NIST Optical Tools Produce Ultra-low-noise Microwave Signals

By combining advanced laser technologies in a new way, physicists at the National Institute of Standards and Technology (NIST) have generated microwave signals that are more pure and stable than those from conventional electronic sources. The apparatus could improve signal stability and resolution in radar, communications and navigation systems, and certain types of atomic clocks.

“This is the quietest, most stable microwave generator that’s ever been made at room temperature,” said project leader Scott Diddams.

Described in Nature Photonics,* NIST’s low-noise apparatus is a new application of optical frequency combs, tools based on ultrafast lasers for precisely measuring optical frequencies, or colors, of light. Frequency combs are best known as the “gears” for experimental next-generation atomic clocks, where they convert optical signals to lower microwave frequencies, which can be counted electronically.

The new low-noise system is so good that NIST scientists actually had to make two copies of the apparatus just to have a separate tool precise enough to measure the system’s performance. Each system is based on a continuous-wave laser with its frequency locked to the extremely stable length of an optical cavity with a high “quality factor,” assuring a steady and persistent signal. This laser, which emitted yellow light in the demonstration but could be another color, is connected to a frequency comb that transfers the high level of stability to microwaves. The transfer process greatly reduces—to one-thousandth of the previous level—random fluctuations in the peaks and valleys, or phase, of the electromagnetic waves over time scales of a second or less. This results in a stronger, purer signal at the exact desired frequency.

The base microwave signal is 1 gigahertz (GHz, or 1 billion cycles per second), which is the repetition rate of the ultrafast laser pulses that generate the frequency comb. The signal can also be a harmonic, or multiple, of that frequency. The laser illuminates a photodiode that produces a signal at 1 GHz or any multiple up to about 15 GHz. For example, many common radar systems use signals near 10 GHz.

NIST’s low-noise oscillator might be useful in radar systems for detecting faint or slow-moving objects. The system might also be used to make atomic clocks operating at microwave frequencies, such as the current international standard cesium atom clocks, more stable. Other applications could include high-resolution analog-to-digital conversion of very fast signals, such as for communications or navigation, and radio astronomy that couples signals from space with arrival times at multiple antennas. (source NIST Tech Beat: June 27, 2011)

NIST Identifies Five Foundational Smart Grid Standards

The Commerce Department’s National Institute of Standards and  Technology (NIST) has advised the Federal Energy Regulatory Commission  (FERC) that it has identified five “foundational” sets of standards for Smart  Grid interoperability and cyber security that are ready for consideration  by federal and state energy regulators.

The standards, produced by the International Electrotechnical Commission (IEC), focus on the information models and protocols important to efficient and reliable grid operations as well as cyber security.

In a letter to FERC Chairman Jon Wellinghoff, NIST’s national coordinator for Smart Grid interoperability, George Arnold, said the standards “are essential to uniform and interoperable communication systems throughout the grid and will accommodate the evolution of the grid and the integration of new technologies.”

In the Energy Independence and Security Act (EISA) of 2007, Congress directed NIST to coordinate development of communication protocols and other standards to achieve an interoperable Smart Grid —a nationwide electric power system that enables two-way flows of energy and information.  Under EISA, once it determines sufficient consensus has been achieved, FERC is charged with instituting rulemaking proceedings to adopt the standards necessary to ensure Smart Grid functionality and interoperability.

The five families of IEC standards will further efforts to achieve efficient and secure intersystem communications, among other FERC priorities identified in the commission’s July 16, 2009, Smart Grid Policy Statement.  These standards will be updated as Smart Grid requirements and technologies evolve.

The standards and their functions are:

• IEC 61970 and IEC 61968: Providing a Common Information Model (CIM) necessary for exchanges of data between devices and networks, primarily in the transmission (IEC 61970) and distribution (IEC 61968) domains.
• IEC 61850: Facilitating substation automation and communication as well as interoperability through a common data format.
• IEC 60870-6: Facilitating exchanges of information between control centers.
• IEC 62351:  Addressing the cyber security of the communication protocols defined by the preceding IEC standards.

To determine whether a standard was ready for consideration by regulators, NIST took a number of factors into account, including the maturity of the standard, the resolution of previously identified issues by its Smart Grid Interoperability Panel, and a satisfactory review of cyber security requirements.

The five IEC standards were among the 25 Smart Grid-relevant standards identified as “ready for implementation” in the NIST Framework and Roadmap for Smart Grid Interoperability Standards, Release 1.0, which was issued in January 2010.  However, these specifications required a cyber security review that could not be completed until NIST finalized its initial Guidelines for Smart Grid Cyber Security, which were published in early September 2010.

NIST anticipates that the release of future standards identified as ready for consideration by regulators—as well as by other Smart Grid stakeholders—also will be organized according to Smart Grid functions and domains of application, such as bulk generation, transmission or customer premises.

NIST’s standards-coordination activities are supported, in part, by the U.S. Department of Energy, the lead agency for federal Smart Grid efforts.

To read summaries of each of the five standards identified for consideration by regulators, go to: http://collaborate.nist.gov/twiki-sggrid/bin/view/SmartGrid/NISTStandardsSummaries (source www.nist.gov)