|Acquisition Program: ||CGX radar suites|
| ||RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is “ITAR Restricted”. The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the “Permanent Resident Card”, or are designated as “Protected Individuals” as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.|| Objective: ||Develop and demonstrate an affordable digitally programmable waveform distribution and beamforming architecture that exploits recent advances in highly efficient “digital” switched-mode amplifiers. The preferred approach will enable lower cost by providing reduced part count, size, weight, power consumption and increased efficiency when compared to more conventional approaches based on heterodyning (analog up-conversion) and analog beamforming.
|| Description: ||Electronically scanned arrays (ESAs) are of considerable interest to the DoD and are realized in both analog and digital beamforming approaches . Conventional analog systems are based on the generation of analog signals which are distributed through power splitters and provided in analog form to each of the elements in an array (or subarray). Analog beamforming is accomplished by use of phase shifters or time delay units which are provided to each element (or subarray). For microwave frequency of operation it is often necessary to perform up conversion of baseband signals via use of analog mixers, filters and preamplifiers. For arrays of 1k – 10k elements this conventional process can be costly due to the relatively high part count and power consumption. Improved art is highly desired.
Recent advances in both wide-bandgap semiconductors and switched-mode amplifiers  have demonstrated power added efficiencies (PAE) of 57% PAE for GaN MMICs Class-E amplifiers. Switched-mode amplifiers are expected to yield PAE of about 70-80% at microwave frequencies. Electronically scanned arrays (ESAs) that can exploit these high efficiencies  are expected to eventually replace more conventional arrays based on conventional amplifiers, vacuum electronics and analog beamforming technology. ESAs that employ switched-mode amplifiers offer potential to provide improved performance, higher efficiency and lower cost.
The topic seeks innovative solutions to signal distribution, beamforming and driver circuitry that optimizes the use of switched-mode amplifiers, from an array system perspective. The focus of the effort is to perform a rigorous investigation into architectures, methodology, and technology that includes both analysis and proof of principal. Subsequent phases will validate the approach by demonstration with representative hardware. Offerors may consider a wide range of innovative technologies however the preferred approach must demonstrate an improvement in performance and / or cost relative to conventional methodology. Solutions must be able to perform in open interfaces and open architectures as envisioned in future Navy and DoD systems planned for acquisition.
|| ||PHASE I: Perform architecture trade studies, modeling and simulations. Architectures are assessed in terms of bandwidth, efficiency, phase noise, phase stability (capacity to be calibrated in array environment) and electronic scanning limitations and other parameters which may be of interest to array performance. Any significant cost drivers are identified.
|| ||PHASE II: Demonstration of a digital distribution and beamforming network that supports a partial array nominally consisting of 16 elements which are driven by digital switched-mode amplifiers. The array shall operate in the transmitter mode.
|| ||PHASE III: Participate in industry development efforts for a full transmitter array demo that exploits open system and open interface architectures. This includes but is not limited to any of the following: Radar (at microwave frequencies), electronic countermeasures, and communications systems.
PRIVATE SECTOR COMMERCIAL POTENTIAL/|| ||DUAL-USE APPLICATIONS: The private sector communications systems such as cell phone towers and satellite tracking systems could benefit from more efficient amplifiers and signal distribution systems. The capacity for frequency reuse enabled by efficient digital beamforming is particularly attractive because it utilizes the frequency spectrum more efficiently.
|| References: ||1. M. I. Skolnik, An Introduction to Radar Systems, McGraw Hill, 2001.
2. F. H. Raab, P. Asbeck, S. Cripps, P. B. Kenington, Z. B. Popovic, N. Pothecary, J. F. Sevic, N. O. Sokal,” Power Amplifiers and Transmitters for RF and Microwave” IEEE Trans Microwave Theory and Tech, Vol. 50, No. 3, MARCH 2002
3. H. Xu, S. GaO, S. Heikman, S. I. Long, U. K. Mishra, and R. A. York, “A High-Efficiency Class-E GaN HEMT Power Amplifier at 1.9 GHz” IEEE Microwave and Wireless Component Letters, 16 p.22 (2006).
4. S. Pajic, Z. B. Povovic, “An Efficient X-Band 16-Element Spatial Combiner of Switched Mode Amplifiers”, IEEE Trans on Microwave Theory and Tech, Vol. 51, No. 7, July 2003.|
|Keywords: ||Switched-mode (Switching) Amplifiers, Electronically Scanned Phased Arrays, Antennas, Digital Beamforming, Transmitters, Wide-Bandgap Semiconductors|