To optimize the T/R module board design, researchers placed the beam former’s input/output to the antenna’s input/output on the same side of the module, enabling component replacement under “power on” conditions. They fabricated the control board on a multilayered FR-4 substrate, placing the T/R filters on the backside of the module to ensure isolation and using grounded coplanar technology to reduce coupling and grounding effects. Using a 4-bit phase shifter, a 5-bit attenuator, and polarization switching, the team attained transmit channel power output of 30 dBm per channel and an overall 30 dB gain. Researchers used a 4-bit phase shifter and 5-bit attenuators for the receive channel as well, demonstrating a noise figure of 2 dB and an overall gain exceeding 20 dB.

Following the August 2004 demonstration, AFRL researchers implemented several design changes to improve the performance and control of the T/R modules.⁵ The first of the new-generation T/R modules have been fabricated, and researchers completed testing in February 2006. Once analyzed, the test results—along with a report on the updated module design—will appear in a future issue of AFRL Technology Horizons. If the AFRL-developed S-band ESA POC panel meets the research team’s requirements, engineers plan to fabricate a 54-panel array to demonstrate the possibility of using a single GDPAA to replace multiple parabolic reflector antennas for telemetry, tracking, and command at AF satellite tracking sites around the globe.

Mr. Paul J. Oleski and Lt Robert Patton, of the Air Force Research Laboratory’s Information Directorate, Dr. Boris Tomasic and Mr. John Turtle, of the Air Force Research Laboratory’s Sensors Directorate, Mr. Sarjit S. Bharj, of Princeton Microwave Technology, Inc., and Dr. Shiang Liu, of The Aerospace Corporation, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451, or place a request at http://www.afrl.af.mil/techconn_index.asp. Reference document IF-H-05-22.

References

¹ Tomasic, B., et al. “The Geodesic Sphere Phased-Array Antenna for Satellite Communication and Air/Space Surveillance — Part 1” AFRL in-house technical report AFRLSN- HS-TR-2004-031, Jan 04.
² Oleski, P. “Space Ground Link Subsystem.” AFRL Technology Horizons, vol 5, no 2 (Apr 04): 20-12. http://www.afrlhorizons.com/Briefs/ Apr04/IF0311.htm.
³ Oleski, P., et al. “Geodesic Dome Phased-Array Antenna.” AFRL Technology Horizons, vol 6, no 4 (Aug 05): 16-18. http://www.afrlhorizons.com/Briefs/Aug05/ IFH0504.htm.
⁴ Bharj, S., et al. “Affordable Antenna Array for Multiple Satellite Links.” Antenna Application Symposium, 2000.
⁵ Bharj, S., et al. “Daisy-Chain-Controlled Multibeam T/R Module for AFSCN.” Antenna Application Symposium, 2004.