Transmit patterns for active linear arrays with peak amplitude andradiated voltage distribution constraints

Distribution functions used in array antenna design typically synthesize specified pattern characteristics without consideration for either the peak amplitude of the radiating elements or the aperture radiated power. There do exist applications, however, in which the pattern synthesis must employ such constraints. In the transmit mode of active array antennas, for example, it is desirable to radiate as much power as possible subject to a per-element peak amplitude constraint while simultaneously suppressing the outer sidelobes. This paper discusses the design considerations of the constrained least squares (CLS) distribution function. In the CLS distribution, most of the radiating elements near the array center are set to their maximum value while only a few of the outer elements are tapered. A method for generating CLS distributions given constraints on both the peak element amplitude and the total effective radiated voltage (ERV) is discussed. The design involves specifying the desired ERV and a weighting function that allows selectively suppressing sidelobes in specified regions. The effects of these design parameters on the far-field patterns are explored     

基于泰勒分布线阵特殊旁瓣技术的研究

提出了基于泰勒加权分布线阵特殊旁瓣要求的设计方法,其波束图是由给定的旁瓣级要求来设计的泰勒分布波束图,在实际需要的特殊旁瓣要求上,设计满足了要求的最窄波束宽度波束图。给出了相应的参数设计,并证明该设计能在要求的最大旁瓣级上获得最大阵增益。借助计算机对线阵进行波束图设计。结果表明,使用该方法设计的波束图能满足特殊旁瓣要求和最大阵增益。     

Rapid method for obtaining footprint patterns for very large antenna arrays

A new antenna pattern synthesis technique that allows the design of large planar antenna array radiating footprint patterns of a specified boundary with controlled ripple and sidelobe levels is presented. The method synthesises the desired footprint as a composition of a set of circular Taylor patterns appropriately weighted with the samples of the pattern obtained after stretching or shrinking a continuous circular aperture distribution developed by the Elliott-Stern method. A footprint of continental Europe radiated by a planar array with a large number of elements shows the technique's performance. The synthesis procedures were completed in about 1 s using a desktop computer.     

Design of line-source antennas for sum patterns with sidelobes of individually arbitrary heights

A design method is presented for the determination of continuous line sources which will yield sum patterns consisting of a narrow main beam and sidelobes whose individual heights can be adjusted to any arbitrary specification. The method is based on a generalized Taylor pattern which is perturbed in successive iterations until the desired pattern results. For practical cases the convergence is rapid, and an economical computer program of general applicability has been written which will terminate when the desired pattern has been achieved within a specified tolerance, at which point a final pattern and aperture distribution are printed out. The theory is illustrated by several cases of practical interest.     

Radiation pattern synthesis for circular aperture horn antennas

A set of radiation pattern functions, suitable for synthesis of radiation patterns from circular aperture horn antennas, is obtained by assuming an aperture distribution consisting of the fields of cylindrical waveguide modes. A technique is presented for using a linear combination of the radiation pattern functions to approximate a desired radiation pattern. Linear combinations of the radiation pattern functions resulting in maximum secondary gain, when used to illuminate a paraboloidal antenna, are obtained empirically. Using spherical wave theory, maximum performance theoretically obtainable from an antenna is derived as a function of the aperture size of the feed system; the feed efficiency resulting from these theoretical limits on performance is compared to the feed efficiency of patterns obtainable from circular aperture horn antennas, and to experimental results of attempts to realize optimum circular aperture horn patterns.     

A linear aperture radiating maximum power within prescribed angular constraints

For fixed aperture size, the aperture taper which maximizes the power radiated into a specified interval (-theta_{0},theta_{0}) is determined, and the properties of the corresponding pattern are compared to the ideal space pattern introduced by Taylor [1]. We consider the case of the linear aperture with no supergaining, although the results are directly applicable to the principal plane patterns of the two dimensional rectangular aperture. It is shown that for an aperture of widtha, as (pialpha/lambda)sin theta_{0}increases, one can not only maximize the power radiated into (-theta_{0},theta_{0}), but also constrain the sidelobe ratio outside (-theta_{0},theta_{0}) below a specified value.     

Analysis and synthesis of axial field patterns of focused apertures

It is shown that the axial field pattern of an aperture focused in the Fresnel region can be synthesized in the same manner as the angular pattern of an aperture in the Fraunhofer region. The aperture distribution which achieves a specified axial pattern is related to the aperture distribution of the specified pattern in the far field through a simple variable transformation. Therefore all analysis and synthesis techniques for far-field patterns can be applied to Fresnel region axial patterns of focused apertures.     

Design of planar arrays to obtain efficient footprint patterns withan arbitrary footprint boundary

An antenna pattern synthesis technique is presented that permits the design of planar antenna arrays with footprint patterns of a specified boundary. This technique is applicable to planar arrays of a wide variety of grid structures and can produce patterns with controlled ripple and sidelobe levels. The approach involves two steps: the first consists in stretching the pure real-continuous aperture (an extension of circular Taylor distributions, developed by Elliott and Stern [1990]) into a distribution with a boundary that is inversely proportional to the flat-top beamwidth; the second is the minimization of a cost function (the square of the difference between the resulting power pattern and the desired one) using the Fletcher-Powell method. A square footprint, produced by a rectangular grid (obtained by sampling this distribution) with the corner elements appropriately removed, is presented as an illustration of the method     

Optimum distribution over a circular aperture for best mean-square approximation to a given radiation pattern

The distribution over a cicular aperture in a ground plane that produces the best mean-square approximation to a specified radiation pattern is derived subject to constraints on the mean-square aperture field strength. The result is derived in terms of the functions most natural for a least square fit: the eigenfunctions of a finite (circular) two-dimensional Fourier transform.     

A synthesis procedure for coated reflector antennas

A procedure is presented for the synthesis of coated axially symmetric reflector antennas to provide specified far-field radiation patterns. The technique stems from ray tracing from the feed to the aperture plane via reflection from the reflector surface. The coating profile required to attenuate the aperture fields is determined based on the reflection of plane waves from metal-backed slabs. The procedure involves two steps. Initially the thickness required to produce the proper magnitude aperture distribution is obtained. Then the reflector is shaped to adjust the phase across the aperture. This procedure is demonstrated in the design of a -40 dB Taylor pattern. Comparison of the results with those obtained using a moment method formulation revealed good agreement between the two formulations     

A one-parameter circular aperture distribution with narrow beamwidth and low sidelobes

A one-parameter circular aperture distribution is developed which provides an optimum compromise between narrow beamwidth, low sidelobes, and low apertureQ. The pattern is a modifiedJ_{1}(x)/x, analogous to the Taylor one-parameter modified sin(x)/xline source distribution. Sidelobe envelope taper is essentially that of a uniformly excited circular aperture; hence the aperture is lowQ. The aperture distribution which is rotationally symmetric is given by a modified Bessel function of zero order. Like all high efficiency distributions, it has a pedestal. All antenna quantities, sidelobe ratio, beamwidth, aperture efficiency, and edge taper, are uniquely related to the parameterH. A table of these quantities is given for sidelobe ratios up to 50 dB. A typical pattern and several distributions are graphed. This new distribution allows tradeoff studies to be made against any design quantity, with all other quantities determined through the one-parameter.     

Near-field quasi-null control with far-field sidelobe levelmaintenance in line source distributions

An improving method, based on the Taylor line source, that allocates a quasi-null in a specified angular position of near-field pattern, and simultaneously controls the general topography of the far-field sidelobe level without significant loss of directivity, compared with optimal efficiency Taylor distribution, of the latter, is presented. The method is based on the application of the simulated annealing technique, by achieving the complex roots of the pattern distribution. An example is developed that demonstrates this accomplishment     

Analysis of active surface reflector antenna for a large millimeterwave radio telescope

The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas     

Radiation efficiency of dense antenna arrays forming flat-top and contour radiation patterns

Infinite 1D and 2D periodic planar arrays of densely spaced radiators that are used to form flat-top and contour patterns are analyzed. It is proposed to determine the amplitude distributions over the antenna aperture as the Fourier transforms of the window functions corresponding to the respective patterns. The proposed distributions are used to derive the explicit expressions showing that the efficiency of an array with a specified flat-top or contour pattern is equal to the mean efficiency of a uniformly excited array in the scan region covered by the specified pattern.     

Measurement distance effects on low sidelobe patterns

Because of the current strong emphasis on low sidelobe antennas, the effects of measurement distance in distorting patterns are reexamined. Previous calculations have used obsolete or suboptimum aperture distributions. The Taylorbar{n}linear distribution is a versatile highly efficient and robust optimum distribution; its use here allows a single curve of sidelobe measurement error versus measurement distance (normalized to far field distance2D^{2}/lambda) for a given sidelobe level. The calculations give data from a uniform distribution to a 60 dB Taylor. For example, the first sidelobe of a 40 dB Taylor pattern is in error 1 dB at a distance of6 D^{2}/lambda.     

Arbitrary footprint patterns obtained by circular apertures

The proposed quasi-analytical method undertakes the shaping of a desired footprint as a composition of several /spl phi/-symmetric circular Taylor patterns exhibiting flat-topped beams. The final pattern is obtained after sampling the obtained circular aperture for circular grid planar arrays. A square and a rectangular footprint pattern, both radiated by a planar array with 1246 elements, demonstrate the performance of the technique.     

Circular aperture distribution with one parameter

A 1-parameter circular aperture distribution is described. It is analagous to the Taylor 1-parameter modified (sin x)/x line source. The new distribution allows aperture design and tradeoff studies to be easily made in terms of sidelobe ratio or edge taper; the distribution is efficient and of low Q. Both the distribution and its corresponding pattern are given by Bessel functions. A table of values of the parameter H, beamwidth, efficiency and edge taper are given against sidelobe ratio.     

Quasi-Analytical Synthesis of Moderate and Large Arrays Radiating Arbitrary "Star-Shaped" Footprint Patterns [Antenna Designer's Notebook]

The proposed quasi-analytical method undertakes the shaping of a desired footprint as a composition of several phi-symmetric circular Taylor patterns exhibiting flat-topped beams. The final pattern is obtained after sampling the circular aperture that is obtained for rectangular-grid planar arrays. A triangular-shaped footprint and a footprint of continental Europe, radiated by planar arrays with moderate and large numbers of elements, show the technique's performance.     

Optimum aperture monopulse excitations

A unified formulation of the optimization of monopulse antenna performance indices for a specified sidelobe envelope function and/or specified nulls of the pattern is presented. The performance indices considered are beam efficiency, gain factor, and angular sensitivity factor of rectangular and circular apertures. The unconstrained optimization of beam efficiency result in an integral equation, the solutions of which are prolate spheroidal wave functions for rectangular aperture and hyperspheroidal wave functions for circular aperture. These functions reduce, respectively, to Legendre and Zernike polynomials in the case of gain factor and angular sensitivity factor. The double orthogonality properties of these eigenfunctions are used for constrained optimization. The results obtained by this technique for the near-in sidelobes constrained at a uniform level are shown to be in agreement with the earlier works. The method is applicable for other aperture surfaces such as elliptical, ellipsoidal, and spherical.     

航管二次雷达发射天线方向图综合

该文介绍航管二次雷达(SSR)发射天线方向图综合的新方法,这种方法以有源相控阵天线为基础。利用带底座的Cosine口径幅度分布综合出所需的定向方向图,辐射用于询问的P1和P3脉冲。在上述口径幅度分布基础上,利用驻相法获得所需的口径相位分布以综合出方位上全向的方向图,辐射用于询问旁瓣抑制(ISLS)的P2脉冲。省去了单独辐射P2脉冲的天线和相应设备。