Applications of hybrid discrete Fourier transform moment method to the fast analysis of large rectangular dipole arrays printed on a thin grounded dielectric substrate

Micro & Optical Tech Letters

2003

In this paper, the use of reflecting microstrip arrays as stable target points, called PS as described above, is investigated for SAR interferometry applications. The reflecting surface of a reflectarray can be designed to scatter most of the incident radiation back in the direction of incidence. This goal is achieved by imposing a phase distribution (n) of the kind [5]:where n is the element position, d gives the spacing between elements, is the wavelength, and i the angle of incidence (Fig. 1). The phase contribution of each element must be chosen not only to satisfy the final distribution given by Eq. (1), but also to compensate for the phase delay ⌬ n ϭ (2/)⌬r n in the different path lengths of the incident field (Fig. 1).The overall design of microstrip reflectarray entails the use of a specified phase design curve. The phase tuning technique based on elements of different size is adopted in this work. The number of radiating elements is used to control reflectarray RCS level, which is directly related to the size of the reflecting surface. When imposing the required RCS values, the proposed planar reflector is obviously advantageous with respect to a tridimensional CR having the same face size. The use of microstrip technology gives itself significant improvements such as low cost, less weight, and easy installation. NUMERICAL RESULTSThe validity of the proposed method has been tested by realizing a reflectarray prototype with a maximum backscattering in the direction i ϭ 23Њ (typically, an incidence angle of ERS-1/2 SAR). At present, a test facility of limited size is available for far-field measurements, so that a 10-GHz array of 7 ϫ 7 elements 0.6 spaced has been designed. Figure 2 shows a photo of the reflectarray, printed on a Diclad870 substrate with r ϭ 2.33 and thickness t ϭ 0.762 mm. Square radiating elements of dimensions spanning from 5.556 mm to 10.186 mm have been chosen from the phase design curve reported in Figure 3. RCS measurements have been performed in the anechoic chamber at the Microwave Laboratory of the University of Calabria. Two X-band pyramidal horns have been used as transmitting and receiving antennas for the monostatic configuration illustrated in Figure 4. A good agreement between simulations and experimental results can be observed in Figure 5, where a maximum backscattering value exists at the required incidence angle i ϭ 23Њ. CONCLUSIONPrinted reflectarrays were proposed in this work as artificial PS for SAR applications. A maximum backscattering in a prescribed direction of incidence was obtained as in standard CR, but using a very thin and flat structure. The new planar reflector avoids the storage of unwanted materials, which usually compromises CR electromagnetic response, thus much more stability is obtained together with less cost and easier installation. The proposed method was tested on a 10-GHz reflectarray prototype. Both numerical and experimental validations show a RCS peak at i ϭ 23Њ, which is the typical ERS1/2 SAR angle of incidence. , where N tot is the to...

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Extension of forward‐backward method with a DFT‐based acceleration algorithm for efficient analysis of radiation/scattering from large finite‐printed dipole arrays

Micro & Optical Tech Letters

2003

“…1(a) and [11,13,15]), whereas it is piecewise sinusoidal (PWS) for the printed dipole arrays (see Fig. 1(b) and [12,14,15]). It should be mentioned at this point that using more than one basis function per dipole does not change the formulation but improves the accuracy.…”

mentioning

confidence: 96%

Extension of forward-backward method with DFT-based acceleration algorithm for the efficient analysis of large periodic arrays with arbitrary boundaries

Microw. Opt. Technol. Lett.

Ertürk

Chou

2005

Self Cite

An extension of the discrete Fourier transform (DFT)-based forward-backward algorithm is developed using the virtual-element approach to provide a fast and accurate analysis of electromagnetic radiation/scattering from electrically large, planar, periodic, finite (phased) arrays with arbitrary boundaries. Both the computational complexity and storage requirements of this approach are O(Ntot) (Ntot is the total number of unknowns). The numerical results for both printed and freestanding dipole arrays with circular and/or elliptical boundaries are presented to validate the efficiency and accuracy of this approach. © 2005 Wiley Periodicals, Inc

“…In recent years, several MoM-based methods have been proposed to improve the operational count and memory-storage requirements of the conventional MoM [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Making use of stationary or nonstationary iterative schemes in the MoM solution reduces the operational count from O(N tot 3 ) (of order N tot 3 ) to O(N tot 2 ), where N tot is the total number of unknowns.…”

Section: Introductionmentioning

confidence: 99%

“…The fast multipole method (FMM) [4] with an operational count O(N tot 1.5 ) and its subsequent extensions such as multilevel FMM (MLFMM) [5] (O(N tot log N tot )), as well as conjugate gradient-fast Fourier transform (CG-FFT) with O(N tot log N tot ) [6] are some successful efforts. Besides, infinite array approximation [7], and hybrid approaches to reduce the total number of unknowns such as a hybrid combination of MoM with either uniform geometrical theory of diffraction (UTD) [8 -10] or discrete Fourier transform (DFT) [11,12] are useful techniques that are available in the literature.…”

Section: Introductionmentioning

confidence: 99%

Extension of forward backward method with DFT based acceleration algorithm for the efficient analysis of large periodic arrays with arbitrary boundaries

IEEE Antennas and Propagation Society International Symposium. Digest. Held in Conjunction With: USNC/CNC/URSI North American R

Chou²,

Ertürk³

approaches a constant maximum value for tapers longer than 15 mm. CONCLUSIONPlanar transmission-line impedance transformers with an unconventional multilayered structure obtained by deposition of highdielectric-constant thin films on bulk substrates have been designed and their performance have been compared to those of transformers printed on very high-dielectric-constant ( r ϭ 80) bulk substrates. The propagation characteristics of the tapered lines were investigated using the finite-element method through a commercially available software package. The dispersion effects and impedance variation with respect to frequency were taken into account in the analysis. The response of the proposed structure does not deteriorate significantly with frequency, thus allowing operation in an acceptable range up to 40 GHz. The investigation of the propagation characteristics of short electrical pulses on the unconventional multilayered structure and on very high-dielectricconstant bulk-substrate tapers was carried out, confirming the better performance of the proposed structure. The propagation of very short pulses without substantial distortion was verified. Finally, the effects of the multilayered taper length on the performance were assessed.The newly proposed multilayered structure presented attractive results. The achieved effective dielectric constant is very high, whereas the structure has very low dispersion, thus allowing the construction of compact high-frequency devices. The lines have both simple cross sections and comfortable transversal dimensions for a wide range of impedances, thus leading to less expensive manufacture. The results obtained thus far indicate that this structure may be suitable for many other applications in microwave components. ACKNOWLEDGMENTThis work was supported by the Research and Development Center, Ericsson Telecomunicações S.A., Brazil. [7], and hybrid approaches to reduce the total number of unknowns such as a hybrid combination of MoM with either uniform geometrical theory of diffraction (UTD) [8 -10] or discrete Fourier transform (DFT) [11,12] are useful techniques that are available in the literature.Recently, a DFT-based acceleration algorithm [13] was used in conjunction with stationary (for example, the forward-backward method (FBM)) and nonstationary (for example, biconjugate gradient stabilized method (BiCGSTABM)) iterative MoM (IMoM) [14,15] to reduce the computational complexity and memory storage of the IMoM solution to O(N tot ) in the analysis of electrically large, planar, periodic, rectangular, finite phased arrays of both freestanding and printed dipoles. In this approach (DFTIMoM), contributions to every receiving element in the array are coming from two different regions: namely, the strong region formed by the nearby elements of the receiving element whose contributions are calculated in an element-by-element fashion, and the weak region formed by the rest of the array elements whose contributions are obtained from the DFT representation of the entire current di...