Electronic Beam Steering Research Articles

CUSTR- A VHF phased array radar for observation of atmospheric dynamics and ionospheric plasma irregularities

A VHF phased array radar for atmospheric dynamics observation is installed at the University of Calcutta, Kolkata. The Calcutta University Stratosphere-Troposphere Radar (CUSTR) operates at 53 MHz with 475 three sub-element Yagi-Uda antenna array. The CUSTR system is a high-power fully active phased array system with a dedicated 2 kW solid-state Transmit-Receiver Module (TRM) attached to each antenna, providing a total peak power of 950 kW with 47.5 kW average power at 5% maximum duty ratio. The system provides electronic beam steering capability to steer the beam 360° in azimuth direction with a maximum off-zenith angle of 40°. The array is configured with 25 sub-arrays and operates either in a combined mode in Doppler Beam Swinging or in Spaced Antenna mode using a multi-channel digital receiver system. The TRM has been designed to provide a very short pulse of 0.5 µs and a long pulse of 128 µs. The system description along with the initial scientific observations such as atmospheric boundary layer, troposphere-lower stratosphere wind measurements along with preliminary wind validation, mesosphere echoes and ionosphere irregularities are presented.

Malfunctioning conformal phased array: Radiation pattern recovery with particle swarm optimisation

AbstractThe electronic beam steering in conformal phased arrays is formed by exciting the multiple antennas with appropriate phase shifts. However, the malfunctioning of phase shifters connected to the central antenna elements in the conformal array distorts the radiation pattern of the array system severely as compared to edge elements resulting in the reduction of the array gain and increase in the side lobe levels. Here, the authors propose a non‐dominated sorting multi‐objective particle swarm optimisation (NS‐MOPSO) technique capable of recalculating the independent phases of working antenna elements in the array in such a manner as to correct the overall radiation pattern. To illustrate the radiation pattern's recovery capabilities of the optimisation technique in case of malfunctioning of any random phase shifter(s), a 1 x 7 microstrip patch antenna array operating at 2.45 GHz on a wedge‐shaped conformal structure was designed in CST simulator. To test, the radiation pattern's recovery capabilities of the NS‐MOPSO approach, phase shifters connected to the antenna elements in the array were made to malfunction. Then the optimisation algorithm recalculates the phases for individual antenna elements to achieve the desired corrected radiation pattern. The simulated and measured radiation pattern recovery results are in good agreement with each other.

Improving estimation performance of compressive sensing‐based multiple‐input multiple‐output radar using electronic beamsteering

AbstractTwo‐dimensional direction‐of‐arrival (DoA) estimation in azimuth and elevation via radar systems equipped with uniform rectangular arrays (URAs) will play an important role in various application areas—most distinctively in future urban air mobility settings with unmanned aerial vehicles. A key factor is the fast and reliable provision of target detections in terms of range and DoA for safe autonomous operation of the vehicle using on‐board antenna arrays with compact installation size. The authors present a technique for improving the performance of DoA estimation using compressive sensing in conjunction with multiple‐input multiple‐output arrays with electronically steered beams in the transmit direction. The simulation study investigates the impact of different design considerations on radar signal processing performance. An optimisation of a radar system using electronic beamsteering in the transmit domain is presented numerically. Based on the architecture of the URAs used, performance and detection accuracy can be improved.

Dynamics of high-power coupled nonlinear oscillator arrays for electronic beam steering technique: case of the triode based van der Pol oscillator

This paper presents the dynamics of coupled nonlinear oscillator arrays (CNOAs) as phase shifter for electronic beam steering technique. The proposed phase shifter uses oscillators of van der Pol type with a fifth-order nonlinear resistance and is built on the two architectures based injection-locked oscillator array (ILOAs) and coupled oscillator arrays (COAs). The dynamics equations of the phase shifter are proposed in the frequency and time domain. With the help of mathematical tools such as bifurcation diagrams, maximum Lyapunov exponent and Hilbert transform, important cartography of different oscillating states is deduced over large range of system parameters. Different behavior of the CNOAs including chaos, 2D-torus, multistability, locked and unlocked states are depicted. The phase shift between output voltages of each pair of coupled oscillators is presented for both architectures. A detailed analysis of locked states shows that the required phase shift is synthesized by slightly varying the frequency of the injected signal, or simply by detuning the free-running frequencies of the edge oscillators in equal but opposite directions. The proposed circuit of the phased shifter is built using the original van der Pol oscillator based on a vacuum triode. The maximal phase shift reaches 63° and 75° respectively for ILOAs and COAs. With the presence of triode in the circuit, the output voltage of each oscillating element in the array reaches 100V around 60KHz and is boosted by increasing the value of the triode bias potential to more than 420V. This, therefore, increases the total power dissipation of a single oscillator in the array to more than 47dB ( 50.12W ). This circuit is a candidate for high-power electronics beam steering at ultrasonic frequency.

Design and Analysis of Microstrip Patch Antenna Array and Electronic Beam Steering Linear Phased Antenna Array with High Directivity for Space Applications.

This study proposes an E-shaped microstrip patch antenna array (MSPAA). The substrate is RT/Duroid5880. Its 2.2 dielectric constant gives it a larger bandwidth than substrate materials with higher dielectric constants. The periphery dimension of a single E patch is 50 × 41 mm2. The areas of 2 × 2 and 3 × 3 MSPAAs are 120 × 96 and 180 × 144 mm2, respectively. Array members are 10 and 7 mm apart horizontally and vertically, respectively. MTM technology builds the projected MSPAA. This work looks at the effects of gain, reflection coefficient (return loss), directivity, bandwidth, and VSWR on proposed 2 × 2 and 3 × 3 MSPAAs with different patch lengths of 30, 40, and 60 mm, patch widths of 40, 50, and 60 mm, and substrate thicknesses of 0.8 and 1.6 mm. Also, this study compares the performance of existing E-shaped MSPAAs with proposed 2 × 2 and 3 × 3 MSPAAs. The suggested MSPAA performs better than the existing E-shaped MSPAA. The series network analyzer measures the prototype MSPAA's experimental outcomes. The polynomial is recommended for estimating the antenna array area with odd and even rows and columns. CST Studio Suite software analyzes and designs antenna arrays, and simulation findings are compared with hardware results. The main benefit of the proposed 2 × 2 MSPAA is that it reduces sidelobes. It has a gain of 8.9 dBi, a directivity of 8.95 dBi, a VSWR of 1.02, a return loss of -32.91 dB, and a bandwidth of 0.1 GHz at both 1.6 and 0.8 mm substrate material thicknesses. Across its operating range of 3.8-4.2 GHz, the recommended array antenna has a radiation gain of 7.01-7.81 dB and an efficiency of 68.51-71.11%. At 4 GHz, this study looks at how electronic steering affects the phase angle of the excitation signal, the number of elements, and the distance between elements in the beam steering linear phased antenna array (BSLPAA) using MATLAB.

On new two-dimensional UHF radar observations of equatorial spread F at the Jicamarca Radio Observatory

We describe a mode for two-dimensional UHF (445 MHz) radar observations of F-region irregularities using the 14-panel version of the advanced modular incoherent scatter radar (AMISR-14). We also present and discuss examples of observations made by this mode. AMISR-14 is installed at the Jicamarca Radio Observatory (JRO, 11.95°S, 76.87°W, ~ 0.5° dip latitude) in Peru and, therefore, allows studies of ionospheric irregularities at the magnetic equator. The new mode takes advantage of the electronic beam-steering capability of the system to scan the equatorial F-region in the east–west direction. Therefore, it produces two-dimensional views of the spatial distribution of sub-meter field-aligned density irregularities in the magnetic equatorial plane. The scans have a temporal resolution of 20 s and allow observations over a zonal distance of approximately 400 km at main F-region heights. While the system has a lower angular and range resolution than interferometric in-beam VHF radar imaging observations available at Jicamarca, it allows a wider field-of-view than that allowed with the VHF system. Here, we describe the mode, and present and discuss examples of observations made with the system. We also discuss implications of these observations for studies of ESF at the JRO.Graphical abstract

Multi-pattern synthesis in fourth-dimensional antenna arrays using BGM-based quasi-Newton memetic optimization method

Abstract The advancement in wireless communication is fueling the growth of innovative antenna array designs toward cost-effective and performance-oriented solutions. This paper proposed unconventional methods to design antenna arrays for multi-pattern synthesis without using attenuators or phase shifters. A low-cost alternative is proposed with “Time-modulation”-based antenna array capable of electronic scanning and beam steering. Here, “Time” is utilized as a fourth-dimensional (4D) array parameter, and that is why “Time-modulated” arrays are also called as 4D antenna arrays. The idea is to control the high-speed switch attached with each antenna periodically to produce desirable current and phase tapering. This article expanded the “Time-modulation” concept to synthesize multiple radiation patterns like monopulse patterns, scanned beam patterns, shaped beam patterns, and cosecant-squared beam patterns for multifunctional radar systems. Suitable time schemes are developed to generate the narrowband sum–difference patterns useful for monopulse radars. Simultaneous scanned beam patterns are also proposed for narrowband communication. Furthermore, to address the wideband applications, shaped flat-top beam patterns and cosecant-squared beam patterns are also proposed. In this regard, 20- and 16-element “Time-modulated” linear array antennas are developed, and the parameters of the arrays are controlled by suitably designed objective functions with quasi-Newton method (QNM)-based memetic optimization method. For this purpose, first a well-known genetic algorithm is adopted to search the potential trust regions in the exploration stage and QNM is used for fine-tuning. Furthermore, the Broyden’s good method-based direction-updating equation is used with QNM to improve the performance.

Target-Conformal Optimization-Based Actuator Placement for Ultrasound-Mediated Hyperthermia in Cancer Treatments

In hyperthermia for cancer treatments, tumors are heated to improve the outcome of radio-and chemotherapies. Using extracorporeal high-intensity focused ultrasound (HIFU) transducers, the heating can be applied noninvasively, accurately, and with high acoustic power. The heating location can be changed by electronic beam steering, within the transducer’s small local heating range, and by mechanically repositioning the transducer, which effectively shifts the local range to enable the treatment of larger tumors. An important problem is the selection of the sonication points, i.e., the discrete locations reachable by electronic beam steering, and the admissible mechanical transducer positions, which must be performed prior to treatment, and can be seen as an actuator selection problem. Clearly, the selected sonication points and transducer positions have a major impact on the achievable tumor temperatures, and their number is directly related to the controller’s complexity and, thereby, real-time feasibility. To address this challenging problem, this brief presents a target-conformal optimization-based actuator placement procedure, designed to assist the clinician in enabling maximum treatment quality using only a limited number of sonication points and transducer positions. The method is computationally tractable, and takes into account the specific tumor geometry and tissue properties.

The Design of a Sliding Rectangular Waveguide Array Antenna for Beam Steering

In this paper, we designed a sliding waveguide array antenna that can be beam-steered via mechanical manipulation. This reduces the vulnerability of electronic beam-steering radars mounted on ships or aircraft to electromagnetic pulse (EMP) attacks. The design frequency was 9.375 GHz. First, the proposed antenna was designed to adjust the phase difference between the arrayed waveguide antennas by changing the length of the rectangular waveguide using a slide. Subsequently, a ridge structure with optimized curvature was attached to the aperture of the rectangular waveguide to obtain stable reflection coefficient characteristics. Finally, eight rectangular waveguide antennas and two dummy antennas were E-plane arrayed at intervals of 0.8λ (25.6 mm) to obtain a beam width of nearly 8°. A beam width of 8° was then obtained by adjusting the length of each waveguide. It was possible to orient the beam of the antenna in intervals of 8° using the phase difference of each antenna. The proposed mechanical beam steering technique can replace electronic beam steering for radar antennas, rendering the structures less vulnerable to EMP attacks.

Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material

In this study, a dual-tuned mode of liquid crystal (LC) material was proposed and adopted on reconfigurable metamaterial antennas to expand the fixed-frequency beam-steering range. The novel dual-tuned mode of the LC is composed of double LC layers combined with composite right/left-handed (CRLH) transmission line theory. Through a multi-separated metal layer, the double LC layers can be loaded with controllable bias voltage independently. Therefore, the LC material exhibits four extreme states, among which the permittivity of LC can be varied linearly. On the strength of the dual-tuned mode of LC, a CRLH unit cell is elaborately designed on three-layer substrates with balanced dispersion values under arbitrary LC state. Then five CRLH unit cells are cascaded to form an electronically controlled beam-steering CRLH metamaterial antenna on a downlink Ku satellite communication band with dual-tuned characteristics. The simulated results demonstrate that the metamaterial antenna features' continuous electronic beam-steering capacity from broadside to -35° at 14.4 GHz. Furthermore, the beam-steering properties are implemented in a broad frequency band from 13.8 GHz to 17 GHz, with good impedance matching. The proposed dual-tuned mode can make the regulation of LC material more flexible and enlarge the beam-steering range simultaneously.

Hybrid Mechanical and Electronic Beam Steering for Maximizing OAM Channel Capacity

Radio frequency-orbital angular momentum (RF-OAM) is a novel approach of multiplexing a set of orthogonal modes on the same frequency channel to achieve high spectrum efficiencies. Since OAM requires precise alignment of the transmit and the receive antennas, the electronic beam steering approach has been proposed for the uniform circular array (UCA)-based OAM communication system to circumvent large performance degradation induced by small antenna misalignment in practical environment. However, in the case of large-angle misalignment, the OAM channel capacity cannot be effectively compensated only by the electronic beam steering. To solve this problem, we propose a hybrid mechanical and electronic beam steering scheme, in which mechanical rotating devices controlled by pulse width modulation (PWM) signals as the execution unit are utilized to eliminate the large misalignment angle, while electronic beam steering is in charge of the remaining small misalignment angle caused by perturbations. Furthermore, due to the interferometry, the receive signal-to-noise ratios (SNRs) are not uniform at the elements of the receive UCA. Therefore, a rotatable UCA structure is proposed for the OAM receiver to maximize the channel capacity, in which the simulated annealing algorithm is adopted to obtain the optimal rotation angle at first, then the servo system performs mechanical rotation, at last the electronic beam steering is adjusted accordingly. Both mathematical analysis and simulation results validate that the proposed hybrid mechanical and electronic beam steering scheme can effectively eliminate the effect of diverse misalignment errors of any practical OAM channel and maximize the OAM channel capacity.

Quantitative Assessment of Boiling Histotripsy Progression Based on Color Doppler Measurements.

Boiling histotripsy (BH) is a mechanical tissue liquefaction method that uses sequences of millisecond-long high intensity focused ultrasound (HIFU) pulses with shock fronts. The BH treatment generates bubbles that move within the sonicated volume due to acoustic radiation force. Since the velocity of the bubbles and tissue debris is expected to depend on the lesion size and liquefaction completeness, it could provide a quantitative metric of the treatment progression. In this study, the motion of bubble remnants and tissue debris immediately following BH pulses was investigated using high-pulse repetition frequency (PRF) plane-wave color Doppler ultrasound in ex vivo myocardium tissue. A 256-element 1.5 MHz spiral HIFU array with a coaxially integrated ultrasound imaging probe (ATL P4-2) produced 10 ms BH pulses to form volumetric lesions with electronic beam steering. Prior to performing volumetric BH treatments, the motion of intact myocardium tissue and anticoagulated bovine blood following isolated BH pulses was assessed as two limiting cases. In the liquid blood the velocity of BH-induced streaming at the focus reached over 200 cm/s, whereas the intact tissue was observed to move toward the HIFU array consistent with elastic rebound of tissue. Over the course of volumetric BH treatments tissue motion at the focus locations was dependent on the axial size of the forming lesion relative to the corresponding size of the HIFU focal area. For axially small lesions, the maximum velocity after the BH pulse was directed toward the HIFU transducer and monotonically increased over time from about 20-100 cm/s as liquefaction progressed, then saturated when tissue was fully liquefied. For larger lesions obtained by merging multiple smaller lesions in the axial direction, the high-speed streaming away from the HIFU transducer was observed at the point of full liquefaction. Based on these observations, the maximum directional velocity and its location along the HIFU propagation axis were proposed and evaluated as candidate metrics of BH treatment completeness.

Algorithm to Correct Measurement Offsets Introduced by Inactive Elements of Transducer Arrays in Ultrasonic Flow Metering

Ultrasonic flow meters (UFMs) based on transducer arrays offer several advantages. With electronic beam steering, it is possible to tune the steering angle of the beam for optimal signal-tonoise ratio (SNR) upon reception. Moreover, multiple beams can be generated to propagate through different travel paths, covering a wider section of the flow profile. Furthermore, in a clamp-on configuration, UFMs based on transducer arrays can perform self-calibration. In this manner, userinput is minimized and measurement repeatability is increased. In practice, transducer array elements may break down. This could happen due to aging, exposure to rough environments, and/or rough mechanical contact. As a consequence of inactive array elements, the measured transit time difference contains two offsets. One offset originates from non-uniform spatial sampling of the generated wavefield. Another offset originates from the ill-defined beam propagating through a travel path different from the intended one. In this paper, an algorithm is proposed that corrects for both of these offsets. The algorithm also performs a filtering operation in the frequency-wavenumber domain of all spurious (i.e., flow-insensitive) wave modes. The advantage of implementing the proposed algorithm is demonstrated on simulations and measurements, showing improved accuracy and precision of the transit time differences compared to the values obtained when the algorithm is not applied. The proposed algorithm can be implemented in both in-line and clamp-on configuration of UFMs based on transducer arrays.

Vari-focal liquid microlens array using an electrically responsive fluid actuated by a ring array patterned electrode.

A transparent fluid dibutyl adipate (DBA) is suitable for fabricating the adaptive lens due to its unique deformation under a direct current (DC) electric field. In this report, a DBA liquid microlens array (LMA) with a tunable focal length is demonstrated. A hydrophobic layer deposited in the ring array patterns on the electrode induced the formation of the DBA liquid microdroplets array self-assembly. The electronegative DBA liquid tends to move to the anode at a DC voltage. The proposed DBA LMA with a diameter of 100µm can change its focal length from 0.92 to 1.42mm when the voltage changes from 0 to 200V. The response time is relatively fast (∼790m s). Due to the high optical transmittance (∼91%) and good thermal stability in the temperature range of -24.8-161.5∘C, our DBA LMA shows good focusing properties and has potential applications in the field of image processing, portable electronic devices, beam steering, ophthalmology, and 3D displays.

Characterizing the steering performance of a diagnostic-therapeutic ultrasound array using measured and synthesized holograms

Acoustic holography is frequently used for the characterization of fields generated by ultrasound transducers. For arrays with electronic focusing and beam steering, separate holograms are needed to represent the 3D field for each combination of array parameters. In this paper, we show that holograms for the field generated by each individual element in an ultrasound array can be recorded in a single hydrophone scan, by interleaving a series of excitations at each measurement location in which each element is driven separately. Such holograms were recorded for a 64-element diagnostic-therapeutic linear array with a nominal focal length of 50 mm and pitch of 0.8 mm, which is smaller than the wavelength at the operating frequency of 1.05 MHz. The resulting holograms reveal aspects of crosstalk and variations between array elements. By summing the elemental holograms with the appropriate phase shifts, holograms are synthesized representing source conditions for cases where the entire array is used to generate different beam configurations, with focal lengths between 35 mm and 60 mm, and steering angles of up to 20°. These synthetic holograms are shown to accurately characterize non-ideal steering behavior of the transducer, confirmed through direct hydrophone measurements. [Work supported by NIH grants R01EB023910 and R01EB025187.]

Design and Proof-of-Concept of a Matrix Transducer Array for Clamp-On Ultrasonic Flow Measurements.

Common clamp-on ultrasonic flow meters consist of two single-element transducers placed on the pipe wall. Flow speed is measured noninvasively, i.e., without interrupting the flow and without perforating the pipe wall, which also minimizes safety risks and avoids pressure drops inside the pipe. However, before metering, the transducers have to be carefully positioned along the pipe axis to correctly align the acoustic beams and obtain a well-calibrated flowmeter. This process is done manually, is dependent on the properties of the pipe and the liquid, does not account for pipe imperfections, and becomes troublesome on pipelines with an intricate shape. Matrix transducer arrays are suitable to dynamically steer acoustic beams and realize self-alignment upon reception, without user input. In this work, the design of a broadband 37×17 matrix array (center frequency of 1 MHz) to perform clamp-on ultrasonic flow measurements over a wide range of liquids ( c=1000-2000 m/s, α ≤ 1 dB/MHz · cm) and pipe sizes is presented. Three critical aspects were assessed: efficiency, electronic beam steering, and wave mode conversion in the pipe wall. A prototype of a proof-of-concept flowmeter consisting of two 36-element linear arrays (center frequency of 1.1 MHz) was fabricated and placed on a 1-mm-thick, 40-mm inner diameter stainless steel pipe in a custom-made flow loop filled with water. At resonance, simulated and measured efficiencies in water of the linear arrays compared well: 0.88 and 0.81 kPa/V, respectively. Mean flow measurements were achieved by electronic beam steering of the acoustic beams and using both compressional and shear waves generated in the pipe wall. Correlation coefficients of between measured and reference flow speeds were obtained, thus showing the operational concept of an array-based clamp-on ultrasonic flowmeter.

Wideband, Beam-Steerable Reflectarray Antennas Exploiting Electronically Reconfigurable Polarization-Rotating Phase Shifters

We present a wideband reflectarray antenna with electronic beam-steering capability. The beam-steerable reflectarray uses an electronically reconfigurable polarization-rotating unit cell (PRUC) that acts as a wideband 1 bit phase shifter. The unit cell consists of four metallic single-headed arrows placed above a ground plane. The four arrows are connected to the unit cell’s bottom surface, which contains two p-i-n diodes for switching and three lumped inductors for RF–DC isolation. Changing the bias states of the two antiparallel p-i-n diodes reconfigures the unit cell between two operating states that provide a +90° and −90° polarization rotation (PR). Simulation results for the unit cell show a wide frequency range of 8.5–11.5 GHz over which the reconfigurable unit cell provides dominant reflection coefficients of >−2 dB and relative phase shifts of 0° and 180° for the two operating states. The proposed unit cell was used to construct a 256-element, fully electronically reconfigurable reflectarray prototype with aperture dimensions of 192 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times192$ </tex-math></inline-formula> mm to demonstrate the design concept. The digital control circuitry needed to individually control the unit cells was also designed and fabricated. Experimental characterization of the reconfigurable reflectarray demonstrated the 2-D beam scanning capability within the scan range of ±60° over a 30% bandwidth.

Touchless Potential Sensing of Differentially Charged Spacecraft Using Secondary Electrons

The secondary electron method has been recently proposed to touchlessly sense the electrostatic potential of non-cooperative objects in geosynchronous equatorial orbits and deep space. This process relies on the detection of secondaries generated at the target surface that is actively irradiated by an electron beam. Although the concept has already been demonstrated with basic geometries, the electric field around complex bodies leads to a highly inhomogeneous distribution of secondary electrons that determines the observability of the system. This paper employs vacuum chamber experiments and particle tracing simulations to investigate the secondary electron flux generated over a spacecraft-like electrode assembly. The differential charging scenario, in which the assembly is charged to multiple potentials, is also studied. A computationally efficient three-dimensional particle tracing framework that couples the electron beam propagation and secondary electron generation processes is introduced and validated, showing its utility as a diagnostic tool. The system geometry, potential field, and electron beam steering configure the observability space of the target, which is limited to well-defined regions where the potentials are measured with high accuracy. The analysis provides theoretical and technical insight into the development of future electron-based touchless potential sensing technologies.

Angular Clustering of Millimeter-Wave Propagation Channels With Watershed Transformation

An angular clustering method based on image processing is proposed in this paper. It is used to identify clusters in 2D representations of propagation channels. The approach uses operations such as watershed segmentation and is particularly well suited for clustering directional channels obtained by beam-steering at millimeter-wave. This situation occurs for instance with electronic beam-steering using analog antenna arrays during beam training process or during channel modeling measurements using either electronic or mechanical beam-steering. In particular, the proposed technique is used here to cluster two-dimensional power angular spectrum maps. The proposed clustering is unsupervised and is well suited to preserve the shape of clusters by considering the angular connection between neighbor samples, which is useful to obtain more accurate descriptions of channel angular properties. The approach is found to outperform approaches based on K-Power-Means in terms of accuracy as well as computational resources. The technique is assessed in simulation using IEEE 802.11ad channel model and in measurement using experiments conducted at 60 GHz in an indoor environment.

Towards the Next Generation Operational Meteorological Radar

AbstractThis article summarizes research and risk reduction that will inform acquisition decisions regarding NOAA’s future national operational weather radar network. A key alternative being evaluated is polarimetric phased-array radar (PAR). Research indicates PAR can plausibly achieve fast, adaptive volumetric scanning, with associated benefits for severe-weather warning performance. We assess these benefits using storm observations and analyses, observing system simulation experiments, and real radar-data assimilation studies. Changes in the number and/or locations of radars in the future network could improve coverage at low altitude. Analysis of benefits that might be so realized indicates the possibility for additional improvement in severe-weather and flash-flood warning performance, with associated reduction in casualties. Simulations are used to evaluate techniques for rapid volumetric scanning and assess data quality characteristics of PAR. Finally, we describe progress in developing methods to compensate for polarimetric variable estimate biases introduced by electronic beam-steering. A research-to-operations (R2O) strategy for the PAR alternative for the WSR-88D replacement network is presented.