EMS Technologies, Defense & Space division, now a part of Honeywell, recently announced the award to build the AEHF BFN, nicknamed nuller, for the fourth AEHF satellite,3 under contract to Northrop Grumman. The satellite is under contract to Lockheed Martin, the AEHF prime contractor and overall space system manager. Northrop Grumman builds and integrates the AEHF payload that consists of processors, antennas, radio frequency subsystems and crosslinks.4 The first satellite is on orbit, launched October 14, 2010, and is due to come online in the fall of 2011.
AEHF provides the Milstar LDR (low data rate) and MDR (medium data rate) waveforms as well as the new AEHF XDR (extreme data rate) waveforms. AEHF protections included anti-jam capabilities, Low Probability of Detection (LPD), a Low Probability of Intercept (LPI), and advanced encryption systems.6 In addition, the waveforms use frequency hopping to communicate over narrow bands that constantly move within the total bandwidth of the system. The equipment is nuclear-hardened to provide survivable protected communications systems that do not degrade in either tactical or strategic environments. These communications systems service the warfighter on land, sea, and air.
The AEHF BFN is a Q-band (EHF) uplink satellite RF receive network that is a part of the High Resolution Coverage Antenna system, providing two spot beams per satellite. The antenna normally receives signals from its entire field of view, but the BFN provides the capability to produce nulls, or areas where no signal is received, within its field of view. In operation, the AEHF BFN acts to null out jammers from the field of view, thus its nickname, the nuller. This is accomplished through multiple RF receive ports that overlap in the field of view and combine to provide the RF data stream. Each of the ports can be observed for the presence of a jamming signal. If jamming is present, a null can be formed to block that region of the field of view.
The nulling is accomplished by independently controlling the amplitude and phase of each of the overlapping RF ports. Samples of the RF signal are made at each of the multiple ports and these data are used to adjust the phase and amplitude of the multiple of the multiple channels to result in a rapidly converging excitation that minimizes the effects of a jammer and allows users to access the satellite. The size and shape of these nulls can be controlled real-time to compensate for various types of emitters. The resultant signals from all ports are then combined to provide the RF data stream for further processing, demodulation and decoding. The system provides assured communications against both hostile interferers and friendly interfering sources.
EMS/Honeywell continues to develop the technology to provide systems that address the warfighters dependence on secure satellite-based communications. In addition, as hosted payloads augment the militarys telecommunications requirements, EMSs advancements in the military use of beam forming network capabilities are being adapted for commercial communication and direct broadcast satellite applications.
The commercial BFN offers similar capabilities as the AEHF application, but without the sophisticated waveforms, enabling safeguards against jamming and unauthorized access. With the military leasing a large percentage of the worldwide SATCOM capacity, continuous and secure communications is imperative. In the highly competitive communications industry, commercial entities that cannot protect their communications link face the possibility of customers moving to other satellite providers or terrestrial applications.
Editors Note:
EMS Receive Beam Forming Networks (RxBFN) offer redundant LNAs, anti-jam nulling, beam shaping, phase control and low loss ferrite phase shifters. Heritage programs include AEHF, LANDSAT, ARTEMIS, TDRSS, NSTAR, ACTS, MILSTAR, DSCS and the Space Shuttle.
About the Author
David Rhodes, a principal engineer within the Defense & Space Division of EMS Technologies, now a part of Honeywell, has worked over the past 20 years on Milstar satellite programs as well as AEHF satellite programs. Rhodes has designed electronics for microwave hardware for both satellite and terrestrial based systems. He also designed wireless computer equipment at LXE, a division of EMS Technologies, prior to joining the Defense and Space Division. After serving in the U.S. Navy, Rhodes began his electronics career at Bell Laboratories where he designed terminal equipment.
References
1 www.as.northropgrumman.com/products/aehf/index.html
2 www.usaf.com/space/space2.htm
3 www.businesswire.com/news/home/20110819005374/en/EMS-Technologies-Awarded-11.5-Million-Contract-Provide
4 www.as.northropgrumman.com/products/aehf/index.html
5 www.losangeles.af.mil/news/story.asp?id=123076020
6 www.globalsecurity.org/space/systems/aehf.htm
This articles introductory image is courtesy of United Launch Alliance