Early applications of AESA transmit-receive modules (TRMs) for military radar have been implemented using “brick” architectures. This has typically entailed the use of bare die housed ceramic packaging, positioned perpendicular to the antenna array and supported with a complex arrangement of cables and connectors. This requires a semi-automated assembly approach resulting in slow production rates and high component/subsystem and subsystem costs.
MACOM has been focused for several years on offering solutions for the radar market based on commercial production techniques and technologies. MACOM has focused on a planar tile approach designed to leverage the economies of scale associated with commercial production based on surface mount technology that allows for the use of low cost plastic packaging for the TRM MMICs and automated assembly. Furthermore, testing can be automated to ensure known good die with the full module tested in seconds.
A precursor to the MPAR program included development of an S-band radar for a European naval platform and MACOM has been working on the base MPAR program for over seven years.
The National Weather Radar Testbed (NWRT) Multi-function Phased Array Radar (MPAR) program is a National Oceanic and Atmospheric Administration (NOAA)/ Federal Aviation Authority (FAA) initiative to combine the operational radar functions of several national networks and have them served by a single radar system for aircraft and weather surveillance. The NOAA National Severe Storms Laboratory (NSSL) originally led the effort to repurpose SPY-1A U.S. Navy surveillance phased array radar and adapt it for weather.
The S-band MPAR program is designed to upgrade the capabilities using AESA architectures underpinning a planar array capable of demonstrating multi-function operation using modern, dual-polarization technology. The ability to combine weather radar and aircraft tracking radar systems using a single radar is designed to translate into savings to the US taxpayer approaching $4.8 billion as it would obviate the need to operate approximately 350 aircraft tracking radar systems and 200 weather radar systems. The ultimate aim is to replace these discrete systems that are operated by multiple operators with approximately 365 multifunctional radar systems based on the MPAR program with the output networked together to allow the National Weather Service (NWS) to use the data for its weather mission requirements.
MACOM’s Scalable Planar ARray (SPAR) Tiles operate at S-band over 2.7 GHz to 2.9 GHz, and contain antenna elements, GaAs and GaN semiconductors, transmit and receive modules and RF and power distribution networks combined with additional signal generation and receive and control electronics.
This experience has allowed the company to support the MPAR program with capabilities that are equivalent to TRL-8 and MRL-8. The company’s work on tiles has also been evaluated by Massachusetts Institute of Technology (MIT) Lincoln Laboratory (LL) from a cost perspective; MIT LL is scheduled to publish a brick vs. tile cost evaluation which shows that tile architectures offer a 5x cost reduction.
In September 2015, MACOM announced successful field tests of MPAR technology in conjunction with MIT LL, with the first MPAR-based system deployed by the National Severe Storms Laboratory in Oklahoma. The field trial was followed by a commercial order from MIT LL for the company’s SPAR Tiles.
The SPAR tiles offer 8 W of output power in dual polarization (i.e. the beams are transmitted both horizontally and vertically) as opposed to the current systems which are non polarimetric. Traditional weather radar systems transmit signals horizontally only and while they are able to detect precipitation, it is not possible to detect precipitation type, volume of precipitation as well as being able to detect aviation hazards such as birds. The AESA architectures that are enabled by the SPAR tiles allow the arrays to split into sub-arrays to enable more accurate beam steering and the transmission of narrow beams, as well as support the requirements for a multifunctional system that can combine the requirements for both weather surveillance and aircraft tracking.
MACOM delivered a 2 x 5 tile (16 inch x 16 inch) array to MIT that has been used for tracking planes and is now being used by NOAA; an 86 panel array is also being built for NOAA which will be evaluated for its suitability as a replacement for the SPY-1A radar. The array will perform as a prototype multifunctional system providing both weather surveillance and aircraft tracking and offer a 260 nautical mile range. The performance of this array will form the basis for a 2020 decision to commence production of an estimated 365 radar systems that will replace the approximately 550 discrete weather and aircraft tracking radars currently in operation in the United States. MACOM estimates that this will translate to a requirement for around 26,000 tiles per annum.
MACOM’s SPAR tile technology has also been selected by MIT LL for use in a test bed for DARPA’s Arrays at Commercial Timescale (ACT) program which is designed to streamline development and manufacturing cycles by leveraging best practices established in the commercial domain. The SPAR tiles will interface with commercial back-end electronics to explore the potential to achieve new capabilities in digital phased arrays for next-generation radar, electronic warfare and communications systems.
The primary work has focused on S-band to date, but MACOM is working on systems designed to operate at up to Ku-band and also at Ka-band. The key consideration to enable higher frequency operation relates to the closer antenna space needed which impacts considerations such as thermal performance. Moving forwards, the closer lattice spacing necessitated by higher frequencies will open the door for solutions that are focused on tighter integration and this will influence the potential semiconductor roadmap.
Most recently, MACOM announced a teaming agreement with Northrop Grumman that establishes MACOM as Northrop Grumman’s exclusive teaming partner for the development and manufacture of radar arrays that use MACOM’s active antenna technology to target a wide range of defense programs and platforms. The agreement builds on the momentum the company has been building to offer commercial manufacturing and commercial economies-of-scale around its AESA technology capabilities in both defense and commercial operations. The partnership with Northrop Grumman will involve MACOM being the exclusive supplier of its planar tile technology, though the companies have been collaborating on programs for a number of years. The partnership focuses primarily on the MACOM’s planar tile expertise so it is conceivable that Northrop Grumman could look to include its own RF and digital capabilities in the SPAR tiles.