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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Interplay Between Thin Film Ferroelectric Composition, Microstructure and Microwave Phase Shifter Performance

One of the keys to successfully incorporating ferroelectric films into Ku-band (12 to 18 GHz) phase shifters is to establish the composition, microstructure, and thickness required to meet the tuning needs, and tailor the film properties to meet these needs. Optimal performance is obtained when the film composition and device design are such that the device performance is limited by odd mode dielectric losses, and these losses are minimized as much as possible while still maintaining adequate tunability. The parameters required to maintain device performance will vary slightly depending on composition, but we can conclude that the best tuning-to-loss figures of merit (K-factor) are obtained when there is minimal variation between the in-plane and out-of-plane lattice parameters, and the full-width half maximum values of the BSTO (002) peaks are less than approximately 0.04 deg. We have observed that for phase shifters in which the ferroelectric crystalline quality and thickness are almost identical, higher losses are observed in films with higher BaISr ratios. The best performance was observed in phase shifters with Ba:Sr = 30:70. The superiority of this composition was attributed to several interacting factors: the B a: Sr ratio was such that the Curie temperature (180 K) was far removed from room temperature, the crystalline quality of the film was excellent, and there was virtually no difference between the inplane and out-of-plane lattice parameters of the film.

Mueller, Carl H.↗
NASA NTRS1990

Control of a GaAs monolithic Ka-band phase shifter using a high-speed optical interconnect

The use of a high-speed optical interconnect in the control of a Ka-band GaAs monolithic phase shifter is described. A 16-b serial control signal was used to modulate the output of a laser transmitter, and the transmitted optical signal was detected and demultiplexed into 16 parallel electrical outputs using a high-speed hybrid GaAs optoelectronic integrated circuit. Four of the parallel output lines were interfaced to the 4-b phase shifter, and high-speed, optically controlled switching of the phase shifter was observed at clock frequencies to 30 MHz using an interferometric technique.

Bhasin, K. B.↗
NASA NTRS1992

Monolithic mm-wave phase shifter using optically activated superconducting switches

A phase shifter is disclosed having a reference path and a delay path, light sources, and superconductive switches. Each of the superconductive switches is terminated in a virtual short circuit, which may be a radial stub. Switching between the reference path and delayed path is accomplished by illuminating the superconductive switches connected to the desired path, while not illuminating the superconductive switches connected to the other path.

Romanofsky, Robert R.↗
NASA NTRS2006

Slow-Wave Phase Shifters, Based on Thin Ferroelectric Films, for Reflectarray Antennas

We have developed relatively broadband K- and Ka-band phase shifters using synthetic (slow-wave) transmission lines employing coupled microstripline "varactors". The tunable coupled microstripline circuits are based on laser ablated BaSrTiO films on lanthanum aluminate substrates. A model and design criteria for these novel circuits will be presented, along with measured performance including anomalous phase delay characteristics. The critical role of phase shifter loss and transient response in reflectarray antennas will be emphasized.

Romanofsky, Robert R.↗
NASA NTRS1991

Comparative study of bolometric and non-bolometric switching elements for microwave phase shifters

The performance of semiconductor and high critical temperature superconductor switches is compared as they are used in delay-line-type microwave and millimeter-wave phase shifters. Such factors as their ratios of the off-to-on resistances, parasitic reactances, power consumption, speed, input-to-output isolation, ease of fabrication, and physical dimensions are compared. Owing to their almost infinite off-to-on resistance ratio and excellent input-to-output isolation, bolometric superconducting switches appear to be quite suitable for use in microwave phase shifters; their only drawbacks are their speed and size. The SUPERFET, a novel device whose operation is based on the electric field effect in high critical temperature ceramic superconductors is also discussed. Preliminary results indicate that the SUPERFET is fast and that it can be scaled; therefore, it can be fabricated with dimensions comparable to semiconductor field-effect transistors.

Tabib-Azar, Massood↗
NASA NTRS1991

Comparative study of bolometric and non-bolometric switching elements for microwave phase shifters

The performance of semiconductor and high critical temperature superconductor switches is compared as they are used in delay-line-type microwave and millimeter-wave phase shifters. Such factors as their ratios of the off-to-on resistances, parasitic reactances, power consumption, speed, input-to-output isolation, ease of fabrication, and physical dimensions are compared. Owing to their almost infinite off-to-on resistance ratio and excellent input-to-output isolation, bolometric superconducting switches appear to be quite suitable for use in microwave phase shifters; their only drawbacks are their speed and size. The SUPERFET, a novel device whose operation is based on the electric field effect in high critical temperature ceramic superconductors is also discussed. Preliminary results indicate that the SUPERFET is fast and that it can be scaled; therefore, it can be fabricated with dimensions comparable to semiconductor field-effect transistors.

Tabib-Azar, Massood↗
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 NTRS1991

Phase shifter technology assessment - Prospects and applications

Capabilities and limitations of MMIC phase shifter technology at microwave and millimeter wave frequencies are reviewed. MMIC-based phase arrays make it possible to integrate active elements at the array face, i.e., to incorporate transmit power amplifiers and/or low noise amplifiers at each antenna element. Active elements make it possible to increase power efficiency and reliability and provide graceful degradation. Monolithic integration of the various transmit/receive functions including phase shifting is considered to be feasible through at least the lower millimeter-wave frequency range (about 30-100 GHz). MMIC integration also allows more flexibility in array design including those that are intended for airborne conformal applications.

Sokolov, Vladimir↗
NASA NTRS2004

Broadband, Low-Loss Phase Shifters Based on Thin Ferroelectric Films

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.

Romanofsky, Robert↗
NASA NTRS2010

Thin-Film Ferro Electric-Coupled Microstripline Phase Shifters With Reduced Device Hysteresis

This work deals with the performance of coupled microstripline phase shifters (CMPS) fabricated using BaxSr 1 -xTiO 3 (BST) ferroelectric thin films. The CMPS were fabricated using commercially available pulsed laser deposition BST films with Ba:Sr ratios of 30:70 and 20:80. Microwave characterization of these CMPS was performed at upper Kuband frequencies, particularly at frequencies near 16 and 18 GHz. X-ray diffraction studies indicate that the 30:70 films exhibit almost a 1:1 ratio between the in-plane and out-of-plane lattice parameters, suggesting that their cubics create strain -free films suitable for producing CMPS devices with reduced hysteresis in the paraelectric state. The quality of performance of the CMPS was studied based on their relative phase shift and insertion loss within the DC bias range of 0 to 400 V (i.e., E-field ranges within 0 to 53 V/micron). The performance of the CMPS was tested as a function of temperature to investigate their operation in the paraelectric, as well as in the ferroelectric, state (i.e., above and below the Curie temperature, respectively). The novel behavior discussed here is based on the experimental observation of the CMPS. This behavior, observed for the aforementioned cation ratio, highlights the relevance of good crystalline structure for high-quality CMPS.

Miranda, Felix A.↗
NASA NTRS2000

Finite Ground Coplanar Waveguide Shunt MEMS Switches for Switched Line Phase Shifters

Switches with low insertion loss and high isolation are required for switched line phase shifters and the transmit/receive switch at the front end of communication systems. A Finite Ground Coplanar (FGC) waveguide capacitive, shunt MEMS switch has been implemented on high resistivity Si. The switch has demonstrated an insertion loss of less than 0.3 dB and a return loss greater than 15 dB from 10 to 20, GHz. The switch design, fabrication, and characteristics are presented.

Ponchak, George E.↗
NASA NTRS2011

Reconfigurable Microwave Phase Delay Element for Frequency Reference and Phase-Shifter Applications

A technique was developed to provide a reconfigurable high-precision micro - wave electrical phase delay for resonators and phase shifters. The invention employs multiple branches of transmission lines with open-ended or ground-ended terminations as configurable bits or digits. This technique minimizes the errors due to limited precision of switching devices. In addition, the proposed linear analytical approach significantly produces a much simpler design than that of other prior inventions at the time of this reporting. Microwave components such as filters, phase delay elements, or resonators require a method that can accurately adjust their frequency responses. Most tuning techniques offer very wide frequency tuning range; however, it is often difficult and expensive to tune their response in a very narrow operating frequency, especially when the tuning element reaches its minimum discrete step due to fabrication tolerances. The problem becomes worse as the operating frequency is in mm-wave frequency range (>26 GHz). The electrical tuning sensitivity of a microwave line is dependent on the position of the tuning element with respect to the reference termination. By placing this tuning element away from this reference with the main transmission line connecting the two elements together the sensitivity of the tuning element can change significantly. This concept can be used in the system that requires multiple tuning sensitivities. In this case, multiple tuning branches are superimposed in the main transmission line. The proposed invention allows the transmission-line electrical length to be accurately programmed using switching elements that have limited accuracy. The invention consists of multiple branches of transmission lines connected to discrete switching devices with open-ended terminations. They are used as discrete tuning elements. These elements are connected to the main microwave transmission line and are separated by a well-defined electrical degree spacing. Each branch is programmed to have different electrical degree sensitivity, such as a combination of discrete steps in each branch, which results in a reflective line with a unique effective phase response. To reduce the number of switching devices, it is desirable to program the devices in binary configuration where each branch represents one bit in the base-2 number system. This invention allows the transmission line electrical length to be tuned precisely with customizable sensitivity based on the known sensitivity of the base tuning circuit. The tuning resolution is dependent on the distance among tuning branches.

Hsieh, Wen-Ting↗
NASA NTRS1982

Pulsed Phase Shifter Improves Doppler Radar

Ability of microwave Doppler radar to measure velocity of slow moving nearby target is enhanced by pulsed 90 degrees phase shifter in radar transmission line between circulator and antenna. Because of phase shifting, Doppler frequency is detected as modulation on carrier instead of baseband signal. Carrier is amplified and filtered before demodulation, resulting in strong, clean demodulated Doppler for measurement and display.

Kobayashi, H. S.↗