Charles M. Jackson

The distributed Josephson inductance phase shifter

The authors report on a novel microwave phase shifter featuring rapid electronic adjustment, continuous phase control true time delay operation, high device fault tolerance, and very broadband operation. By coupling a large number of superconducting quantum interference devices (SQUIDs) to a superconducting microstrip transmission line, a variable magnetic medium in which the wave velocity is controlled electronically is created. The authors have measured 60 degrees phase shift at 10 GHz, and wideband operation from 5 to 15 GHz for an 8-cm-long Nb transmission line coupled to 1600 SQUIDs, each containing a single Nb/AlO/sub x//Nb tunnel junction. The observed phase shift corresponds to a change in wave velocity of about 1 part in 60.<<ETX>>

Monolithic high-T/sub c/ superconducting phase shifter at 10 GHz

Describes a monolithic high-temperature superconductor (HTS) phase shifter integrated into a 10-GHz microstrip line. The HTS monolithic phase shifter uses over 2000 integrated (SQUID) (superconducting quantum interference device) devices per wavelength. Phase shifts of 20 degrees were observed in transmission line circuits, and phase shifts of greater than 190 degrees were observed in the resonant circuits. The high coupling limit is the best model for the circuit. This HTS phase shifter is suitable for integration into phased-array antenna systems for communications applications.<<ETX>>

Novel monolithic phase shifter combining ferroelectrics and high temperature superconductors

Abstract We describe a monolithic phase shifter which combines the low loss of high temperature superconductivity (HTS) with the variable dielectric properties of a ferroelectric material SrTiO3. Phase shifts greater than 28 degrees per wavelength were observed around 30 K. Benefits of the combination of HTS and ferroelectric materials are described. The compatibility of YBa2Cu3O7-x and other ferroelectric materials is discussed.

10 GHz high temperature superconductor phase shifter

An HTS (high-temperature superconductor) phase shifter with a single-SQUID (superconducting quantum interference device) device has been developed and tested at 10 GHz. Circuit parameters have been determined, and the performance has been modeled. A lumped-element equivalent circuit for the phase shifter is presented, and a qualitative fit to the measured data is provided. It is noted that this phase shifter is the first step toward a multiple device circuit with broadband true-time delay phase-shifter performance.<<ETX>>

Microwave De-embedding techniques applied to acoustics

This paper describes the use of the microwave techniques of time domain reflectometry (TDR) and de-embedding in an acoustical application. Two methods of calibrating the reflectometer are presented to evaluate the consistency of the method. Measured and modeled S-parameters of woodwind instruments are presented. The raw measured data is de-embedded to obtain an accurate measurement. The acoustic TDR setup is described.

Finite-difference, time-domain analysis of a folded acoustic transmission line

Recently designed, modern versions of renaissance woodwind instruments such as the recorder and serpent use square cross sections and a folded acoustic transmission line. Conventional microwave techniques would expect that this bend would cause unwanted reflections and impedance discontinuities. This paper analyses the folded acoustic transmission line using finite-difference, time-domain techniques and shows that the discontinuity can be compensated with by the use of a manufacturable method.

A Phenomenological Investigation of Anomalous Performance in Flex Coaxial Cables

In this study, we investigate anomalous flex cable performance in a phased-array antenna on advanced EHF. A number of low-gain IF paths were found in one local-oscillator region during thermal cycle testing, subsequently causing an out-of-specification condition. Utilizing advanced diagnostic tools, the contractor determined that the root cause of the gain drop was a failure in a flex coaxial cable. We outline the development of an analytical phenomenology model employed in understanding the failure pathology and verifying the root cause. We have developed 3-D finite-element models using Ansoft High Frequency Structure Simulator (HFSS) that mimic the insertion loss behavior associated with cable failure modes. To synthesize a particular loss characteristic, we use an equivalent circuit model consisting of parallel- LC sections. A closed-form analytical expression for resonance frequency was derived, linking the circuit and physical parameters; linear regression is used to fit measured data to the HFSS cable model. Using the phenomenology model, we determined that the root cause of the failures is a delamination of the layered outer sheath of the cable. Two mechanisms were discovered: 1) spurs in the outer layer and 2) complete layer separation over short cable lengths. The first mechanism induces a small frequency-independent increase in the loss and is inversely proportional to the spur delamination angle. This loss is attributable to conventional aging and considered benign. With the second mechanism, the delamination gap induces a sharp resonance in the loss at a discrete frequency and is reminiscent of a low-order filter. This phenomenon is a malignant loss responsible for our anomalous out-of-specification condition. We completed a parametric study using the phenomenology model, and determined that: 1) resonance frequency is inversely proportional to the gap width (Wg) ; 2) resonance frequency is proportional to the square root of the gap size (?{dg}) ; 3) insertion loss amplitude is proportional to the air gap size and width; and 4) the Q of a given delamination region is proportional to the square root of the gap size.

High-T/sub c/ superconducting microstrip resonators and filters on LaAlO/sub 3/

The authors discuss recent developments in high-Q microstrip resonators and filters using various deposition processes. They successfully developed sputtering, metalorganic vapor deposition (MOCVD), and laser deposition processes that produces high-quality high-T/sub c/ superconducting (HTS) films on LaAlO/sub 3/. For the double-sided MOCVD process, replacing the Ag ground plane with an HTS ground plane in silver ground plane eliminates extra surface losses due to normal metal ground conductors. These two-sided microwave circuits yield higher microwave performances than one-sided HTS circuits and much higher performance than identical Ag circuits. HTS surface resistances less than 330 mu Omega at 10 GHz were achieved. Q-values of 9600 at 1.3 GHz were achieved in meanderline resonators.<<ETX>>