Multibeam Sparse Tiled Planar Array for Joint Communication and Sensing

Multibeam analog arrays have been proposed for millimeter-wave joint communication and sensing (JCAS). We study multibeam planar arrays for JCAS, providing time division duplex communication and full-duplex sensing with steerable beams. In order to have a large aperture with a narrow beamwidth in the radiation pattern, we propose to design a sparse tiled planar array (STPA) aperture with affordable number of phase shifters. The modular tiling and sparse design of the array are non-convex optimization problems, however, we exploit the fact that the more irregularity of the antenna array geometry, the less the side lobe level. We propose to first solve the optimization by the maximum entropy in the phase centers of tiles in the array; then we perform sparse subarray selection leveraging the geometry of the sunflower array. While maintaining the same spectral efficiency in the communication link as conventional uniform planar array (CUPA), the STPA improves angle of arrival estimation when the line-of-sight path is dominant, e.g., the STPA with 125 elements distinguishes two adjacent targets with 20$^\circ$ difference in the proximity of boresight whereas CUPA cannot. Moreover, the STPA has a 40$\%$ shorter blockage time compared to the CUPA when a blocker moves in the elevation angles.Comment: Manuscript submitted to IEEE Trans. Wireless Communication. On August 25, 2022. 27 pages, 16 figure

Wideband data-independent beamforming for subarrays

The desire to operate large antenna arrays for e.g. RADAR applications over a wider frequency range is currently limited by the hardware, which due to weight, cost and size only permits complex multipliers behind each element. In contrast, wideband processing would have to rely on tap delay lines enabling digital filters for every element.As an intermediate step, in this thesis we consider a design where elements are grouped into subarrays, within which elements are still individually controlled by narrowband complex weights, but where each subarray output is given a tap delay line or finite impulse response digital filter for further wideband processing. Firstly, this thesis explores how a tap delay line attached to every subarray can be designed as a delay-and-sum beamformer. This filter is set to realised a fractional delay design based on a windowed sinc function. At the element level, we show that designing a narrowband beam w.r.t. a centre frequency of wideband operation is suboptimal,and suggest an optimisation technique that can yield sufficiently accurate gain over a frequency band of interest for an arbitrary look direction, which however comes at the cost of reduced aperture efficiency, as well as significantly increased sidelobes. We also suggest an adaptive method to enhance the frequency characteristic of a partial wideband array design, by utilising subarrays pointing in different directions in different frequency bands - resolved by means of a filter bank - to adaptively suppress undesired components in the beam patterns of the subarrays. Finally, the thesis proposes a novel array design approach obtained by rotational tiling of subarrays such that the overall array aperture is densely constructed from the same geometric subarray by rotation and translation only. Since the grating lobes of differently oriented subarrays do not necessarily align, an effective grating lobe attenuation w.r.t. the main beam is achieved. Based on a review of findings from geometry,a number of designs are highlight and transformed into numerical examples, and the theoretically expected grating lobe suppression is compared to uniformly spaced arrays.Supported by a number of models and simulations, the thesis thus suggests various numerical and hardware design techniques, mainly the addition of tap-delay-line per subarray and some added processing overhead, that can help to construct a large partial wideband array close in wideband performance to currently existing hardware.The desire to operate large antenna arrays for e.g. RADAR applications over a wider frequency range is currently limited by the hardware, which due to weight, cost and size only permits complex multipliers behind each element. In contrast, wideband processing would have to rely on tap delay lines enabling digital filters for every element.As an intermediate step, in this thesis we consider a design where elements are grouped into subarrays, within which elements are still individually controlled by narrowband complex weights, but where each subarray output is given a tap delay line or finite impulse response digital filter for further wideband processing. Firstly, this thesis explores how a tap delay line attached to every subarray can be designed as a delay-and-sum beamformer. This filter is set to realised a fractional delay design based on a windowed sinc function. At the element level, we show that designing a narrowband beam w.r.t. a centre frequency of wideband operation is suboptimal,and suggest an optimisation technique that can yield sufficiently accurate gain over a frequency band of interest for an arbitrary look direction, which however comes at the cost of reduced aperture efficiency, as well as significantly increased sidelobes. We also suggest an adaptive method to enhance the frequency characteristic of a partial wideband array design, by utilising subarrays pointing in different directions in different frequency bands - resolved by means of a filter bank - to adaptively suppress undesired components in the beam patterns of the subarrays. Finally, the thesis proposes a novel array design approach obtained by rotational tiling of subarrays such that the overall array aperture is densely constructed from the same geometric subarray by rotation and translation only. Since the grating lobes of differently oriented subarrays do not necessarily align, an effective grating lobe attenuation w.r.t. the main beam is achieved. Based on a review of findings from geometry,a number of designs are highlight and transformed into numerical examples, and the theoretically expected grating lobe suppression is compared to uniformly spaced arrays.Supported by a number of models and simulations, the thesis thus suggests various numerical and hardware design techniques, mainly the addition of tap-delay-line per subarray and some added processing overhead, that can help to construct a large partial wideband array close in wideband performance to currently existing hardware

Adaptive multibeam antennas for spacelab. Phase A: Feasibility study

The feasibility was studied of using adaptive multibeam multi-frequency antennas on the spacelab, and to define the experiment configuration and program plan needed for a demonstration to prove the concept. Three applications missions were selected, and requirements were defined for an L band communications experiment, an L band radiometer experiment, and a Ku band communications experiment. Reflector, passive lens, and phased array antenna systems were considered, and the Adaptive Multibeam Phased Array (AMPA) was chosen. Array configuration and beamforming network tradeoffs resulted in a single 3m x 3m L band array with 576 elements for high radiometer beam efficiency. Separate 0.4m x 0.4 m arrays are used to transmit and receive at Ku band with either 576 elements or thinned apertures. Each array has two independently steerable 5 deg beams, which are adaptively controlled

Linear Array Thinning with Cavity backed U-slot Patch Antenna using Genetic Algorithm

In this paper, a thinned linear array with Cavity backed U-slot Patch has been investigated using the Genetic Algorithm to minimize peak sidelobe level and the number of antenna elements. One of the essential steps in the Genetic Algorithm method is a crossover, which uses the Paired Top Ten and Combined Top Five rules applied to the Cavity backed U-slot Patch antenna. The peak sidelobe level value is -18.63 dB with a array filling of 63.33% at the broadside angle using Combined Top Five rules. In Paired Top Ten, the peak sidelobe level value is -19.48 dB with a array filling of 70%. The two methods are still better as compared to a dense array. This study is essential in the development of radar technologies since it needs a low sidelobe level

Distributed digital subarray antennas

A system that incorporates distributed digital subarrays working cooperatively as a single array can potentially increase the output signal-to-noise ratio and provide better spatial resolution compared with using the subarrays individually. However, collectively combining periodic widely separated subarrays results in unacceptable grating lobes, and these lobes cannot be suppressed using traditional windowing methods. In this research, we focus on distributed subarray antennas that are comprised of subarrays that can operate individually or collectively. We develop techniques for grating lobe suppression on both the transmitting and receiving sides of the distributed array system. Traditional solutions and new methods are examined in detail via numerical simulation to quantify the performance limitations when applied in combination. One contribution of this research is a hybrid approach that uses a combination of suppression techniques on both the transmitting and receiving sides. Another contribution is the development of new receiving processing methods to suppress grating lobes and improve the signal-to-clutter ratio and signal-to-interference ratio. A final contribution shows the relationship between thermal noise, array errors, and the grating lobe suppression effectiveness. The consideration of array errors addresses the issue of array calibration and synchronization, which are critical concerns when multiple arrays operate coherently.http://archive.org/details/distributeddigit1094538927Major, Taiwan ArmyApproved for public release; distribution is unlimited

Photonic wideband phased array: an optical time steered antenna based on a new true time delay unit

L’attività di ricerca svolta durante il corso di dottorato e descritta dettagliatamente all’interno della tesi è stata diretta al progetto di una innovativa rete ottica di formazione del fascio per antenne a schiera a banda larga esenti dal fenomeno del beam squint. La rete di formazione del fascio proposta è basata sull’utilizzo di un chip ottico integrato modulare che consente di realizzare il True Time Delay implementando switched delay lines. Le caratteristiche del sistema ne consentono l’utilizzo in architetture ad array e a subarray, e la sua modularità rende possibile, in principio, il pilotaggio del sistema radiante, integrando in un unico componente le linee di ritardo di ciascun elemento della schiera. Nella sua prima parte la tesi di dottorato introduce alle antenne ad alte prestazioni richieste dalle moderne applicazioni, focalizzando l’attenzione sui Phased Array, sistemi radianti destinati a svolgere un ruolo di primo piano grazie alla loro flessibilità e potenzialità. Un’analisi ragionata delle soluzioni proposte in letteratura viene, quindi, proposta al fine di evidenziare i principi di funzionamento e le principali problematiche connesse all’implementazione di reti ottiche di formazione del fascio. Inoltre, vengono descritte e discusse le architetture ottiche utilizzate sia per il controllo della fase che per il controllo del ritardo. Successivamente viene presentata la nuova unità ottica integrata di tipo True Time Delay. Le configurazioni di utilizzo del chip ottico studiate e messe a punto durante gli anni del corso di dottorato vengono presentate nel dettaglio, chiarendo le scelte e le strategie di progetto utilizzate in modo da ottimizzare le prestazioni del sistema. Viene presentato il progetto di un prototipo di antenna a schiera basato sul nuovo modulo True Time Delay e un modello accurato dell’intero sistema, implementato allo scopo di verificare il funzionamento dell’antenna e determinarne le prestazioni. Il modello sviluppato tiene in conto delle reali caratteristiche dei dispositivi disponibili in commercio da utilizzarsi all’interno della rete e del sistema radiante, degli inevitabili errori realizzativi relativi a ciascun componente e delle caratteristiche peculiari del nuovo modulo di ritardo. Per compensare gli effetti degli errori suddetti è stata prevista all’interno della rete un’unità di compensazione. Per rendere semplice ed efficace determinarne i parametri è stato sviluppato un algoritmo evolutivo capace di sfruttare al meglio le potenzialità dell’unità così da evitare inutili complessità. Infine, viene proposta una nuova architettura, interamente ottica, di una rete di formazione del fascio per antenne a schiera capaci di irradiare sia fasci somma che fasci differenza beam squint free