Sense-and-Adapt Architectures for Radio Transmitters in Changing Environments
Abstract
AbstractSense-and-adapt architectures for radio transmitters in changing environmentsPI: Taylor Barton, University of Colorado Bo"ulderThe objective of this research is to investigate circuit architectures enabling RF transmitters tooperate in environments in" which loading conditions vary. Example applications range from HFto Ka band and above, and include active scan coefficient variati""on in phased array systems,environmental or operator effects in mobile applications, and imaging and industrialapplications. Becau""se power amplifiers (PAs) are typically designed to operate into a fixedimpedanceload, reflected power due to driving point impedan""ce mismatch leads to substantialsystem degradation. Examples of adverse effects include instability, reduced delivered power,and e"xcess power dissipation leading to temperature rise and device failure. Isolators orcirculators can be inserted between the PA and" varying load to protect the active devices, but atthe expense of efficiency, size, and weight.The transmitter architectures propo"sed in this work will sense load mismatch conditions andautomatically react in order to reduce mismatch and keep efficiency high. T"o achieve this goal,our technical approach has three research areas: (1) fundamental research to understandcapabilities and limita""tions of impedance tuning techniques, with a focus on energy efficiency;(2) design of novel integrated sensors in III-V materials f"or in-situ characterization; and (3)control algorithm development to enable closed-loop sense-and-adapt behavior whilemaintaining" stability.Our architectural approach will draw on the PI~s experience with outphasing PAs, in whichload modulation of multiple am""plifiers is induced as a means of modulating output power. Wewill show that, by reconfiguring the power combining network, load imp"edance variation can bereduced using an outphasing-like power combining architecture. Our research will furthermoreinclude analysi"s of the relative losses and performance metrics of multiple methods of tuning,such as power combining, direct tuning with multiple"" types of devices, and topologies tominimize the number of tunable elements required.To support adaptive behavior of this structur""e, the second major research component of thisprogram will focus on sensor circuits that can be monolithically integrated with the"" PA.Integration of sensors such as RF and dc power, reflected power, or direct impedance sensingwill enable measurement of operati"ng conditions at the device plane. The objective in this area isto understand the fundamental capabilities available in III-V techn"ologies, in which limiteddevice availability restricts the possible topologies. Finally, we will close a control loop based onthe"" sensed operating conditions to automatically react to varying loads, while traversing a path inthe impedance plane that avoids PA"" instabilities.The completed design will be benchmarked against conventional techniques in terms of energyefficiency, frequency op""erating range, and physical size and weight. We will target X bandtransmission in Gallium Nitride MMIC technology for the hardware"" demonstration of ourapproach; additionally, this research will include a technical analysis of how this technique canbe extended"" to higher frequencies.Currently available alternatives to our proposed technology include isolators and circulators,too bulky to"" be practical, or conventional tunable matching networks having higher insertion lossand lacking the ability for automatic control"" based on tightly-integrated sensors. By reducingSWaP-C in phased-array and related systems, the proposed research will result in m""ore effectiveuse of existing communications and RADAR applications, and can enable new and innovativeuses of the electromagnetic s"pectrum in support of the Navy and Marine Corps mission.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 29, 2017
- Source ID
- N000141712951
Entities
People
- Taylor Wallis Barton
Organizations
- Office of Naval Research
- Regents of the University of Colorado
- United States Navy