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The power-weighted distribution method is used to satisfy radiation pattern requirements at a certain targeted sidelobe level (SLL) suppression. This article reports a detailed discussion of theoretical and experimental approaches for the application of the Kaiser function in power-weighted linear array prototypes. An exploration of the design and realization of a Kaiser function-based linear array was presented. Furthermore, performance evaluations were performed for several important factors in the Kaiser function-based linear array configuration. The performance evaluations include feeding network variations, number of element (N) variations, and inter-element distance (d) variations. The prototype of Kaiser function-based linear array was configured by a serial feeding type on the folded structure of a proximity-coupled feeding network. The Kaiser function parameter, $\beta $ , is used to determine the set of weighting coefficients. In the application of $\beta $ value of 2, the SLL suppression is 34.63 dB – 34.78 dB for simulation result, and 27.96 dB – 33.47 dB for measurement result. A performance comparison with a uniform linear array and a Chebyshev function-based linear array in an equal configuration is also shown. The Kaiser function utilization as a weighting coefficient in a linear array design shows a significant increase of 20 dB – 30 dB in SLL suppression compared to the one with a uniform distribution, and 5 dB – 8 dB in SLL suppression compared to the Chebyshev function-based linear array. The implementation of the power-weighted distribution method with Kaiser functions resulted in good results for the development of more complex designs with a larger number of antenna array elements.

Multiple-input-multiple-output (MIMO) optical wireless communication systems are potential candidates for high-speed data transmission in indoor environments. In this work, we present an experimental evaluation of two different MIMO systems, i.e., conventional-MIMO (c-MIMO) and imaging-MIMO (i-MIMO) in terms of design considerations. Both systems use the same transmitter configuration featuring a one-dimensional (light-emitting diode) LED transmitting array. On the receiver side, the c-MIMO system employs a similar one-dimensional receiving avalanche photodetector (APD)-based array, whereas the i-MIMO system uses a customized imaging camera-based receiver design. To assess the performance of the two systems, the channel matrix and the bit-error rate are calculated based on the experimental data. At distances shorter than 50 m, the proposed c-MIMO system demonstrates a good transmission performance, particularly when the maximum likelihood detection (MLD) technique is applied. Whereas, at long distances ranging from 40 m to 65 m, the proposed i-MIMO system can ensure an error-free transmission due to the efficient spatial separation between the emitted optical beams. Furthermore, the experimental results confirm that our systems have the potential for high data rates over longer distances in indoor environments.

Multiple-input-multiple-output (MIMO) optical wireless communication systems are potential candidates for high-speed data transmission in indoor environments. In this work, we present an experimental evaluation of two different MIMO systems, i.e., conventional-MIMO (c-MIMO) and imaging-MIMO (i-MIMO) in terms of design considerations. Both systems use the same transmitter configuration featuring a one-dimensional (light-emitting diode) LED transmitting array. On the receiver side, the c-MIMO system employs a similar one-dimensional receiving avalanche photodetector (APD)-based array, whereas the i-MIMO system uses a customized imaging camera-based receiver design. To assess the performance of the two systems, the channel matrix and the bit-error rate are calculated based on the experimental data. At distances shorter than 50 m, the proposed c-MIMO system demonstrates a good transmission performance, particularly when the maximum likelihood detection (MLD) technique is applied. Whereas, at long distances ranging from 40 m to 65 m, the proposed i-MIMO system can ensure an error-free transmission due to the efficient spatial separation between the emitted optical beams. Furthermore, the experimental results confirm that our systems have the potential for high data rates over longer distances in indoor environments. [ABSTRACT FROM AUTHOR]

Angle-based localization of a source at unique coordinates in the three-dimensional (3-D) space utilizes traditionally the two-dimensional (2-D) angle of arrival (AOA) measurements from planar arrays. This paper investigates the positioning performance and develops an optimal solution for the 3-D localization using one-dimensional (1-D) space angle (SA) measurements that has the appeal of involving linear arrays only. The localization performance by SA is less understood and the positioning algorithms from the literature are suboptimal and have restrictions on the altitudes and orientations of the linear array receivers. This paper establishes the basic concept of using SA for localization, and conducts analytical comparison of SA and AOA positionings by cross arrays, where the contrasts in the angle observation accuracy, the geometric dilution effect and overall localization performance are elaborated. A solution that can reach the Cramér-Rao Lower Bound performance under Gaussian noise is also proposed that does not have restriction on the placement of the linear array receivers. It consists of an initial solution by semidefinite relaxation and a refined solution by an algebraic estimator. Simulations validate the theoretical investigation and the algorithm performance. [ABSTRACT FROM AUTHOR]

In adaptive beamforming by compact arrays, the excitation amplitude and phase of each array element require dynamic optimization for controlling the radiation pattern at different angular sectors. If the objective function of adaptive beamformer is defined by some properties other than the deterministic properties of arrays such as directivity or signal-to-noise ratio, evolutionary optimization is advantageously implemented to minimize the objective function. Nevertheless, the convergence time of most of the evolutionary optimization methods exponentially increases by the number of array elements $N$. For large $N$ , the above convergence issue slows down the beamforming agility. To improve the above inefficiency, we first express the array factor by a Schelkunoff polynomial of order $N - 1$. Second, a discrete optimization method like genetic algorithm optimally factorizes the polynomial into two polynomials of orders $N - 1 - P$ and $P$ , where $N - 1 - P \ge P$. Third, the locations of zeros of these polynomials are optimized across the visible region by a continuous optimization method like particle swarm optimization to attain the desired objective function. When these two polynomials are multiplied, the resultant polynomial of order $N - 1$ demonstrates improved features with respect to the original polynomial of order $N - 1$ in sensitivity, sidelobe level, and convergence. Representative examples include airborne radars. [ABSTRACT FROM AUTHOR]

In this article, a novel beam shaping technique is developed to synthesize the array factor (AF) radiation pattern of linear and planar antenna arrays. The proposed method is established based on the expanding of AF using Legendre transform in conjunction with an integrand operator. A system of linear equations is derived and its solution is obtained using least-square method (LSM) for the required pattern. In addition, an iterative procedure is introduced to reduce the number of elements of the primary designed array for a specified mean square error (mse). Then, the proposed method is applied to synthesize the AF of planar and ring antenna arrays. To verify the performance of the proposed method, a few comprehensive well-known linear, planar, and ring arrays are examined. The obtained results show that the introduced method can be used to design the AF pattern of many types of practical arrays with good accuracy. [ABSTRACT FROM AUTHOR]

An elevation and azimuth direction-finding (DF) method is presented by introducing the pattern reconfigurable antenna (PRA) into a two-element array. An equivalent multidimensional array is built by the two-element PRA array with switchable beams of same or opposite directions. With the introduction of same- and opposite-direction modes of PRAs, the elevation and azimuth angles are estimated by the methods of time-modulated array (TMA) and amplitude comparison, respectively. Meanwhile, a 2-D lookup table is built to correct the coning-error effect of the amplitude comparison. Compared with the conventional 2-D DF method with two orthogonal linear arrays, only a single linear array with not less than two elements is needed in the proposed method. Hence, it has the advantages of simple structure, compact size, and low cost. Simulated results are provided to verify the proposed 2-D DF method, and an S-band two-element PRA array is constructed to demonstrate its experimental feasibility. [ABSTRACT FROM AUTHOR]

Ultrasound (US) is an attractive modality for wireless power transfer (WPT) to biomedical implants with millimeter (mm) dimensions. To compensate for misalignments in WPT to a mm-sized implant (or powering a network of mm-sized implants), a US transducer array should electronically be driven in a beamforming fashion (known as US phased array) to steer focused US beams at different locations. This paper presents the theory and design methodology of US WPT links with phased arrays and mm-sized receivers (Rx). For given constraints imposed by the application and fabrication, such as load (RL) and focal distance (F), the optimal geometries of a US phased array and Rx transducer, as well as the optimal operation frequency (fc) are found through an iterative design procedure to maximize the power transfer efficiency (PTE). An optimal figure of merit (FoM) related to PTE is proposed to simplify the US array design. A design example of a US link is presented and optimized for WPT to a mm-sized Rx with a linear array. In measurements, the fabricated 16-element array (10.9×9×1.7 mm3) driven by 100 V pulses at fc of 1.1 MHz with optimal delays for focusing at F = 20 mm generated a US beam with a pressure output of 0.8 MPa. The link could deliver up to 6 mW to a ∼ 1 mm3 Rx with a PTE of 0.14% (RL = 850 Ω). The beam steering capability of the array at -45o to 45o angles was also characterized. [ABSTRACT FROM AUTHOR]

This article presents an innovative design technique for feeding phase antenna arrays using coherently radiating periodic structure (CORPS) technology for reducing the number of phase shifters (PSs) in limited-scan applications with low sidelobe level (SLL). The proposed configuration is implemented taking advantage of the phase interpolation property of a CORPS network of one layer. This configuration is built by interconnecting $2\times 3$ CORPS networks in a strategic way in order to provide a reduction in the number of PSs while maintaining the scanning capability. Experimental results and full-wave simulations based on CST Microwave Studio reveal that the proposed design technique reduces the recombination losses and generates a better phase slope with respect to the basic CORPS network providing a reduction in the number of PSs. As a novel contribution, this article provides the full antenna system design in order to analyze and study the PSs reduction performance and scanning capabilities of the proposed technique to feed linear antenna arrays. The proposed design technique provides a reduction in the number of PSs for a scanning range of ±25° in linear arrays. The array design model includes the application of the raised cosine amplitude distribution to generate a radiation pattern with minimum SLL. The linear array system was validated by experimental measurements of the full system prototype and full-wave simulations results are provided to verify the accuracy of the array model and to take mutual coupling into account. The proposed case provides a good design compromise with respect to other cases in the state of the art. [ABSTRACT FROM AUTHOR]

A complementary source array with enhanced beamwidth is presented based on the substrate-integrated waveguide (SIW) in this communication. The orthogonal complementary source consists of a SIW slot and a vertical monopole, of which the radiation pattern is heart-shaped, pointing to the direction perpendicular to both slot and monopole. To achieve an enhanced beamwidth from the heart-shaped pattern, the complementary sources are cascaded to form an array. In particular, the slots are etched alternately on both sides of the central axis to achieve an in-phase excitation, while the monopoles are uniformly loaded with an alternate antiphase excitation. This arrangement makes the heart-shaped pattern of each complementary source element alternately point to either side of the array axis, so that the synthesized radiation beamwidth is enhanced in the E-plane. Based on the proposed idea, a nine-element line array is designed, fabricated, and tested. Compared with the same-sized referenced SIW slot array with an E-plane half-power beamwidth (HPBW) of only 80°, the proposed complementary source array extends the HPBW to 180°. [ABSTRACT FROM AUTHOR]

In this article, a 16 × 4 linear array of β-Ga2O3-based metal-semiconductor-metal structured photodetector is described for solar-blind sensing operation at a wavelength of 254 nm. The β-Ga2O3 film is grown by using metal-organic chemical vapor deposition (MOCVD) equipment, and the photodetectors are finished in constructing with standard photolithography and ion beam sputtering procedures. The results show that the dark current (Idark), photo-to-dark current ratio (PDCR), photo responsivity (R), specific detectivity (D*), exterl quantum efficiency (EQE), and linear dynamic region (LDR) are 1.94 pA, 2.95 × 107, 139.56 A/W, 2.55 × 1015 Jones, 6.8 × 104 %, and 149.4 dB, at 10 V bias and 2000 μW/cm2 light intensity illumination. In addition, the standard deviation of R for this photodetector array is 10%. Overall, such a 16 × 4 linear array of β-Ga2O3-based photodetector array makes a progress in the field of Ga2O3 photodetectors. [ABSTRACT FROM AUTHOR]

Simulation involves predicting the responses of a physical system. In this article, we simulate opto-acoustic signals generated in a 3-D volume due to the absorption of an optical pulse. A separable computational model is developed, which splits processing into two steps, permitting an order-of-magnitude improvement in computational efficiency over a nonseparable model. The simulated signals represent acoustic waves, measured by a probe with a linear transducer array, in a rotated and translated coordinate frame. Light is delivered by an optical source that moves with the probe’s frame. Spatiotemporal impulse response for rectangular-element transducer geometry is derived using Green’s function solution to the acoustic wave equation. The approach permits fast and accurate simulation for a probe with an arbitrary trajectory, which is useful for modeling freehand acquisitions. For a 3-D volume of n3 voxels, computation is accelerated by a factor of n. This may potentially have application in opto-acoustic imaging, where clinicians visualize structural and functional features of biological tissue for assessment of cancer and other diseases. [ABSTRACT FROM AUTHOR]

Pulsed laser diodes (PLDs) promise to be an attractive alternative to solid-state laser sources in photoacoustic tomography (PAT) due to their portability, high-pulse repetition frequency (PRF), and cost effectiveness. However, due to their lower energy per pulse, which, in turn, results in lower fluence required per photoacoustic signal generation, PLD-based photoacoustic systems generally have maximum imaging depth that is lower in comparison to solid-state lasers. Averaging of multiple frames is usually employed as a common practice in high PRF PLD systems to improve the signal-to-noise ratio of the PAT images. In this work, we demonstrate that by combining the recently described approach of subpitch translation on the receive-side ultrasound transducer alongside averaging of multiple frames, it is feasible to increase the depth sensitivity in a PLD-based PAT imaging system. Here, experiments on phantom containing diluted India ink targets were performed at two different laser energy level settings, that is, 21 and $27~\mu \text{J}$. Results obtained showed that the imaging depth improves by ~38.5% from 9.1 to 12.6 mm for 21- $\mu \text{J}$ energy level setting and by ~33.3% from 10.8 to 14.4 mm for 27- $\mu \text{J}$ energy level setting by using $\lambda $ /4-pitch translation and average of 128 frames in comparison to $\lambda $ -pitch data acquired with the average of 128 frames. However, the achievable frame rate is reduced by a factor of 2 and 4 for $\lambda $ /2 and $\lambda $ /4 subpitch translation, respectively. [ABSTRACT FROM AUTHOR]

A four-element printed antenna array operating at 25-GHz frequency with complementary split ring resonator (CSRR) has been proposed for beamforming applications. The CSRR elements have been used to suppress the mutual coupling in the proposed array. The existence of the CSRR configuration in antenna array controls the unnecessary surface current flow between the array elements, and thus the mutual coupling between array elements has been significantly reduced up to −55 dB. The effect of mutual coupling on the array radiation patterns has been studied in the presence and absence of CSRRs. The effectiveness of the CSRR has been studied by steering the main beam as well as the nulls in different angles. By implementing the CSRR elements in array antenna, the distorted array patterns have been recovered and are presented. The proposed antenna array with the CSRR has the advantage of easy and low-cost fabrication and it offers excellent coupling suppression without changing the antenna profile. The commercially available simulation tools such as MATLAB and Ansys HFSS have been used for array weights calculation and antenna design respectively. Finally, the fabricated prototype has been experimentally verified, and it shows that the analytical and computed results agree well with the measured results.

Sparse arrays have potential advantages over their regularly spaced counterparts, but they will generate undesired grating lobes. This paper investigates a sparse linear phased-array for grating lobe suppression and arbitrary transmit-receive beampattern synthesis. To achieve these aims, a modified twolevel nested-array is developed, which provides increased degrees-of-freedom than a standard uniform linear array with the same number of elements via the difference co-array processing algorithm in the receiver. A least squares and iterative algorithm is also devised for linear array arbitrary transmit-receive beampattern design with minimum number of antenna elements. Moreover, the nested-array design is exploited for minimum variance distortionless response adaptive beamforming and direction finding. The effectiveness of the proposed approach is verified through extensive numerical results.

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 $1 \times 4\,\,1$ -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 $4 \times 4\,\,2$ -D microstrip planar array. This planar array can achieve an impedance bandwidth of 19.15% and an enhanced gain of 18.30 dBi. [ABSTRACT FROM AUTHOR]

In this article, a densely integrated and unified paralleled amplifier and antenna architecture is proposed and demonstrated for next-generation millimeter-wave (mmW) and terahertz (THz) front-end modules. It makes use of topologically paralleled transistors cohabitated within a compact rectangular patch antenna (CRPA) as a unified cell. This design simultaneously amplifies and radiates power without resorting to any power divider, input and output matching networks, or power combiner whatsoever, therefore, greatly reducing front-end loss, size, and complexity. Then, the unified unit cell is self-consistently distributed to form a unified planar array with active elements between array elements as power feeders. In this demonstration, the input power is sequentially amplified, radiated through each array element, and spatially added up, resulting in low on-board circuit losses and efficient radiation. In this article, we investigate and present challenges and early results of implementing this unification concept of active circuitry and antenna at mmW frequencies. Using a standard 65-nm CMOS process, a set of chips were designed, fabricated, and tested under different amplifier biasing conditions at 146 GHz for experimental demonstration. The realized low-loss, matched, and compact unified prototypes have demonstrated an amplified radiation, with power enhancement of 3.4 dB through single element and 6 dB through $2 \times 2$ layout compared to their respective passive counterparts. Moreover, frequency tuning is observed varying drain bias and self-matching is improved with increasing gate bias. Therefore, the feasibility of a unique feature in the architectural implementation of low-loss, compact, and densely integrated and topologically cohabitated mmW and THz front-end modules is confirmed. [ABSTRACT FROM AUTHOR]

The design of phased arrays able to generate arbitrary-shaped beams through a sub-arrayed architecture is addressed here. The synthesis problem is cast in the excitation matching framework, so as to yield clustered phased arrays providing optimal trade-offs between the complexity of the array architecture (i.e., the minimum number of control points at the sub-array level) and the matching of a reference pattern. A synthesis tool based on the $k$ -means algorithm is proposed for jointly optimizing the sub-array configuration and the complex sub-array coefficients. Selected numerical results, including pencil beams with sidelobe notches and asymmetric lobes as well as shaped main lobes, are reported and discussed to highlight the peculiarities of the proposed approach also in comparison with some extensions to complex excitations of state-of-the-art sub-array design methods. [ABSTRACT FROM AUTHOR]

In this study, a 50-pixel linear array of 4H–SiC ultraviolet avalanche photodiodes operating in Geiger mode is reported for the first time. The 50 pixels within the linear array are all capable of detecting single photons but with a small number of them suffering from extra leakage current near avalanche breakdown. The enhanced leakage is likely correlated with structural defects existing within the epitaxial structure, which would lead to higher dark count rate (DCR) at the same single photon detection efficiency (SPDE) in Geiger mode. For a low-leakage avalanche photodiode device within the linear array, a room temperature SPDE of 15.4% at 280 nm is obtained with a corresponding DCR of 2.5 Hz/μm2.

Objective: The purpose of this paper is to present a more convenient and practical alternate way of increasing the lateral discrete array sampling while using a typical λ pitch linear array transducer at receive for photoacoustic tomography (PAT) application. Methods: We have employed a linear translation-based approach, in which the array transducer is translated by sub-pitch amount to create an augmented RF frame data having denser lateral spatial sampling. The denser λ/2 and λ/4 pitch data were reconstructed and compared against conventional λ pitch reconstructed PAT image using simulation and tissue mimicking phantom experiments in terms of improvements in resolution and contrast. Results: The results from experiments demonstrate a 34.48% improvement in lateral resolution (LR), measured in terms of full-width at half-maximum of the lateral profile of point spread function, and a maximum of 7-dB improvement in contrast is achieved while using a λ/2-pitch configuration when compared to the conventional λ-pitch configuration. Conclusion: It was demonstrated that λ/2- and λ/4-pitch configurations result in better LR and contrast than λ-pitch configuration. Significance: Based on the results obtained, the proposed method has the potential to serve as an easy-to-integrate and simple way of achieving better image quality without requiring to increase the system complexity with existing transducer array probe technology in regular clinical scanners. [ABSTRACT FROM AUTHOR]

Linear arrays along radiating (E-plane) and nonradiating (H-plane) edges are designed for broadside radiation pattern at 5.8 GHz using U-shaped series- and corner-feed configurations, respectively. U-shaped feedlines are used to reduce the interelement spacing and size of the array. A 25-element radiating edge linear array provides 19.9 dBi gain with sidelobe level (SLL) and cross polar (X-pol) level of less than −15.3 and −33.8 dB, respectively. Nonradiating edge linear array is designed up to 31 elements using the corner-feed configuration to achieve 18 dBi gain with SLL and X-pol level of less than −15.2 and −22.5 dB, respectively. Furthermore, a planar array is designed using the series and corner feeds in E- and H-planes. A $15 \times 15$ -element array is designed to achieve 24.4 dBi gain with SLL and X-pol level of less than −14.7 and −18.8 dB, respectively, in both the E- and H-planes. This array eliminates the need of complex-, multilayer-, and lossy-feed network and improves SLL and X-pol level. A planar array of $9 \times 9$ elements is fabricated, and the measured results are in agreement with the simulated results. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate $1 \times 8$ linear metal–semiconductor–metal arrays of UV-C photodetectors based on optical-float-zone grown bulk (100)-oriented $\beta $ -Ga2O3. The as-grown polished bulk samples exhibited an RMS roughness of 1.4 nm and the full-width at half-maxima of 0.19°. The average peak responsivity (257 nm), dark current, photo-to-dark current ratio, and UV-to-visible rejection ratio of the devices in the array were measured to be 4 AW $^{-1}$ , 0.23 nA, $\sim 10^{2}$ , and $\sim 10^{3}$ , respectively, at a bias of 40 V. The uniformity as well as the variability of the detector parameters across the devices in the array was investigated before and after wire bonding. [ABSTRACT FROM AUTHOR]

Phased arrays are widely used due to their low power and small area usage. However, phased arrays depend on the narrowband assumption and, therefore, are not suitable for high-bandwidth applications. Emerging communication standards require increasingly higher bandwidths for improved data rates, which results in a need for timed arrays. However, high power consumption and large area requirements are drawbacks of radio frequency (RF) timed arrays. To resolve these issues, we introduce the first true-time-delay digital beamforming IC, which eliminates beam squinting error by adopting a baseband true-time-delay technique. Furthermore, we present a constant output impedance current-steering digital-to-analog converter (DAC), which improves the spurious-free dynamic range (SFDR) of a bandpass delta–sigma modulator by 7 dB. Due to the new DAC architecture, the 16-element beamformer improves SFDR by 13.7 dB from the array. Measured error vector magnitudes (EVMs) are better than 37 dB for 5-MBd quadratic-amplitude modulation (QAM)-64, QAM-256, and QAM-512. The prototype beamformer achieves nearly ideal beam patterns for both conventional and adaptive beamforming (i.e., adaptive nulling and tapering). The difference between normalized measured beam patterns and normalized simulated beam patterns is less than 1 dB within the 3-dB beamwidth. The beamformer, including 16 bandpass analog-to-digital converters (ADCs) occupies 0.29 mm2 and consumes 453 mW in total power. [ABSTRACT FROM AUTHOR]

In this paper, we study the spectrum sensing problem when the sensing device is equipped with an uncalibrated multiantenna array. We consider an unknown Toeplitz structure for the covariance matrix of the signal of interest and unknown uncorrelated noise variances. We propose two new invariant constant false-alarm rate detectors with less computational cost than the generalized likelihood ratio test: 1) the Rao test and 2) a separating function estimation test (SFET). We calculate approximate expressions for the false-alarm and detection probabilities of the proposed Rao test-based detector. In addition, we derive the exact false-alarm probability of the proposed SFET for the case of two antennas. Moreover, we obtain an accurate approximation for the false-alarm probability of the proposed SFET for the general case using the method of moments. The accuracy of these expressions is validated by Monte-Carlo experiments. The simulation results show that the proposed detectors outperform state-of-the-art detectors. [ABSTRACT FROM AUTHOR]

A novel low-cost, high-gain millimeter-wave antenna has been presented. The antenna is a 6 × 5 proximity-coupled planar array suitable for 5G cellular applications. Good agreement between simulated and measured results achieved shows that the proposed antenna structure is efficient in achieving broadband characteristics and low sidelobe levels with a compact size. The antenna has a gain of 21 dBi over a bandwidth of 27.5–28.5 GHz. It also exhibits an impedance bandwidth of 9.8% from 26.04 to 28.78 GHz. [ABSTRACT FROM AUTHOR]

In elastography, conventional linear array (CLA)-based RF data acquisition provides more accurate displacement measurements in the direction of beam propagation (axial direction) when compared to the perpendicular direction (lateral). Obtaining good quality lateral displacement estimates in ultrasound (US) elastography will lead to several benefits such as obtaining accurate inverse solutions, improving shear strain elastogram quality, getting good quality poroelastograms, and obtaining reliable rotation elastograms. For accomplishing high-precision lateral displacement estimation (LDE), one of the popular methods is by interpolating additional A-lines in between neighboring RF A-lines. We describe a method wherein true RF A-lines (not interpolated) are acquired and augmented at subpitch locations using CLA transducer, instead of interpolating the data, and using this new frame data for further image formation and/or processing to yield better lateral resolution and LDE. We demonstrate the proposed method by translating the US beam of CLA transducer in subpitch range by the following two approaches: 1) actuator-assisted beam translation and 2) electronic translation of subaperture of a CLA by activating odd and even number of consecutive elements sequentially, referred to as electronic beam translation. The performances of the different methods were studied through simulations and experiments on phantoms. The results demonstrate that these methods yield better quality LDE compared to those obtained from interpolation of RF A-lines. These methods may provide affordable ways to obtain subpitch precision LDE using CLA. [ABSTRACT FROM PUBLISHER]

Multielement transducers enabling novel cost-effective fabrication of imaging arrays for medical applications have been presented earlier. Due to the favorable low lateral coupling of the screen-printed PZT, the elements can be defined by the top electrode pattern only, leading to a kerfless design with low crosstalk between the elements. The thick-film-based linear arrays have proved to be compatible with a commercial ultrasonic scanner and to support linear array beamforming as well as phased array beamforming. The main objective of the presented work is to investigate the performance of the devices at the transducer level by extensive measurements of the test structures. The arrays have been characterized by several different measurement techniques. First, electrical impedance measurements on several elements in air and liquid have been conducted in order to support material parameter identification using the Krimholtz–Leedom–Matthaei model. It has been found that electromechanical coupling is at the level of 35%. The arrays have also been characterized by a pulse-echo system. The measured sensitivity is around −60 dB, and the fractional bandwidth is close to 60%, while the center frequency is about 12 MHz over the whole array. Finally, laser interferometry measurements have been conducted indicating very good displacement level as well as pressure. The in-depth characterization of the array structure has given insight into the performance parameters for the array based on PZT thick film, and the obtained information will be used to optimize the key parameters for the next generation of cost-effective arrays based on piezoelectric thick film. [ABSTRACT FROM AUTHOR]

In this letter, we propose a new efficient method to estimate the direction-of-arrival (DOA) and range of near-field sources in a decoupled way. First, a non-Hermitian cumulant matrix is constructed, whose eigenvectors associated with zero eigenvalues are used to directly estimate the DOA by using the MUSIC algorithm. Then, the ranges are estimated with the estimated DOA by orthogonalizing the remained eigenvectors. Compared with other modified 2-D MUSIC, the proposed algorithm can greatly reduce the computational complexity by avoiding a 2-D search with only one matrix and one eigenvalue decomposition. Simulation results show the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This letter introduces a novel, fast, efficient, and global optimization algorithm called hybrid invasive weed optimization and wind-driven optimization (IWO/WDO). The proposed algorithm is implemented to synthesize the uniformly excited (an = 1, Øn = 0) linear sparse array pattern having a minimum sidelobe level (SLL), and null control with constraint on beamwidth to minimize the interference effect by optimizing the element position-only. Three examples of (N = 10, 28, and 32)-element linear array synthesis are considered to illustrate the efficacy of the proposed algorithm. The results are compared to those obtained by IWO, WDO, PSO, CLPSO, DE, and BBO algorithms. Simulation studies demonstrate that this algorithm achieves minimum SLL of -23.5, -13.22, and -19.7 dB as compared to -17.35, -10.5, and -15.70 dB obtained by the IWO algorithm for 10-, 28-, and 32-elements array, respectively. Also, it yields a null depth level (NDL) larger than -84.5 dB in all cases. The learning characteristics show a faster convergence at around 100 iterations. The simulation results demonstrate the improved performance of hybrid IWO/WDO algorithm compared to other six algorithms in terms of null control, minimum SLL, beamwidth control, and the rate of convergence. [ABSTRACT FROM PUBLISHER]