Engineering topics

Simons, Rainee N.

Publications and source records attributed to Simons, Rainee N..

At least 163 records · Page 9

NASA NTRS1992

Ka-Band Dual Frequency Array Feed for a Low Cost ACTS Ground Terminal

Because of low cost and ease of fabrication, microstrip arrays are attractive as feeds for reflector antenna systems. This paper describes the development of a 4x4 microstrip array which will be used as a feed for a low cost ACTS ground terminal. The array feed consisting of four 2x2 subarrays is fed with coplanar waveguide power dividing networks. The patch radiator is designed to excite two orthogonal, linearly polarized waves at Ka-band frequencies (around 20 and 30 GHz). Test results for the developed array are presented.

Lee, Richard Q.↗

NASA NTRS1991

Coplanar waveguide feeds for phased array antennas

The design and performance is presented of the following coplanar waveguides (CPW) microwave distribution networks for linear as well as circularly polarized microstrip patches and dipole arrays: (1) CPW/microstrip line feed; (2) CPW/balanced stripline feed; (3) CPW/slotline feed; (4) grounded CPW/balanced coplanar stripline feed; and (5) CPW/slot coupled feed. Typical measured radiation patterns are presented, and their relative advantages and disadvantages are compared.

Simons, Rainee N.↗

NASA NTRS1991

Theoretical and experimental characterization of coplanar waveguide discontinuities for filter applications

A full-wave analysis of shielded coplanar waveguide two-port discontinuities based on the solution of an appropriate surface integral equation in the space domain is presented. Frequency-dependent scattering parameters for open-end and short-end coplanar waveguide (CPW) stubs are computed using this method. The numerically derived results are compared with measurements performed in the frequency range 5-25 GHz and show very good agreement. From the scattering parameters, lumped-element equivalent circuits have been derived to model the discontinuities. The inductors and capacitors of these models have been represented by closed-form equations, as functions of the stub length, to compute the circuit element values for these discontinuities.

Dib, Nihad I.↗

NASA NTRS1991

Coplanar waveguide feeds for phased array antennas

The design and performance is presented of the following Coplanar Waveguides (CPW) microwave distribution networks for linear as well as circularly polarized microstrip patches and dipole arrays: (1) CPW/Microstrip Line feed; (2) CPW/Balanced Stripline feed; (3) CPW/Slotline feed; (4) Grounded CPW/Balanced coplanar stripline feed; and (5) CPW/Slot coupled feed. Typical measured radiation patterns are presented, and their relative advantages and disadvantages are compared.

Simons, Rainee N.↗

NASA NTRS1990

Experimental investigations on channelized coplanar waveguide

A new variant of coplanar waveguide (CPW) which was termed channelized coplanar waveguide (CCPW) is presented. Measured propagation characteristics for CCPW such as epsilon(eff) and unloaded Q as a function of geometrical parameters and frequency are presented. The measured and modeled epsilon(eff) are also compared. Equivalent circuit model element values are presented for a CCPW open circuit and a CCPW right angle bend. A CCPW matched T-junction, matched 1:3 junction, and a novel coax-to-CCPW in-phase, N-way, radial power divider are also demonstrated.

Simons, Rainee N.↗

NASA NTRS1990

A new rectangular waveguide to coplanar waveguide transition

A new rectangular waveguide to coplanar waveguide (CPW) transition is described. The transition uses a ridge in one of the broad walls of the waveguide and a nonradiating slot in the opposite wall to split and rotate the electromagnetic fields of the rectangular waveguide TE10 mode into the CPW fields.

Ponchak, George E.↗

NASA NTRS1990

Coplanar waveguide fed phased array antenna

A K-band four element linear phased array was designed and tested. Coplanar waveguide (CPW) is used for the microwave distribution system. A CPW to twin strip transition is used to interface with the printed dipole antennas. MMIC phased shifters are used for phase control.

Simons, Rainee N.↗

NASA NTRS1990

Coplanar waveguide discontinuities for P-I-N diode switches and filter applications

A full wave space domain integral equation (SDIE) analysis of coplanar waveguide (CPW) two port discontinuities is presented. An experimental setup to measure the S-parameters of such discontinuities is described. Experimental and theoretical results for CPW realizations of pass-band and stop-band filters are presented. The S-parameters of such structures are plotted in the frequency range 5 to 25 GHz.

Dib, N. I.↗

NASA NTRS1989

Screen-Printed YBa2Cu3O7-x Films On Alumina

Superconducting films made in relatively simple process. Thick films of YBa2Cu3O7-x superconductor deposited on highly-polished alumina substrates by screen printing. In addition to simplicity, screen-printing technique offers advantage that patterns for electronic and microwave circuits and devices printed directly, without additional etching steps.

Bansal, Narottam P.↗

NASA NTRS1989

Improved Coplanar Waveguides

Three new types of coplanar waveguide transmission lines proposed: suspended, striplinelike suspended, and inverted. Numerical analyses of propagation of electromagnetic fields of new and of more-conventional plain and conductor-backed coplanar waveguides showed new waveguides offered several advantages over conventional ones. Configurations promise lower attenuation and reduce effects of manufacturing errors.

Simons, Rainee N.↗

NASA NTRS1989

Optically-Controlled Microwave Devices And Circuits

NASA Technical Memorandum discusses physical basis and dc and microwave characteristics of optically-controlled microwave devices described in literature. Emphasis on responses of GaAs/GaAlAs high-electron-mobility transistors (HEMT's) and GaAs metal/semiconductor field-effect transistors (MESFET's) to light. Devices used to detect radio-frequency modulation of optical signals, to control gains of amplifiers, and to provide injection locking of oscillators.

Bhasin, Kul B.↗

NASA NTRS1989

Channelized coplanar waveguide: Discontinuities, junctions, and propagation characteristics

A new variant of CPW which has been termed channelized CPW, CCPW, is presented. Measured and computed propagation characteristics are presented. Lumped equivalent circuit element values for a CCPW open circuit and right angle bend have been obtained. CCPW power divider junctions and a coax-to-CCPW in-phase, radial power divider are also presented.

Simons, Rainee N.↗

NASA NTRS1988

Modeling of some coplanar waveguide discontinuities

Presented are lumped equivalent circuit models for several coplaar waveguide discontinuities such as an open circuit, a series gap, and a symmetric step, and their element values as a function of the discontinuity physical dimensions. The model element values are de-embedded from measured S parameters. The frequency dependence of the effective dielectric constant is measured and compared to computed values.

Simons, Rainee N.↗

NASA NTRS1988

Optoelectronic gain control of a microwave single stage GaAs MESFET amplifier

Gain control of a single stage GaAs MESFET amplifier is demonstrated by the use of optical illumination of photon energy greater than the GaAs bandgap. The optical illumination is supplied by a semiconductor laser diode and is coupled to the Schottky gate of the MESFET by an optical fiber. The increase in gain is observed to be as much as 5.15 dB when the MESFET is biased close to pinchoff, that is, V(sub gs) equals -1.5 V and with optical illumination of 1.5 mW. The computed maximum available gain (MAG) and current gain (bar h sub 21 bar) from the de-embedded s-parameters show that MAG is unaffected by optical illumination, however, bar h(sub 21)bar increases by more than 2 dB under optical illumination of 1.5 mW. The maximum frequency of oscillation (F sub max) and the unity current gain cut-off frequency (F sub t) obtained by extrapolating the MAG and bar h(sub 21)bar curves, respectively, show that the F(sub max) is insensitive to optical illumination but F(sub t) increases by 5 GHz.

Simons, Rainee N.↗

NASA NTRS1988

High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.

Bansal, Narottam P.↗

NASA NTRS1988

Modeling of Some Coplanar Waveguide Discontinuities

Presented are lumped equivalent circuit models for several coplanar waveguide discontinuities such as an open circuit, a series gap, and a symmetric step, and their element values as a function of the discontinuity physical dimensions. The model element values are de-embedded from measured S-parameters. The frequency dependence of the effective dielectric constant was measured and compared to computed values.

Simons, Rainee N.↗

NASA NTRS1988

Synthesis and characterization of high-T(sub c) screen-printed Y-Ba-Cu-O films on alumina

Thick films of YBa2Cu3O(sub 7-x) have been deposited on highly polished alumina substrates by the screen printing technique. To optimize the post-printing heat treatment, the films were baked at various temperatures for different lengths of time and oxygen-annealed at a lower temperature. The resulting films were characterized by electrical resistivity measurements, x-ray diffraction, and optical and scanning electron microscopy. Properties of the films were found to be highly sensitive to the post-printing thermal treatment. Films baked for 15 min at 1000 C in oxygen were hard, adherent, near single phase, and superconducting with T(sub c)(onset) approx 96 K, T(sub c)(zero) approx 66 K and Delta T sub c (10 to 90 percent) approx 10 K.

Bansal, Narottam P.↗

NASA NTRS1988

Synthesis and characterization of high-T(c) screen-printed Y-Ba-Cu-O films on alumina

Thick films of YBa2Cu3O(sub 7-x) have been deposited on highly polished alumina substrates by the screen printing technique. To optimize the post-printing heat treatment, the films were baked at various temperatures for different lengths of time and oxygen-annealed at a lower temperature. The resulting films were characterized by electrical resistivity measurements, X-ray diffraction, and optical and scanning electron microscopy. Properties of the films were found to be highly sensitive to the post-printing thermal treatment. Films baked for 15 min at 1000 C in oxygen were hard, adherent, near single phase, and superconducting with T(sub c) (onset) approx 96 KK, T(sub c) (zero) approx 66 K and Delta T sub c (10 to 90 percent) approx 10 K.

Bansal, Narottam P.↗