C. H. Mueller

(YBa2Cu3O7−δ,Au)/SrTiO3/LaAlO3 thin film conductor/ferroelectric coupled microstripline phase shifters for phased array applications

We report on the design, fabrication, and testing of novel YBa2Cu3O7−δ/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3/LaAlO3 (Au/STO/LAO) coupled microstrip line phase shifters (CMPS). These CMPS were tested at frequencies within the Ku and K bands (12–20 GHz), at temperatures from 24 to 77 K, and at dc voltages (Vdc) from zero to 350 V. A relative insertion phase shift (Δφ) of 390° was measured for an eight-element YBCO/STO/LAO CMPS at Vdc=350u2009V, 16 GHz, and 40 K. At 77 K, a Δφu2009∼260° was obtained for the CMPS at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. At both temperatures, the phase shifter exhibits a figure of merit of ∼30°/dB. To our knowledge, these are the best results published so far at these frequencies where miniaturization, insertion loss, and phase delay are key considerations.

Design and development of ferroelectric tunable microwave components for Kuand K-band satellite communication systems

Integration of a high-temperature superconductor with a nonlinear dielectric ferroelectric such as strontium titanate, i.e., SrTiO/sub 2/ (STO), has created a new class of electrically tunable low-loss microwave components. We have designed and fabricated frequency and phase agile components using a conductor/ferroelectric/dielectric two-layered microstrip configuration. Some examples of these components are: microstrip ring resonators, local oscillators, edge coupled filters, and phase-shifter circuits. These structures have been fabricated using YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// or gold conductor-based microstrip lines fabricated on lanthanum aluminate (LaAlO/sub 3/) or magnesium oxide (MgO) substrates coated with an STO thin film. Frequency and phase agility are achieved using the nonlinear dc electric-field dependence of the relative dielectric constant of STO ferroelectric thin him (E/sub rSTO/). In this paper, we will present an assessment of the progress that our group has achieved thus far toward integration of this technology into wireless and satellite communication systems.

Small-Size X-Band Active Integrated Antenna With Feedback Loop

A small-sized active integrated antenna (AIA), consisting of a transmission feedback oscillator loaded with a microstrip antenna is presented in this paper. The oscillator antenna, which consists of a NEC super low noise high frequency field effect transistor (HF FET) integrated into the center of a segmented patch antenna, was designed for X-band at 8.50 GHz, and occupies a 5 times 6 mm2 area. The active integrated antenna demonstrates stable oscillations and excellent radiation patterns at X-band design frequencies. When biased using a single 1.5 volt battery connected between the source and drain and with the gate terminal open, the antenna effective isotropic radiated power (EIRP) and direct current (DC)-to-radiated radio frequency (RF) conversion efficiency are +11.2 dBm and 10.5%, respectively. The radiated power level and directivity are +4.5 dBm and 6.7 dBi, respectively. The phase noise at 100 kHz offset from the carrier is -87.5 dBc/Hz, which is a notable improvement over existing AIA designs. The AIA features compact size and simple geometry, yet provides radiated power levels and radiation efficiencies that are comparable to values typically obtained using circuits that occupy larger areas, and use thicker substrates with much lower dielectric constant values.

Analysis and Optimization of Thin-Film Ferroelectric Phase Shifters

Microwave phase shifters have been fabricated from (YBa2Cu3O(7-delta) or Au)/SrTiO3 and Au/Ba(x)Sr(1-x)TiO3 films on LaAlO3 and MgO substrates. These coupled microstrip devices rival the performance of their semiconductor counter-parts parts at Ku- and K-band frequencies. Typical insertion loss for room temperature ferroelectric phase shifters at K-band is approximately equal 5 dB. An experimental and theoretical investigation of these novel devices explains the role of the ferroelectric film in overall device performance. A roadmap to the development of a 3 dB insertion loss phase shifter that would enable a new type of phased array antenna is discussed.

Room temperature thin film Ba/sub x/Sr/sub 1-x/TiO/sub 3/ Ku-band coupled microstrip phase shifters: effects of film thickness, doping, annealing and substrate choice

We report on measurements taken on thirteen Ku-band coupled microstrip phase shifters (CMPS) using thin ferroelectric films of Ba/sub x/Sr/sub 1-x/TiO/sub 3/. This CMPS design is a recent innovation designed to take advantage of the high tunability and tolerate the high dielectric constant of ferroelectric films at Ku- and K-band frequencies. These devices are envisioned as a component in low-cost steerable beam phased array antennas. Comparisons are made between devices with differing film thickness, annealed vs. unannealed, Mn-doped vs. undoped, and also substrates of LaAlO/sub 3/ and MgO.

A LARGE SCALE PRODUCTION TEST OF THIN FILM Ba x Sr 1−x TiO 3 MICROWAVE PHASE SHIFTERS FABRICATED ON LaAlO3 SUBSTRATES

ABSTRACT Many individual tunable ferroelectric-based microwave components have demonstrated excellent performance. However data on the production of many identical devices has been lacking. This paper will present data from NASA Glenn Research Centers fabrication of 822 phase shifters using commercially obtained pulsed laser deposited BaxSr1-xTiO3 (BST) thin films. These phase shifters of identical design were fabricated on 31 BST-coated LaAlO3 wafers. Issues of phase shifter performance, repeatability, yield, and long term stability will be addressed. Phase shifter tunability and insertion losses will be compared with BST microstructural film characteristics and also with manufacturing induced physical variations in the electrodes.

Quarter-wave VHF microstrip antenna characterized in anechoic chamber

A quarter-wave microstrip antenna for VHF communication systems has been fabricated and tested. The antenna is physically small, with a metallic ground plane. The antenna gain is +0.6 dBi, and the maximum H-plane cross-polarization levels are 10 dB below the maximum E-plane co-polarization levels. Measurements are performed in an anechoic antenna range designed for higher frequency testing (≫1.5 GHz). The feasibility and limitations of performing VHF antenna tests under these conditions are presented.

High temperature permittivity measurements of Alumina Enhanced Thermal Barrier (AETB-8) material for CEV antenna radomes

Alumina Enhanced Thermal Barrier (AEBT-8) material is currently being considered as a potential radome material for phased array antennas that will be conformally mounted to the outer surface of NASAs Orion Crew Exploration Vehicle. Accordingly, there is a need to establish if the dielectric properties of the AEBT-8 material change as a function of temperature. In this paper we discuss the measurements of the real (ε<inf>r</inf>) and imaginary (ε<inf>r</inf>) parts of the dielectric constant of AEBT-8 at temperatures from 25- 900°C and in the frequency range from 2–18 GHz. Our results show that neither ε<inf>r</inf> or ε<inf>r</inf> showed a measurable temperature dependence when tested in the aforementioned temperature range. Comparison at room temperature to measurements taken using the waveguide technique showed good agreement for ε<inf>r</inf>, but the ε<inf>r</inf> values for the AETB-8 material are so low that diffraction phenomena limits the accuracy of the results obtained using the free space technique.

TUNABLE MICROSTRIP FILTERS USING SELECTIVELY ETCHED FERROELECTRIC THIN-FILM VARACTORS FOR COUPLING

ABSTRACT We report on the use of patterned ferroelectric films to fabricate proof of concept tunable one-pole microstrip filters with excellent transmission and mismatch/reflection properties at frequencies up to 24 GHz. By controlling the electric field distribution within the coupling region between the resonator and input/output lines, sufficiently high loaded and unloaded Q values are maintained so as to be useful for microstrip filter design, with low mismatch loss. In the 23–24 GHz region, the filter was tunable over a 100 MHz range, the loaded and unloaded Q values were 29 and 68, respectively, and the reflection losses were below −16 dB, which demonstrates the suitability of these films for practical microwave applications.

Concept for a low cost, high efficiency precipitation radar system based on ferroelectric reflectarray antenna

This work proposes a concept on a novel scanning phased array, based on thin film ferroelectric phase shifters, for an X-band precipitation monostatic radar.