Figure - available via license: CC BY
Content may be subject to copyright.
Source publication
Two efficient probe-compensated near-field-far-field transformations with spherical scanning for antennas having two dimensions very different from the third one are here developed. They rely on the nonredundant sampling representations of the electromagnetic fields and on the optimal sampling interpolation expansions, and use effective antenna mod...
Similar publications
This paper considers the problem of G1 curve interpolation using a special type of discrete logarithmic spirals. A “logarithmic arc spline” is defined as a set of smoothly connected circular arcs. The arcs of a logarithmic arc spline have equal angles and the curvatures of the arcs form a geometric sequence. Given two points together with two unit...
![Different yield loci on the π\documentclass[12pt]{minimal}...](publication/339871713/figure/fig1/AS:960130782875674@1605924425946/Different-yield-loci-on-the-pdocumentclass12ptminimal-usepackageamsmath_Q320.jpg)
A new linear yield criterion in terms of principal stresses is developed for the purpose of overcoming the analytical difficulty of mechanical parameters when using the nonlinear Mises yield criterion. This developed yield criterion is established through the parabola interpolation method and the mathematical averaging method, which can be called a...
The experimental assessment of an effective near-field - far-field (NF-FF) transformation technique with plane-polar scanning, which requires a nonredundant, i.e. minimum, number of NF data, is provided in this communication. Such a technique relies on the nonredundant sampling representations of the electromagnetic fields and, to shape the antenna...
Punch optimization is important in improving the technological process of belt perforation. Research about this process can rarely be found in the scientific literature. The objective of this paper is to determine the effective geometry of the piercing punches with a spherical bowl used for polymer composite belts. In order to fulfill this goal, th...
This paper deals with the experimental testing of effective probe compensated near-field-far-field (NF-FF) transformations with spherical scanning requiring a minimum number of NF data. They rely on nonredundant sampling representations of the voltage measured by the probe, based on very flexible source modellings suitable for nonvolumetric antenna...
Citations
... Obviously, the larger the AUT size, the greater the number of measurements and, as a consequence, the longer the acquisition time. The theoretical results concerning the nonredundant sampling representations of the radiated or scattered electromagnetic (EM) fields [33] have been exploited to develop NF/FF transformations [16,[26][27][28], which make use of a smaller number of measurement points as compared to that utilised by classical Hansen's technique [15]. These techniques have proven to be effective from a numerical and experimental standpoint without impairing the accuracy of the FF reconstruction process. ...
... The choice of the modelling surface is crucial for obtaining a sampling representation that is really non-redundant and substantially depends on the given AUT, since the choice criterion is that the modelling surface is chosen such that it adheres as much as possible to its actual geometry. Thus, the modelling surface has been chosen in [16,26,27] coincident with that of an oblate spheroid [16,27] or that obtained by two circular bowls sharing the apertures and with eventually different lateral bendings (double bowl modelling) [26] to characterise a quasi-planar AUT, while in [16,26,27] a prolate spheroidal surface [16,27] or that bounding a cylinder terminated by two hemispherical caps (rounded cylinder) [26] has been adopted for a long AUT. ...
... The choice of the modelling surface is crucial for obtaining a sampling representation that is really non-redundant and substantially depends on the given AUT, since the choice criterion is that the modelling surface is chosen such that it adheres as much as possible to its actual geometry. Thus, the modelling surface has been chosen in [16,26,27] coincident with that of an oblate spheroid [16,27] or that obtained by two circular bowls sharing the apertures and with eventually different lateral bendings (double bowl modelling) [26] to characterise a quasi-planar AUT, while in [16,26,27] a prolate spheroidal surface [16,27] or that bounding a cylinder terminated by two hemispherical caps (rounded cylinder) [26] has been adopted for a long AUT. ...
An effective near-field to far-field transformation using a reduced number of near-field measurements collected via a spherical scan over the upper hemisphere, due to the presence of a flat metallic ground, is devised in this paper. Such a transformation relies on the non-redundant sampling representations of electromagnetic fields and exploits the image principle to properly account for the metallic ground, supposed to be of infinite extent and realised by perfectly conducting material. The sampling representation of the probe voltage over the upper hemisphere is developed by modelling the antenna under test and its image by a very adaptable convex surface, which is able to fit as much as possible the geometry of any kind of antenna, thus minimising the volumetric redundancy and, accordingly, the number of required samples as well as the measurement time. Then, the use of a two-dimensional optimal sampling interpolation algorithm allows the reconstruction of the voltage value at each sampling point of the spherical grid required by the classical near-field-to-far-field transformation developed by Hansen. Numerical examples proving the effectiveness of the developed sampling representation and related near-field-to-far-field transformation techniques are reported.
... In this framework, a special mention must be reserved for the spherical NF-FF transformation as it is the only one that guarantees knowledge of the full radiation pattern. On the other hand, it is the most complicated from analytical and computational viewpoints, so that many efforts have been spent on its optimization (see [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] as a non-exhaustive list of references). In particular, for keeping accuracy, the reduction in the time needed to perform the NF measurements is a key point of optimization strategies since it is much longer than that required to realize the NF-FF transformation (usually attained offline). ...
... As a matter of fact, according to these results, the smaller the area of surface enclosing the AUT, the lower the number of required NF samples. In particular, an appropriate choice of the AUT model permits the evaluation of the optimal parameters to be used and the reduction in the number of parallels and samples on them when going toward the poles [14][15][16][17]. Unfortunately, the AUT models proposed so far cannot best fit the geometry of some volumetric radiating systems such as those mounted on modular CubeSats. ...
... Note that, on the contrary of roids and cylinders terminated by spherical caps having only two geometri freedom, the composite surface in Figure 1 possesses four geometrical de dom, i.e., height and radius of the central body and radii of the lateral b permitting the best fit for the geometry of 3-D modular radiating system their modules are arranged. Accordingly, it minimizes the volumetric redu tains the spherical and flexible models [15,17] as particular cases, and, for racy, guarantees a non-redundant number of needed samples, thus saving time for the data acquisition. An optimal sampling interpolation (OSI) algo sequently developed to use these non-redundant data for an accurate comp NF values that are utilizable in the classical NF-FF transformation [13]. ...
A very flexible source model is proposed here to reduce the volumetric redundancy when considering the pattern reconstruction of three-dimensional modular antennas by means of a near-field spherical scan using a non-redundant sampling representation. Since this last facet is based on the appropriate choice of antenna model for the evaluation of the optimal parameters to be used, the proposed geometry guaranteed the minimum number of needed samples and then a significant time saved for data acquisition on the near-field spherical grid. Then, an optimal interpolation algorithm used these non-redundant samples for an accurate evaluation of the near-field data that were usable in the classical near-field to far-field transformation. The reliability and accuracy of the reconstruction process were proven by means of numerical tests. These last showed a remarkable reduction (about 53%) in needed near-field samples as compared to those required by the classical near-field to far-field transformation and this was achieved without any loss in accuracy.
... In particular, prolate and oblate spheroids were adopted to model these kind of AUTs, and optimal sampling interpolation (OSI) formulae [34] were properly utilized to effectively evaluate, from the acquired non-redundant NF samples, the NF data at the points set by the classical spherical grid [14]. These results were extended, in [18], to the case in which a real and not ideal probe was employed. This is possible when the voltage detected at its terminals has approximately the same spatial bandwidth as the antenna field [35]. ...
... An electrically small probe, exhibiting a first order azimuthal dependence (first-order probe), guarantees that the above condition is fulfilled and, therefore, the theoretical results in [32,33] can be properly exploited to represent the measured voltage too. The corresponding probe, which compensated non-redundant NTFF transformation [18], considered a long AUT as enclosed in a cylinder terminated by two spherical caps, and a quasi-planar one in two circular bowls having the same aperture and possibly different radii of the lateral bends (two-bowls). Finally, the experimental validation [22] of this last transformation, and that [21] was relevant to the probe compensated version of the non-redundant NTFF transformation [15], thoroughly proved their efficacy from the practical point of view too. ...
... between the meridian plane through the observation point P and the surface , 1, 2 R the distances between P and the two tangency points 1, 2 P on the curve ' When is the azimuthal circle at '( ) , results to be constant, the angular parameter ' can be properly adopted for describing it, and the related bandwidth [18,32] is ...
This research falls in the antenna measurements related topic, and deals with the problem occurring in the classical spherical near-to-far-field (NTFF) transformation, when it becomes unpractical to mount the antenna under test (AUT) with its center at the center of the scanning sphere. This issue reflects in a growth of the number of near-field (NF) samples to be acquired, since this number depends on the radius of the minimum sphere, which contains the antenna, and is centered at the scanning sphere center. The non-redundant sampling representations of the electromagnetic field are conveniently exploited, to develop an effective spherical NTFF transformation for non-centered AUTs with quasi-planar geometry, requiring a minimum amount of NF samples, and nearly the same as that for a centered mounting of the AUT. Then, the NF data needed to perform the classical NTFF transformation are determined in efficient way from the acquired non-redundant NF samples by employing an accurate 2-D sampling interpolation scheme. Thus, it is possible to significantly save measurement time. Some simulation and laboratory results are reported to show the effectiveness of the developed technique, which takes into account a non-centered AUT mounting.
... The wanted FF radiation pattern can be then determined through near to FF transformation (NTFFT) techniques [1][2][3][4][5][6]. The most attractive NTFFT from the full FF reconstruction viewpoint is that where the NF measurements are carried out over a spherical surface [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], since it does not suffer from the truncation error, like those using a planar or a cylindrical scanning. ...
... These techniques make use of optimal sampling interpolation (OSI) formulas to precisely recover the massive input NF data for the CS NTFFT from the gathered NR samples. By applying the NR sampling representations [23,24] to the voltage detected by an electrically small probe, whose spatial bandwidth is almost the same of the AUT field [25], and shaping a quasi-planar AUT with a double bowl (a surface got by joining together two bowls with the same circular aperture) and a long antenna with a rounded cylinder (a cylinder terminated by hemispherical caps), probe compensated NR NTFFTs with spherical scan have been proposed in [15]. At last, the effectiveness of these NTFFTs and of the probe compensated version of those in [12] has been experimentally confirmed in [18] and [19], respectively. ...
... The so attainable time saving depends both on the way the NF measurements are collected and on the decrease in the amount of the NF samples to be gathered. These NTFFTs utilise the NR sampling representations [23,24] and adopt suitable OSI expansions to evaluate, from the samples acquired along the spiral, the NF data required by the CS NTFFT in its original version [11] or the revisited one [12,15]. The NR representations and the related OSI expansions have been attained by assuming a volumetric AUT as enclosed in a sphere [26][27][28], whereas a long AUT has been modelled by a prolate spheroid or by a rounded cylinder and a quasi-planar one by an oblate spheroid or by a double bowl [29][30][31][32][33][34]. ...
The theoretical foundations of the near to far field transformation (NTFFT) techniques with spiral scannings have been properly applied to develop a non‐redundant spherical spiral NTFFT which properly accounts for a mounting of a volumetric antenna under test (AUT) in an offset configuration, due to any practical constraints. Such an NTFFT, based on the non‐redundant sampling representations of electromagnetic fields using spherical modelling of the AUT, requires the same number of near‐field (NF) spiral data when the AUT is mounted both in onset and offset configuration because this number depends only on the area of the modelling sphere centred at the AUT centre. Moreover, it employs an efficient two‐dimensional (2D) optimal sampling interpolation (OSI) formula to recover, from the spiral NF samples, the massive number of NF data required by the classical spherical NTFFT, which is related to the radius of the smallest sphere enclosing the AUT and centred at the scanning sphere centre. It is so possible to get a remarkable measurement time saving when the AUT is offset mounted. Numerical and experimental results, fully assessing the effectiveness of the developed NTFFT and the related 2D OSI algorithm, are shown.
... Indeed, the NR NFTFFTs [10] considered an ideal probe and, therefore, did not account for the effects related to the use of a real probe. Probe compensated NR NFTFFTs for long or quasi-planar AUTs, assumed as contained in a cylinder terminated by two spherical caps or in two circular bowls with equal aperture radii, have been developed in [13] when adopting a nondirective probe. As a matter of fact, it has been proved [25] that the voltage detected by this type of probe exhibits practically the same spatial bandwidth of the EM field radiated by the AUT and, thus, the results in [22,23] can be utilized to achieve an NR representation of such a voltage too. ...
... As a matter of fact, it has been proved [25] that the voltage detected by this type of probe exhibits practically the same spatial bandwidth of the EM field radiated by the AUT and, thus, the results in [22,23] can be utilized to achieve an NR representation of such a voltage too. At last, the NR NFTFFTs [13] and the probe compensated version of those in [10] have been experimentally assessed in [17] and [16] respectively. ...
... In order to apply the above two-dimensional OSI formula to accurately recover, from the acquired NR samples, the voltages V p and V r of the probe and rotated probe at the positions on the scanning sphere specified by the CS NFTFFT [9] or by its version as rearranged in [10,13], the following points must be stressed: i) the coordinates of the sampling points on the scan sphere are set by the proposed NR sampling representation in the reference frame, S ' but have to be determined in the S one to drive the positioner controllers at the acquisition stage; ii) the positions of the input NF data for the NFTFFT are, obviously, given in S, but have to be expressed in S ' to execute the interpolation. It is a simple task to verify that the relations linking the coordinates of S and S ' are: ...
Background
The development of fast Near-Field (NF) measurement techniques allowing the precise determination of the Far-Field (FF) radiation features of an antenna is becoming more and more challenging nowadays.
Objective
The goal of the article is the development of an NF To FF Transformation (NFTFFT) with spherical scan for offset mounted volumetric Antennas Under Tests (AUTs) requiring, unlike the classical technique, a reduced set of NF data, that is of the same amount as for the onset mounting case, thus making data gathering faster. In fact, the number of NF data needed by the standard approach may considerably increase in this case, since the size of the smallest sphere surrounding the AUT and centered at the center of the measurement sphere rises.
Methods
This goal has been achieved by profitably exploiting the non-redundant sampling representation of electromagnetic field and assuming a volumetric AUT as contained in a sphere. An optimal sampling interpolation algorithm is then employed to precisely reconstruct the input NF data for the traditional spherical NFTFFT from the reduced set of the collected ones.
Conclusion
The numerical simulations and experimental tests demonstrate the effectiveness of the developed approach accounting for an offset mounting of the AUT.
... The non-redundant sampling representations [18] can be exploited also for the voltage measured by a non-directive probe, because its spatial bandwidth practically coincides with that of the AUT radiated field. Accordingly, the hypothesis of an ideal probe made by Bucci et al. [13] has been relaxed by D'Agostino et al. [14], thus developing efficient probe compensated NTFF transformations with spherical scan tailored for quasiplanar or long antennas, which require a non-redundant, i.e. minimum, number of NF data. In particular, quasi-planar AUTs have been considered as contained in an oblate ellipsoid [13] or in a surface consisting of two circular bowls having the same aperture and eventually different lateral surfaces (double bowl) [14], whereas a prolate ellipsoid [13] or a cylindrical surface with two hemispherical caps (rounded cylinder) [14] has been employed to model long antennas. ...
... Accordingly, the hypothesis of an ideal probe made by Bucci et al. [13] has been relaxed by D'Agostino et al. [14], thus developing efficient probe compensated NTFF transformations with spherical scan tailored for quasiplanar or long antennas, which require a non-redundant, i.e. minimum, number of NF data. In particular, quasi-planar AUTs have been considered as contained in an oblate ellipsoid [13] or in a surface consisting of two circular bowls having the same aperture and eventually different lateral surfaces (double bowl) [14], whereas a prolate ellipsoid [13] or a cylindrical surface with two hemispherical caps (rounded cylinder) [14] has been employed to model long antennas. The experimental validations of the aforementioned non-redundant spherical NTFF transformations [13] and [14] have been then provided by D'Agostino et al. [15] and [16], respectively. ...
... Accordingly, the hypothesis of an ideal probe made by Bucci et al. [13] has been relaxed by D'Agostino et al. [14], thus developing efficient probe compensated NTFF transformations with spherical scan tailored for quasiplanar or long antennas, which require a non-redundant, i.e. minimum, number of NF data. In particular, quasi-planar AUTs have been considered as contained in an oblate ellipsoid [13] or in a surface consisting of two circular bowls having the same aperture and eventually different lateral surfaces (double bowl) [14], whereas a prolate ellipsoid [13] or a cylindrical surface with two hemispherical caps (rounded cylinder) [14] has been employed to model long antennas. The experimental validations of the aforementioned non-redundant spherical NTFF transformations [13] and [14] have been then provided by D'Agostino et al. [15] and [16], respectively. ...
Background
This paper provides the experimental validation of an efficient iterative procedure to correct known position errors in a spherical near to far-field (NTFF) transformation for elongated antennas which uses a minimum number of NF measurements.
Method
This transformation exploits a non-redundant sampling representation of the voltage detected by the probe obtained by shaping a long antenna with a prolate ellipsoid. The uniform samples, those at the points set by the representation, are accurately reconstructed from the acquired not regularly distributed (non-uniform) ones by using an iterative scheme, which requires a one to one relationship between each uniform sampling point and the corresponding non-uniform one. Then a 2-D optimal sampling formula is adopted to evaluate the input data needed to perform the traditional spherical NTFF transformation from the retrieved non-redundant uniform samples.
Conclusion
Finally, laboratory proofs have been reported to demonstrate the validity of the presented technique from a practical viewpoint.
... NF-FF transformation using spherical scanning (Hald et al., 1998) is particularly appealing due to its unique feature of allowing full antenna pattern reconstruction. To reduce the number of NF data to be acquired and the related measurement time, non-redundant spherical NF-FF transformations for antennas with one or two predominant dimensions were proposed in Bucci et al. (2001) andD'Agostino et al. (2011a), then later experimentally validated in D' Agostino et al. (2013aAgostino et al. ( , 2013b. They have been obtained by properly applying the non-redundant sampling representations of electromagnetic (EM) fields (Bucci et al., 1998;Bucci & Gennarelli, 2012) to the voltage measured by the scanning probe and developing optimal sampling interpolation (OSI) expansions, which allow fast and accurate recovery of the NF data needed by the classical NF-FF transformation (Hald et al., 1998) from the collected nonredundant ones. ...
... In this context, a technique relying on the conjugate gradient iteration method and exploiting the fast Fourier transform (FFT) for unequally spaced data (Dutt & Rokhlin, 1993) has been proposed to correct known probe position errors in the classical NF-FF transformations with planar (Wittmann et al., 1998) and spherical (Wittmann et al., 2004) scannings. In any case, these techniques are unsuitable for non-redundant spherical NF-FF transformations (Bucci et al., 2001;D'Agostino et al., 2011aD'Agostino et al., , 2013aD'Agostino et al., , 2013b. ...
... For a meridian, bandwidth W , parameter , and related phase function γ are (D'Agostino et al., 2011a;Bucci et al., 1998): ...
Two techniques are developed to efficiently compensate known positioning errors affecting the near-field measurements in a non-redundant spherical near-field–far-field transformation for quasi-planar antennas, and they are fully assessed through numerical and experimental tests. They rely on a non-redundant sampling representation of the voltage measured by the probe, obtained by assuming that the antenna is enclosed in a surface formed by two circular bowls with the same aperture diameter. Both techniques use a two-step procedure. In the first step, the near-field data at the points fixed by the sampling representation are recovered from the irregularly spaced measured ones by properly applying an iterative technique or the singular value decomposition method. Then the near-field data needed by the standard spherical near-field–far-field transformation are effectively reconstructed by means of an optimal sampling interpolation algorithm.
... Note that, according to these plots, the maximum and meansquare reconstruction errors corresponding to the chosen values of the OSI parameters are about −45 dB and −60 dB, respectively. At last, the developed interpolation algorithm has been applied to retrieve the NF data needed to carry out the spherical NF-FF transformation [55], as modified in [63,64]. The reconstructed FF pattern in the H-plane is shown in Figure 12. ...
... An interesting and significant phenomenon at this frequency band is the oxygen absorption that results in atmospheric attenuation of 10-15 dB/km. Because of this phenomenon, the worldwide 7 GHz continuous unlicensed frequency band (59)(60)(61)(62)(63)(64)(65)(66) is the most suitable option for wireless local area networks (WLAN), wireless personal area networks (WPAN), and body area networks (BAN) communications [1]. High level of atmospheric attenuation results in the reduction of cochannel interference and the risk of signal interception that makes 60 GHz frequency spectrum a natural candidate for short range communication purpose [2,3]. ...
With the advent of high data rate 3G and 4G wireless communication systems and the app-based use paradigm, wireless connectivity through multiple air interfaces has become a common requirement in the RF architecture of mobile communication devices. Modern wireless handsets frequently incorporate three or more antennas to enable cellular voice and data, Wi-Fi, and GPS connectivity, across multiple bands. Multiple antenna systems are frequently designed to implement diversity or spatial multiplexing schemes, as in the case of WCDMA and LTE, to increase resiliency and capacity of wireless links and to operate multiple voice/data links simultaneously. Concurrently, ultrawideband (UWB) systems used in short range communications, remote sensing, and through-the-wall radar imaging have introduced a new paradigm in the antenna design where the mitigation of pulse distortion is of the essence, thus requiring a shift in antenna design approach and the introduction of novel radiating systems.
This special issue is intended to reflect current R&D trends and novel approaches in the analysis and synthesis of antenna systems and associated RF front-ends for next generation mobile communication devices, applicable to various device form factors such as smartphones, tablets, laptops and wearable computers as well as for UWB communication systems and radars. A particular emphasis has been paid to the analysis and design of broadband, multiband, and reconfigurable antennas for wireless and UWB applications, as well as to the identification of special materials and integration techniques with the host platform. Important efforts have been devoted to the characterization of the radio channel as well as to the most innovative near-field-far-field transformation techniques employed to determine the radiation properties of the antennas employed in the modern wireless communication systems
... The near-field -far-field (NF-FF) transformation with spherical scanning is particularly interesting and has attracted considerable attention [1][2][3][4][5][6][7][8][9][10][11], since it allows the complete reconstruction of the radiation pattern of the antenna under test (AUT). In this framework, the application of the nonredundant sampling representations of the electromagnetic (EM) fields [12,13] to the voltage measured by the scanning probe has allowed the development of effective nonredundant spherical NF-FF transformations [8][9][10][11] typically requiring a number of NF data remarkably smaller than that needed when employing the classical transformation [4]. ...
... The near-field -far-field (NF-FF) transformation with spherical scanning is particularly interesting and has attracted considerable attention [1][2][3][4][5][6][7][8][9][10][11], since it allows the complete reconstruction of the radiation pattern of the antenna under test (AUT). In this framework, the application of the nonredundant sampling representations of the electromagnetic (EM) fields [12,13] to the voltage measured by the scanning probe has allowed the development of effective nonredundant spherical NF-FF transformations [8][9][10][11] typically requiring a number of NF data remarkably smaller than that needed when employing the classical transformation [4]. As a matter of fact, the NF data required by this last are accurately reconstructed from the acquired nonredundant data by means of an optimal sampling interpolation (OSI) expansion. ...
... To this end, an approach relying on the conjugate gradient iteration method and adopting the unequally spaced fast Fourier transform [14] has been proposed [15,16]. Unfortunately, such an approach is not suitable for the nonredundant NF-FF transformations with spherical scan [8][9][10][11], wherein the nonredundant samples are interpolated via OSI expansions to get the NF data needed to perform the classical transformation. Moreover, a direct reconstruction of the NF data needed for the transformation from the irregularly spaced samples is not advisable [17] and a more convenient and viable strategy is to first retrieve the uniform samples from the nonuniform ones and then determine the requested NF data via an accurate and stable OSI expansion. ...
An efficient technique for compensating known probe positioning errors in a nonredundant spherical near-field - far-field (NF-FF) transformation, using an oblate ellipsoid to model a quasi-planar antenna, is experimentally assessed in this work. It employs an iterative approach to recover the nonredundant NF samples at the points fixed by the sampling representation from the collected irregularly spaced ones. The NF data required by the classical spherical NF-FF transformation are then efficiently determined from the nonredundant NF samples by means of an optimal sampling interpolation algorithm. Some experimental results, carried out at the UNISA Antenna Characterization Lab and assessing the effectiveness of the technique, are shown.
... Since the AUT has been assumed quasi-planar, an effective modelling is obtained by choosing Σ coincident with the smallest surface formed by two circular bowls with the same aperture diameter 2a, but with bending radii c and c' of the upper and lower arcs eventually different to fit the actual AUT geometry better (see Figs. 1 and 2). Such a modelling has been successfully applied to develop nonredundant NF–FF transformations with spherical[22,23], spherical spiral[24,25], and planar wide mesh[26,27]scannings, when dealing with quasiplanar antennas. It can be easily verified that, for such a modelling, ' = 2 b + b' + c + c'' change depending on the range of the radial distance ρ (seeFig. ...
The experimental assessment of an effective near-field - far-field (NF-FF) transformation technique with plane-polar scanning, which requires a nonredundant, i.e. minimum, number of NF data, is provided in this communication. Such a technique relies on the nonredundant sampling representations of the electromagnetic fields and, to shape the antenna, adopts a surface formed by two circular bowls with the same aperture diameter, but eventually different bending radii of the upper and lower arcs. An optimal sampling interpolation algorithm allows the efficient reconstruction of the NF data needed by the classical NF-FF transformation with plane-rectangular scanning from the acquired nonredundant plane-polar ones. A remarkable measurement time saving is so obtained.
