1650 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES,VOL. 51, NO. 6, JUNE 2003 Silicon-Based Reconfigurable Antennas—Concepts, Analysis, Implementation, and Feasibility Aly E. Fathy, Senior Member, IEEE, Arye Rosen, Fellow, IEEE, Henry S. Owen, Member, IEEE, Francis McGinty, David J. McGee, Gordon C. Taylor, Robert Amantea, Senior Member, IEEE, P. K. Swain, Stewart M. Perlow, Senior Member, IEEE, and Moniem ElSherbiny Abstract—We report on an innovative reconfigurable antenna concept with significant practical relevance based on the dynamic definition of metal-like conductive plasma channels in high-resis- tivity silicon that are activated by the injection of dc current. The plasma channels are precisely formed and addressed using current high-resolution silicon fabrication technology. These dynamically defined plasma-reconfigurable antennas enable frequency hop- ping, beam shaping, and steering without the complexity of RF feed structures. This concept shows promise for delivering the performance and capabilities of a phased array, but at a reduced cost. However, challenges such as p-i-n biasing circuit complexity and their nonlinearities, as well as antenna efficiency, would still require further investigations. Index Terms—Holographic antennas, plasma antennas, reconfigurable antennas, silicon, SPIN devices. I. BACKGROUND T HE last several years have seen an exponential growth in the development of reconfigurable antennas, i.e., antennas whose aperture can be dynamically modified to enable different functions at different times. The antenna aperture can be specif- ically tailored to the application at hand, greatly increasing an- tenna efficiency and signal-processing speed, while maintaining a high degree of flexibility. The development efforts include real-time or even partial reconfigurability using either semicon- ductor or microelectromechanical switches (MEMS). For ex- ample, Chang et al. [1] utilized p-i-n diode switches to recon- figure a leaky mode patch antenna. Along these lines, we have developed an exciting and innovative approach based on silicon technology to implement dynamic antenna aperture reconfiguration. It is based on using lateral p-i-n devices as conductive radiating elements in a REConfigurable APerture (RECAP) [2]. p-i-n devices act as plasma islands when injected by carriers, thus allowing full control on form, shape, and function of these plasma metallic-like radiators [3]. This approach generally leads to a high level of reconfiguration flexibility and numerous attainable configurations. They can be used to reconfigure, hop, shape, and steer the antenna radiation pattern. Manuscript received May 2, 2002; revised October 30, 2002. This work was supported by Dr. S. Russel, and Dr. L. Corey and J. Smith, both of the Defense Advanced Research Projects Agency. A. E. Fathy, A. Rosen, H. S. Owen, F. McGinty, D. J. McGee, G. C. Taylor, R. Amantea, P. K. Swain, and S. M. Perlow are with the Sarnoff Corporation, Princeton, NJ 08540 USA. M. ElSherbiny is with Future Technology Inc., Laguna Niguel, CA 92677 USA. Digital Object Identifier 10.1109/TMTT.2003.812559 Antenna functionality depends on the antenna’s radiating ele- ments’ parameters, such as the sizes, shapes, and positions of the radiating elements over the aperture. Modifying (i.e., reconfig- uring) the parameters of these radiating elements enables using the same antenna aperture for multiple functions [4]–[10]. For example, the conventional method to achieve reconfigurability is to allow reconnectivity between the various predefined con- ducting regions, using multiple switches to change the size or shape of the antenna aperture. In our approach, there are no predefined conductive patterns, only well-defined channels on the Surface of the high resistivity silicon wafer. Lateral p-i-n devices are the basic building blocks of these channels (SPIN devices), which are optimized to achieve a relatively high con- ductivity (10 carrier/cm ) that is near that of a metal, under dc control [11]. Injection of dc current into a SPIN device will create carriers in the intrinsic region (I-region), which will ap- pear to be metal-like and conductive at RF frequencies. The con- ductivity of the surface p-i-n devices depends on a number of factors, including the carrier lifetime, carrier concentration, and channel depth. Our approach is based on semiconductor (i.e., silicon) pro- cessing technology. Silicon technology was selected to develop these SPIN devices to create well-defined plasma channels, as high resolution is easily achieved today utilizing lithographic technology on silicon. We have developed novel processing techniques to achieve high-performance high-yield lateral p-i-n devices. The developed process in silicon also has the potential for low-cost mass production, and high degree of integration as dc feed lines, control circuitry, and even RF-feed can be part of the developed antennas. This innovative plasma concept can enable a truly reconfig- urable aperture, rather than the conventional switchable config- urations that use multiple switches. For comparison and illustra- tion, Fig. 1 shows a conventional reconfigurable copper dipole antenna, and a similar one made of plasma. The conventional reconfigurable dipole will use the multiplicity of switches to change the dipole length, whereas the plasma approach dynam- ically defines the dipole shape and length using SPIN devices with dc control. We have proposed the configuration shown in Fig. 2 for im- plementing reconfigurable antennas. The antenna comprises an active semiconductor (silicon) layer, on which an - grid of SPIN devices is formed. These diodes are addressable by an integrated control circuitry located at the back of the radiating aperture. The dc-bias lines are feed-through p-i-n’s that are part 0018-9480/03$17.00 © 2003 IEEE