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At least 829 records · Page 46

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NASA NTRS2007

Characteristics of Coplanar Waveguide on Sapphire for High Temperature Applications (25 to 400 degrees C)

This paper presents the characteristics of coplanar waveguide transmission lines fabricated on R-plane sapphire substrates as a function of temperature across the temperature range of 25 to 400 C. Effective permittivity and attenuation are measured on a high temperature probe station. Two techniques are used to obtain the transmission line characteristics, a Thru-Reflect-Line calibration technique that yields the propagation coefficient and resonant stubs. To a first order fit of the data, the effective permittivity and the attenuation increase linearly with temperature.

Ponchak, George E.↗

NASA NTRS2007

Slotted antenna waveguide plasma source

A high density plasma generated by microwave injection using a windowless electrodeless rectangular slotted antenna waveguide plasma source has been demonstrated. Plasma probe measurements indicate that the source could be applicable for low power ion thruster applications, ion implantation, and related applications. This slotted antenna plasma source invention operates on the principle of electron cyclotron resonance (ECR). It employs no window and it is completely electrodeless and therefore its operation lifetime is long, being limited only by either the microwave generator itself or charged particle extraction grids if used. The high density plasma source can also be used to extract an electron beam that can be used as a plasma cathode neutralizer for ion source beam neutralization applications.

Foster, John↗

NASA NTRS2008

Using COMSOL Multiphysics Software to Model Anisotropic Dielectric and Metamaterial Effects in Folded-Waveguide Traveling-Wave Tube Slow-Wave Circuits

The electromagnetic effects of conventional dielectrics, anisotropic dielectrics, and metamaterials were modeled in a terahertz-frequency folded-waveguide slow-wave circuit. Results of attempts to utilize these materials to increase efficiency are presented.

Starinshak, David P.↗

NASA NTRS2009

Ka-Band Waveguide Hybrid Combiner for MMIC Amplifiers with Unequal and Arbitrary Power Output Ratio

The design, simulation and characterization of a novel Ka-band (32.05 +/- 0.25 GHz) rectangular waveguide branchline hybrid unequal power combiner is presented. The manufactured combiner was designed to combine input signals, which are nearly in phase and with an amplitude ratio of two. The measured return loss and isolation of the branch-line hybrid are better than 22 and 27 dB, respectively. The application of the branch-line hybrid for combining two monolithic microwave integrated circuit (MMIC) power amplifiers with output power ratio of two is demonstrated. The measured combining efficiency is 92.9% at the center frequency of 32.05 GHz.

Simons, Rainee N.↗

NASA NTRS2009

Ka-Band Waveguide Hybrid Combiner for MMIC Amplifiers With Unequal and Arbitrary Power Output Ratio

The design, simulation and characterization of a novel Ka-band (32.05 +/- 0.25 GHz) rectangular waveguide branch-line hybrid unequal power combiner is presented. The manufactured combiner was designed to combine input signals, which are in phase and with an amplitude ratio of two. The measured return loss and isolation of the branch-line hybrid are better than 22 and 27 dB, respectively. The application of the branch-line hybrid for combining two MMIC power amplifiers with output power ratio of two is demonstrated. The measured combining efficiency is approximately 93 percent over the above frequency band.

Simons, Rainee N.↗

NASA NTRS2007

Integrated Radial Probe Transition From MMIC to Waveguide

A radial probe transition between a monolithic microwave integrated circuit (MMIC) and a waveguide has been designed for operation at frequency of 340 GHz and to be fabricated as part of a monolithic unit that includes the MMIC. Integrated radial probe transitions like this one are expected to be essential components of future MMIC amplifiers operating at frequencies above 200 GHz. While MMIC amplifiers for this frequency range have not yet been widely used because they have only recently been developed, there are numerous potential applications for them-- especially in scientific instruments, test equipment, radar, and millimeter-wave imaging systems for detecting hidden weapons.

Samoska, Lorene↗

NASA NTRS2010

High Efficiency Ka-Band Solid State Power Amplifier Waveguide Power Combiner

A novel Ka-band high efficiency asymmetric waveguide four-port combiner for coherent combining of two Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifiers (SSPAs) having unequal outputs has been successfully designed, fabricated and characterized over the NASA deep space frequency band from 31.8 to 32.3 GHz. The measured combiner efficiency is greater than 90 percent, the return loss greater than 18 dB and input port isolation greater than 22 dB. The manufactured combiner was designed for an input power ratio of 2:1 but can be custom designed for any arbitrary power ratio. Applications considered are NASA s space communications systems needing 6 to 10 W of radio frequency (RF) power. This Technical Memorandum (TM) is an expanded version of the article recently published in Institute of Engineering and Technology (IET) Electronics Letters.

Wintucky, Edwin G.↗

NASA NTRS2007

Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

Kumar, Sushil↗

NASA NTRS2007

Characteristics of Coplanar Waveguide on Sapphire for High Temperature Applications (25 to 400 C)

Ponchak, George E.↗

NASA NTRS2011

A Hollow-Waveguide Gas Correlation Radiometer for Ultra-Precise Column Measurements of Formaldehyde on Mars

We present preliminary results in the development of a miniaturized gas correlation radiometer that implements a hollow-core optical fiber (hollow waveguide) gas correlation cell. The substantial reduction in mass and volume of the gas correlation cell makes this technology appropriate for an orbital mission -- capable of pinpointing sources of trace gases in the Martian atmosphere. Here we demonstrate a formaldehyde (H2CO) sensor and report a detection limit equivalent to approximately 30 ppb in the Martian atmosphere. The relative simplicity of the technique allows it to be expanded to measure a range of atmospheric trace gases of interest on Mars such as methane (CH4), water vapour (H2O), deuterated water vapour (HDO), and methanol (CH3OH). Performance of a formaldehyde instrument in a Mars orbit has been simulated assuming a 3 meter long, 1000 micron inner diameter hollow-core fiber gas correlation cell, a 92.8 degree sun-synchronous orbit from 400 km with a horizontal sampling scale of 10 km x 10 km. Initial results indicate that for one second of averaging, a detection limit of 1 ppb is possible.

Wilson, Emily L.↗

NASA NTRS2011

Higher Order Mode Coupling in Feed Waveguide of a Planar Slot Array Antenna

A simple technique was developed to account for the higher order mode coupling between adjacent coupling slots in the feed waveguide of a planar slot array. The method uses an equation relating the slot impedance to the slot voltage and a reaction integral involving the equivalent magnetic current of the slot aperture and the magnetic field coupled from an adjacent slot. In the proposed method, one uses the Elliott s design technique to determine tilt angles and lengths of the coupling slots. The radiating slots are modeled as shunt admittances, and the coupling slots are modeled as series impedances.

Rengarajan, Sembiam↗

NASA NTRS2011

A Truncated Waveguide Phase Shifter

The design, fabrication and performance of a simple phase shifter based upon truncated circular and square waveguides is presented. An emphasis is placed upon validation of simple analytical formulae that describe the propagation properties of the structure. A test device is prototyped at approximately 40GHz; however, the concepts explored can be directly extended to millimeter and submillimeter applications.

Lourie, Nathan P.↗

NASA NTRS2011

Vector Reflectometry in a Beam Waveguide

We present a one-port calibration technique for characterization of beam waveguide components with a vector network analyzer. This technique involves using a set of known delays to separate the responses of the instrument and the device under test. We demonstrate this technique by measuring the reflected performance of a millimeter-wave variable-delay polarization modulator.

Eimer, J. R.↗

NASA NTRS2012

Strut Shaping of 34m Beam Waveguide Antenna for Reductions in Near-Field RF and Noise Temperature

Strut shaping of NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antenna has been implemented to reduce near-field RF exposure while improving the antenna noise temperature. Strut shaping was achieved by introducing an RF shield that does not compromise the structural integrity of the existing antenna. Reduction in the RF near-field level will compensate for the planned transmit power increase of the antenna from 20 kW to 80 kW while satisfying safety requirements for RF exposure. Measured antenna noise temperature was also improved by as much as 1.5 K for the low elevation angles and 0.5 K in other areas.

near-field↗

NASA NTRS2012

Fabrication of Silicon Backshort Assembly for Waveguide-Coupled Superconducting Detectors

The Cosmology Large Angular Scale Surveyor (CLASS) is a ground-based instrument that will measure the polarization of the cosmic microwave background to search for gravitational waves from a posited epoch of inflation early in the universe s history. We are currently developing detectors that address the challenges of this measurement by combining the excellent beam-forming attributes of feedhorns with the low-noise performance of Transition-Edge sensors. These detectors utilize a planar orthomode transducer that maps the horizontal and vertical linear polarized components in a dual-mode waveguide to separate microstrip lines. On-chip filters define the bandpass in each channel, and the signals are terminated in resistors that are thermally coupled to the transition-edge sensors operating at 150 mK.

Crowe, E.↗

NASA NTRS2013

Investigation of Truncated Waveguides

The design, fabrication, and performance of truncated circular and square waveguide cross-sections are presented. An emphasis is placed upon numerical and experimental validation of simple analytical formulae that describe the propagation properties of these structures. A test component, a 90-degree phase shifter, was fabricated and tested at 30 GHz. The concepts explored can be directly applied in the design, synthesis and optimization of components in the microwave to sub-millimeter wavebands.

Lourie, Nathan P.↗

NASA NTRS2014

Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064-nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Especially, using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to104 at 10 mHz. The PW-ECLs compactness and low cost make it a candidate to replace traditional Nd:YAGnon-planar ring oscillators and fiber lasers in applications which require a single longitudinal-mode.

diode↗

NASA NTRS2012

Strut Shaping of 34m Beam Waveguide Antenna for Reductions in Near-Field RF and Noise Temeperature

Struts shaping of the NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antenna has been implemented to reduce near-field RF exposure while improving the antenna noise temperature. Strut shaping was achieved by introducing an RF shield that does not compromise the structural integrity of the existing structure. Reduction in the RF near-field exposure will compensate for the planned transmit power increase of the antenna from 20 kW to 80 kW while satisfying safety requirements for RF exposure. Antenna noise temperature was also improved by as much as 1.5 K for the low elevation angles and 0.5 K in other areas. Both reductions of RF near-field exposure and antenna noise temperature were verified through measurements and agree very well with calculated results.

reflector↗