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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

RF MEMS and Their Applications in NASA's Space Communication Systems

Radio frequency (RF) and microwave communication systems rely on frequency, amplitude, and phase control circuits to efficiently use the available spectrum. Phase control circuits are required for electronically scanning phase array antennas that enable radiation pattern shaping, scanning, and hopping. Two types of phase shifters, which are the phase control circuits, are most often used. The first is comprised of two circuits with different phase characteristics such as two transmission lines of different lengths or a high pass and low pass filter and a switch that directs the RF power through one of the two circuits. Alternatively, a variable capacitor, or varactor, is used to change the effective electrical path length of a transmission line, which changes the phase characteristics. Filter banks are required for the diplexer at the front end of wide band communication satellites. These filters greatly increase the size and mass of the RF/microwave systems, but smaller diplexers may be made with a low loss varactor or a group of capacitors, a switch and an inductor.

Williams, W. Daniel↗
NASA NTRS1983

Design considerations for high-power VHF radar transceivers: The Poker Flat MST radar phase control system

Sixty-four separate 50-kW peak-power transmitters are distributed throughout the 200 x 200 meter Poker Flat MST radar antenna array. The relative phase of each transmitter is automatically controlled by a 64-channel unit located in the main building at the edge of the antenna. The phase control unit is described. In operation the RF pulse from a transmitter coupler is power divided and compared with the phase reference in a mixer. The mixer output is low-pass filtered and sampled near the center of the resulting video pulse by an amplifying sample-and-hold integrated circuit. Phase control is effected by maintaining the mixer output pulse near zero volts by amplifying the sample-and-hold output which then drives the voltage-controlled phase shifter in the direction to null the mixer output. The voltage-controlled shifter achieves over 360 deg phase shift in the range from 0.7 to 24 volts. When the voltage into the shifter tracks to either voltage limit the wrap-around control resets the voltage so that the shifter is always operating within its control range.

Ecklund, W. L.↗
NASA NTRS2010

Nanoionics-Based Switches for Radio-Frequency Applications

Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

Nessel, James↗
NASA NTRS1973

Automatic quadrature control and measuring system

Quadrature is separated from amplified signal by use of phase detector, with phase shifter providing appropriate reference. Output of phase detector is further amplified and filtered by dc amplifier. Output of dc amplifier provides signal to neutralize quadrature component of transducer signal.

Hamlet, J. F.↗
NASA NTRS1977

Tracking a phase-shift-keyed signal

In detector, phase shifter is used to generate negative phase shift opposing detected phase angle. This produces converted series sideband and component carrier, with residual carrier signal and converted series sideband and component carrier added together to produce tracking signal.

Villarreal, S.↗
NASA NTRS1993

High-Temperature-Superconductor Films In Microwave Circuits

Report discusses recent developments in continuing research on fabrication and characterization of thin films of high-temperature superconducting material and incorporation of such films into microwave circuits. Research motivated by prospect of exploiting superconductivity to reduce electrical losses and thereby enhancing performance of such critical microwave components as ring resonators, filters, transmission lines, phase shifters, and feed lines in phased-array antennas.

Bhasin, K. B.↗
NASA NTRS1998

A Fresh Look at Coupled-Oscillator Spatial Power Combining

Quasi-optical oscillators were proposed a little more than ten years ago as a means of developing the power levels needed for applications at millimeter frequencies using large numbers of individual semiconductor devices each of which produces only a modest amount of power [J.W. Mink, IEEE Trans. MTT., vol. 34, p. 273, 19861. An operating system was demonstrated soon after [Z.B. Popovic et. al, Int. J. Infrared and Millimeter Waves, v. 9, p. 647, 1988] in the form of a so-called grid oscillator. This device constituted a rectangular array of oscillating devices that are mutually coupled so that they oscillator coherently. The interconnecting lines in one direction serve as radiators so that the oscillators radiate directly, and the radiated fields add. Subsequently, coupled oscillators using resonant transmission line lengths was demonstrated by Mortazawi and Itoh [IEEE Trans. MTT., vol. 38, p. 86,1990). In recent work, coupled-oscillator power combiners have received less attention, with amplifier/combiners receiving more attention. Specific weaknesses of spatial-combining oscillators have motivated this transition. Namely, the oscillators employ low-Q resonators (resulting in low signal quality) and no clear means of modulation has been identified until recently. In this presentation, we review coupled-oscillator combiners in broad terms, indicating the features that make particular systems viable. We indicate how these features can be reconciled to functional requirements for system applications. Comparisons are drawn between two approaches to obtain mutual coupling: One employs low-Q oscillator circuits at each site, with concomitantly high propensity for the oscillators to couple. The other approach employs moderate-Q oscillators at each site with the concomitant requirement to tune the oscillators so that they share a range of frequencies over which they can couple and lock. In either case, precise frequency control and modulation can be achieved through locking to an external frequency source that ensures high quality signals. A recent development in coupled-oscillator arrays provides a means for beam-steering the radiation field of coupled oscillators through de-tuning of the edge elements in the array. This detuning introduces a progressive phase shift across the oscillator array. This 0 suggests architectures that can replace the functionality of a phased array without the cost 0 incurred by phase shifters. A comprehensive theory of the phase interactions among devices in such arrays is under development [e.g., Pogorzelski, York, and Maccarini, 1998 AP-S International Symposium, Atlanta, GA. June, 19981.

Pearson, L.W.↗
NASA NTRS2013

A 2x2 W-Band Reference Time-Shifted Phase-Locked Transmitter Array in 65nm CMOS Technology

This paper presents a complete 2x2 phased array transmitter system operating at W-band (90-95 GHz) which employs a PLL reference time-shifting approach instead of using traditional mm-wave phase shifters. PLL reference shifting enables a phased array to be distributed over multiple chips without the need for coherent mm-wave signal distribution between chips. The proposed phased array transmitter system consumes 248 mW per array element when implemented in a 65 nm CMOS technology.

PLL Reference↗
NASA NTRS1992

Zone plate lens antennas for millimeter and submillimeter wavelengths

Zone plate lenses are a type of focusing element which function essentially as differential phase shifters, having a relatively few, coarsely quantized phase delays across the incident beam of radiation. The major advantages are ease of fabrication and much reduced thickness, compared to conventional refractive focusing elements. These considerations are both of particular importance for the submillimeter range, in which manufacturing tolerances for curved optical elements can pose significant problems, and where the absorption of readily available dielectric materials is quite large. In this presentation we briefly review the theory of zone plate lens operations, present a relatively simple method for calculating the aperture efficiency of zone plate lenses used as antennas, and show some theoretical and measured results in the 100 GHz range.

Goldsmith, Paul F.↗
DOE OSTI2021

Inverse Biot–Savart Optimization for Superconducting Accelerator Magnets

Superconducting (SC) magnets for accelerator concepts are often synthesized by numerically optimizing magnetic field waveforms, a process that requires a subsequent solution of a constrained inverse problem to identify suitable SC magnet windings. When the desired field distribution is intuitive, the inverse process is facilitated by seeding preconceived coil distributions into design optimization methods for refinement. With more complex magnetic field distributions, an initial design may be unknown, and topology optimization tools are required to synthesize current distributions without a priori guidance from a subject matter expert. In this work, we develop a constrained inverse Biot-Savart topology optimization methodology that synthesizes optimal distributions of current density in racetrack-like SC coils. The problem structure is exploited through a computationally efficient quadratic programming formulation, and the method is applied to recently published magnetic field waveforms for a recirculating proton phase shifter, a proton therapy gantry, and dipole magnets with sharp field transitions. The method and results herein identify novel winding configurations that can help magnet designers bring accelerator concepts to fruition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Novel High-Power Microwave Circulator Employing Circularly Polarized Waves

A novel four-port circulator is presented which uses an inline ferromagnetic element to allow for transmission or reflection depending on the sense of the incident circularly polarized wave. This configuration has been shown to reduce the dependency on ferrite anisotropy and support higher power, low rf loss, operation. An analytic analysis of this device is presented here alongside corroborating cold test data of the first prototype. High-power operation was performed at 2.856 GHz, with input power levels up to 8 MW for 3.5 μs in a pressurized nitrogen environment. The results from this research not only demonstrate ability to eliminate the use of greenhouse insulators, such as SF6, but also provide conceptual groundwork for a new class of ultrahigh power (50 MW+) nonreciprocal networks including circulators, isolators, phase shifters, and rf switches.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1995

Method and Apparatus for Measuring Fluid Flow

The invention is a method and apparatus for monitoring the presence, concentration, and the movement of fluids. It is based on utilizing electromagnetic measurements of the complex permittivity of the fluids for detecting and monitoring the fluid. More particularly the apparatus uses one or more microwave probes which are placed at the locations where the measurements are to be made. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids, based on their dielectric constant at the probe. The apparatus can be used for multiple purposes including measures of flow rates, turbulence, dispersion, fluid identification, and changes in flow conditions of multiple fluids or multiple states of a single fluid in a flowline or a holding container. The apparatus includes a probe consisting of two electrical conductors separated by an insulator. A radio frequency signal is communicated to the probe and is reflected back from the portion of the probe exposed to the fluid. The radio frequency signal also provides a reference signal. An oscillator generates a second signal which combined with each of the reference signal and the reflected signal to produce signals of lower frequencies to facilitate filtering and amplifying those signals. The two signals are then mixed in a detector to produce an output signal that is representative of the phase and amplitude change caused by the reflection of the signal at the probe exposed to the fluid. The detector may be a dual phase detector that provides two such output signals that are in phase quadrature. A phase shifter may be provided for selectively changing the phase of the reference signal to improve the sensitivity of at least one of the output signals for more accurate readings and/or for calibration purposes. The two outputs that are in quadrature with respect to each other may be simultaneously monitored to account for drift errors. The output signals are digitized and provided to a computer at a sample rate which may be very high. The computer is operable to identify the fluid based on its complex permittivity as may be useful for identifying the flow rates, determining the fluid mixture ratio, detecting impurities in the fluid, and so forth. Novelty is believed to reside in the use of the real part of complex permittivity to measure small difference in permittivity of the fluid.

Arndt, G. Dickey↗
NASA NTRS1983

Beam forming networks for mm-wave satellite communications

Technology features of a beam forming network (BFN) employing ferrite devices to provide multiple beam antenna pattern control for satellites used in telecommunications are described. The BFN produces the phase and amplitude distribution for each horn in an antenna array, with the number of horns in the array being equal to the number of outputs in the BFN. One configuration involves microwave switches and permits illumination of a single feed horn at a time using ferrite latching circulators that function by reversing the circulation direction. A more flexible version, yielding a variable amplitude distribution across the feed horn array to accommodate changing traffic patterns or serving a TDMA system, includes the capability of forming nulls in the system with a variable phase shifter in the input ports. The antenna scan angles in phased arrays can be limited to 8 deg from center. Acceptable insertion losses have been demonstrated in BFN with hundreds of ports and switching rates as high as 10 kHz.

Sharon, T. E.↗
NASA NTRS1988

Wide-Band, Wide-Scan Antenna For Circular Polarization

Circular polarization generated by linearly polarized elements. Basic two-by-two subarray of antenna elements made of microstrip patches. Patches arranged in orthogonal pattern. Fed through different phase shifters so signal at feed points have same orthogonal relationship in phase. Antennas of this general type useful in communications and phased-array radar.

Huang, John↗
NASA NTRS1983

Digital Phase-Shift Standard

Digital phase-shift standard used in combination with oscillator to calibrate other phase standards and phase-angle voltmeters. Phase-shifter circuit provides two square-wave outputs, A and B, with phase difference between them selectable in 30 degrees increments. Circuit is used with input signals as low as 1 volt rms, in almost any waveform.

Cramp, J. A.↗
NASA NTRS1986

Double reference pulsed phase locked loop

A double reference pulse phase locked loop is described which measures the phase shift between tone burst signals initially derived from the same periodic signal source (voltage controlled oscillator) and delayed by different amounts because of two different paths. A first path is from the transducer to the surface of a sample and back. A second path is from the transducer to the opposite surface and back. A first pulse phase locked loop including a phase detector and a phase shifter forces the tone burst signal delayed by the second path in phase quadrature with the periodic signal source. A second pulse phase locked loop including a second phase detector forces the tone burst signals delayed by the first path into phase quadrature with the phase shifted periodic signal source.

Heyman, J. S.↗
NASA NTRS1992

Quartz/fused silica chip carriers

The primary objective of this research and development effort was to develop monolithic microwave integrated circuit (MMIC) packaging which will operate efficiently at millimeter-wave frequencies. The packages incorporated fused silica as the substrate material which was selected due to its favorable electrical properties and potential performance improvement over more conventional materials for Ka-band operation. The first step towards meeting this objective is to develop a package that meets standard mechanical and thermal requirements using fused silica and to be compatible with semiconductor devices operating up to at least 44 GHz. The second step is to modify the package design and add multilayer and multicavity capacity to allow for application specific integrated circuits (ASIC's) to control multiple phase shifters. The final step is to adapt the package design to a phased array module with integral radiating elements. The first task was a continuation of the SBIR Phase 1 work. Phase 1 identified fused silica as a viable substrate material by demonstrating various plating, machining, and adhesion properties. In Phase 2 Task 1, a package was designed and fabricated to validate these findings. Task 2 was to take the next step in packaging and fabricate a multilayer, multichip module (MCM). This package is the predecessor to the phased array module and demonstrates the ability to via fill, circuit print, laminate, and to form vertical interconnects. The final task was to build a phased array module. The radiating elements were to be incorporated into the package instead of connecting to it with wire or ribbon bonds.

Source record↗