Search

The U.S. Government operates seven distinct radar networks, providing weather and aircraft surveillance for public weather services, air traffic control, and homeland defense. In this paper, we describe a next-generation multimission phased-array radar (MPAR) concept that could provide enhanced weather and aircraft surveillance services with potentially lower life cycle costs than multiple single-function radar networks. We describe current U.S. national weather and aircraft surveillance radar networks and show that by reducing overlapping airspace coverage, MPAR could reduce the total number of radars required by approximately one-third. A key finding is that weather surveillance requirements dictate the core parameters of a multimission radar—airspace coverage, aperture size, radiated power, and angular resolution. Aircraft surveillance capability can be added to a phased array weather radar at low incremental cost because the agile, electronically steered beam would allow the radar to achieve the much more rapid scan update rates needed for aircraft volume search missions, and additionally to support track modes for individual aircraft targets. We describe an MPAR system design that includes multiple transmit–receive channels and a highly digitized active phased array to generate independently steered beam clusters for weather, aircraft volume search, and aircraft track modes. For each of these modes, we discuss surveillance capability improvements that would be realized relative to today's radars. The Federal Aviation Administration (FAA) has initiated the development of an MPAR “preprototype” that will demonstrate critical subsystem technologies and multimission operational capabilities. Initial subsystem designs have provided a solid basis for estimating MPAR costs for comparison with existing, mechanically scanned operational surveillance radars., United States. Federal Aviation Administration (FA8721-05-C-0002)

An innovative design exploits dual polarization and digital beamforming to provide a radar solution for simultaneous aircraft surveillance and weather sensing. Most people immediately recognize the importance of radar systems to the Federal Aviation Administration (FAA), which relies on radar to track and manage air traffic, and to the National Weather Service, which provides forecasts and emergency weather information. Yet, the National Aeronautics and Space Administration, the Departments of Agriculture and Homeland Security, the Environmental Protection Agency, and other federal agencies depend on civilian networks of eight distinct radar systems for a wide variety of information: identification and tracking of vehicles, radar imaging from space, and climate data, to name a few. However, these 10- to 40-year-old systems are nearing the end of their designed lifespans. MIT Lincoln Laboratory has proposed a multifunction phased-array radar (MPAR) system as the replacement for these aging systems. Unlike the current civilian radar systems that use rotating dish antennas, the MPAR system has no moving parts, instead utilizing four antenna faces for 360 degree scanning, and electronically shapes its radar beam. The MPAR's resulting beam agility permits faster full-volume scan rates and increased resolution, and enables one radar unit to perform various weather and aircraft surveillance tasks. In addition, an MPAR system's surveillance capabilities would likely exceed those of current radar systems by allowing more frequent weather scans and providing vertical resolution and height estimates for aircraft., Published in Tech Notes, 2011. This technology won a 2011 R&D 100 Award. Sponsored in part by the Federal Aviation Administration (FAA).

The measured results from all X-band electronically scanned array using an overlapped subarray architecture are presented. The 2D architecture uses a 12 x 12 element subarray with 3 to 1 overlapping. The active electronic scanned array is a receive only implementation consisting of switch, low noise amplifier, phase shifter and attenuator. Measured far-field patterns and excitation at the aperture using near-field scanner demonstrates desired design goals of a 20 degree sector beam with low sidelobes. Finally, the scan performance of the sector subarray beam is measured at 20 and 40 degrees. A three tile implementation is constructed and measured.

Conventional microstrip antenna feeding techniques using microstrip transmission lines or coaxial probes limit the bandwidth to a few percent due to feed radiation and reactive mismatch. Proximity-coupled feeds can be used as an alternative to direct contact feeds on thick substrates by coupling to an embedded microstrip line or by stacking several patches. Proximity-coupled element bandwidths of up to 25 percent have been achieved with single patch elements, but no models presented thus far can predict the effects of inter- element coupling upon resonant frequency and bandwidth. This report presents an infinite array analysis that is applied to three types of proximity-coupled rectangular microstrip elements. The spectral dyadic Green's function for a two layer rounded dielectric slab is used do that all surface wave and mutual coupling effects are included. A method-of-moments with three types of expansion modes is used to efficiently solve for the unknown current distribution, and a model for microstrip traveling wave feed lines in an infinite array described. Theoretical results are presented for scanning input impedance as a function of substrate parameters, array spacing, and element geometry.