Showing papers by "Randy L. Haupt published in 2010"

Dual Polarization Interleaved Spiral Antenna Phased Array With an Octave Bandwidth

Abstract: A technique to design dual polarization spiral antenna phased arrays using mono polarization spirals is presented. The proposed technique consists of two interleaved subarrays, one for each polarization. The position of every spiral antenna is optimized through a genetic algorithm so that each array is nearly the size of the platform while having low sidelobes. Both resulting arrays have the same properties and are steerable. This method also helps to increase the bandwidth. An 80-element spiral array (spiral of width 0.25 m) with dual polarization is demonstrated, its beam can be steered ±30°, over almost one octave (1.97:1). The physical rejection of the sidelobes (i.e., without weighting) is about - 10 dB.

Optimization of a Photonically Controlled Microwave Switch and Attenuator

Abstract: A silicon-based photoconductive switch and attenuator for microwave signals has been demonstrated and optimized for low insertion loss and high attenuation response upon illumination from a standard infrared LED. This device is fabricated within a coplanar waveguide for easy integration into a planar antenna for photonic control of an array. A general tradeoff exists between the goals of low insertion loss and high attenuation range. However, design and process enhancements are found to improve the device performance. A device that offers up to 20-dB attenuation with insertion loss of only 0.6 dB at 2.0 GHz is demonstrated. These devices show a frequency range where the insertion phase shift upon attenuation is significantly less than 1°/dB.

Adaptive nulling with weight constraints

Abstract: Adaptive nulling algorithms that minimize the total array output power from the array require constraints on the adaptive weights, otherwise nulls would be placed in the main beam and the desired signal rejected. The concept of cancellation patterns is reviewed and extended to partial adaptive nulling. Cancellation patterns are then extracted from adaptive nulling results with a genetic algorithm and a 32 element dipole array model. The cancellation patterns provide insight into the constraints needed for the successful implementation of a power minimization adaptive algorithm.

Dynamic array thinning for adaptive interference cancellation

Abstract: This paper describes an approach to adaptive nulling that changes an array thinning configuration to move sidelobe nulls. Dynamically thinning an array requires that each element in the array can be made active by connecting it to the feed network with a switch. If the number of active elements remains constant, then the gain of the array remains constant. Our results show that nulls can be placed in the array factor by changing the thinning configuration.

Dynamic thinning strategy for adaptive nulling in planar antenna arrays

Abstract: An approach for the suppression of undesired signals impinging on a planar array is presented in this paper. The procedure is based on a dynamic thinning enforced to the array to move sidelobe nulls. Towards this aim, each element of the array is equipped with a radio-frequency switch which is used to connect/disconnect the element to the feeding network. While changing the thinning sequences, the number of active elements is kept as constant as possible to maintain unaltered the antenna gain. A set of representative results is reported to show the effectiveness of the approach.

Linear and Planar Array Factor Synthesis

Abstract: This chapter contains sections titled: Synthesis of Amplitude and Phase Tapers Analytical Synthesis of Amplitude Tapers Numerical Synthesis of Low-Sidelobe Tapers Aperiodic Arrays Low-Sidelobe Phase Taper Suppressing Grating Lobes Due to Subarray Weighting Plane Wave Projection Interleaved Arrays Null Synthesis ]]>

Antenna Array Basics

Abstract: This chapter contains sections titled: History of Antenna Arrays Electromagnetics for Array Analysis Solving for Electromagnetic Fields Antenna Models Antenna Array Applications Organization and Overview ]]>

Array Factor Analysis

Abstract: This chapter contains sections titled: The Array Factor Uniform Arrays Fourier Analysis of Linear Arrays Fourier Analysis of Planar Arrays Array Bandwidth Directivity Amplitude Tapers z Transform of the Array Factor Circular Arrays Direction Finding Arrays Subarrays Errors Fractal Arrays ]]>

Broadband linear array with photoconductive attenuators

Abstract: This paper describes the design, construction, and testing of an 8 element broadband array with photoconductive attenuators at each broadband monopole element. The photoconductive attenuators are controlled by an IR LED and vary between on and off with a small reflection coefficient and small insertion loss. Test results for the elements and array are presented. Low sidelobe Chebyshev amplitude tapers are demonstrated by controlling the illumination of the photoconductive weights.

Element selection for partial adaptive nulling

Abstract: Partial adaptive nulling selects a subset of all the elements in an array to have adaptive weights. Making only a few of the elements adaptive requires less hardware and reduces computational complexity compared to fully adaptive arrays. Partial adaptive nulling was first advocated in the 1980's [1] and is important in power minimization adaptive algorithms [2]. This paper examines the effects of adaptive element selection for a partially adaptive array.

Array Beamforming Networks

Abstract: This chapter contains sections titled: Transmission Lines S Parameters Matching Circuits Corporate and Series Feeds Slotted Waveguide Arrays Blass Matrix Butler Matrix Lenses Reflectarray Array Feeds for Reflectors Array Feeds for Horn Antennas Phase Shifters Transmit/Receive Modules Digital Beamforming Neural Beamforming Calibration ]]>

Improving axial ratio of a planar phased array of spirals

Abstract: A new planar spiral-like antenna array with wide band properties is presented here. The WAVES method is used along with a hexagonal spiral antenna to obtain a wide frequency band. This design allows a steering angle range of +/- 30° and a good circular polarization over the bandwidth.

A dual polarization phased array with connected spirals

Abstract: A spiral antenna is a broadband element exhibiting circular polarization: right-hand circularly polarized (RHCP) or left hand circularly polarized (LHCP) depending on its winding An array of spirals with dual polarization must therefore have spirals winding both right and left A simple configuration alternates every other RHCP element with a LHCP element In that case, the spacing is such that the frequency at which the grating lobes appear (so the maximum frequency of the array) is lower than the minimum frequency of the spiral (and, so, of the array, with a return loss less than −10dB)

Array Factors and Element Patterns

Abstract: This chapter contains sections titled: Pattern Multiplication Wire Antennas Aperture Antennas Patch Antennas Broadband Antennas ]]>