X-Band Radar Transmit/Receive (T/R) Modules
In order to estimate the capabilities of missile defense radars such as the AN/TPY-2s used both as Forward Based X-Band (FBX) radars and THAAD theater missile defense battery radars it is necessary to assess the power output of the radars. There do not appear to be any public official numbers for the peak or average powers of these radars. However, one can estimate these based on the peak and average powers of transmit/receive modules making up their antennas. This post discusses and assesses these power outputs for the TPY-2 and other X-band missile defense radars (SBX, GBR-P). In particular, it argues that the average power outputs of the modules are 6, 10 and 16 watts for the GBR-P, SBX, and TPY-2 radars respectively
Background
An essential part of the U.S. Ballistic Missile Defense System (BMDS) is a “family” of long-range phased-array X-Band radars manufactured by the Raytheon Company. The most important of these radars are the AN/TPY-2 radars, which are employed both as Forward-Based X-band (FBX) radars in the BMDS and as the radars for THAAD theater missile defense batteries. A second radar in this family is the single Sea-Based X-band (SBX) radar, currently deployed in the northern Pacific and used for missile defense testing and as part of the U.S. Ground-Based Midcourse (GMD) national missile defense system. Other members of this radar family include the never-built very-large Ground-Based Radar (GBR) proposed for the Clinton Administrational National Missile Defense system and the Prototype Ground Based Radar (GBR-P) built at the U.S. missile defense test range on Kwajalein Atoll in the Pacific Ocean. During the George W. Bush Administration, the Missile Defense Agency had planned to move to the GBR-P to central Europe and rename it the European Mid-Course Radar (EMR). However, these plans were cancelled in 2010 when the Obama Administration announced its new European Phased Adaptive Approach missile defense program, and the GBR-P remains in a non-operational status at Kwajalein.
All these radars have active array antennas comprised of large numbers of transmit/receive (T/R) modules that both produce and receive microwave energy. They all use the same basic T/R modules, although as discussed here, at least three different generations of modules with differing power outputs are used. For each type of radar, the peak power for each radar will be given by the peak power of the transmit/receive modules times the number of modules, and the average power of the radar is then just its peak power times the maximum duty cycle (the fraction of the time the modules is transmitting).
Here it is concluded that the first generation modules used in the GBR-P have a peak power of about 6 watts and an average power of about 1.2 watts. Since the GBR-P has 16,896 of these modules, its peak and average powers would be about 100 kW and 20 kW respectively. The second generation modules used in the SBX appear to have a peak power of about 10 w and an average power of about 2.0 watts. This gives peak and average powers for the SBX of 450 kW and 91 kW, based on 45,254 modules. Figures on the powers of the third generation modules used in the AN/TPY-2 radars do not appear to be publicly available, but the available information suggests they are likely to be about 16 watts peak and 3.2 watts average power. This gives peak and average powers of about 410 kW and 81 kW based on 25,344 modules.
The Transmit/Receive (T/R) Modules
The Raytheon Company T/R modules used in these radars are based on gallium arsenide monolithic microwave integrated circuit (MMIC) technology, which combine functions such as amplification, phase shifting, attenuation, and phase shifting on a single chip, and at least three different versions, with differing powers, have been used in its X-band missile defense radars.[1] According to a June 2006 Raytheon fact sheet, it had produced over 175,000 X-band T/R modules for missile defense radars, passing through three design iterations, and these modules were used in the Ground Based Radar – Prototype (GBR-P), the Sea-Based X-band (SBX), and the Terminal High Altitude Area Defense (THAAD) radars.[2]
In September 1992, Raytheon won a $491.2 million contract to build four X-band radars: a THAAD demonstration/validation (Dem/Val) radar for early THAAD testing, two THAAD User Operational Evaluation System (UOES) radars, and a GBR prototype at Kwajalein.[3] The UOES radars were to be used as part of two UOES THAAD units, with a total of 40 interceptors that would be used for further testing and operational assessment as well as being deployable for actual use if necessary.[4] However, the interceptors for these UOES units were never built. At that time, the plan was for the GBR-P to use traveling wave tubes rather than modules to avoid stressing the T/R module production capabilities.[5]
The THAAD Dem/Val radar was apparently completed by late 1994.[6] The first UOES radar was delivered to the White Sands Missile Range (WSMR) in April 1996 and the second was apparently delivered in about August 1996.[7] Each of the UOES radars had an antenna aperture of 9.2 m2, with 25,344 T/R modules, subdivided into 72 subarrays of 352 elements each. (The eventual production THAAD radars would have the same aperture and number of modules as the UOES radars.) The Dem/Val radar antenna was half the size of that of the UOES radars, with an aperture of 4.6 m2 and it contained 12,672 modules, although additional antenna area and modules could be added to bring it up to the UOES configuration.[8]
In 1992 Raytheon was also chosen to produce X-band T/R modules for these radars The U.S. Army had identified the production of these modules as the “long pole” in THAAD development.[9] At this time it was expected that as many as 75,000 modules would be built.[10]
By May 1994, Raytheon (along with subcontractor Texas Instruments) had produced about 10,000 modules, and production was expected to peak at about 5,900/month later in the year.[11] Ultimately Raytheon produced and delivered about 42,000 6-watt peak-power modules.[12] This suggests that production was likely complete in 1995. At the same time, subcontractor Texas Instruments had also produced about 28,000 6-watt X-band T/R modules, was “very close” to producing 10-watt modules, and had developed a 16-watt module that was close to meeting DoD specifications.[13] Thus a total of about 70,000 6-watt peak-power T/R modules had been produced, consistent with a 1994 report that a total of 68,000 were needed for the GBR program.[14] (A 2000 paper says “about 65,000” modules were built.[15]) These 6 watt-peak-power modules apparently represent the first of the three design iterations. At the end of the production run, these modules were being produced for “less than $1,000 each.”[16]
Thus by 1996, Raytheon had built 1 prototype and 2 UOES THAAD radars, which used a total of 63,360 modules.[17] Thus these three radars account for most of the first generation T/R modules.
In November 1994, Raytheon received a new contract for the GBR-P which now called for it to use T/R modules rather than traveling wave tubes. However, assuming a total of 70,000 first-generation T/R modules were built, there would not be enough modules remaining after construction of the three THAAD radars for the 16,896 needed for the GBR-P. This problem was solved by dismantling the THAAD Dem/Val radar.[18] The modules removed from the Dem/Val radar plus the unused ones (again assuming a total of 70,000) would have totaled about 19,300 T/R modules, enough for the 16,896 modules on the GBR-P. Construction of the GBR-P on Kwajalein began in October 1996 and was completed in September 1997.[19]
Unlike radars powered using vacuum tubes, radars using solid-state modules cannot be efficiently operated using the high voltages that can be used to produce peak powers hundreds or thousands of times greater than their average power.[20] Thus such radars must use relatively long pulses and high duty cycles in order to generate adequate average powers. An average power greater than 10% of the peak power would be typical.[21] Thus, for example, a 2001 Defense Science Board report stated that X-band modules readily available at that time had a 10 watt peak power and a 2 watt average power.[22] A 1991 MITRE briefing on the GBR used a duty cycle of 0.21.[23] Here it is thus assumed that the T/R modules have an average power of 20% of their peak power.
Thus it appears that the two THAAD UOES radars (no longer in use) and the GBR-P radar were built using the first design iteration 6-watt peak-power T/R modules. Assuming these modules had duty cycles of 20%, they would have had average powers of about 1.2 watts.
In 1996, Raytheon was selected to produce an improved version of the GBR, which would use 10 watt T/R modules, which at that time were expected to begin deliveries in 1997.[24] On October 12, 2004, Raytheon announced that it had recently produced its 100,000th T/R module. This event was described as marking the end of basic deliveries for the GBR, and as having been accomplished one month ahead of time.[25]
Subtracting out the previous 42,000 modules built by Raytheon, this suggests that about 58,000 of these newer 10-watt T/R transmitters were built. This would not be enough for the 69,632 T/R modules the never-built GBR on Shemya Island would have required, but would be more than enough for the 45,264 modules needed for the single SBX that was built instead. This indicates that the SBX uses these nominally10-watt modules, which represent the second T/R module design iteration. A 10-watt peak power is consistent with a November 2002 Missile Defense Agency document that stated the T/R modules on the SBX would have 1.4 times the power of the modules on the GBR-P.[26] Similarly, a January 2006 paper contained figures provided by the Raytheon Company showing that the “State of the art” for GaAS MMIC power amplifiers was a peak power of 10 w.[27]
In August 2000, Raytheon won a Lockheed Martin contract for more than $1.4 billion to design, develop and manufacture the first production THAAD radars.[28] The THAAD and the essentially identical Forward-Based X-band (FBX) radars were given the designation of AN/TPY-2 and merged into a single program. The first “production-representative” THAAD radar (AN/TPY-1 #1) was completed in March 2004.[29] The second radar (AN/TPY-1 #2) was completed in 2004-2005 and deployed in 2006 as an FBX in northern Japan, about 1,000 km from the North Korean ballistic missile test launch site.[30] The third AN/TPY-2 radar was completed in late 2006, and deployed as an FBX to Israel in 2007. As noted above, as of June 2006, Raytheon had produced over 175,000 T/R modules, suggesting that by that time it had produced roughly 75,000 additional modules. This would be about right for three AN/TPY-2 radars, which each use 25,344 modules.
These 75,000 T/R modules are presumably the third design iteration. There does not appear to be any publicly available data on their power output, but it seems likely to be higher than that of the second generation. Published data indicate that the state of the art for X-band modules at that time was a peak power of 10-20 watts.[31] Given that, as noted earlier, Texas Instruments was developing a 16 w power module in the mid-1990s, it is plausible that this third generation of T/R modules would have a similar level of performance. Here we assume a peak power of 16 watts, corresponding to an average power of 3.2 watts.
As of the end of 2011, seven AN/TPY-2s had been delivered (four FBX, two THAAD, and one for development and testing). Current plans call for a total of at least 11 radars, not including two scheduled to be delivered to the United Arab Emirates by 2014, six of which will be used as THHAD battery radar. There is no public indication that the later AN/TPY-2 radars use different versions of the modules than the first three, although this cannot be completely ruled out. However, the next major surface-based X-band phased-array radars, the Navy’s Aegis SPY-3 and possibly its Air and Missile Defense Radars, will reportedly use new technology Gann modules that are intended to be capable of significantly higher powers.
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Several figures showing the state of the art in X-band modules from 2006, 2007 and 2008 are below:
Figures from Eli Brookner, “Phased Arrays and Radars – Past, Present and Future, Microwave Journal, January 2006. The figures were provided to Brookner by Raytheon.
From Eli Brookner, “Phased-Array and Radar Breakthroughs,” 2007 IEEE Radar Conference.
From Eli Brookner, “Phased-Array and Radar Astounding Breakthroughs – An Update,” Radar 2008: IEEE 2008 Radar Conference (citing Aethercomm, GaN Transistors for Radar,” Microwave Journal, January 2008.
[1] A description of such MMIC T/R modules is Bruce A. Kopp, Michael Borkowski, and George Jerinic, “Transmit/Receive Modules,” IEEE Transactions on Microwave Theory and Techniques, Vol. 50, no. 3 (March, 2002), pp. 827-834. A more recent survey of the current state of X-band T/R modules is Bruce A. Kopp, “S- and X-Band Radar Transmit/Receive Overview,” Proceedings of the 2007 IEEE Radar Conference (New York: IEEE, 2007), pp. 948-953. A brief history of Raytheon’s development of T/R modules and active electronically steered array antenna is “Pioneering Phased Array Systems and Technologies: Active Electronically Steered Antennas,” Technology Today, Raytheon Company, Vol. 3, No. 1, pp. 19-23.
[2] “Sea-Based X-band Radar (SBX) for Missile Defense,” Raytheon Company Factsheet, June 12, 2006. The point of the factsheet was not to announce the completion of this number of modules, which, as will be seen subsequently, likely occurred as much as a year earlier.
[3] “Raytheon Wins $491.2 Million Ground-Based Radar Contract,” Aerospace Daily, September 1992.
[4] David Hughes, “Lockheed Readies THAAD for White Sands Testing,” Aviation Week and Space Technology, July 11, 1994, pp. 50-
[5] “Army Adds GBR Oversight, Production Line To Reduce Risk,” Aerospace Daily, April 8, 1993.
[6]“Raytheon Ramping Up Solid State Module Production for GBR,” Aerospace Daily, December 22, 1993.
[7] M. Sarcione, J. Mulcahey, D. Schmidt, K. Chang, M. Russell, R. Enzmann, P. Rawlinson, W. Guzak, R. Howard, and M. Mitchell, “The Design Development and Testing of the THAAD (Theater High Altitude Area Defense) Solid State Phased Array (formerly Ground Based Radar),” 1996 IEEE International Symposium on Phased Array System and Technology, October 15-18, 1996, Boston, MA., pp. 260-265.
[8] Sarcione, et. al., “The Design Development and Testing.”
[9] “Raytheon Ramping Up.”
[10] David Hughes, “Ground-based Radar Exploits MMIC Modules,” Aviation Week and Space Technology, October 5, 1992, pp. 66-67.
[11] David Hughes, “Lockheed Readies THAAD for White Sands Testing,” Aviation Week and Space Technology, July 11, 1994, p. 50.
[12]United States of America v. Raytheon Company and Texas Instruments Inc., Antitrust Complaint, U. S. District Court for the District of Columbia, Civil No.: 1:97CV01515, filed July 2, 1997, p. 5. Available at:
[13] Ibid. In 1996 Raytheon purchased Texas Instruments, but to settle anti-trust concerns had to agree to sell the TI unit that produced the T/R modules.
[14] Hughes, Lockheed Readies THAAD,” p. 50.
[15] Eli Brookner, “Phased-Arrays for the New Millennium,” 2000 IEEE International Conference on Phased Array Systems and Technology, Dana Point, CA, May 20-26, pp. 3-19. Michael A. Dornheim, “THAAD Program Future Tied to Test Results,” Aviation Week and Space Technology, March 3, 1997, p. 64, also describes these modules as having peak powers of 6-8 watts.
[16] Brookner, “Phased Arrays for the New Millennium,” (citing E.D. Cohen, “Trends in the Development of MMICs and Packages for Active Electronically Scanned Arrays (AESAs),” in 1996 IEEE International Symposium on Phased Array Systems and Technology, October 15-18, 1996, pp. 1-4.)
[17] Sarcione, et. al., “The Design Development and Testing.”
[18] Report of the Defense Science Board Task Force on Future DoD Airborne High-Frequency Radar Needs/Resources, April 2001, p. 2.
[19] Jim Bennett, “GBR-P reaches transition point,” The Kwajalein Hourglass, September 26, 2000, pp. 1, 8.
[20] Merrill I. Skolnik, Introduction to Radar Systems, 3rd ed. (New York: McGraw-Hill, 2001), p. 707.
[21] Ibid.
[22] Report of the Defense Science Board Task Force on Future DoD Airborne High-Frequency Radar Needs/Resources, April 2001.
[23]Davis, et.al., “Comparison of the Surveillance Capabilities.”
[24] United States of America v. Raytheon Company and Texas Instruments Inc., p .5.
[25] “Raytheon Delivers 100,000th Best of Breed Module in Support of Missile Defense Systems,” News Release, Raytheon Company, October 12, 2004.
[26] Missile Defense Agency (MDA), “Information Report: Sea-Based X-Band Radar (SBX),” November 2, 2002, p. 9.
[27] Eli Brookner, “Phased Arrays and Radars – Past, Present and Future, Microwave Journal, January 2006.
[28] “Raytheon gets $1.4 Billion for THAAD Radar Development,” Aerospace Daily and Defense Report, August 11, 2000.
[29] Marc Selinger, “Raytheon Finished First Production Radar for THAAD,” Aerospace Daily and Defense Report,” March 15, 2004.
[30] John Liang, “MDA Chief: FBX Radar on Track for Deployment to Japan in January,” Inside Missile Defense, December 21, 2005; Hans Greimel, “U.S. Activated High-Power X-Band Radar Outpost in Northern Japan Amid N Korea Concerns,” Associated Press, September 28, 2006; “Raytheon Ships Second Ballistic Missile Defense System Radar,” Press Release, Raytheon Company, December 11, 2006.
[31] Eli Brookner, “Phased-Array and Radar Astounding Breakthroughs – An Update,” Radar 2008: IEEE 2008 Radar Conference (citing Aethercomm, GaN Transistors for Radar,” Microwave Journal, January 2008; Eli Brookner, “Phased-Array and Radar Breakthroughs,” 2007 IEEE Radar Conference.
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