Time and Frequency MeasurementsCharacterization of Oscillators and AmplifiersTechnical Contacts: Stefania Romisch Trudi Peppler Please contact the technical staff before shipping instruments or standards to the address listed below. Mailing Address:
back to top of page | back to index of time and frequency measurements Oscillator Frequency Calibration (77100C) NIST provides calibration services for oscillators with an output frequency of 1 Hz to 50 GHz. The relative standard uncertainty is nominally that of the NIST frequency standard, which is 5 x 10^{-15}, but is limited by noise in the oscillator under test. The frequency stability of the oscillator can also limit the calibration, because oscillators often change frequency during shipment. Higher frequencies (50 Hz to 110 GHz) are covered under Service ID Number 77140S. back to top of page | back to index of time and frequency measurements Characterization of Atomic Frequency Standards (77110C) An atomic standard is characterized by comparing it against UTC (NIST). This characterization test determines the long-term performance of the standard in the time domain and requires 30 days of measurements. The 5-MHz output of the standard is sampled every 720 seconds and it is compared with the 5-MHz UTC (NIST) signal using the NIST time scale measurement system. The square root of the Allan deviation σ _{y} (τ) is computed to 2 x 10^{-15}, which is the frequency stability of UTC (NIST) for averaging times longer than 1 day. The fractional frequency drift of UTC (NIST) is less than 2 x 10^{-16 }per day. The offset between UTC (NIST) and TAI used to determine the uncertainty of this calibration is conservatively set at 10^{-14}. The actual values transferable to the standard are often limited by the standard’s own stability and noise properties. back to top of page | back to index of time and frequency measurements Characterization of Oscillators: Time Domain (77120C) NIST provides services to characterize the short-term performance, in the time domain, of frequency sources with a frequency of 5 MHz. The 5-MHz output of the source under test is sampled at 1s intervals and compared with the 5-MHz UTC (NIST) signal. The stability in terms of the square root of the Allan deviation σ _{y} (τ) is then computed and to 4 x 10^{-13}/T^{1/2} for averaging times up to 10,000 s. The frequency offset is measured with a relative standard uncertainty of 10^{-14}, limited by the offset between UTC (NIST) and TAI used to determine the uncertainty of this calibration. The actual values transferable to the frequency source under test are often limited by the source's own stability and noise properties. back to top of page | back to index of time and frequency measurements Characterization of Oscillators and Amplifiers: Phase Noise in the Frequency Domain (77130C) NIST provides calibration services of the phase noise of single oscillators and amplifiers. For frequencies of 5 MHz to 26 GHz, phase modulation (PM) noise S_{φ}(ƒ) of single oscillators and amplifiers can be determined for Fourier frequency offsets from the carrier of 0.1 Hz to 10 MHz. The PM noise is measured for only a few user-specified frequency offsets (typically 3 points per decade). All measurements of phase noise are made relative to 1 rad ^{2} /Hz. At a carrier frequency of 5 MHz, S_{φ}(ƒ) can be measured to -145 dB for a frequency offset of 1 Hz and -190 dB for an offset of 10 kHz. At a carrier frequency of 100 MHz, S_{φ}(ƒ)can be measured to -50 dB for a frequency offset of 1 Hz and -190 dB for an offset of 50 kHz. A typical value of standard uncertainty is 1 dB, but specific values depend on the carrier frequency and the offset frequency. Specific measurement requirements should be discussed prior to placing an order. PM noise for frequencies above this range (but less than 110 GHz) are covered under Service ID Number 77140S. back to top of page | back to index of time and frequency measurements Characterization of Oscillators and Amplifiers: Amplitude Noise in the Frequency Domain (77131C) NIST provides calibration services of amplitude noise of single oscillators and amplifiers. For frequencies from 1 MHz to 26 GHz, amplitude modulation (AM) noise S_{α}(ƒ)of single oscillators and amplifiers can be determined for Fourier frequency offsets from the carrier of 0.1 Hz to 10 MHz. The AM noise is measured for only a few user specified frequency offsets (typically 3 points per decade). All measurements of amplitude noise are made relative to 1 Hz. At a carrier frequency of 5 MHz, S_{α}(ƒ) can be measured to -140 dB for a frequency offset of 1 Hz, and -180 dB for an offset of 10 kHz. At a carrier frequency of 100 MHz, S_{α}(ƒ) can be measured to -30 dB for a frequency offset of 1 Hz and -180 dB for an offset of 50 kHz. A typical value of standard uncertainty is 1 dB, but specific values depend on the carrier frequency and the offset frequency. Specific measurement requirements should be discussed prior to placing an order. AM noise for frequencies above this range (but less than 110 GHz) are covered under Service ID Number 77140S. back to top of page | back to index of time and frequency measurements References—Calibration and Characterization of Oscillators and Amplifiers Introduction to the Time Domain Characterization of Frequency Standards, J. Jesperson, Proc. 25th Annu. Precise Time and Time Interval (PTTI) Meeting, Pasadena, CA, 83-102 (Dec. 1991). An Introduction to Frequency Standards, L. Lewis, Proc. IEEE 79 (7), 927-935 (July 1991). Properties of Signal Sources and Measurement Methods, D. A. Howe, D. W. Allan, and J. A. Barnes, in Characterization of Clocks and Oscillators, edited by D. B. Sullivan, D. W. Allan, D. A. Howe, and F. L. Walls, Natl. Inst. Stand. Technol. Tech. Note 1337, 14-16 (1990). Characterization of Clocks and Oscillators, D. B. Sullivan, D. W. Allan, D. A. Howe, and F. L. Walls, eds., NIST Tech. Note 1337 (Mar. 1990). Frequency and Time-Their Measurement and Characterization, S. R. Stein, Precision Frequency Control, Vol. 2, edited by E. A. Gerber and A. Ballato (Academic Press, NY), 191–232 (1985). back to top of page | back to index of time and frequency measurements Program questions: |