Conventional Phased Array Antenna Research Articles

Design Procedure of a Frequency Reconfigurable Metasurface Antenna at mmWave Band

The use of the millimeter wave (mmWave) spectrum and further exploration of sub-mmWave has led to a new era in wireless communication, as the need for higher data rates grows. High frequencies, on the other hand, incur a higher path loss, requiring an increase in antenna gain requirements. Metasurfaces, which emerge as a promising technology for mitigating path loss effects by utilizing two dimensional (2D) arrays of engineered meta-atoms resembling metamaterials that control the surface’s electromagnetic response have been introduced. Currently, metasurfaces are primarily considered as passive reflecting devices in wireless communications, assisting conventional transceivers in shaping propagation environments. This paper presents an alternative application of metasurfaces for wireless communications as active reconfigurable antennas for next generation transceivers. A framework that demonstrates the design process of a metasurface antenna structure was introduced and further used to design a 4 × 4 array and its reconfigurable counterpart. In contrast to conventional phased array antennas, a reconfigurable metasurface (RMS) antenna does not require phase-shifters and amplifiers, which leads to reduced cost. Instead, each individual element achieves reconfigurability by shifting the resonating frequency using semiconductor devices such as PIN diodes. The proposed metasurface antenna is designed to operate at a frequency of 28 GHz and 40 GHz. In addition, an increase in gain and directivity was observed when diodes were added to the metasurface antenna array. However, due to PIN diodes being connected to metallic strips in the metasurface antenna array, loss can occur due to power dissipation, which results in a decrease in radiation efficiency.

Adaptive Gradient Search Algorithm for Displaced Subarrays With Large Element Spacing

In this letter, an adaptive gradient search algorithm for displaced subarray optimization is presented. The displaced subarray technique, which is able to suppress the high grating lobes caused by large interelement spacing (i.e., over one-half wavelength), has attracted much attention. In this case, it could reduce the number of active elements as well as the cost of conventional phased array antennas. However, the optimal solution of each displaced subarray location is hard to achieve. The proposed algorithm is a practical method to solve such a nonconvex problem. By gradually reducing the iteration step size, when the search times of each step are enough, the solution is able to converge to a satisfying solution. The effectiveness and the stable performance of our proposed method are verified by various numerical examples.

Digitally Reconfigurable Transmitarray With Beam-Steering and Polarization Switching Capabilities

In this paper, a novel digitally reconfigurable unit-cell and $4\times 4$ transmitarray operating at X-band is proposed that allows the implementation of beamforming and polarization conversion operations in a programmable way. The lower layer of transmitarray responsible for beam steering consists of two PIN diodes and a circular type patch which has two states of operations with 0 and $\pi $ phase responses which we name “State1” and “State2”. “State1” and “State2” can be represented by a digital notation as “1” and “0” elements. Similarly, the upper layer of the transmitarray responsible for polarization conversion operation consists of two states of operation which we name as “State3” and “State4”, respectively. “State3” and “State4” also can be represented by digital notations as “1” or “0” elements. By coding “0” and “1” elements for the lower side of the transmitarray in a 1-bit sequence, we can steer the beam in our desired direction. Similarly, by coding “0” and “1” elements in a 1-bit sequence element for the upper layer, we can get X-polarized and Y-polarized beams. Combining the upper layer 1-bit sequence and lower layer 1-bit sequence, we can get both polarization conversion and beam steering simultaneously. A $4\times 4$ array with our proposed unit cell was designed and fabricated. A good agreement between simulated and measured results was observed. The proposed design is a promising concept because it can be fabricated using the conventional fabrication process, it is cost-effective compared to conventional phased array antenna for satellite and radar applications. A $4\times 4$ array was taken just to check the transmission and reflection coefficients of the proposed unit cells. A very small transmitarray was manufactured and experimentally characterized just as a proof of concept, to verify that the unit cells work properly.

Construction of a Cost-Effective Phased Array Through High-Efficiency Transmissive Programable Metasurface

Programmable metasurfaces have shown great potential in the areas of low-complexity phase array systems in comparison with the conventional phased array antennas. In this document, a 1-bit transmissive programable metasurface with high efficiency is proposed for the cost-effective beam-steering phased array. The designed transmissive metasurface is made up of reconfigurable cells with perfect 1-bit phase tuning and less transmission losses. Through dynamically programming the 1-bit code distributions of the metasurface, real-time scanning pencil beams in desired directions can be created.

Multiaperture Antenna Architecture Design for Azimuth Uniform Sampling in High-Resolution Wide-Swath SAR

Azimuth multichannel synthetic aperture radar (SAR) is an essential remote sensing device to obtain images with high resolution and wide swath (HRWS). However, using a conventional multichannel phased array antenna, azimuth uniform sampling cannot be ensured, if the operated pulse repetition frequency of the system deviates from the optimum value. A novel multichannel antenna architecture design approach in HRWS SAR is proposed for uniform sampling. Phase center positions of both transmitting aperture and receiving subapertures can be adjusted flexibly by invalidating the elements of the antenna. First, a limited number of elements of receiving subapertures can be closed to adjust receive phase center spacing. The transmit phase center could be further adjusted, if the azimuth nonuniform sampling still cannot be fully compensated for. With this multiaperture antenna architecture, azimuth uniform sampling could be ensured and system performances are obviously improved. Advantages of the proposed azimuth multiaperture antenna architecture adjust method are verified by a simulation experiment.

Space-Time Modulated Wideband Array Antenna

This letter generalizes the use of linearly frequency modulated (LFM) continuous-wave waveform and time delays for frequency diverse array (FDA) functionality implementation to a general space-time modulated (STM) array antenna, which imposes no specific requirements on the transmitted waveforms. It uses diverse time delays instead of diverse frequency increments to implement the FDA. The transmit beampattern characteristics of the STM array under a general pulse waveform including monochromatic, LFM, and LFM pulse with Gaussian envelope cases are analyzed. Moreover, an STM wideband eight-element antenna operating in 4–6 GHz is designed and implemented. It is shown that STM generates autoscanning beampattern characteristics, which are rather different from that of a conventional phased-array antenna and of great importance in some specific radar and communication applications.

Development of frequency diverse array radar technology: a review

Electronic beam steering with greater efficiency is a vibrant feature of a phased array antenna, but for all the range cells, it is fixed at a specific angle. To mitigate this problem, frequency diverse array (FDA) antenna was proposed. This study presents a review on the development of FDA technology in radar and navigation applications. FDA is different from a conventional phased array antenna radar in a sense that it uses a small frequency offset across the array, which helps to generate a range, angle and time-dependent beam pattern. This pattern assures the energy transmission towards the desired angle and range cell. In addition, this study also focuses the research on getting range-angle uncoupled beam patterns along with diverse hybrid cognitive FDA design, available in the literature, for improved radar performance.

Ninja array antenna: novel approach for low backscattering phased array antenna

This study presents a novel concept of a low backscattering phased array antenna, a Ninja array antenna. One of the advantages of the Ninja array antenna over the conventional phased array antenna is low backscattering performance over its operating frequency band, which is not available using a conventional phased array antenna with a band-pass radome. The Ninja array antenna is designed in the same manner as the design of reflectarrays, so that the main lobe of its scattering field is directed to a specific direction except for backscattering one. As a result, its backscattering is reduced in comparison with that of the conventional phased array antenna. Although the Ninja array antenna is composed of non-identical array elements such as the reflectarray, it works as a phased array antenna because desired amplitude and phase of excitation can be obtained numerically via an array element pattern. Numerical simulation is performed and the scattering/radiation performance of the Ninja array antenna is demonstrated.

Design of Compact Beam-Steering Antennas Using a Metasurface Formed by Uniform Square Rings

In this paper, we propose two designs of slot-fed metasurface antenna for beam steering applications. Both designs have the same two-layer stacked configuration consisting of either a single-slot or a double-slot radiator and a metasurface superstrate. In contrast to existing phase-gradient metasurfaces with varying unit elements for beam steering, our proposed metasurface is formed by uniform square rings. At operating frequencies, each square ring acts as an individual resonating element. By exciting the elements in sequence with different phase delays through the slot radiator, the generated antenna beam can be steered. In the first design, the position of the single-slot radiator is shifted to achieve the beam steering functionality; while for the second antenna, to avoid mechanically moving the feeding slot, a double-slot-feeding structure is proposed with two slots excited with varying phase differences. Simulation and experimental results show that beam steering angles of −35° to 35° can be achieved for the single-slot-feeding design and beam steering angles of −30° to 30° are realizable for the double-slot-feeding configuration. Comparing with conventional phased array antennas, our proposed designs have compact size with moderate to high antenna gain.

X-band SAR imaging with a liquid-crystal-based dynamic metasurface antenna

Synthetic aperture radar (SAR) synthesizes a large effective aperture via coherent processing of multiple measurements taken from a moving platform. We present an approach for SAR imaging using an X-band (10–13.7 GHz) dynamic metasurface antenna (MSA). This newly developed antenna has over 6000 liquid-crystal-switched radiating elements that cover a circular area with an approximate diameter of 0.45 m. The MSA’s main beam can be steered electronically to spherical angles of up to ±70°. To the best of our knowledge, we present the first-reported laboratory-scale imaging experiments with a liquid-crystal-switched MSA. We leverage the beam-steering capabilities of the MSA in a spotlight SAR mode to achieve a measured cross-range resolution of 1.6 cm, a 62% improvement over the 4.2 cm cross-range resolution achieved with the same aperture without the metasurface-enabled beam steering. The dynamic MSA offers the superior image resolution of a beam-steering device without the hardware burden of conventional phased array antennas.

A phased array antenna with a broadly steerable beam based on a low-loss metasurface lens

A new concept for a gradient phase discontinuity metasurface lens integrated with a phased array antenna possessing a broadly steerable beam is presented in this paper. The metasurface lens is composed of a metallic H-shaped pattern and the metallic square split ring can achieve complete 360° transmission phase coverage at 30° phase intervals. The metasurface can refract an incident plane wave to an angle at will by varying the lattice constant. We demonstrate that the beam steering range of the phased array antenna is between 12° and 85° when the metasurface lens with a refracting electromagnetic wave is employed at 45°. Interestingly, the proposed array antenna has a much higher gain than a conventional phased array antenna at low elevation angles. It is expected that the proposed array antenna will have potential applications in wireless and satellite communications. Furthermore, the proposed array antenna is fabricated easily and is also low in cost due to its microstrip technology.

Truncation Diffraction Phenomena of Floquet Waves Radiated From Semi-Infinite Phased Array Antenna in a General Focus Problem

This paper presents uniform formulations of radiation mechanisms, analogous to the ray decompositions of diffraction theory, from a semi-infinite and periodic array of antennas. The antenna array is excited to radiate the electromagnetic (EM) fields focused at a relatively arbitrarily selected location. The ray decomposition results from a closed-form formulation by asymptotically evaluating the radiation integral of Floquet modes that are obtained by applying the Poisson sum formula to the summation of elemental radiations. The analysis is relatively general and will reduce to the case of a conventional phased array antenna that is excited to radiate directive beams focused in the far zone, and exhibits consistent phenomena. Theoretical investigations as well as numerical examinations are presented to demonstrate the radiation mechanisms.

Compact phased array antenna system based on dual‐band operations

ABSTRACTThis article presents a novel approach to shrink the size of the conventional phased array antenna fed by Butler matrix. The proposed size reduction of the phased array antenna is obtained by designing the whole system to operate at dual frequency bands. Due to the dual‐band operation, an N‐element phased array antenna can be used to generate 2N radiation beams, leading to a great size reduction. To verify this design concept, a dual‐band feed network is built based on a dual‐band 4 × 4 Butler matrix. By integrating this dual‐band feed network with a four‐element antenna array, eight distinct radiation beams can be realized. An experimental prototype operating at 5 and 8 GHz is designed and fabricated. It can achieve the same function as the conventional phased array antenna system using single‐band 8 × 8 Butler matrix, realizing a great size reduction. The simulated and measured results show good agreement with the design theory. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1391–1396, 2014

Non Unuiform Phased array Beamforming with Covariance Based Method

Many papers have investigated phased array radars beam-forming so far. In these papers the power at a specific point of interest is written by a combination of transmitted power by means of each antenna. In this paper we will introduce a new approach which will use of cross correlation matric like MIMO radars to define beam-pattern of array and then by introducing an optimization problem to steering the available power at desire directions, it is shown that with an approach to optimum choosing of antenna placement, it is possible to concentrate the transmitter power on desire direction better than conventional phased array antennas with half wave length spacing. It should be say that some papers have investigated non uniform arrays but those papers usually use of multiple of half wave length in their elements spacing and in addition their approach to choosing these spaces is different and pretty more complicated from presented approach. Simulation is performed to analyze the presented algorithm and compare it's performance with conventional phased arrays with half wave length spacing for linear and planar array. MATLAB software is being employed for simulations.

Low-DC Voltage-Controlled Steering-Antenna Radome Utilizing Tunable Active Metamaterial

In this paper, we experimentally realized a steering antenna using a type of active metamaterial with tunable refractive index. The metamaterial is realized by periodically printed subwavelength metallic resonant patterns with embedded microwave varactors. The effective refractive index can be controlled by low direct-current (dc) bias voltage applied to the varactors. In-phase electromagnetic waves transmitting in different zones of such metamaterial slab experience different phase delays, and, consequently, the output direction of the transmitted wave can be steered with progressive phase shift along the interface. This antenna has a simple structure, is very easy to configure the beam direction, and has a low cost. Compared with conventional phased-array antennas, the radome approach has more flexibility to operate with different feeding antennas for various applications.

Miniaturized Reflectarray Unit Cell Using Fractal-Shaped Patch-Slot Configuration

This letter introduces a new class of miniaturized reflectarray unit cells with increased phase swing employing Minkowski fractal-shaped patch-slot elements. Square, 1st Minkowski, and 2nd Minkowski fractal patches are designed as a reflectarray unit cell. A slot with variable lengths of 0 <; Ls <; 6 mm is used in the ground plane to perform the phase variation function. The resonant frequency corresponding to the maximum phase swing is reduced from 10.6 GHz for the square patch down to 8.8 and 8.3 GHz for the first- and second-order Minkowski fractal patches, respectively, which is equivalent to 17% and 22% size reduction. Unit cells with different patch type and slot length are fabricated, and close agreement is observed between the measured and simulated results. As it has been proven for conventional phased array antennas, this size reduction can lead to a decrease in mutual coupling in reflectarray antennas. Alternatively, it allows for smaller distance between reflectarray antenna elements, which renders a wider beam-scanning range.

Range-Angle-Dependent Beamforming by Frequency Diverse Array Antenna

This paper proposes a range-angle-dependent beamforming for frequency diverse array (FDA) antenna systems. Unlike conventional phased-array antenna, the FDA antenna employs a small amount of frequency increment compared to the carrier frequency across the array elements. The use of frequency increment generates an antenna pattern that is a function of range, time and angle. The range-angle-dependent beamforming allows the FDA antenna to transmit energy over a desired range or angle. This provides a potential to suppress range-dependent clutter and interference which is not accessible for conventional phased-array systems. In this paper, a FDA radar signal model is formed and the range-angle-dependent beamforming performance is examined by analyzing the transmit/receive beampatterns and the output signal-to-interference-plus-noise ratio (SINR) performance. Extensive simulation examples and results are provided.

Aperture-Sparsity Analysis of Ultrawideband Two-Dimensional Focused Array

We investigate the effects of aperture sparsity on the focusing performance and the angular-resolution capability of a two-dimensional focused array antenna excited by ultrawideband (UWB) impulse waveforms. The UWB-focusing array is characterized by a planar square aperture and a design parameter referred to as array spatial bandwidth. Spatial bandwidth is a function of the number of array elements, inter-element spacing, and frequency bandwidth. Performance analysis is carried out by generating computer plots of three-dimensional and two-dimensional antenna patterns for different values of array spatial bandwidth that hold for large aperture sparsity and large aperture density. The antenna patterns are peak-amplitude pattern, peak-power pattern, and energy pattern, whose narrow beamwidth and low sidelobe level are robust against aperture sparsity that may be caused by removed or failed elements. The half-power beamwidth (HPBW) of the antenna patterns, the focal distance, and the far-field distance of the UWB-focused array are expressed in terms of array spatial bandwidth. Computer simulation results show that UWB-focused-array beamforming based on impulse waveforms achieves efficient focusing of the radiation energy in the radiation-near-field region and beyond, and yields improvement in focusing performance and angular resolution for increased values of array spatial bandwidth. Such practical advantages are achieved without encountering grating lobes, large sidelobe level, or distortion of the radiation beam pattern that often limit the performance of the conventional narrowband phased array antennas.

Ranging in a Single-Input Multiple-Output (SIMO) System

In this letter, optimal ranging in a single-input multiple-output (SIMO) system is studied. The theoretical limits on the accuracy of time-of-arrival (TOA) (equivalently, range) estimation are calculated in terms of the Cramer-Rao lower bound (CRLB). Unlike the conventional phased array antenna structure, a more generic fading model is employed, which allows for the analysis of spatial diversity gains from the viewpoint of a ranging system. In addition to the optimal solution, a two-step suboptimal range estimator is proposed, and its performance is compared with the CRLBs.

A miniaturized phased array aperture antenna based on bulk ferroelectric material

AbstractIn this article, we proposed a novel miniaturized phased array aperture antenna using a voltage‐controllable ferroelectric material with high dielectric constant. This antenna system combines the phase shifters and the radiating elements in a single structure, that could significantly simplify the complexity and the cost of the conventional phased array antenna systems. Simulation results on such structure are given, which agrees well with the theoretical analysis. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 37–40, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22060