Semiconductors & ICs

Cryogenic Pound Circuits for Cryogenic Sapphire Oscillators

Two modern cryogenic variants of the Pound circuit have been devised to increase the frequency stability of microwave oscillators that include cryogenic sapphire-filled cavity resonators. Invented in the 1940s and named after its inventor (R. V. Pound), the original Pound circuit is a microwave frequency discriminator that provides feedback to stabilize a voltage-controlled microwave oscillator with respect to an associated cavity resonator. Heretofore, Pound circuits used in conjunction with cryogenic resonators have included room-temperature electronic components coupled to the resonators via such inter-connections as coaxial cables. The thermo mechanical instabilities of these inter-connections give rise to frequency instabilities. In a cryogenic Pound circuit of the present improved type, all of the active electronic components, the inter-connections among them, and the inter-connections between them and the resonator reside in the cryogenic environment along with the resonator and, hence, are thermo-mechanically stabilized to a large degree. Hence, further, frequency instabilities are correspondingly reduced.

Posted in: Semiconductors & ICs, Briefs, TSP

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Microstrip Antenna Arrays on Multilayer LCP Substrates

Antennas, feedlines, and switches are embedded in and on flexible sheets. A research and development effort now underway is directed toward satisfying requirements for a new type of relatively inexpensive, lightweight, microwave antenna array and associated circuitry packaged in a thin, flexible sheet that can readily be mounted on a curved or flat rigid or semi-rigid surface. A representative package of this type consists of microwave antenna circuitry embedded in and/or on a multilayer liquid- crystal polymer (LCP) substrate. The circuitry typically includes an array of printed metal microstrip patch antenna elements and their feedlines on one or more of the LCP layer(s). The circuitry can also include such components as electrostatically actuated microelectromechanical systems (MEMS) switches for connecting and disconnecting antenna elements and feedlines. In addition, the circuitry can include switchable phase shifters described below.

Posted in: Semiconductors & ICs, Briefs, TSP

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Multichannel X-Band Dielectric-Resonator Oscillator

Unlike other DROs, this one is electrically tunable. A multichannel dielectric-resonator oscillator (DRO), built as a prototype of a local oscillator for an X-band transmitter or receiver, is capable of being electrically tuned among and within 26 adjacent frequency channels, each 1.16 MHz wide, in a band ranging from ≈7,040 to ≈7,070 GHz. The tunability of this oscillator is what sets it apart from other DROs, making it possible to use mass-produced oscillator units of identical design in diverse X-band applications in which there are requirements to use different fixed frequencies or to switch among frequency channels.

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Semiconductor Bolometers Give Background-Limited Performance

These devices can be fabricated inexpensively by use of established silicon-processing techniques. Semiconductor bolometers that are capable of detecting electromagnetic radiation over most or all of the infrared spectrum and that give background-limited performance at operating temperatures from 20 to 300 K have been invented. The term “background-limited performance” as applied to a bolometer, thermopile, or other infrared detector signifies that the ability to detect infrared signals that originate outside the detector is limited primarily by thermal noise attributable to the background radiation generated external to the bolometer. The signal- to-noise ratios and detectivities of the bolometers and thermopiles available prior to this invention have been lower than those needed for background-limited performance by factors of about 100 and 10, respectively.

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LC Circuits for Diagnosing Embedded Piezoelectric Devices

Failures are readily identified through changes in resonance frequencies. A recently invented method of nonintrusively detecting faults in piezoelectric devices involves measurement of the resonance frequencies of inductor-capacitor (LC) resonant circuits. The method is intended especially to enable diagnosis of piezoelectric sensors, actuators, and sensor/actuators that are embedded in structures and/or are components of multilayer composite-material structures.

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Improved Method of Manufacturing SiC Devices

Several improvements promise to make manufacture of SiC devices more economical. The phrase, “common-layered architecture for semiconductor silicon carbide” (“CLASSiC”) denotes a method of batch fabrication of microelectromechanical and semiconductor devices from bulk silicon carbide. CLASSiC is the latest in a series of related methods developed in recent years in continuing efforts to standardize SiC-fabrication processes. CLASSiC encompasses both institutional and technological innovations that can be exploited separately or in combination to make the manufacture of SiC devices more economical. Examples of such devices are piezoresistive pressure sensors, strain gauges, vibration sensors, and turbulence-intensity sensors for use in harsh environments (e.g., high-temperature, high-pressure, corrosive atmospheres).

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Alumina or Semiconductor Ribbon Waveguides at 30 to 1,000 GHz

The waveguides would be configured to exploit low-loss electromagnetic modes. Ribbon waveguides made of alumina or of semiconductors (Si, InP, or GaAs) have been proposed as low-loss transmission lines for coupling electronic components and circuits that operate at frequencies from 30 to 1,000 GHz. In addition to low losses (and a concomitant ability to withstand power levels higher than would otherwise be possible), the proposed ribbon waveguides would offer the advantage of compatibility with the materials and structures now commonly incorporated into integrated circuits.

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