Daniel L. Rascoe

Full wave analysis of microwave monolithic circuit devices using a generalized Yee-algorithm based on an unstructured grid

A generalized Yee-algorithm is presented for the temporal full-wave analysis of microwave monolithic integrated circuit (MMIC) devices. This algorithm has the significant advantage over the traditional Yee-algorithm in that it is based on unstructured and irregular grids. Thus, using the generalized Yee-algorithm, MMIC devices that contain curved conductors or complex geometries can be more accurately and conveniently modeled using standard automatic grid generation techniques. The generalized Yee-algorithm is based on the time-marching solution of the discrete form of Maxwells equations in their integral form. A correction scheme is introduced that is stable, maintains second-order accuracy, and maintains the divergenceless nature of the flux densities. Furthermore, by structuring the algorithm as a series of sparse matrix-vector multiplications, the generalized Yee-algorithm can be efficiently implemented on vector or parallel high performance computers.

Design and performance of a high-T/sub c/ superconductor coplanar waveguide filter

The design of a coplanar waveguide low-pass filter made of YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) on an LaAlO/sub 3/ substrate is described. Measurements were incorporated into simple models for microwave CAD analysis to develop a final design. The patterned and packaged coplanar waveguide low-pass filter of YBCO, with dimensions suited for integrated circuits, exhibited measured insertion losses when cooled in liquid nitrogen superior to those of a similarly cooled thin-film copper filter throughout the 0 to 9.5 GHz passband. Coplanar waveguide models for use with thin-film normal metal (with thickness either greater or less than the skin depth) and YBCO are discussed and used to compare the losses of the measured YBCO and copper circuits. >

Ka-band MMIC beam-steered transmitter array

A 32 GHz six-element linear transmitter array utilizing monolithic microwave integrated circuit (MMIC) phase shifters and power amplifiers was developed, fabricated, and tested. The array is composed of an RF signal distribution subsystem, a set of two MMIC carriers, and a patch antenna subsystem. The mean and standard deviation of the phase shift was 7.0+or-1.6% over the range 0 degrees to 300 degrees . The mean and standard deviation of output power at 1 dB gain compression was 13.6+or-0.3 dBm. Several externally tuned devices are capable of producing as much as 21.5 dBm with a power-added efficiency of 14.5% at 1-dB gain compression. The array provides a beamwidth of 7.5 degrees and has demonstrated acceptable beam steering over +or-8 degrees .<<ETX>>

Jet Propulsion Laboratory/NASA Lewis Research Center space qualified hybrid high temperature superconducting/semiconducting 7.4 GHz low-noise downconverter for NRL HTSSE-II program

A deep space satellite downconverter receiver was proposed by Jet Propulsion Laboratory (JPL) and NASA Lewis Research Center (LeRC) for the Naval Research Laboratorys (NRL) high temperature superconductivity space experiment, phase-II (HTSSE-II) program. Space qualified low-noise cryogenic downconverter receivers utilizing thin-film high temperature superconducting (HTS) passive circuitry and semiconductor active devices were developed and delivered to NRL. The downconverter consists of an HTS preselect filter, a cryogenic low-noise amplifier; a cryogenic mixer, and a cryogenic oscillator with an HTS resonator. HTS components were inserted as the front-end filter and the local oscillator resonator for their superior 77 K performance over the conventional components. The semiconducting low noise amplifier also benefited from cooling to 77 K. The mixer was designed specifically for cryogenic applications and provided low conversion loss and low power consumption. In addition to an engineering model, two space qualified units (qualification, flight) were built and delivered to NRL. Manufacturing ,integration and test of the space qualified downconverters adhered to the requirements of JPL class-D space instruments and partially to MIL-STD-883D specifications. The qualification unit has /spl sim/50 K system noise temperature which is a factor of three better than a conventional downconverter at room temperature. Commercial applications such as intersatellite links and V-SATS are envisioned to benefit by >3 dB link margin, or a factor of 2 in antenna size, from a future hybrid HTS/semiconducting cryogenic receiver employing new InP based HEMT LNA. In a spread spectrum communication network, the number of users per beam would more than double.

Ka-band MMIC beam steered planar array feed

A 32-GHz, 21-element array feed incorporating 63 MMIC (monolithic microwave integrated circuit) devices and providing electronic beam steering using 21 VLSI control chips is under development. An innovative building-block construction approach providing easy verification of device performance prior to integration in the array is described. In addition, the subarray layer concept with plug-in RF connectors allows for easy removal of a layer for repairing one of the components. This planar array demonstrates state-of-the-art design technology required for implementation of Ka-band transmit arrays in future NASA (US National Aeronautics and Space Administration) deep-space missions.<<ETX>>

A Ka-band MMIC array feed transmitter for deep space applications

A Ka-band solid-state transmitter capable of power greater than 5 W is being developed. The transmitter consists of an array of 21 elements each driven by a single stage MMIC (monolithic microwave integrated circuit) power amplifier, a MMIC three-stage preamplifier, and a MMIC four bit phase shifter. The design of the array, measurements of the antenna pattern of the full array, and an electronically beam steered subarray are reported.<<ETX>>

Design and performance of low-noise hybrid superconductor/semiconductor 7.4 GHz receiver downconverter

Low noise receivers play critical role in space applications. Thin film high-critical-temperature-superconducting (HTS) passive circuits were combined with GaAs microwave devices to achieve ultra low noise and small size receiver downconverter at 77 K. HTS pre-select filter, a cryogenic mixer, and a hybrid oscillator with an HTS resonator were designed, fabricated and interconnected to produce a low-noise hybrid superconductor/semiconductor 7.4 GHz microwave receiver. When cooled to 77 K, the downconverter plus cables inside a cryogenic refrigerator had a noise figure of approximately 0.7 dB with conversion gain of 18 dB. In addition to reduce noise figure, advantages of small size and low power consumption are observed due to the use of HTS circuits in the downconverter.<<ETX>>

High-T/sub c/ superconducting coplanar waveguide filter

Coplanar waveguide (CPW) low-pass filters made of YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) on LaAlO/sub 3/ substrates, with dimensions suited for integrated circuits, were fabricated and packaged. A complete filter gives a true idea of the advantages and difficulties in replacing thin-film metal with a high-temperature superconductor in a practical circuit. Measured insertion losses in liquid nitrogen were superior to the loss of a similar thin-film copper filter throughout the 0- to 9.5-GHz passband. These results demonstrate the performance of fully patterned YBCO in a practical CPW structure after sealing in a hermetic package.<<ETX>>

Modeling of planar quasi-TEM superconducting transmission lines

Design oriented modeling of high-temperature superconducting thin-film microwave circuits is difficult when film thickness is on the order of the penetration depth of the fields. Involved formulas for loss, phase velocity and characteristic impedance can be derived from the Bardeen-Cooper Schrieffer (BCS) theory of superconductivity. The parameters required by these formulas do not correspond to readily measurable observables that depend on the manufacturing process of the superconductor. An application of the phenomenological loss equivalence method in modeling the microwave behavior of planar quasi-TEM superconducting transmission lines is presented. Measured and modeled S-parameters of a superconducting coplanar waveguide lowpass filter agree to within 0.3 dB in magnitude and 0.5 radians in phase. Extracted values for the penetration depth and the real part of the conductivity of the superconducting film are within 10% of the findings of other researchers. >

A coplanar waveguide filter using thin-film high temperature superconductor

The design of a coplanar waveguide low-pass filter mode of high-critical-temperature superconducting YBCO film on a LaAlO/sub 3/ substrate is described. The patterned and packaged coplanar waveguide low-pass filter of YBCO exhibited measured insertion losses in liquid nitrogen superior to the loss of similar thin-film copper filter throughout the 0-to-9.5-GHz passband. Coplanar waveguide models for use with thin-film normal metal (with thickness either greater or less than the skin depth) and YBCO are discussed and used to compare the losses of the measured YBCO and copper circuits.<<ETX>>