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A simple geometrical estimate resulting from rigorous asymptotic evaluation of the Fourier transform integral leads one to conclude that the angular range of the far-field obtainable using planar near-field measurement techniques is limited by the extent of the scan plane and the separation of this plane from the antenna under test. Here, it is shown that this angular range can be extended to a full hemisphere through proper selection of the measurement parameters and careful treatment of the transform integral. In particular, it is noted that the transverse spectrum of the field can possess singularities. These singularities are spectrally filtered by the finite size of the scan plane resulting in a “muting” effect that must be accounted for in the data processing. This is accomplished through the analytic approximation of the bandlimited singularities. Three hardware examples are shown that demonstrate this more detailed approach comparing the results with corresponding patterns obtained using spherical near-field measurement. [ABSTRACT FROM AUTHOR]

The measured radiation field of an antenna may be expanded in a series of vector spherical modes in a specified spherical coordinate system. Such an expansion may be resolved, by means of an iterative algorithm, into two constituent vector spherical mode expansions in two other specified spherical coordinate systems. The sum of these constituent expansions is equal to the original total radiation field. The purpose of such a resolution is to separate the radiation fields due to two identified parts of the original antenna which together constitute the entire radiating structure. Once the resolution has been accomplished, one may study the radiation from the currents on the two parts of the antenna individually including mutual interaction to all orders. This is to be distinguished from measurement of the radiation fields of the two parts individually because that measurement does not include the mutual interaction. A demonstration measurement of a two antenna system is described and iterative postmeasurement processing is employed to identify the radiation from currents on the two constituent antennas of the overall radiating structure. The results are compared with those of an earlier approximate noniterative algorithm developed for the same purpose and the differences are discussed. [ABSTRACT FROM PUBLISHER]

A chamber calibration technique for spherical near-field antenna measurements proposed by Pogorzelski is experimentally demonstrated. The chamber was purposely degraded by introducing a metal plate situated so as to produce a strong specular reflection from the antenna under test to the chamber probe. The effects of this artifact were easily observed in the raw data. The chamber with the artifact was calibrated using an open ended waveguide calibration antenna and the resulting calibration coefficients were used to correct the raw measurement producing a result very similar to the measurement carried out in the undegraded chamber over about 30 to 35 dB of dynamic range. [ABSTRACT FROM AUTHOR]

A probe calibration technique is described that removes artifacts from spherical near-field antenna measurements. The technique is based on preliminary calibration measurements of a known antenna, a process that characterizes the probe and any stationary objects in the measurement chamber including the walls in terms of a set of correction coefficients. These coefficients are then used in a correction algorithm that recovers the correct antenna pattern from the corrupted measurement data. [ABSTRACT FROM AUTHOR]

The distribution of the phase of the oscillations of a set of mutually injection locked electronic oscillators is investigated for the case of a hexagonal nearest neighbor coupling topology. It is shown that planar distributions are not, in general, steady-state solutions of the system of nonlinear differential equations governing the system. An exact steady-state solution of the equations is obtained and shown to be planar only for six discrete azimuth angles. The degree of deviation from a planar distribution is determined and its impact on the directivity of a phased array excited by the oscillator output signals is estimated. [ABSTRACT FROM AUTHOR]

The Cao-York concept of using a linear array of mutually injection locked oscillators to provide local oscillator signals for an agile beam receiver is demonstrated using a 15 circuit array of L-band voltage controlled oscillators coupled to nearest neighbors. The concept involves mixing each 1.265 GHz local oscillator (l-o) signal with a corresponding 1.950 GHz signal received by an element in an antenna aperture and combining the resulting 685 MHz intermediate frequency (i-f) signals. A normally incident wave is simulated using a power divider to provide 15 equal in-phase signals to the r-f ports of the mixers and the i-f combining is accomplished using a similar power divider in reverse. The "antenna beam" is steered through this "normally incident wave" by antisymmetrically detuning the end oscillators of the array and a plot of the i-f combiner output represents the receive beam shape. Finally, this system is used to demonstrate the Kott sidelobe suppression technique. [ABSTRACT FROM AUTHOR]

Design, fabrication, and test of a 25-element planar coupled oscillator based phased array is described. The array operates at S-band and is shown to produce an agile beam which is steerable via adjustment of the perimeter oscillator tuning biases only. A phase diagnostic system is described which displays the aperture phase distribution during the far field measurements of the radiated beam Measured results are presented both with and without the diagnostic system present. Without the diagnostic system, the beam pointing was achieved by setting the perimeter oscillator biases to be values previously used in the measurements with the diagnostic system present. The far field was then measured without the benefit of a knowledge of the aperture phase distribution. Finally, the results of far field measurements are described in which the beam position was incremented from a position previously measured with the diagnostic system in place to a new position by incrementing the perimeter oscillator biases by a fixed amount. [ABSTRACT FROM AUTHOR]

Arrays of voltage-controlled oscillators can be coupled by means of a network so as to mutually injection lock and thus oscillate as an ensemble. This ensemble may be used to excite the elements of a phased array antenna in such a manner as to radiate an agile beam. Design of the coupling network requires attention to three key parameters: the interoscillator coupling strength, the network bandwidth, and the oscillator loading. These parameters can be related to the network admittance matrix elements, which, in turn, are related to the lumped element values. This provides convenient formulas for use in designing networks, which provide the necessary values of the above three key design parameters. [ABSTRACT FROM AUTHOR]

Presents a study which considered a patented technique for suppressing the sidelobes of an array antenna. Concept of linear and two-dimensional arrays with uniform illumination; Conclusions.

Focuses on the use of injection-locked voltage controlled oscillators coupled to nearest neighbors to control the aperture phase of one and two-dimensional phased-array antennas. Overview of the two-dimensional continuum model; Beamstring in two dimensions; Computations of the measurements.

Demonstrates a novel means of achieving cophasal far-filled radiation for a circularly polarized microstrip reflectarray with elements having variable rotation angles. Tests conducted for two Ka-band half-meter microstrip reflectarray; Characteristics of the microstrip patches used in the development of reflectarrays; Mathematical analysis of the rotation element angles approach.

In the above-named article [ibid., vol. 51, no. 4, pp. 794?801, Apr. 2003], the line below (8), Y should be Y0. Also, (18) is incorrect. The correct equation is provided. These changes decrease the computed numerical values of for Qnet the presented examples thus supporting the conclusion that is small even more strongly than the values in the original article. [ABSTRACT FROM PUBLISHER]