This research work proposes an efficient four-wave mixing (FWM) based routing and wavelength assignment (RWA) scheme for the improvement of connection blocking probability in WDM/DWDM networks. However, the traditional RWA schemes are less efficient for the better quality of transmission, and the proposed RWA scheme partitions the entire fiber transmission window into N number of bands and assigns wavelength randomly from one of the band based on connection length. Finally, the analytical result proves that the mechanism reduces the FWM effect significantly in terms of connection blocking probability with higher partition, lower FWM effect and better performance.
This paper deals with an efficient methodology aimed at monitoring the radiated electromagnetic emissions along a high-speed railway system in the hundreds of kilohertz range. In particular, the proposed approach allows a compressed representation of the spatial distribution of the frequency spectrum of the radiated magnetic field generated by the currents placed on the railway conductors by electrical apparatus on board of running railway vehicles. The main idea underlying this work is that the standing wave nature of current distribution along the railway line results in a spatial distribution of radiated magnetic field which can be effectively represented by resorting to the emerging compressive sensing theory. To this aim, wireless magnetic-field sensors are assumed to be deployed along the railway line and used to provide spatial samples of the magnetic field spectrum. The main advantages of the proposed approach include a smaller number of sensors when compared with the number foreseen by the straightforward use of the conventional Nyquist-Shannon sampling approach, and a simple treatment of nonuniform spatial distribution of sensors. Suitability of the proposed approach is supported by measurement data and electromagnetic models already available in the related literature, whereas effectiveness of field spatial reconstruction is proved through numerical simulations. Although the application presented in this work is specific to the magnetic field distribution in a limited frequency range, the proposed approach has a general validity and could be effectively exploited for distributed monitoring of other physical quantities, in other frequency ranges, related to electromagnetic compatibility and safety/security issues in high-speed railway systems.
A novel wide band microstrip line-fed antenna with defected ground structure is proposed for circularly polarized characteristics. This antenna is suitable for C-band and partially X-band operation. Antenna1 structure consists of microstrip-line-feed, and the square-shaped slot with defect is incorporated in the ground plane. Furthermore, a rectangular and circular patch embedded in the square slot that improves the performance of the radiating Antenna2 and Antenna3 structure, respectively. The proposed Antenna3 is compact in size and shows a good quality of polarization at resonant frequency band. Antenna3 shows the measured impedance bandwidth of 40.72 % (6.45-9.75 GHz) and also shows the variations of 3-dB axial ratio bandwidth at the 6.806 GHz and 9.13 GHz frequencies with the simulated results, respectively. The return loss, axial ratio, gain, efficiency and radiation pattern of the proposed Antenna3 remain consistent for resonant frequency band. The antenna is practically fabricated and simulated. Measured result shows a good agreement with simulated and theoretical ones.
This paper introduces novel derived transformation equations to design Tri-band filters. The design utilizes the approach adopted for tri-band bandpass filter design based on asymmetric half-wavelength resonator. The obtained optimized filter by this approach is used as a reference, and the proposed transformation is applied to calculate the new filter design hardware parameters that satisfy its given specifications. The reference tri-band filter is designed to have: insertion better than 1.3 dB and return loss less than -10 dB at the resonance frequencies 1.4 GHz, 4 GHz and 5.6 GHz for L-Band DAB, Radar (G-band) and Radar (C-band) applications, respectively. To verify the transformation technique two tri-band filters are designed. The first tri-band filter is for WVL, WiMAX and WiLAN while the second tri-band filter is for UMTS, WiLAN and X-band Satellite applications. The momentum simulations for these filters show that the resulting filters specifications are: the insertion loss is better than 1.3 dB and the return loss is less than -10 dB at the resonance frequencies 1.3 GHz, 3.6 and 5.7 GHz for the first one. While the insertion loss is better than 1.4 dB and the return loss is less than -10 dB at the resonance frequencies 1.9 GHz, 5.35 GHz and 8.25 GHz for the second filter, respectively. A set of prototype of the final design of the proposed filters with optimal parameters was fabricated for experimental verification. The RT 5880 substrate is utilized in this design All the results are obtained using circuit and momentum simulation of the Agilent Design Simulator (ADS) package and the performance characteristics have been measured using the Rohde & Schwarz ZVB20 vector 4 port network analyzer. Analysis and comparison of the obtained results show that all the simulated and the measured results agree well.
This paper proposes a double negative metamaterial surface as a superstrate for a multilayer cylindrical dielectric resonator antenna (MCDRA). The aim is to achieve a broadband and high gain Electromagnetic Band Gap (EBG) antenna that can be used in harsh propagation areas to satisfy all the requirements for the 60 GHz wireless communications offering a bandwidth of 7 GHz in the unlicensed ISM band (57−65 GHz), permitting to reach data rates of 10 Gbit/s and more. To meet these objectives various techniques are combined. Numerical and experimental results showed satisfactory performances with achievable impedance bandwidth of more than 10.5% (from 58.1 to 64.2 GHz) and a 18 dBi gain, an enhancement of 13 dBi compared to a homogenous DRA without metamaterial superstrate. The proposed antenna exhibits directive and stable radiation pattern in the entire operating band.
Two new microstrip tri-mode modified ring resonators (Resonator A and Resonator B) are presented and discussed through mode analysis method. The characteristic difference between these two resonators is that the center frequency of the tri-mode Resonator B is still the same as that of traditional dual-mode ring resonator, while the center frequency of Resonator A will be shifted up compared with that of traditional ring resonator. Based on these two novel resonators, two bandpass filter examples are designed, fabricated and measured. The simulations and measurements are in good agreement which validate the design ideas.
Extracting instantaneous frequency (IF) of Micro-Doppler (M-D) is the key to estimating Micro-motion parameters. In this paper, firstly, the micro-motion model of the coning was set up. Meanwhile, the theoretical analysis and derivation of the micro-Doppler were performed. Then we introduced occlusion effect and Time Frequency transform to better accord with the complexity and reality of feature extraction of Micro-Doppler in the real world. Besides other computational complex separation methods, we extended the Viterbi algorithm for some cases and proposed two novel means, selecting local maximum value and extracting central position, to solve the dilemma which unable the Viterbi algorithm. Finally corresponding simulation correct the performance of the two methods in different Signal to Noise Ratio (SNR).The simulation analysis showed that the methods were effective if time-frequency map was not polluted seriously by noise.
A novel microstrip tri-band bandpass filter is proposed and implemented using hybrid resonator with independently controllable center frequencies and good in-between isolation. This hybrid resonator is constructed by a stepped-impedance stub resonator and a single end shorted resonator. The stepped-impedance stub resonators are applied to achieve the first and second passband, while the third passband is implemented by single end shorted resonators. By applying the even-odd mode approach, the resonance frequency ratio between even mode and odd mode inside the stepped-impedance stub resonators is attained. Furthermore, the filter with multi-path coupling structure can generate the transmission zeros at the edge of the passband, which can effectively improve the filter passband selectivity. Finally, a tri-band filter operating at 1.91, 2.73, and 3.45 GHz is designed and fabricated. The measurement results accord well with the full-wave electromagnetic designed responses.
This paper is a continuation of our previous published work in which a water-loaded metal diagonal horn antenna has been designed at 2450 MHz for hyperthermia application and simulated results are compared with those measured. In the present study, theoretical investigations of Specific Absorption Rate (SAR) distribution in a homogeneous biological phantom (muscle) due to direct contact water-loaded metal diagonal horn antenna at 915 and 2450 MHz for hyperthermia application is presented. It is estimated theoretically that, at both the operating frequencies, a reasonable impedance matching is achieved at the interface between the antenna aperture and the biological phantom, where a computation of aperture admittance and reflection coefficient has been performed. Furthermore, it is confirmed through theoretical and simulation studies that the proposed horn antenna gives circularly symmetric SAR distribution in transverse plane in the biological phantom at 915 and 2450 MHz. The simulated and theoretical SAR distributions at 2450 MHz are compared with those determined at 915 MHz. In addition, thermal simulation results based on Pennes' Bio-heat equation (BHE) are applied to the realistic muscle model at 915 and 2450 MHz. The reduction of blood flow rate on temperature distribution is also studied.
A method to design a miniaturized two-element quasi-Yagi antenna (QYA) with size and gain requirements is presented for portable ultra high frequency (UHF) radio frequency identification (RFID) reader applications. The antenna consists of a driver dipole and a ground reflector, and these elements are serially connected with a coplanar strip line. The ends of both elements are folded back toward each other to reduce the lateral size of the antenna. A detailed design procedure of the proposed antenna is explained, along with a performance comparison for the input impedance, voltage standing wave ratio (VSWR), broadside gain, front-to-back (F/B) ratio, and total efficiency. A prototype antenna, covering the 860―960 MHz UHF RFID band with a gain > 4 dBi, is fabricated on an FR4 substrate with dimensions limited to 90 mm by 90 mm. The total width of the proposed antenna is reduced by approximately 41% compared to the conventional QYA without miniaturization, and an F/B ratio is improved by 1―8 dB in the band. Experiment results show that the proposed antenna has the desired impedance characteristics with a frequency band of 853―1,098 MHz for a VSWR < 2, and a stable broadside gain of 4.0―5.3 dBi in the UHF RFID band. Moreover, a measured F/B ratio > 13 dB is obtained.
This paper presents a novel approach for bandwidth enhancement and gain improvement of a microstrip patch antenna array for IEEE 802.16a 5.8 GHz Wi-MAX applications. A split ring resonator (SRR) has been designed to load the microstrip patch antenna array. The unloaded antenna array resonates at 5.8 GHz with gain of 4.3 dBi and bandwidth of 425 MHz, whereas when loaded with split ring resonator the gain approaches to 5.7 dBi and bandwidth increases to 610 MHz which corresponds to bandwidth enhancement of 3%. The electrical dimension of the patch is 0.23λ x 0.3λ.
An integrated eight-element antenna array has been proposed for ultra-wideband (UWB) applications. It consists of eight UWB antenna elements and an eight-way binary-tree modified Wilkinson power divider. Any two adjacent elements in the array are connected to each other and share a common side, thus leading to a connected antenna array. Moreover, this arrangement can be utilized to avoid grating lobe level at higher frequencies. Each antenna element comprises a square ring patch and is excited by a tapered balun to achieve low cross-polarization levels. In order to validate the design, a prototype has been fabricated and measured. Both simulated and measured results confirm that the proposed integrated antenna array achieves a good performance of a reflection coefficient below -10 dB from 2.9 GHz to 10.8 GHz, including stable radiation patterns with low side lobe and cross-polarization levels, thus the antenna is promising for applications in UWB imaging systems.
The performance of wireless communication systems is predominantly dependent on propagation environment and respective radiating antennas. Due to the shorter wavelength at Millimeter Wave (MmW) frequencies, the propagation loss through the objects in indoor environments is typically very high. To improve the channel capacity and to reduce inter-user interference, a high gain directional antenna is desired at MmW frequencies. Traditional antennas used in MmW devices are not suitable for low-cost commercial devices due to their heavy, bulky and expensive configurations. This paper focuses on design and development of a very compact (44.61 mm x 9.93 mm x 0.381 mm) high gain Antipodal Linear Tapered Slot Antenna (ALTSA) utilizing Substrate Integrated Waveguide (SIW) technology at 60 GHz. Received signal strength (RSS), path loss (PL) and capacity are studied for MmW based wireless applications utilizing ALTSA with Radio Frequency (RF) measurement equipment in narrow hallway environment.
Recently, we have presented a novel approach to design metamaterial-inspired notch filters that can be integrated within horn antennas of receiving systems to mitigate the effects of narrowband interfering signals. The filter module consists of a single Split Ring Resonator (SRR), whose rejection band needs to be matched to the bandwidth of the particular interfering signal we want to suppress. Extending our previous work, we show here how it is possible to control the bandwidth of such a filtering module by using different metamaterial-inspired resonators. In particular, we show that, while a reduction of the rejection band can be easily obtained by increasing the miniaturization rate of the resonator, the enlargement of the rejection band cannot be obtained in the same way by simply reducing the resonator quality factor. We show that a solution of the latter problem can be worked out by applying the ``critical coupling'' concept and considering the filtering module to be made of two equal SRRs with a proper optimal separation. The effectiveness of the approach is demonstrated trough proper full-wave simulations and experiments on a fabricated prototype. The proposed technique, used here to design a filtering module for a specific radiating system, has a more general relevance and can be applied to all cases where the operation bandwidth of a component is limited by the resonant nature of a single metamaterial-inspired particle.
This paper presents the Social Network Optimization, a new population based algorithm inspired by the recent explosion of social networks and their capability to drive people's decision making process in everyday life. Early experimental studies have already proven the SNO effectiveness in the optimized design of planar and conformal antennas. Here this novel optimization procedure is described in detail, tested and compared with other traditional evolutionary algorithms, and finally used for the design of different microwave circuits.
A transparent dielectric resonator (DR) reflectarray that works in the C-band (6.5 GHz) is proposed in this paper. Here, the reflectarray element has a metallic stripof adjustable length placed underneathto act as a phase shifter. Floquet method isapplied for characterizing the reflection properties of the element anda 7×7 full-fledge reflectarray was constructed using glass and the low-cost FR4. By varying the length of the under-loading strip, it is found that the proposed DRA reflectarray element is able to provide a compensating phase of greater than 300˚. Measurements and simulations were conducted to analyze the reflection coefficient, antenna gain, and radiation patterns. The reflectarray has a maximum gain of 14.38 dBi in the broadside direction, and the 1-dB bandwidth of the DRA reflectarray is found to be around 8%. The use of DR has enabled antenna size miniaturization, and it can be useful for the design of small-size reflectarrays.
A compact dual-band frequency reconfigurable microstrip-line fed open-end omnidirectional slot antenna is proposed in this paper suited for cognitive radio front end system. The antenna is capable of frequency switching at different frequency bands by changing the resonance length using two PIN diodes. The resonance frequency is tuned by a single varactor diode, placed at a certain location along the slot. The proposed antenna has a wide tuning range in the dual bands: 1.57 to 3.1 GHz and 3.8 to 5 GHz. The designed antenna has compact size of 40×40 mm2. An approximate transmission line model of the proposed antenna is derived to calculate the proper positioning of the diodes, and the design has been verified through numerical simulations and measured results.
This paper presents the analytical design formulas for the bandpass filters which are built on the asymmetrically coupled-line conductor-backed coplanar transmission lines (CBCTLs) in multilayer configuration. The full-wave simulation is employed to characterize the far-field patterns of space-wave and surface-wave radiations as well as the frequency-dependent conductor, dielectric, and radiation losses. Good agreement among the results of full-wave simulation, transmission-line model, and measurement justifies the design procedure and validates the analytical design formulas. By properly placing the dielectric materials in multilayer configuration, a bandpass filter for minimizing the radiated power loss and improving the stopband characteristic can be achieved.
In some satellite navigation receiver systems, there is not enough space to settle several antennas for multi-port multi-band application generally. A triple-deck circularly polarized antenna with three ports for receiving and sending satellites signal is studied in this paper. The design idea in this paper is to place several single-feed microstrip antennas layer by layer for saving space. All patch antennas are probe-fed, and the probe connected to the upper patch goes through the clear hole in lower substrates. The structure of the multi-band antenna is investigated thoroughly. How to tune this kind of antenna is a big problem in application, and one special parameter is given to adjust the performance of the antenna. The designed triple-deck antenna works at the bands of GPS, BDS and 1.66 GHz independently. The formal two bands are RHCP, and the third band is LHCP, so it can receive and send signals at the same time. Both simulated and measured results show that all three working bands can cover the system use differently. Axial ratio less than 3 dB at center frequency is obtained, and absolute gain at center frequency is more than 4 dBic. The advantages of this antenna are compact in size for multi-port multi-band use and easy fabrication.
In this paper, a design of a dual-band series-fed dipole pair (SDP) antenna using proximity-coupled strip and split-ring resonator (SRR) directors is presented. Two different types of directors are placed close to the top element of the SDP antenna. First, a thick strip director is used to enhance the bandwidth and gain characteristics of the SDP antenna. Next, a pair of SRR directors is appended to both sides of the strip director to create a new resonance for dual-band operation. The performance of three different SDP antenna structures (with a strip director, with a pair of SRRs, and with both directors) are compared with the conventional SDP antenna without directors. When the strip and SRR directors are used together, the mutual coupling might affect the impedance matching of the original frequency band of the SDP antenna, and the distance between the two directors is an importance parameter to decide the performance of the antenna. The effects of the distance between the strip and the SRR directors on the input voltage standing wave ratio (VSWR) and realized gain characteristics are studied. A prototype of the proposed dual-band SDP antenna operating in the global positioning system L1 (1.563-1.587 GHz) and 1.7-2.8 GHz bands is designed and fabricated on an FR4 substrate. The experiment results show that the antenna has dual-band characteristics in the 1.56-1.63 GHz and 1.68-2.87 GHz frequency bands for a VSWR < 2. Measured gain is 5.9-7.5 dBi in the former frequency band, whereas it ranges from 6.2 dBi to 7.3 dBi in the latter.