Papers by Robert Romanofsky
In the past few years, our group has designed, fabricated and tested several ferroelectric tunabl... more In the past few years, our group has designed, fabricated and tested several ferroelectric tunable components, in collaboration with NASA Glenn Research Center. Among the components studied are microstrip tunable resonators, filters, diplexers, and couplers. Tunable filters with gold as well as YBCO high temperature superconductor (HTS) electrodes have been studied using the conductor/ferroelectric/dielectric two-layered microstrip configuration. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of the ferroelectric thin film. Two pole ferroelectric tunable HTS filters using the YBCO/STO/LAO two-layered microstrip yielded low insertion loss as low as 1.5 dB, and large frequency tunability (∼2.3 GHz) at 24 K, with a peak electric field of 80 kV cm −1 for electrical tuning. The critical design issues for realizing practical tunable filters will be addressed. These include design for (i) large tunability, (ii) low insertion l...
Broadband, Low-Loss Phase Shifters Based on Thin Ferroelectric Films
Several different types of microwave transmission line phase shifters based on thin ferroelectic ... more Several different types of microwave transmission line phase shifters based on thin ferroelectic films have been developed at the NASA Glenn Research Center. These include a series of coupled microstrip lines, slotline incorporating Marchand balms, odd-mode coplanar strips, and hybrid devices incorporating a switch to toggle the output termination between an open and virtual short circuit. A review of the theory of operation of each of these devices will be presented along with measured performance. Also, devices of the first variety have been subjected to total dose (proton) radiation exposure using a 200 MeV beam energy with a total dose up to nearly 1 kRad (Si). Results of these radiation tests will be discussed.
Cellular Reflectarray Antenna
The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that m... more The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.
This work proposes a concept on a novel scanning phased array, based on thin film ferroelectric p... more This work proposes a concept on a novel scanning phased array, based on thin film ferroelectric phase shifters, for an X-band precipitation monostatic radar.
Integration of a high-temperature superconductor with a nonlinear dielectric ferroelectric such a... more Integration of a high-temperature superconductor with a nonlinear dielectric ferroelectric such as strontium titanate, i.e., SrTiO/sub 2/ (STO), has created a new class of electrically tunable low-loss microwave components. We have designed and fabricated frequency and phase agile components using a conductor/ferroelectric/dielectric two-layered microstrip configuration. Some examples of these components are: microstrip ring resonators, local oscillators, edge coupled filters, and phase-shifter circuits. These structures have been fabricated using YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// or gold conductor-based microstrip lines fabricated on lanthanum aluminate (LaAlO/sub 3/) or magnesium oxide (MgO) substrates coated with an STO thin film. Frequency and phase agility are achieved using the nonlinear dc electric-field dependence of the relative dielectric constant of STO ferroelectric thin him (E/sub rSTO/). In this paper, we will present an assessment of the progress that our group ...
An external, noncontact electrooptic measurement system, designed to operate at the wafer level w... more An external, noncontact electrooptic measurement system, designed to operate at the wafer level with conventional wafer probing equipment and without any special circuit preparation, has been developed. Measurements have demonstrated the system's ability to probe continuous and pulsed signals on microwave integrated circuits on arbitrary substrates with excellent spatial resolution. In addition, it has been shown that the electrooptic probe tip can measure voltage values on an integrated circuit chip, even in areas where physical contact made by a test instrument would be inappropriate. Experimental measurements on a variety of digital and analog circuits, including a GaAs selectively doped heterostructure transistor prescaler, an NMOS silicon multiplexer, and a GaAs power amplifier MMIC (monolithic microwave integrated circuit) are reported.<<ETX>>
WFL: Microwave Applications of Thin Ferroelectric Films
A Review of Antenna Technologies for Future NASA Exploration Missions
NASA's plans for the manned exploration of the Moon and Mars will rely heavily on the develop... more NASA's plans for the manned exploration of the Moon and Mars will rely heavily on the development of a reliable communications infrastructure from planetary surface-to-surface, surface-to-orbit and back to Earth. Future missions will thus focus not only on gathering scientific data, but also on the formation of the communications network. In either case, unique requirements become imposed on the antenna technologies necessary to accomplish these tasks. For example, proximity (i.e., short distance) surface activity applications such as robotic rovers, human extravehicular activities (EVA), and probes will require small size, lightweight, low power, multi-functionality, and robustness for the antenna elements being considered. In contrast, trunk-line communications to a centralized habitat on the surface and back to Earth (e.g., relays, satellites, and landers) will necessitate high gain, low mass antennas such as novel inflatable/deployable antennas. Likewise, the plethora of low...
Superconducting Field-Effect Transistors
Devices offer switching speeds greater than semiconducting counterparts. High-Tc superconducting ... more Devices offer switching speeds greater than semiconducting counterparts. High-Tc superconducting field-effect transistors (SUPEFETs) investigated for use as electronic switches in delay-line-type microwave phase shifters. Resemble semiconductor field-effect transistors in some respects, but their operation based on different principle; namely, electric-field control of transition between superconductivity and normal conductivity.
Future Space Communications subsystems will utilize GaAs Monolithic Microwave Integrated Circuits... more Future Space Communications subsystems will utilize GaAs Monolithic Microwave Integrated Circuits (MMIC's) to reduce volume, weight, and cost and to enhance system reliability. Recent advances in GaAs MMIC technology have led to high-performance devices which show promise for insertion into these next generation systems. The status and development of a number of these devices operating from Ku through Ka band will be discussed along with anticipated potential applications.
at NASA Lewis Research Center
Since the discovery of high temperature superconductivity in 1987, NASA Lewis Research Center has... more Since the discovery of high temperature superconductivity in 1987, NASA Lewis Research Center has been involved in efforts to demonstrate its advantages for applications involving microwave electronics in space, especially space communications. The program has included thin film fabrication by means of laser ablation. Specific circuitry which has been investigated includes microstrip ring resonators at 32 GHz, phase shifters which utilize a superconducting, optically activated switch, an 8x8 32 GHz superconducting microstrip antenna array, and an HTS-ringresonator stabilized oscillator at 8 GHz. The latter two components are candidates for use in space experiments which will be described in other papers. Experimental data on most of the circuits will be presented as well as, in some cases, a comparison of their performance with an identical circuit utilizing go_d or cop_er metallization.
This work proposes a concept on a novel scanning phased array, based on thin film ferroelectric p... more This work proposes a concept on a novel scanning phased array, based on thin film ferroelectric phase shifters, for an X-band precipitation monostatic radar.
Physical Layer Communications Technologies: Harsh Planetary Environments
IEEE Microwave Magazine
IEEE Open Journal of Nanotechnology
Commercially available, chemical vapor deposition grown, graphene has been used to realize voltag... more Commercially available, chemical vapor deposition grown, graphene has been used to realize voltage-gate tunable, microwave power detectors. Corbino disc structures with chrome/gold contacts have been fabricated on top of graphene deposited on P-type silicon substrates with silicon dioxide gate oxides. Devices of varying sizes were used to detect a 433.92 MHz signal. These test structures exhibited a peak power detection sensitivity of 3.25 mV/mW at 292 K and 5.43 mV/mW at 80 K. The improved graphene detectors exceed the sensitivity of previously reported graphene detectors, 0.86 mV/mW, as well as previously explored carbon nanotube bolometers, 0.36 mV/mW.
Past, present and future of ferroelectric and multiferroic thin films for array antennas
Multidimensional Systems and Signal Processing
In addition to providing a number of microwave components with frequency agility and voltage-cont... more In addition to providing a number of microwave components with frequency agility and voltage-controlled impedance matching, ferroelectric thin films have enabled electrical-control of beam-steerabilty in both reflectarray and phased array antennas. We present a brief history of developments, beginning in the 1830s, which led to the realization of array antennas based on ferroelectric thin films. We highlight key performance differences provided by competing thin film deposition techniques, and we discuss the outlook of the impact that voltage-controlled magnetism and magnetoelasticity (provided by emerging multiferroic thin films) will have on future array antenna technologies.
Thermoelectric Graphene Nano-Constrictions as Detectors of Microwave Signals
IEEE Transactions on Nanotechnology
IETE Journal of Education
Nasa Sti Recon Technical Report N, Sep 1, 1995
Demands on the mixer were twofold. First, to optimize receiver sensitivity since front-end gain w... more Demands on the mixer were twofold. First, to optimize receiver sensitivity since front-end gain was limited, the mixer An X-band Si-diode singlybalanced mixer developedspecif-was required not only to downconvert the signal without ically for cryogenic operation is presented. In order to reduce adversely affecting the pre-amplifier but also to minimize the thermal demands on a mechanical cooler, the mixer was signal degradation. Hence, low conversion loss, a low noise designed to operate with a minimum of local oscillator (LO) figure,and ahighport-to-port isolation were desirable. Second, power. That is, since the LO had to be cooled to reduce phase the mixer had to minimize thermal demands on the cooler by noise, it was desirable to minimize the LO drive.Novel embed-operating with a starved local oscillator (LO). Because the LO ding circuit strategy was responsible for nearly theoreticalper-was inherently inefficient and had to be cooled in order to formance.The signal-matchingcircuit simultaneouslyprovided reduce phase noise, minimizing the required drive level of the a reactive termination to the image, sum, and first, second, and mixer was tantamount to reducing the cooling power requirethird LO harmonic frequencies. A conversion loss of 3.2 dB at ment. For example, ifthe LO is stabilized with a superconduct-77 K with an LO drive of +1 dBm was measured. This loss ing resonator and has an efficiency of I0 percent and if the included IF filter, dc block, and hybrid coupler losses. Mixer mixer requires 10dBm of LO drive, then the cryocooler heat conversion loss is shown to be consistent with the theoretical load capacity must be increased by about 100 roW. Cooling performance limit expected from the intrinsic diode. The rela-the mixer increases the overall receiver sensitivity and permits tionship among junction capacitance, flat-band potential, and convenient integration of all the critical front-end functions. conversion loss is examined. Many conventional mixerswith competing performance would severely tax the cooler. Figure 1 shows the conversion loss performance of a very good commercially available mixer Lewis Research Center
Discriminator stabilized superconductor/ferroelectric thin film local oscillator
Multi-mode broadband patch antenna
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Papers by Robert Romanofsky