Dual-polarization, low-power X-band phased array radars offer an attractive radar technology for short-range weather observations. These systems offer 2-D phase-phase steering, without motors or other moving parts. Two-dimensional high-speed (inertia-less) beam steering combined with dual polarization, programmable/adaptive waveforms, and the ability to combine multiple radars into networks is leading to new atmospheric science research opportunities related to hazardous storm forecasting and response, understanding of cloud physics, water resource management, monitoring of the movement and dispersal of hazardous plumes, and other areas. Over the past three years, the Radar Science group at Stony Brook University in partnership with Raytheon Technologies has been experimenting with novel sampling strategies for weather observations using different generations of the SKYLER dual-polarization X-band phased array radars. Here, examples of weather observations collected by SKYLER are presented along with information on the novel observational strategies based on the Multisensor Agile Adaptive Sampling (MAAS) framework.

A novel analytical method is presented for evaluating the electrical performance of a radome for a dual-polarized phased-array antenna under rain conditions. Attenuation, reflections, and induced cross polarization are evaluated for different rainfall conditions and radome types. The authors present a model for estimating the drop size distribution on a radome surface based on skin surface material, area, inclination, and rainfall rate. Then, a multilayer radome model based on the transmission-line-equivalent circuit model is used to characterize the radome’s scattering parameters. Numerical results are compared with radar data obtained in the Next Generation Weather Radar (NEXRAD) and Collaborative Adaptive Sensing of the Atmosphere (CASA) systems, and good agreement is found.

The Phase-Tilt Weather Radar is an X-band (9.41GHz) phased array radar based on a novel, low-cost architecture that mechanically tilts in elevation and electronically scans in azimuth. This architecture has been developed specifically for low-cost, small-scale radar applications and in dense radar networks. The electronic scanning in azimuth combined with mechanical elevation tilt allow for increased scan speed at severely reduced maintenance costs. This paper presents the calibration and preliminary data results of the Phase-Tilt Weather Radar. Measurements from a severe thunderstorm in Amherst, MA, US will be presented, along with initial calibration analysis and tests performed. Analysis of the data indicates good weather sensitivity and dual polarimetric performance, commensurate with similarsized, mechanical X-band radars.

This paper describes the calibration and validation of one-dimension scanned phased array antenna for an X-band weather radar being developed at the Engineering Research Center for the Collaborative Adaptive Sensing of the Atmosphere (CASA). The antenna aperture is based on a linear array of vertical subarrays. Each subarray is fed by a separate Transmit/Receive (T/R) module which provides phase, amplitude and polarization diversity. The characterization and calibration of the array are based on single element measurements obtained from a portable near-field probe test system. The calibration is validated by measuring the antenna radiation pattern in a near-field antenna range. In addition, thermal stability tests are performed to estimate the system performance loss.

A novel analytical method for evaluating the electrical performance of a flat, tilted radome for a dual-polarized phased-array antenna under rain conditions is presented. Attenuation, reflections and induced cross-polarization are evaluated for different rainfall conditions. A new radome model is presented which takes into account the properties of the skin surface, area, inclination, radome structure, and rainfall rate. The radome is modeled as consisting of multiple layers, including a wet layer. Attenuation and propagation effects through the radome are characterized using a transmission line equivalent circuit model. Knowledge of the rainfall rate and surface properties of the radome is used to determine the radome performance. Calculated results are compared with radar data obtained with the NEXRAD and CASA systems, where good agreement between measurements and simulations was found.

This paper describes the transmit/receive module for the X-band Phase-Tilt array antenna being developed at the Engineering Research Center for the Collaborative Adaptive Sensing of the Atmosphere (CASA). Architecture, fabrication and electrical performance are described. The RF subsystem is designed with commercial-off-the-shelf GaAS MMICs. The design includes a custom PIN diode based diversity switch that provides polarization diversity to the array elements in both transmit and receive channels. The module operates at 9.36 GHz and has a bandwidth of 1.0 GHz. Gain and phase are controlled by a 6-bit digital attenuator and 6-bit digital phase shifter respectively. Commands and RF switching signals are controlled with a FPGA. The T/R modules were fully tested using a measurement station developed specifically for this purpose.

In this paper the scanning performance of the X-band phased-array antenna to be used for a solid state weather radar system is discussed. A simple and low-cost antenna array architecture based on series-fed array of dual-polarized aperture coupled microstrip patch antennas was designed, implemented and tested in order to prove the concept of low-cost phased array radar system for metereological applications. The measured results presented indicates a good scanning performance.

This chapter focuses on the interaction of commonly used devices within an industrial network in order to explain the operation of industrial network protocols. These devices include operational devices such as sensors, motors, gauges, and other intelligent electronic devices; Remote Terminal Units (RTUs) and/or Programmable Logic Controllers (PLCs); Human Machine Interface (HMI) Control System Assets; Supervisory Management Workstations; Data Historians; and Business Information Consoles or Dashboards. Industrial networks are typically very distributed and vary considerably in all aspects, including the link layer and network protocols used, as well as the topology. SCADA and industrial control system networks may utilize bus, ring, star, and tree topologies depending upon the specific type of control process that is in operation and the specific protocols that are used. Industrial networks are made up of many specific automated processes, called control loops. Multiple control loops may be required to perform even more complex control processes. They may be controlled by a central HMI, or they may themselves be part of a larger control loop, acting as inputs or outputs into another level of logic, controlled by a master or central PLC.

Over the past several years, UMass has developed and deployed two mobile Doppler radars for severe storm research. One is a W-band (95 GHz) Doppler radar that is used for fine-scale observations of tornadic features. It features a very narrow (0.18°) beamwidth. The other is a dual-polarized X-band Doppler radar used for coarser scale observations and polarimetric measurements for scatterer identification, and precipitation estimation. We show sample observations by these systems obtained during the 2009 and 2010 VORTEX2 experiments. UMass is presently developing a dual-polarized, solid-state, phased-array radar.

This paper describes the X-band Phase-Tilt Radar antenna array being developed at the Engineering Research Center for the Collaborative Adaptive Sensing of the Atmosphere (CASA) for use in distributed, collaborative and adaptive sensing (DCAS) networks. The architecture of the radar and its component parts including the T/R module, passive antenna elements, and array controller are described in detail. Test data for the full array will be presented in the final paper.

Digital beam forming is an important radar processing technique used in many communication and radar sensing applications. This paper presents a low-cost digital beam forming system which takes advantage of four eight channel analog-to-digital (A-to-D) converter chips and dynamic FPGA reconfiguration. A full digital beam forming algorithm capable of forming up to 24 beams from 64 antenna input signals is described. FPGA reconfiguration is performed in 400 ms allowing for FPGA ret asking of the associated radar for weather and aircraft tracking. Beam forming performance of 64.2 GOPs per second for weather tracking and 72.2 GOPs per second for aircraft tracking is reported. The complete low cost digital beam forming board, including parts and assembly, costs less than $3,000.

In this paper the evaluation of dual-polarized scanning performance of a large planar array antenna for a solid state radar for weather is discussed. The antenna array is designed to operate at 9.36 GHz ±50 MHz, and the transmission and reception mode is configured to work alternatively. The antenna array architecture based on a series-fed array configuration of Dual-Polarized Aperture Coupled Patch Antennas (DP-ACPA) was designed and implemented to achieve the required radar polarimetric performance at low cost. Measured patterns of the array in the elevation and azimuth plane are used to evaluate the two principal polarimetric radar parameters (Zdr and LDR) over the scanning range in azimuth plane. It is shown that the biases in the differential reflectivity due the cross-polarization of this antenna configuration are negligible in comparison with the biases produced for the mismatch antenna patterns (H and V).

This paper discusses the systems architecture of the CASA Phased Array Radar System, the Phase-Tilt Escan Radar System, for deployment in a CASA DCAS network of low power, solid-state phased array radars. The paper highlights the high-level system's architecture accompanied by measured data from the subsystems.

The West Coast of Washington and the NE and SW comers of Wyoming are regions of the contiguous United States where NEXRAD coverage is incomplete. One approach to addressing these gaps is to install additional NEXRAD-class radars. Another potential approach is to install small radar networks of the type being investigated in the CASA project. This paper compares these two approaches. We provide a meteorological and user-need assessment of present radar coverage in these regions (based on a recent feasibility study led by J. Brotzge) as well as an objective assessment of the radar-coverage that would be achieved using the large radar and small radar approaches. For this evaluation we consider two classes of radar: long-range radars having similar attributes to the WSR-88D (i.e., 10 cm wavelength, >250 km maximum range, 1 degree beamwidth, -500 kW peak power); and short-range radars having attributes similar to those operating in CASA's Oklahoma prototype network (i.e., 3 cm wavelength, 40 km maximum range, 2 degree beamwidth). We first establish the number of both types of radar that would be needed to provide coverage over a given rectangular ground-domain. Next, we quantify the coverage-versus-altitude for both weather-event detection and precipitation estimation over these regions, considering the blockage caused by both the curved earth and the local terrain.

This paper describes the design of a dual-polarized microstrip series-fed linear array as part of the phase-tilt active planar array antenna being designed for weather sensing for the CASA Engineering Research Center. The dual-polarized planar array antenna is composed of 64 linear array columns, each one formed by 32 aperture coupled patch antenna elements in cascade and excited by a 2 W solid state transmit and receive (TR) module. A straightforward synthesis method is used in order to achieve the desired amplitude and phase excitation of each linear array. Radiation patterns computed using method of moments (MoM) and measured in a compact range system are presented in order to validate the synthesis method proposed.

This paper discusses an approach to evaluating network topologies of scalable, low power, solid-state phased array radars that improve the coverage of the lower troposphere (<3 km), which is absent in coverage available with current weather sensing networks.

This paper presents the design and implementation of a complete phase shifter system using vector (polar) modulation, suitable for solid-state phased array radar applications, providing a cost effective solution which overcomes the main constraints involved with traditional systems. The performance characteristics for an intermediate frequency (150 MHz) are shown. Finally a four channel prototype was built to evaluate the network connectivity of the phase shifter.

The recently established National Science Foundation Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) will be deploying the first generation of an automated network of four low-power, short-range, X-band, polarimetric, Doppler radars, known as NetRad, in central Oklahoma in late 2005. This network is developed with the goal of tracking tornadoes with high spatial and temporal resolution as well as mapping severe weather events in the lowest 2 km of the troposphere. Each radar node has been developed to accomplish this system goal through the coordinated interaction with other radars in the network via a real-time, closed-loop software control system. This paper will describe the characteristics of the individual radar nodes in the system, with emphasis on those aspects of the design that lend themselves toward operation as a coordinated network. Calibration results and performance characteristics of the single node radar of the first generation system will also be presented.