediction is carried out using knowledge based neural network (KBNN) model as this approach requires very less amount of training patterns. The suggested approach is validated by fabricating and characterizing three prototypes. A very good agreement is attained in measured, simulated and predicted results.
We present the numerical parametric study of a reconfigurable plasma antenna array (PAA) composed of a metallic half-wavelength dipole and a set of cylindrical plasma discharges arranged in a planar square lattice. Our results, obtained with the linear embedding via Green's operators (LEGO) method, indicate that beam-forming and beam-steering functionality can be achieved and controlled by appropriately choosing the number and position of the active plasma discharges around the dipole. Furthermore, we show that an external static magnetic field and the plasma density have a noticeable effect on the radiation pattern of the antenna.
In this article, a method of broadband flat gain enhancement for a planar double-dipole quasi-Yagi antenna using multiple directors is proposed. The proposed antenna consists of two dipole drivers with different lengths, a truncated ground plane, and three parasitic strip directors. First, the length ratio of the two dipoles is adjusted to increase the gain in the low-frequency region. Next, three parasitic strip directors are employed to increase the impedance bandwidth and improve the gain of the antenna in the middle- and high-frequency regions. A detailed design procedure for the proposed antenna, covering a frequency band of 1.70-2.70 GHz with a gain > 8 dBi, is explained, along with a step-by-step analysis of the effects of placing each director on input impedance, voltage standing wave ratio (VSWR), and gain characteristics. Experiment results show that the proposed antenna has the desired impedance characteristics with a frequency band of 1.66-2.88 GHz (53.7%) for a VSWR < 2, and a stable flat gain of 8.0-8.4 dBi in the 1.70-2.70 GHz frequency range. Moreover, a measured front-to-back ratio > 11 dB within the band is achieved.