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NASA NTRS2012

Design and Performance of Micro-Spec, an Ultra Compact High-Sensitivity Far-Infrared Spectrometer for SPICA

Micro-Spec (u-Spec) is a high-performance spectrometer working in the 250-700-micrometer wavelength range, whose modules use low-loss superconducting microstrip transmission lines on a single 4-inch-diameter silicon wafer. Creating the required phase delays in transmission lines rather than free space allows such an instrument to have, in principle, the performance of a meter-scale grating spectrometer. Such a dramatic size reduction enables classes of instruments for space that would be impossible with conventional technologies. This technology can dramatically enhance the long-wavelength capability of the space infrared telescope for cosmology and astrophysics SPICA. u-Spec is analogous to a grating spectrometer. The phase retardation generated by the reflection from the grating grooves is instead produced by propagation through a transmission line. The power received by a broadband antenna is progressively divided by binary microstrip power dividers, and the required phase delays are generated by different lengths of microstrip transmission lines. by arranging these outputs along a circular focal surface, the analog of a Rowland spectrometer can he created. The procedure to optimize the Micro-Spec design is based on the stigmatization and minimization of the light path function in a two-dimensional hounded region, which results in an optimized geometry arrangement with three stigmatic points. In addition, in order to optimize the overall efficiency of the instrument, the emitters are directed to the center of the focal surface. The electric field amplitude and phase as well as the power transmitted and absorbed throughout the region are analyzed. Measurements are planned in late summer to validate the designs.

Cataldo, Giuseppe↗

NASA NTRS2001

Electrical Transmission on the Lunar Surface: DC Transmission - Part 1

This report summarizes a portion of the results from a grant at Auburn University to study the electrical and thermal energy management for lunar facilities. Over the past year (June 1989 to May 1990) the following topics have been investigated: June 1989 to November 1989 - Literature survey, assessment of lunar power needs, and overview study of the requirements of a lunar power system; November 1989 to April 1990 - Develop models for the study of dc electrical power transmission lines for the lunar surface; March 1990 to May 1990 - Develop models for the study of ac electrical power transmission lines for the lunar surface. Because of the large amount of information in the model development and application to a wide parameter space this report is being bound separately. This report specifically contains the model development and parameter study for dc electrical power transmission lines. The end of the funding year (May 1990) will conclude with an annual report including the literature survey, the overview of the requirements of a lunar power system, and summaries of the dc and ac models of electrical transmission lines.

Gordon, Lloyd B.↗

NASA NTRS2002

Low-Loss, High-Isolation Microwave Microelectromechanical Systems (MEMS) Switches Being Developed

Switches, electrical components that either permit or prevent the flow of electricity, are the most important and widely used electrical devices in integrated circuits. In microwave systems, switches are required for switching between the transmitter and receiver; in communication systems, they are needed for phase shifters in phased-array antennas, for radar and communication systems, and for the new class of digital or software definable radios. Ideally, switches would be lossless devices that did not depend on the electrical signal's frequency or power, and they would not consume electrical power to change from OFF to ON or to maintain one of these two states. Reality is quite different, especially at microwave frequencies. Typical switches in microwave integrated circuits are pin diodes or gallium arsenide (GaAs) field-effect transistors that are nonlinear, with characteristics that depend on the power of the signal. In addition, they are frequency-dependent, lossy, and require electrical power to maintain a certain state. A new type of component has been developed that overcomes most of these technical difficulties. Microelectromechanical (MEMS) switches rely on mechanical movement as a response to an applied electrical force to either transmit or reflect electrical signal power. The NASA Glenn Research Center has been actively developing MEMS for microwave applications for over the last 5 years. Complete fabrication procedures have been developed so that the moving parts of the switch can be released with near 100-percent yield. Moreover, the switches fabricated at Glenn have demonstrated state-of-the-art performance. A typical MEMS switch is shown. The switch extends over the signal and ground lines of a finite ground coplanar waveguide, a commonly used microwave transmission line. In the state shown, the switch is in the UP state and all the microwave power traveling along the transmission line proceeds unimpeded. When a potential difference is applied between the cantilever and the transmission line, the cantilever is pulled downward until it connects the signal line to the ground planes, creating a short circuit. In this state, all the microwave power is reflected. The graph shows the measured performance of the switch, which has less than 0.1 dB of insertion loss and greater than 30dB of isolation. These switches consume negligible electrical power and are extremely linear. Additional research is required to address reliability and to increase the switching speed.

Ponchak, George E.↗

NASA NTRS1984

Millimeter wave transmission systems and related devices

A survey was made of the state-of-the-art in millimeter (20 GHz to 300 GHz) wave transmission systems and related devices. The survey includes summaries of analytical studies and theoretical results that were obtained for various transmission line structures. This material was supplemented by further analysis where appropriate. The transmission line structures are evaluated in terms of electrical performance, ease of manufacture, usefulness for building other devices and compatibility with solid state devices. Descriptions of waveguide transmission lines which have commonly been used in the microwave frequency range are provided along with special attention given to the problems that these guides face when their use is extended into the millimeter wave range. Also, guides which have been introduced specifically to satisfy the requirements of millimeter wave transmission are discussed in detail.

Hebert, L. M.↗

DOE OSTI2024

Electron cyclotron emission quasi-optical transmission system on the HL-3 tokamak

A new quasi-optical (QO) Electron Cyclotron Emission (ECE) transmission system has been established on the HL-3 tokamak, which includes a focusing QO mirror combination and a long-distance transmission line. This system was developed to meet the requirements for poloidal spatial resolution and the high signal-to-noise ratio needed for magnetohydrodynamic (MHD) instability studies using ECE on the HL-3. The QO mirror combination was installed inside the vacuum chamber for focusing. Laboratory test results, theoretical calculations, and synthetic ECE simulation results indicate that the Gaussian beam can meet the spatial resolution requirements for the accurate measurement of the MHD instability on the q = 1/2/3 surfaces, corresponding to the poloidal mode numbers m = 3/6/9. This includes good diagnostic poloidal spatial resolution for the important 2/1 and 3/2 modes. At the front end of the transmission line, a high-efficiency mode converter was designed to transition the TE 10 mode to the HE 11 mode for input into the transmission line, with an insertion loss of less than 1.5 dB. A 30 m long-distance corrugated oversized waveguide was constructed, with transmission losses ranging from 6 to 10 dB in the 60–120 GHz range. Polarization adjustment results show that the polarization offset and geometric spatial polarization angle change consistently, which can provide a reference for polarization adjustment in other complex structured transmission lines. As a result, the newly established ECE QO transmission system will provide strong support for future physics research involving ECE on the HL-3.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2025

Impact of Geomagnetic Induced Current Neutral Blocking Devices on Distance Relays in Sub-transmission Networks with IBR

Geomagnetically induced currents (GICs) can flow through transmission lines during geomagnetic disturbances, such as solar flares or coronal mass ejections. These currents can cause problems like transformer saturation and equipment damage. The most common method of mitigating GICs involves installing GIC neutral blocking devices (NBDs) in transformer neutrals. However, the wide application of capacitive GIC blocking devices may have unintended adverse effects on other devices, such as distance protection relays. As the number of inverter-based resources being connected to the transmission and sub-transmission systems increases, the likelihood of a sub-transmission line protected by a distance relay connected to a transformer with NBDs is increasing. Therefore, distance relays fed by IBRs and transmission lines with GIC-NBDs must be studied. This paper studies the effect of GIC-NBDs on a 69kV sub-transmission line of various lengths fed by a 25 MVA IBR and synchronous source. This work focused on the behavior of the GIC-NBDs using the measured apparent phase-to-ground and phase-to-phase impedance calculated by the relay and the source impedance ratio (SIR) during various electrical faults.

Patel, Trupal R [Sandia National Laboratories (SNL↗

NASA NTRS2013

Implementation of a Novel Low-Cost Low-Profile Ku-Band Antenna Array for Single Beam Steering from Space

Phased array antennas afford many advantages over traditional reflector antennas due to their conformality, high aperture efficiency, and unfettered beam steering capability at the price of increased cost and complexity. This paper eliminates the complex and costly array backend via the implementation of a series fed array employing a propagation constant reconfigurable transmission line connecting each element in series. Scanning can then be accomplished through one small (less than or equal to 100mil) linear motion that controls propagation constant. Specifically, each element is fed via a reconfigurable coplanar stripline transmission line with a tapered dielectric insert positioned between the transmission line traces. The dielectric insert is allowed to move up and down to control propagation constant and therefore induce scanning. We present a 20 element patch array design, scanning from -25 deg. less than or equal to theta less than or equal to 21 deg. at 13GHz. Measurements achieve only10.5 deg. less than or equal to theta less than or equal to 22 deg. scanning due to a faulty, yet correctable, manufacturing process. Beam squint is measured to be plus or minus 3 deg. for a 600MHz bandwidth. This prototype was improved to give scanning of 3.5 deg. less than or equal to theta less than or equal to 22 deg. Cross-pol patterns were shown to be -15dB below the main beam. Simulations accounting for fabrication errors match measured patterns, thus validating the designs.

Reconfigurable Transmission Lines↗

NASA NTRSDate not supplied

A Compact Dual-Band Bowtie Antenna for RF and ISM bands Operation

Traditionally, bowtie antennas have been known to exhibit wide impedance characteristics, omnidirectional radiation patterns, and linear polarization. There is a broad range of applications from medical imaging, archaeological survey, and Ground Penetrating Radar (GPR) to trackers and sensor networks where wideband bowtie antenna designs are required for their operations. Broadening the bandwidth of bowtie antenna requires widening the flare angle of the bowtie arms, which consequently results in a large surface area that may not be suitable for space-constrained applications. Moreover, drawback attributes of the wideband bowtie designs feature inconsistent radiation pattern across the bandwidth and low signal-to-noise (SNR) ratios. As it is known, the SNR would be improved in dual- or multi-band antennas due to their reduced bandwidth. To this end, dual-band/multi-band antennas are preferred over wideband antennas in applications where more than a single frequency of interest is present. Previously, a two-port double-dipole elements was reported, whose arms were orthogonally interleaved to facilitate operation in both the standard WLAN frequency bands (J. M. Steyn and et. al, Progress in Electromagnetic Research, Vol. – 10 pp. 151-161). Even though the antenna is not very compact it does exhibit good cross-polarization, moderate gain in both frequency bands. Another dual-band bowtie antenna which excites two bands using a single transmission line was reported (Wen Chao Zheng and et. al, IEEE Trans. Antennas propag., 2014). The design was compact and did not need multi-port feeding network. In this paper, a dual-band compact bowtie antenna operating at 900 MHz (RF band) and 2.45 GHz (ISM band) using a single excitation port is introduced. It is printed on a 1.54mm thick dielectric substrate (εr = 3.38). The antenna consists of two sets of bowtie arms, a microstrip transmission line to feed the bowtie arms, and a ground plane acting as a reflector to partially reduce the back radiation. One of the bowtie arms of each frequency is printed on the top layer and the other arm, which is mirror imaged, is printed on the bottom layer of the substrate. The length of the bowtie controls the resonance frequency of the antenna and the flare angle controls the bandwidth of the antenna. The microstrip transmission line, connected to a 50 Ω SMA probe, feeds the bowtie antenna. The compact antenna can be used for both RF and ISM band applications. The bowtie arms at the lower frequency band are miniaturized by elongating their electrical lengths. The influence of miniaturizing the bowtie arms and the supporting partial ground plane is observed in the reduced peak gain and degraded front-to-back ratio. These are partly neutralized using four quarter-wave choke-slots in the ground plane with two on each side of the feeding transmission line. The proposed antenna is numerically investigated and finalized by the finite-element based full-wave EM solver, ANSYS HFSS. The miniaturization has reduced the ground plane size by ~45% and the arms size by ~41%. In addition to the size reduction benefits, the antenna shows reasonable peak gain and front-to-back ratio in both the bands. The corresponding results will be presented and discussed at the conference.

Saininad Naik↗

NASA NTRS1984

Feasiblity study for a 34 GHz (Ka band) gyroamplifier

The feasibility of using a gyroklystron power tube as the final amplifier in a 400 kW CW 34 GHz transmitter on the Goldstone Antenna is investigated. A conceptual design of the gyroklystron and the transmission line connecting it with the antenna feed horn is presented. The performance characteristics of the tube and transmission line are compared to the transmitter requirements for a deep space radar system. Areas of technical risk for a follow-on hardware development program for the gyroklystron amplifier and overmoded transmission line components are discussed.

Stone, D. S.↗

NASA NTRS1998

Finite Ground Coplanar (FGC) Waveguide: It's Characteristics and Advantages for Use in RF and Wireless Communication Circuits

To solve many of the problems encountered when using conventional coplanar waveguide (CPW) with its semi-infinite ground planes, a new version of coplanar waveguide with electrically narrow ground planes has been developed. This new transmission line which we call Finite Ground Coplanar (FGC) waveguide has several advantages which make it a better transmission line for RF and wireless circuits. Since the ground planes are electrically narrow, spurious resonances created by the CPW ground planes and the metal carrier or package base are eliminated. In addition, lumped and distributed circuit elements may now be integrated into the ground strips in the same way as they traditionally have been integrated into the center conductor to realize novel circuit layouts that are smaller and have less parasitic reactance. Lastly, FGC is shown to have lower coupling between adjacent transmission lines than conventional CPW.

Ponchak, George E.↗

NASA NTRS1971

Sound propagation and absorption in foam - A distributed parameter model.

Liquid-base foams are highly effective sound absorbers. A better understanding of the mechanisms of sound absorption in foams was sought by exploration of a mathematical model of bubble pulsation and coupling and the development of a distributed-parameter mechanical analog. A solution by electric-circuit analogy was thus obtained and transmission-line theory was used to relate the physical properties of the foams to the characteristic impedance and propagation constants of the analog transmission line. Comparison of measured physical properties of the foam with values obtained from measured acoustic impedance and propagation constants and the transmission-line theory showed good agreement. We may therefore conclude that the sound propagation and absorption mechanisms in foam are accurately described by the resonant response of individual bubbles coupled to neighboring bubbles.

Manson, L.↗

NASA NTRS1993

Development of Si(1-x)Ge(x) technology for microwave sensing applications

The progress for the first year of the work done under the Director's Discretionary Fund (DDF) research project entitled, 'Development of Si(1-x)Ge(x) Technology for Microwave Sensing Applications.' This project includes basic material characterization studies of silicon-germanium (SiGe), device processing on both silicon (Si) and SiGe substrates, and microwave characterization of transmission lines on silicon substrates. The material characterization studies consisted of ellipsometric and magneto-transport measurements and theoretical calculations of the SiGe band-structure. The device fabrication efforts consisted of establishing SiGe device processing capabilities in the Lewis cleanroom. The characterization of microwave transmission lines included studying the losses of various coplanar transmission lines and the development of transitions on silicon. Each part of the project is discussed individually and the findings for each part are presented. Future directions are also discussed.

Mena, Rafael A.↗

NASA NTRS1975

Digital transmitter for data bus communications system

An improved digital transmitter for transmitting serial pulse code modulation (pcm) data at high bit rates over a transmission line is disclosed. When not transmitting, the transmitter features a high output impedance which prevents the transmitter from loading the transmission line. The pcm input is supplied to a logic control circuit which produces two discrete logic level signals which are supplied to an amplifier. The amplifier, which is transformer coupled to the output isolation circuitry, converts the discrete logic level signals to two high current level, ground isolated signals in the secondary windings of the coupling transformer. The latter signals are employed as inputs to the isolation circuitry which includes two series transistor pairs operating into a hybrid transformer functioning to isolate the transmitter circuitry from the transmission line.

Proch, G. E.↗

NASA NTRS2002

Coupling Between Microstrip Lines and Finite Ground Coplanar Lines Embedded in Polyimide Layers for 3D-MMICs on Silicon

Three-dimensional circuits built upon multiple layers of polyimide are required for constructing Si/SiGe monolithic microwave/mm-wave integrated circuits on CMOS (low resistivity) Si wafers. It is expected that these circuits will replace the ones fabricated on GaAs and reduce the overall system cost. However, the closely spaced transmission lines that are required for a high-density circuit environment are susceptible to high levels of cross-coupling, which degrades the overall circuit performance. In this paper, theoretical and experimental results on coupling and ways to reduce it are presented for two types of transmission lines: a) the microstrip line and b) the Finite Ground Coplanar (FGC) line. For microstrip lines it is shown that a fence of metalized via-holes can significantly reduce coupling, especially in the case when both lines are on the same polyimide layer or when the shielding structure extends through several polyimide layers. For closely spaced microstrip lines, coupling is lower for a metal filled trench shield than a via-hole fence. Coupling amongst microstrip lines is dependent on the ratio of line separation to polyimide thickness and is primarily due to magnetic fields. For FGC lines it is shown that they have in general low coupling that can be reduced significantly when there is even a small gap between the ground planes of each line. FGC lines have approximately 8 dB lower coupling than coupled coplanar waveguides (CPW). In addition, forward and backward characteristics of the FGC lines do not resemble those of other transmission lines such as microstrip. Therefore, the coupling mechanism of the FGC lines is different compared to thin film microstrip lines.

Ponchak, G. E.↗

NASA NTRS1991

Analysis and characterizations of planar transmission structures and components for superconducting and monolithic integrated circuits

The analysis and modeling of superconducting planar transmission lines were performed. Theoretically, the highest possible Q values of superconducting microstrip line was calculated and, as a result, it provided the Q value that the experiment can aim for. As an effort to search for a proper superconducting transmission line structure, the superconducting microstrip line and coplanar waveguide were compared in terms of loss characteristics and their design aspects. Also, the research was expanded to a superconducting coplanar waveguide family in the microwave packaging environment. Theoretically, it was pointed out that the substrate loss is critical in the superconducting transmission line structures.

Itoh, Tatsuo↗

NASA NTRS1995

Parallel and series FED microstrip array with high efficiency and low cross polarization

A microstrip array antenna for vertically polarized fan beam (approximately 2 deg x 50 deg) for C-band SAR applications with a physical area of 1.7 m by 0.17 m comprises two rows of patch elements and employs a parallel feed to left- and right-half sections of the rows. Each section is divided into two segments that are fed in parallel with the elements in each segment fed in series through matched transmission lines for high efficiency. The inboard section has half the number of patch elements of the outboard section, and the outboard sections, which have tapered distribution with identical transmission line sections, terminated with half wavelength long open-circuit stubs so that the remaining energy is reflected and radiated in phase. The elements of the two inboard segments of the two left- and right-half sections are provided with tapered transmission lines from element to element for uniform power distribution over the central third of the entire array antenna. The two rows of array elements are excited at opposite patch feed locations with opposite (180 deg difference) phases for reduced cross-polarization.

Huang, John↗

NASA NTRS2005

Control Software for a High-Performance Telerobot

A computer program for controlling a high-performance, force-reflecting telerobot has been developed. The goal in designing a telerobot-control system is to make the velocity of the slave match the master velocity, and the environmental force on the master match the force on the slave. Instability can arise from even small delays in propagation of signals between master and slave units. The present software, based on an impedance-shaping algorithm, ensures stability even in the presence of long delays. It implements a real-time algorithm that processes position and force measurements from the master and slave and represents the master/slave communication link as a transmission line. The algorithm also uses the history of the control force and the slave motion to estimate the impedance of the environment. The estimate of the impedance of the environment is used to shape the controlled slave impedance to match the transmission-line impedance. The estimate of the environmental impedance is used to match the master and transmission-line impedances and to estimate the slave/environment force in order to present that force immediately to the operator via the master unit.

Kline-Schoder, Robert J.↗

NASA NTRS2008

Microwave Radiometers from 0.6 to 22 GHz for Juno, a Polar Orbiter around Jupiter

A compact radiometer instrument is under development at JPL for Juno, the next NASA New Frontiers mission, scheduled to launch in 2011. This instrument is called the MWR (MicroWave Radiometer), and its purpose is to measure the thermal emission from Jupiter's atmosphere at selected frequencies from 0.6 to 22 GHz. The objective is to measure the distributions and abundances of water and ammonia in Jupiter's atmosphere, with the goal of understanding the previously unobserved dynamics of the subcloud atmosphere, and to discriminate among models for planetary formation in our solar system. The MWR instrument is currently being developed to address these science questions for the Juno mission. As part of a deep space mission aboard a solar-powered spacecraft, MWR is designed to be compact, lightweight, and low power. The entire MWR instrument consists of six individual radiometer channels with approximately 4% bandwidth at 0.6, 1.25,2.6,5.2, 10,22 GHz operating in direct detection mode. Each radiometer channel has up to 80 dB of gain with a noise figure of several dB. The highest frequency channel uses a corrugated feedhorn and waveguide transmission lines, whereas all other channels use highly phase stable coaxial cables and either patch array or waveguide slot array antennas. Slot waveguide array antennas were chosen for the low loss at the next three highest frequencies and patch array antennas were implemented due to the mass constraint at the two lowest frequencies. The six radiometer channels receive their voltage supplies and control lines from an electronics unit that also provides the instrument communication interface to the Juno spacecraft. For calibration purposes each receiver has integrated noise diodes, a Dicke switch, and temperature sensors near each component that contributes to the noise figure. In addition, multiple sensors will be placed along the RF transmission lines and the antennas in order to measure temperature gradients. All antennas and RF transmission lines must withstand low temperatures and the harsh radiation environment surrounding Jupiter; the receivers and control electronics are protected by a radiation-shielding enclosure on the Juno spacecraft that also provides for a benign and stable operating temperature environment. This paper will focus on the concept of the MWR instrument and will present results of one breadboard receiver channel.

receiver↗