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Engineering topics

Hellwig, H.

Publications and source records attributed to Hellwig, H..

Government and industry interactions in the development of clock technology

It appears likely that everyone in the time and frequency community can agree on goals to be realized through the expenditure of resources. These goals are the same as found in most fields of technology: lower cost, better performance, increased reliability, small size and lower power. Related aspects are examined in the process of clock and frequency standard development. Government and industry are reviewed in a highly interactive role. These interactions include judgements on clock performance, what kind of clock, expenditure of resources, transfer of ideas or hardware concepts from government to industry, and control of production. Successful clock development and production requires a government/industry relationship which is characterized by long-term continuity, multidisciplinary team work, focused funding and a separation of reliability and production oriented tasks from performance improvement/research type efforts.

Hellwig, H.↗

A small, passively operated hydrogen maser

The paper describes a compact passive hydrogen maser with unique features including a reduction in size. It uses a passive operation mode, permitting the use of a small microwave TE(011) cavity dielectrically loaded by a low loss alumina. The Teflon coated quartz bulb common in other masers has been replaced by a Teflon coating on the inside wall of the cavity producing a simpler designed and a more rugged H-maser package. The cavity and the attached endcaps comprise the vacuum envelope, allowing the use of a single vacuum system. The dimensional stability of the ceramic cavity under barometric changes is sufficiently within the range of the electronic cavity servo so that a second vacuum system is not required. For temperature control, a single oven is located in the magnetic shield nest.

Howe, D. A.↗

Relationships Between the Performance of Time/Frequency Standards and Navigation/Communication Systems

The relationship between system performance and clock or oscillator performance is discussed. Tradeoffs discussed include: short term stability versus bandwidth requirements; frequency accuracy versus signal acquisition time; flicker of frequency and drift versus resynchronization time; frequency precision versus communications traffic volume; spectral purity versus bit error rate, and frequency standard stability versus frequency selection and adjustability. The benefits and tradeoffs of using precise frequency and time signals are various levels of precision and accuracy are emphasized.

Hellwig, H.↗

A review of precision oscillators

Precision oscillators used in PTTI applications include quartz crystal, rubidium gas cell, cesium beam, and hydrogen maser oscillators. A general characterization and comparison of these devices is given including accuracy, stability, environmental sensitivity, size, weight, power consumption, availability and cost. Areas of special concern in practical applications are identified and a projection of future performance specifications is given. An attempt is made to predict physical and performance characteristics of new designs potentially available in the near future.

Hellwig, H.↗