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17 - ELECTROMAGNETICS The electromagnetics program of the ONR has supported basic elec- tromagnetics research in radiation, propagation, and scattering that is highly relevant to the development of Navy radar, communication, and remote sensing systems. Because the electronic devices and circuits that comprise these systems are rapidly changing, there continue to be urgent requirements to solve new and challenging electromagnetic prob- lems. We, therefore, encourage the ONR to continue supporting basic research in electromagnetics. We also recommend that the ONR increase its support of research in the areas of advanced sensor devices and sys- tems for remote sensing, and the electromagnetic analysis and modeling of monolithic integrated circuits. ADVANCED SENSOR DEVICES AND SYSTEMS FOR REMOTE SENSING Radar and radiometer systems show great promise for remotely sensing oceanic and atmospheric parameters that are critical to naval operations. Microwave instruments on the SEASAT satellite launched by the National Aeronautics and Space Administration (NASA) in 1977 demon- strated that synoptic measurements of ocean wave heights, surface winds, and sea-ice coverage can be achieved. The Navy has not been able to fully exploit these early successes owing to the unavailability of suitable satellite platforms. Nevertheless, the Navy has placed sensors on the GEOSAT satellites and is currently planning the N-ROSS experiments to further advance remote sensing techniques. The ONR has supported research that is relevant to the Navy's remote sensing objectives: research programs that study rough (ocean) surface scattering of electromagnetic waves and the microwave emissiv- ity of the ocean that may have payoff in detecting ship wakes. These studies and others that are suggested below should provide important information that will enhance the Navy's remote sensing efforts. Background: The electromagnetic sensing systems for N-ROSS and remote sensing satellites launched by other agencies represent modest technological advances over SEASAT systems. However, the Navy's abil- ity to remotely sense the ocean environment should be greatly enhanced by recent and future technological advances in devices, signal process- ing, and algorithm development. For example, the rapid improvement of microwave, millimeter wave, and infrared components should have major impact on the sensitivity, accuracy, and reliability of advanced sensor systems. Similarly, improvements in computers and signal processing techniques permit the real-time analysis of data and opportunities for adaptive systems that focus surveillance on specific areas or objects such as ships. Finally, increased understanding of electromagnetic propagation and scattering should enhance modeling efforts and the development of useful algorithms that are necessary for extracting oceanic and atmospheric information from sensor data.
- 18 - Objectives: We recommend that the ONR support basic research on advanced concepts for remote sensing instruments. We also encourage the ONR to increase its support of basic electromagnetic studies useful to the development of remote sensing algorithms that can be used to determine environmental parameters such as, for example, wind speed and direction, water vapor and precipitation, ocean currents (both surface and deep ocean), and sea ice. This support should be provided coopera- tively with other ONR programs that have responsibility for programs in oceanography and atmospheric sciences. Participation in such programs by the electronics groups, however, should be limited to only those cases where it is clear that innovative electronic components or sys- tems concepts are being attempted. At present, few oceanographers and atmospheric physicists know the possibilities that are presented by modern electronic technology. Traditionally, they have been more interested in the "science" of their own disciplines and have provided little support for the development of innovative prototype sensors. Cooperative efforts with the electronics program should accelerate the use of modern device technology and systems concepts in measuring the ocean environment. Research Programs: Examples of high risk areas that the elec- tronics program might consider include the following: o Approaches to improve spatial resolution of targets by passive radiometer systems. o Development of low-loss planar antenna arrays for radiometer applications. o Theoretical studies on the imaging of ocean surfaces by syn- thetic aperture radars (SARs). o Use of thinned arrays for space applications. o Effects of surface currents on radiative emissibility and nor- malized radar cross-sections. o Multifrequency doppler radars to measure ocean surface cur- rents . o Novel millimeter wave sensors to measure atmospheric water vapor. ELECTROMAGNETIC ANALYSIS AND MODELING INTEGRATED CIRCUITS As radar, communication, and computing systems process data at higher speeds and operate at higher frequencies and wider bandwidths, the Navy must be concerned with the performance limits placed on integrated circuits by electromagnetic propagation, scattering, and radiation. Circuit designers of high-speed digital and microwave and millimeter wave analog circuits are increasingly confronted by electromagnetics problems that hamper the design and operation of circuits. Therefore, there is a growing need to develop elec- tromagnetic models of devices that can be used in CAD. Background: For many years the ONR has supported a number of high-quality research efforts that have provided valuable insights into obtaining electromagnetic solutions relevant to the Navy's interests.
- 19 - Basic theoretical studies have greatly enhanced the ability to analyze and compute radiative properties of antennas and the scattering characteristics of radar targets. Recently, ONR support has included the study of electromagnetic phenomena in modern integrated circuits. The electromagnetic interactions in high-speed integrated circuits, pulse transmission in planar structures, and the coupling between integrated microstrip transmission lines are examples of new ONR- supported studies. We recommend that additional research support be provided in this area that is aimed at placing radiating elements on monolithic integrated circuits. Objectives: Antennas are important components in radar and communication systems. In the past, antenna design could be accom- plished quite independently of the circuit and system designs. The advent of monolithic integrated circuits, however, suggests that radiating elements might be integrated into the monolithic structure at millimeter wavelengths. This approach minimizes long transmission paths, which will improve the noise performance of the system. For this approach to succeed, a number of important technical issues must be resolved. For example, viable device models must be created owing to the increased role that CAD software will play in the design and fabrication process; new and innovative architectures are needed to efficiently utilize the chip real estate; new electronic components such as phase shifters must be created; and the propagation, coupling, and radiative properties of millimeter waves must be understood for the monolithic circuit. We encourage the electronics program to support basic research that addresses the above issues and those related to the eventual implementation of monolithic millimeter wavelength technology. The advantages that this technology presents for compact radar and communication systems indicate that the payoff will be great in the future. The analysis and modeling of monolithic integrated circuits require that researchers must be well-versed in both solid state electronics and electromagnetics. Consequently, we encourage the electronics program's support of an interdisciplinary research program in which the principal investigators are closely coupled to integrated circuit design and fabrication. Recent advances in optoelectronic devices and superconductivity present new opportunities for research support by the ONR in the following two areas. Optical Control of Microwave Devices: Recently, there has been considerable work done on the development of new devices for use in monolithic optical integrated circuits. To date, optical integrated circuits and monolithic microwave integrated circuits have generally been considered to be two separate fields of research. However, the fact that the same materials, such as GaAs, can be effectively used to produce both optical and microwave devices suggests that the two fields may merge to produce optical microwave monolithic integrated circuits. These require strong backgrounds in both electromagnetics and solid state areas. There have been successful techniques for optical con- trols of microwave signals, including optical modulation and switching, optical phase shifters, or optical generation and detection of micro-
- 20 - wave signals. Since the conventional microwave waveguides and phase shifters are usually bulky, the use of optical components will reduce size and weight problems. The optical system may also be immune from electromagnetic interference. Thus the research in the optical control of microwave devices, including the monolithic optoelectronic inte- grated circuits, should be very important for future electronic systems. Superconducting Antennas and Integrated Circuits: The recent discovery of high-temperature superconducting materials has revived interest in the research on microwave integrated circuits and antennas using superconducting materials, which was under intensive investiga- tion in the late 1960s. The major reason is that superconductors will reduce the conducting loss significantly in the propagation structures such as transmission lines and antennas, thus enhancing the responsiv- ity or the signal-to-noise ratio. The possibility of high-temperature superconductors may not only eliminate the necessity of cooling systems but also significantly improve the performance of the microwave antenna system. However, more work is necessary to evaluate the overall performance of a superconducting microwave integrated circuit with antennas.
