Analog and Mixed-Signal Circuit Design

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					                                                               Analog and Digital Systems Group

                                                 Analog and Mixed-Signal Circuit Design
                                          Oak Ridge National Laboratory              When possible, ADS engineers
                                          (ORNL) researchers, because of the         perform board- and system-level
                                          unique and leading-edge nature of          design using commercially available
                                          their investigations, often encounter      sensors, integrated circuits, modules,
                                          situations in which no commercially        and subsystems to reduce cost. Other
                                          available instrumentation meets their      MSSE and Laboratory resources are
                                          measurement needs. In other cases,         tapped when the use of custom
                                          researchers’ goals are to advance the      sensors, materials, or integrated
                                          state of the art by increasing the         circuits is beneficial.
               Purpose: When ORNL
                                          range, resolution, or accuracy of
                                                                                     Development of “front-end” circuitry
    When       researchers, industrial    scientific measurements in their fields
                                                                                     such as sensor excitation and signal
State of the
               partners, or colleagues    of expertise. Sometimes the sheer
               from government or                                                    conditioning is accelerated by
                                          number of measurements required to
     Art       military agencies have
               a unique measurement       collect all required data or to properly   modeling with PSPICE and similar
Is Not Quite   requirement, the ADS       control an experiment precludes the        simulation packages. Modeled
   Enough      Group has the expertise
               and the experience to      use of off-the-shelf instruments.          designs import easily into printed-
               move the requirement                                                  circuit layout software for rapid
               from a concept to a        The Analog and Digital Systems             production of prototype boards.
               design to
               implementation in a        (ADS) Group stands ready to partner        Small quantities of circuit boards and
               laboratory or in the       with these scientists and provide          instruments are usually built in-
               field.                     electronics development and other          house. Larger quantities are usually
               ADS’s analog and           measurements-related capabilities          outsourced to trusted fabrication
               mixed-signal circuit
               design capabilities        that will enable their research to         houses.
               effectively bridge the     move forward.
               gap between unusual                                                   Success Story: DDS Mass
               (often one-of-a-kind)
               sensors and the latest     Capabilities                               Spectrometer
               data acquisition and
               control systems in an      ADS has established expertise in the       Spectrometrists in the Chemical
               impressive variety of      following areas critical to scientific     Sciences Division had a great idea:
               R&D applications.          measurement, data acquisition, and         use Direct Digital Synthesis (DDS) to
               Complementary              control:                                   generate the frequencies used for
               Capabilities: ADS
               analog and mixed-          • Sensor-electronics integration.          exciting the electrodes in a digital ion-
               circuit design expertise                                              trap mass spectrometer. DDS would
               meshes well with other     • High-precision data conversion.          allow the frequencies to be varied in
               ADS and MSSE
               strengths in the           • Data multiplexing and telemetry.         arbitrarily small steps, greatly
               following:                                                            increasing the resolution of the
                                          • Low-noise signal conditioning of
               • RF circuit and                                                      measurement.
                 antenna design.            high-speed and low-level signals.
               • Sensor development.
               • Real-time
                                          • High-voltage biasing and pulsing.        The catch? To capitalize on the
                 computation.             • Board- and system-level design.          frequency selectivity and stability
               • Programmable                                                        offered by the DDS approach,
                 device applications.     • Electromagnetic emissions and            extremely stable high-voltage
               • Embedded
                 intelligence.              susceptibility control.                  supplies, extremely fast high-voltage
               • Power electronics.
               • Optics and image
                                          • Efficient power conversion and           pulsing, and extremely low-jitter
                 processing.                distribution.                            generation and distribution of the
               • Electronic signature                                                clock and switching signals were
                 analysis.                • Interfacing disparate systems.
               • Radiation detection                                                 required. In addition to implementing
                 and characterization.    • Built-in test and calibration.           the DDS and clock-generation
               • Nanotechnology.
                                          • Wireless sensor networks.                algorithms in a field-programmable
                                                                                     gate array (FPGA), ADS developed
                Analog and Digital Systems Group
the power conditioning and high-voltage switching           delivering them from a depth of 100 meters and over
circuitry that completed the package. When the ADS          distances of up to a kilometer to the USNS Hayes, the
prototype circuit board was used to replace the             Navy’s noise analysis laboratory ship.
electronics in a modern laboratory-grade mass spec, an
immediate 5× resolution improvement was realized.           Every link of the signal processing chain had to be ultra-
                                                            accurate to maintain the precise gain and phase
                                                            relationships between hydrophone signals that allow the
                                                            topside computers to form the arrays’ sensitivity
                                                            patterns into the narrow beams required to attenuate the
                                                            ocean’s background noise and to focus on specific
                                                            portions of the submarine being tested.

                                                            Powering thousands of channels of electronics through
                                                            kilometers of cables presented another set of challenges.
                                                            The use of 300-VDC power transmission through the
                                                            umbilical cables minimizes power loss in the cables but
                                                            requires conversion to much lower voltages inside the
                                                            underwater pressure vessels. The ADS-developed power
                                                            conversion and conditioning subsystem delivers the
       Separation of the isotope peak in this segment       low-noise power required for precise amplification,
    of a DDS mass spectrum for perfluorotributylamine       filtering, and digitization. It also achieves the high
                     is clearly evident.
                                                            efficiency required for keeping the signal conditioning
                                                            and data telemetry electronics cool, ensuring high
Another 5× increase in resolution is expected in the next   reliability and long life.
generation of the DDS timing circuitry.
                                                            For over a decade now, the AMFIP II system has been
Success Story: Acoustic Measurements                        used by the Navy to ensure that our nation’s submarine
Facilities Improvement Program, Phase II                    fleet keeps its edge by maintaining its silence.
The U.S. Navy faced a dilemma: The new Seawolf class
of fast-attack submarines being planned was going to be
so stealthy that no existing noise-measurement sonar
system would be able even to verify that the new boats
met their unprecedented noise-generation specifications.

The Navy turned to ORNL for assistance, and ADS
personnel, members of the Real-Time Systems Group,
and industrial partner Planning Systems, Incorporated,
worked together to develop the most sensitive sonar
system ever deployed. Considering that the acoustic
noise levels emitted by the Seawolf are considerably
lower than the background noise levels even in the
quietest seas on the planet, the challenge of not only
detecting these emissions but of accurately measuring                   Nighttime deployment of an HGA
                                                                             from the USNS Hayes.
them over a wide bandwidth was daunting.

MSSE’s Real-Time Systems Group led the effort to            Contact Information
develop the data acquisition and analysis system based      For more information on ADS’s analog and mixed-signal
on two Cray SuperServer highly paralleled processors.       development capabilities, please contact William H.
ADS members took responsibility for conditioning and        (Andy) Andrews ( at
digitizing signals from the three 10-meter-tall,            865-574-5677 or Dwight Clayton (
1,000-hydrophone high-gain arrays (HGAs) and                at 865-576-8134.