The proliferation of wireless services is driving innovative phased array solutions that are able to provide better cost/performance tradeoffs. In this context, the use of irregular array ...architectures provides a viable solution. This paper reviews and highlights some of the most recent advances in this field, including clustered, thinned, sparse, and time-modulated arrays, and their proposed design methodologies.
This communication presents linear and planar binomial arrays for extremely low sidelobe level (SLL) on a single substrate using series feed configuration. Binomial distribution is achieved using ...tapered patch width. A seven-element linear binomial array using U-shaped series feed is designed and compared with a conventional series-fed array having identical radiating elements. A conventional series-fed array provides a gain of 14.9 dBi and an SLL of −14.5 dB. However, the binomial array provides SLL of −28 dB with 12.5 dBi gain at 5.76 GHz. A planar series-fed binomial array is designed using series and corner feed lines in E- and H-planes, respectively. A <inline-formula> <tex-math notation="LaTeX">3\times3 </tex-math></inline-formula> element series-fed planar binomial array is fabricated, and the measured results agree with simulated values. It provides SLL of less than −28 dB in both E- and H-planes with 12.8 dBi gain at 5.76 GHz. Both linear and planar binomial arrays provide extremely low SLL.
A series-fed millimeter-wave (mm-wave) microstrip linear array with single-layer structure and wide operating bandwidth is proposed and investigated. The antenna array simply consists of a microstrip ...line and a series of short stubs that are periodically introduced on one edge of the microstrip line, at an interval of about one guide wavelength. Owing to the perturbation of the additional stubs, the original symmetrical E-field distributions on the two opposite edges of the microstrip line become asymmetrical, and the intensities of the equivalent magnetic currents are unequal and unable to cancel each other out as in a pure microstrip line. As a result, the stub-loaded microstrip line can radiate effectively, producing broadside radiation patterns. The introduction of stubs can also generate an extra resonant mode, which combines with the resonant mode of the microstrip line, yielding a wide bandwidth of over 20%. In addition, the microstrip array is simply fed by a coaxial probe, without involving any complex feeding network. Therefore, the array configuration is very simple and compact. For demonstration, a <inline-formula> <tex-math notation="LaTeX">1 \times 4\,\,1 </tex-math></inline-formula>-D microstrip linear array operating at 27 GHz is fabricated and tested. The measured results show that the array has an impedance bandwidth of 21.40%, an average realized gain of 12.18 dBi, and a first sidelobe level (FSLL) of about −13 dB. Moreover, the FSLL can be decreased to −28.4 dB by tapering the width of the microstrip line. Finally, the design is extended to realize a <inline-formula> <tex-math notation="LaTeX">4 \times 4\,\,2 </tex-math></inline-formula>-D microstrip planar array. This planar array can achieve an impedance bandwidth of 19.15% and an enhanced gain of 18.30 dBi.
A new linear sparse array based on the nested array is proposed, which enjoys all the good properties of the two-level nested array, and can provide more degrees of freedom (DOF). The new array is ...constructed by two uniform linear arrays (ULAs) and an additional sensor. The sensor locations, the array aperture, and the achievable DOF from its difference co-array (DCA) are all benefited for closed-form expressions. Furthermore, the resulting DCA is kept as a hole-free ULA. The optimal numbers of sensors in the two ULAs provided the total number of physical sensors are derived. This new array can resolve more sources and achieve better angle estimation performance than the two-level nested array. Simulation results validate these conclusions.
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In array processing, mutual coupling between sensors has an adverse effect on the estimation of parameters (e.g., DOA). While there are methods to counteract this through appropriate modeling and ...calibration, they are usually computationally expensive, and sensitive to model mismatch. On the other hand, sparse arrays, such as nested arrays, coprime arrays, and minimum redundancy arrays (MRAs), have reduced mutual coupling compared to uniform linear arrays (ULAs). With <inline-formula><tex-math notation="LaTeX">N</tex-math></inline-formula> denoting the number of sensors, these sparse arrays offer <inline-formula><tex-math notation="LaTeX">O({N}^{2})</tex-math></inline-formula> freedoms for source estimation because their difference coarrays have <inline-formula><tex-math notation="LaTeX"> O({N}^{2})</tex-math></inline-formula>-long ULA segments. But these well-known sparse arrays have disadvantages: MRAs do not have simple closed-form expressions for the array geometry; coprime arrays have holes in the coarray; and nested arrays contain a dense ULA in the physical array, resulting in significantly higher mutual coupling than coprime arrays and MRAs. This paper introduces a new array called the super nested array, which has all the good properties of the nested array, and at the same time achieves reduced mutual coupling. There is a systematic procedure to determine sensor locations. For fixed <inline-formula><tex-math notation="LaTeX">N</tex-math></inline-formula>, the super nested array has the same physical aperture, and the same hole-free coarray as does the nested array. But the number of sensor pairs with small separations (<inline-formula><tex-math notation="LaTeX">\lambda /2,2\times \lambda /2</tex-math></inline-formula>, etc.) is significantly reduced. Many theoretical properties are proved and simulations are included to demonstrate the superior performance of these arrays. In the companion paper, a further extension called the <inline-formula><tex-math notation="LaTeX">Q</tex-math></inline-formula>th-order super nested array is developed, which further reduces mutual coupling.
In array processing, mutual coupling between sensors has an adverse effect on the estimation of parameters (e.g., DOA). Sparse arrays such as nested arrays, coprime arrays, and minimum redundancy ...arrays (MRA) have reduced mutual coupling compared to uniform linear arrays (ULAs). These arrays also have a difference coarray with O (N 2 ) virtual elements, where N is the number of physical sensors, and can therefore resolve O (N 2 ) uncorrelated source directions. But these well-known sparse arrays have disadvantages: MRAs do not have simple closed-form expressions for the array geometry; coprime arrays have holes in the coarray; and nested arrays contain a dense ULA in the physical array, resulting in significantly higher mutual coupling than coprime arrays and MRAs. In a companion paper, a sparse array configuration called the (second-order) super nested array was introduced, which has many of the advantages of these sparse arrays, while removing most of the disadvantages. Namely, the sensor locations are readily computed for any N (unlike MRAs), and the difference coarray is exactly that of a nested array, and therefore hole-free. At the same time, the mutual coupling is reduced significantly (unlike nested arrays). In this paper, a generalization of super nested arrays is introduced, called the Qth-order super nested array. This has all the properties of the second-order super nested array with the additional advantage that mutual coupling effects are further reduced for Q > 2. Many theoretical properties are proved and simulations are included to demonstrate the superior performance of these arrays.
The second edition of this book adds eight new contributors to reflect a modern cutting edge approach to genomics. It contains the newest research results on genomic analysis and modeling using ...state-of-the-art methods from engineering, statistics, and genomics. These tools and models are then applied to real biological and clinical problems. The book's original seventeen chapters are also updated to provide new initiatives and directions.
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Sidelobes (SLs) in the two-way radiation pattern are of serious concern in a radar array. Several techniques have evolved to mitigate the problem, which include amplitude tapering, genetic algorithm ...(GA) optimization, thinning transceiver aperture, and two-weight amplitude distribution. With such optimization schemes, the SLs can be considerably suppressed but at the cost of a reduction in directivity or taper efficiency. Furthermore, such amplitude tapers require a complex feeding network design. This work alleviates such design restrictions and proposes a systematic approach to lower the SLs in radar two-way shared aperture arrays. The proposed methodology can achieve an SL level (SLL) of below −52 dB in both linear and planar arrays, which is about 18 dB enhancement in SLL compared with uniform transmit and thinned receive arrays. In addition, as a result of the equal transceiver array size in the proposed design, an improvement of approximately 0.44 dB and 0.68 dB in directivity is achieved in linear and planar arrays, respectively. A novel feeding architecture is also illustrated to reduce the cost and complexity of the overall feeding network. A set of full-wave simulations have also been performed to validate the theoretical results.
Phased array technology has been evolving steadily with advances in solid-state microwave integrated circuits, analysis and design tools, and reliable fabrication practices. With significant ...government investments, the technologies have matured to a point where phased arrays are widely used in military systems. Next-generation phased arrays will employ high levels of digitization, which enables a wide range of improvements in capability and performance. Digital arrays leverage the rapid commercial evolution of digital processor technology. The cost of phased arrays can be minimized by utilizing high-volume commercial microwave manufacturing and packaging techniques. Dramatic cost reductions are achieved by employing a tile array architecture, which greatly reduces the number of printed circuit boards and connectors in the array.
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