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Rectangular pulse and modulated rectangular pulse. (a) Rectangular pulse with the rising and falling edges of Gaussian pulse; (b) the sine wave modulated rectangular pulse.
Source publication
Time modulated linear antenna arrays consisting of printed dipoles above a ground plane are simulated using the finite-difference time-domain (FDTD) method. The FDTD method brings great convenience to the investigation of the time domain responses of the time modulated arrays. In conjunction with the near-to-far field transformation in time domain,...
Context in source publication
Context 1
... the sake of obtaining the far-field pattern in a broad range of frequencies, the sine wave modulated rectangular pulse is adopted to stimulate the excitation between the two arms of each dipole. Shown in Figure 2 are the rectangular pulse with the rising and falling edges and the sine wave modulated rectangular pulse in free space within one pulse repetition period T p . As can be seen, by setting the proper value of t 0 and T , the rising and falling edges in rectangular pulse can be well approximated. ...
Citations
... According to studies, very low or ultra-low SLLs with improved radiation properties can be obtained using uniformly or non-uniformly excited arrays by implementing adjustable switch configurations. [45][46][47][48][49][50] The ability to use TMLAs in emerging domains like tracking radar systems, 51,52 path-finding, 53 direction of arrival evaluation, 54 automatic beam steering, 55-58 and so on was made possible through elaborative research works in this field. ...
... The SLL max of À31 42 ; À25.5045 ; À24.10, À30.8046 ; À22.98, À29.69 47 ; À25.27, À39.6048 ; À31.90 dB 49 are compared with WOA-based proposed method which implies a considerably improved SLL max of À40.28 dB.Optimizing the 16-element LAA using WOA yields a high DRR of 7.6835 which increases the complexities of the feed network as precise attenuators are needed to implement that, whereas the current amplitude excitations are the T A B L E 7 Comparison of WOA-based results with other algorithms for the 16-element TMLA design Abbreviations: BAT, bat algorithm; CSO, cuckoo search optimizer; DE, differential evolution; FFA, firefly algorithm; GWO, grey wolf optimizer; HBM, honey bee mating; HPBW, half-power beamwidths; PSO, particle swarm optimizer; RGA, real-code genetic algorithm; SLL, sidelobe level; TMLA, time-modulated linear arrays; WOA, whale optimization algorithm.F I G U R E 5 Optimal radiation patterns of 16-element TMLA using WOA-based approach. TMLA, time-modulated linear arrays; WOA, whale optimization algorithm same for all the elements of TMLA, and the value of DRR is 1. ...
This article presents an approach to design a non‐uniformly excited linear array antenna (LAA) and an alternate solution to LAAs in the form of time‐modulated linear arrays (TMLA) for optimum far‐field radiation pattern synthesis. The performance analysis of both the antenna arrays is studied, and the advantages and limitations of the proposed design approaches are presented with numerical outcomes. The far‐field radiation pattern is optimized to reduce the interference by simultaneously lowering the sidelobe levels and increasing the directivities of LAAs and TMLAs. A recently proposed meta‐heuristics computation technique called whale optimization algorithm (WOA) is employed to get the optimal results. The current excitation amplitude and the inter‐element spacing of the 16‐element LAA are optimized with WOA to attain the desired results. However, due to the large dynamic range ratios (DRRs) of excitation weights, array feed network complexities are increased, which restricts the design of typical LAAs. TMLAs can be regarded as an alternative solution where the problem of large DRRs as well as the design complexities of LAAs are eliminated. The concept of ‘time’ is vital in time‐modulation as it plays the role of an added degree of freedom realized by periodically turning ON and OFF the radio‐frequency switches with an electronic control circuit to achieve an enhanced array radiation pattern. WOA is utilized to determine the optimal switch‐ON time periods for each array element and the optimal inter‐element spacing of a 16‐element TMLA. A set of numerical results validates the advantages of TMLAs over LAAs, and the limitations of TMLAs with respect to LAAs are also indicated. The performance of both the arrays is then compared with other published literature results to establish the superiority of the proposed approach.
... [13][14][15] RF switches are used to ON and OFF particular elements of the array for a specific duration to obtain radiation pattern according to the desired application. 8,[16][17][18] Since time-modulation is used, array weights are obtained, and the process is more accurate compared to the conventional method and also improves the control system performance. The array elements excitation amplitudes can be derived from the expansion of binomial series or Dolph-Chebyshev 19 polynomial or Taylor 20 series. ...
Optimization for the reduction of power losses in sidebands and side lobes of time-modulated antenna array (TMLAA) is dealt in this work. Optimization for the reduction of power in TMLAA is analyzed by considering two ways of the power loss analysis: one with the minimization of power loss with optimization of Toff instant with Ton instant as zero for each element along with optimal inter-element spacing with uniform amplitude and second, by taking optimization of Ton and Toff instant of each element of TMLAA along with optimal inter-element spacing with uniform amplitude. Distance between any two consecutive antennas and switch ON and OFF instants are considered as optimizing variables for reduction of power due to sidebands at harmonic frequencies and side lobes at the fundamental harmonic. Towards this approach, an evolutionary algorithm-based approach called harmony search algorithm (HSA) is applied. Optimal values of the variable parameters of the TMLAA are obtained after optimization by using particle swarm optimization (PSO) and HSA. MATLAB simulation results are presented in this work for different array sets of 16-, 20-, 24-, 28-, and 32-element antenna arrays. To validate in electromagnetic (EM)-simulated environment, a 16-element TMLAA is designed in CST-MWS with parameters obtained after optimization, and these results are validated with those of MATLAB results.
... This yields to a very small time step size to maintain the stability of the FDTD method. [2][3][4][5][6][7][8][9] As a result, the conventional FDTD method needs very long computational time to complete the calculation. To overcome this problem, the weakly-conditionally-stable finite difference time domain (WCS-FDTD) method 10 has been proposed, which weakens the Courant-Firedrich Levy (CFL) stability condition. ...
In this article, a hybrid algorithm based on traditional finite‐difference time‐domain (FDTD) and weakly conditionally stable finite‐difference time‐domain (WCS‐FDTD) algorithm is proposed. In this algorithm, the calculation domain is divided into fine‐grid region and coarse‐grid region. The traditional FDTD method is used to calculate the field value in the coarse‐grid region, while the WCS‐FDTD method is used in the fine‐grid region. The spatial interpolation scheme is applied to the interface of the coarse grid region and fine grid region to insure the stability and precision of the presented hybrid algorithm. As a result, a relatively large time step size, which is only determined by the spatial cell sizes in the coarse grid region, is applied to the entire calculation domain. This scheme yields a significant reduction both of computation time and memory requirement in comparison with the conventional FDTD method and WCS‐FDTD method, which are validated by using numerical results.
... Co-axial Continuous Transverse stub antenna array is a multimode structure and supports number of waveguide modes [1][2][3][4][5][6][7][8][9][10]. The inclined CCTS antenna occupies less space compared to normal CCTS antenna. ...
In today’s modern world the expectation of people is excellent performance in compact size. In wireless communications there several technologies developed in day to day life to improve the effectiveness of the communication. Now in these days the major concern is about wastage of available spectrum. To reduce the wastage of spectrum there are so many technologies available like cognitive radio. For the proper implementation of these technologies need a proper antennae section. This design focused mainly on the performance of double inclined continuous transverse stub antenna array for high frequency communication. The proposed inclined A-shaped co-axial continuous transverse antenna structure has been proved to radiate for high frequency bands. The proposed Novel double inclined coaxial continuous transverse stub antenna array radiates for multiple frequencies of range 3 GHz 10 GHz.These operating frequencies are primarily suitable for satellite C-band and high frequency wireless communication applications.
... In the simulation of many algorithms of patch antenna, because the FDTD method has many advantages [6][7][8], it can be used to simulate the complex patch antenna commendably. Maxwell equations can be transformed into scalar field model by calculating in rectangular coordinate system, and then numerical difference coefficient in the second rank precision is employed to replace differential quotient. ...
In this paper, a composite heterostructure mesh-shaped patch antenna based on left handed material (LHM) is presented. The method of finite difference time domain (FDTD) is used. The results show that electromagnetic wave resonance occurs near 4.52 GHz, where the equivalent permittivity and permeability of composite material are both negative. The composite antenna’s gain improves 9.047 dB, its return loss reduces 20.26 dB compared to the conventional antenna’s ones. The results indicate that this composite patch antenna system can reduce return loss of the antenna and increase the gain obviously.
... When the step line operates at the microwave and millimeter wave bands, conventional circuit theory is not suitable for precise analysis of transmission characteristics of step line [2,3]. In order to solve this problem, some common full wave methods, such as Finite Difference Time Domain (FDTD), Method of Moment (MOM) and Finite Element Method (FEM) can be utilized [4][5][6][7][8][9]. Circuit designers, however, may not be familiar with these field methods and are better at constructing equivalent circuits with circuit parameters and working out transmission characteristics from the circuit, although some work has begun to focus on the extraction of distributed circuit parameters from the field results. ...
The static circuit parameters extracted from the field results of non-uniform microstrip line provides an efficient way to predict dynamic effect of non-uniform structure. The predictable frequency range of the static circuit parameters on prediction of the transmission characteristics of step microstrip line is researched in this paper. The circuit parameters are extracted from the full wave results of step line, respectively, at three frequencies (9 GHz, 15 GHz and 20 GHz). On one hand, the time domain transmission characteristics of step line can be solved from the equivalent circuit constructed by these extracted circuit parameters. On the other hand, the frequency domain S-parameter can be derived by the static distributed characteristic impedance. By comparing these time and frequency domain results obtained from the static circuit parameters with those obtained directly from the full wave method, the available condition of the static circuit parameters of the step microstrip line can be analyzed. This comparison shows that the static circuit parameters can be used in frequency bands from DC up to 20 GHz. To verify the accuracy of the static parameters used to predict the transmission characteristics of step line, the measured S11 is also given for comparison.
... CTS technology offers greater tunable bandwidth than waveguide or patch antennas. The different forms of CTS antenna include coaxial, coplanar and rectangular waveguide [2][3][4]16]. This structure exhibits very low Q and impedance characteristics. ...
... Design procedures for a coaxial CTS array includes selection of the following parameters [3][4][5] distance between two adjacent stub elements (L 2 ), width of the dielectric fill material (L 1 ), dielectric conductor (D 1 ), diameter of the outer conductor (D 2 ), diameter of the stub (D 3 ). For the purpose of an illustrative design, the width of stub element L 1 has been selected to be of half a wavelength of dielectric material. ...
This paper proposes the design and analysis of co-axial continuous transverse stub multiband
antenna (CCTS) for multiple high frequency Applications. Coaxial continuous transverse stub antenna is used to operate on multiple frequency bands with small size and low cost. This proposed antenna consists of two stubs, arranged longitudinally to form a waveguide skeleton like structure. The advantages of CCTS antenna are used to produce omnidirectional radiation pattern in the horizontal plane. This antenna can radiate for the frequency range of 24.5 GHz to 35 GHz which is suitable for portion of K band and Ka band wireless applications. This proposed structure produces very good radiation pattern in both vertical and horizontal plane with minimum acceptable return loss. The simulation software used in this design is CST Microwave Studio and MATLAB.
... The time domain analysis is inevitable in electromagnetic problems. The finite-difference time-domain (FDTD) method is the differential equation based time domain method and has been extensively used for analysis of antennas, especially, wide band antennas [1][2][3][4][5]. However, the FDTD method can be very time consuming, practically, along with optimization techniques, due to the fact that the determining the fields at free space nodes and terminating computational space using absorbing boundary conditions are necessary in the FDTD method. ...
In this paper, the fast Fourier transform (FFT) to perform spatial convolutions of the time domain discrete Green's functions (DGF) method related to the analysis of the antenna with more than one dimension has been proposed. For this aim, the discrete Green's functions and the currents on the antenna have been appropriately defined periodic so as to use the zero padded fast Fourier transform. The computational complexity of this approach is O(NwNxNyNz log(NxNyNz)), contrary to O(NwN2xN2yN2z)for direct implementation of the convolutions. Simulation results demonstrate the great efficiency of the FFTbased spatial convolutions in the modeling of planar antennas.
... Four-dimensional (4D) antenna arrays, which are also termed as time modulated arrays in literature [1][2][3][4][5][6][7][8], are formed by introducing a fourth dimension, time, into conventional antenna arrays operating in the 3-dimensional space. As compared to conventional arrays, the 4D arrays have much more flexibility in pattern synthesis, due to the additional degree of design freedom, time. ...
... For example, low sidelobe level (SLL) patterns can be synthesized in 4D arrays with uniform static amplitude and phase excitations. In the past decade, many studies have been carried out to synthesize desired patterns and suppress the sideband level (SBL) in 4D linear and planar arrays using various optimization algorithms [3][4][5][6][7][8][9][10][11]. Recently, some studies show that 4D arrays have promising potentials for some practical applications, such as harmonic beamforming without phase shifting [12,13], direction finding [14,15], monopulse radar design [16,17], adaptive nulling [18,19], and directional modulation for secure communication [20]. ...
An efficient approach is presented for the design of a low sidelobe four-dimensional (4D) planar antenna array, taking into account mutual coupling and platform effect. The approach is based on the combination of the active element patterns and the differential evolution (DE) algorithm. Different from linear and circular arrays, the mutual coupling compensation in a planar array is more complicated since it requires numerous data of the active element patterns in different azimuth planes. In order to solve this problem, a useful interface program is developed to get these data from commercial software HFSS automatically. Also different from conventional low sidelobe arrays with tapered amplitude excitations, the low sidelobe in the 4D array is realized using time-modulation technique under uniform static amplitude and phase conditions. The DE algorithm is used to optimize the time sequences which are equivalent to the complex excitations in conventional arrays. Both computed results and simulated results in HFSS show that a -30 dB sidelobe pattern can be synthesized in a 76-element planar array with an octagonal ground plane and a radome, thus verifying the proposed approach.
... In order to simulate the currents on the element and the coupling among different elements accurately, fullwave method is necessary. Common numerical methods to solve the problems of antenna arrays include method of moments (MOM) [5][6][7], finite element method (FEM) [8], and finite difference time domain (FDTD) [9,10]. MOM is based on integral equations. ...
In this paper, an improved equivalence principle algorithm is proposed to solve the radiation problems of large antenna arrays with periodic structures. This method is a hybridization in which the typical scheme of periodic Green's function is combined with the original equivalence principle algorithm. The repeated elements are changed from the original antenna units into the surfaces enclosing the original ones. The proposed approach is compared with periodic method of moments which is based on the integral equation and the periodic Green's function. Numerical results validate the feasibility of the improved method.
