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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 2 • Date March 2000

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Displaying Results 1 - 25 of 33
  • A review of wireless SAW sensors

    Page(s): 317 - 332
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    Wireless measurement systems with passive surface acoustic wave (SAW) sensors offer new and exciting perspectives for remote monitoring and control of moving parts, even in harsh environments. This review paper gives a comprehensive survey of the present state of the measurement systems and should help a designer to find the parameters required to achieve a specified accuracy or uncertainty of measurement. Delay lines and resonators have been used, and two principles have been employed: SAW one-port devices that are directly affected by the measurand and SAW two-port devices that are electrically loaded by a conventional sensor and, therefore, indirectly affected by the measurand. For radio frequency (RF) interrogation, time domain sampling (TDS) and frequency domain sampling (FDS) have been investigated theoretically and experimentally; the methods of measurement are described. For an evaluation of the effects caused by the radio interrogation, we discuss the errors caused by noise, interference, bandwidth, manufacturing, and hardware tuning. The system parameters, distance range, and measurement uncertainty are given numerically for actual applications. Combinations of SAW sensors and special signal processing techniques to enhance accuracy, dynamic range, read out distance, and measurement repetition rate (measurement bandwidth) are presented. In conclusion, an overview of SAW sensor applications is given. View full abstract»

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  • Micromachined resonant temperature sensors: theoretical and experimental results

    Page(s): 333 - 340
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    Describes the study of quartz temperature sensors based on new bulk acoustic wave microresonators operating in thickness modes. First, we compare the thermal sensitivity and the electromechanical coupling coefficients of singly or doubly rotated cuts. These investigations allow us to select some cuts with both a good thermal sensitivity and piezoelectric characteristics. In the second part, emphasis is placed on the micromachining of resonators suspended by four bridges. These two theoretical considerations lead to the choice of three cuts. Experimental measurements are then presented. The temperature-frequency characteristics of the resonators are measured over the range 20 to 100 /spl deg/C. Motional resistances and Q factors are determined at room temperature. View full abstract»

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  • Lam/spl acute/e-mode miniaturized quartz temperature sensors

    Page(s): 341 - 345
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    Lam/spl acute/e-mode is very useful for realization of a miniaturized quartz crystal resonator because its resonant frequency principally depends only on the contour dimensions. Because the heat capacitance for the miniaturized quartz crystal resonator is small and the frequency response versus temperature is very rapid, the quartz crystal resonator is useful for application in temperature sensors. In addition, because a Lam/spl acute/e-mode quartz crystal resonator has zero temperature coefficients, designated LQ/sub 1/ cut and LQ/sub 2/ cut, and, particularly, the resonator for LQ/sub 1/ cut has a comparatively large value of the second-order temperature coefficient /spl beta/, a Lam/spl acute/e-mode quartz crystal resonator can be obtained with the large first-order temperature coefficient or when /spl beta/=0. In this paper, when cut angles /spl phi/=45/spl deg/ and /spl theta/=45/spl deg/, /spl alpha/ has a value of 44.6/spl times/10/sup -6///spl deg/C in the calculation and 39.9/spl times/10/sup -6///spl deg/C in the experiments with /spl beta/=0; when /spl phi/=51.5/spl deg/ and /spl theta/=45/spl deg/, /spl alpha/=68.1/spl times/10/sup -6///spl deg/C in the calculation and 62.0/spl times/10/sup -6///spl deg/C in the experiments with a value of /spl beta/ larger than that of /spl phi/=45/spl deg/ and /spl theta/=45/spl deg/. For both cut angles, the calculated frequency change vs. temperature is found to be sufficiently large and slightly larger than the measured one. View full abstract»

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  • Long-term stability and performance characteristics of crystal quartz gauge at high pressures and temperatures

    Page(s): 346 - 354
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    Good long-term stability of high precision quartz pressure sensors is necessary for various applications ranging from pressure transient analysis to permanent monitoring systems for optimal reservoir management in the petroleum industry. A crystal quartz gauge (CQG/sup 1/) is a dual-mode, thickness-shear, quartz pressure sensor that has been used in oil field services for the past 8 years. High accuracy, resolution, and fast response time of this sensor enable a reliable estimate of formation permeability and oil/water interfaces in reservoirs that help reduce the overall cost of oil and gas production. The sensing resonator characteristics can be described in terms of equivalent circuit parameters (motional resistance and capacitance), resonator-Q and the short-term frequency stability of both the B- and C-modes of vibrations at various temperatures. The pressure reading errors of manufactured gauges are less than 8.89 kPa (1 psi) (plus 0.01% of the reading because of the uncertainty of the dead-weight tester). The pressure resolution is better than 20.7 Pa (0.003 psi) over a 1-s gate time. An extremely effective dynamic compensation algorithm yields corrected pressure readings with a very fast response time as short as a strain-gauge-based pressure transducer while retaining the high performance of a quartz gauge. Recent long-term stability tests of CBGs show a negligibly small drift of the order of a few tenths of 1 psi (0.1 psi=689 Pa) at 103 MPa (15 kpsi) and 175/spl deg/C for a period of more than 1 yr. These results confirm that the CQG characteristics exceed the demanding specifications for both the well tests and permanent monitoring systems. View full abstract»

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  • Langasite, langanite, and langatate bulk-wave Y-cut resonators

    Page(s): 355 - 360
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    Materials in the langasite family are of current interest for both bulk wave and surface wave devices. Piano-convex Y-cut bulk wave resonators have been built and tested on overtones 1 through 9 using LGS (langasite; La/sub 3/Ga/sub 5/SiO/sub 14/), LGN (langanite; La/sub 3/Ga/sub 5.5/Nb/sub 0.5/O/sub 14/), and LGT (langatate; La/sub 3/Ga/sub 5.5/Ta/sub 5.5/O/sub 14/). Frequencies and motional inductances are compared with calculated values, with good agreement except for the motional inductance of LGT. For all three materials, frequency variation is an essentially parabolic function of temperature. For LGN and LGT, reported values of the Q-frequency product are significantly above the classical limit for AT-cut quartz. A maximum 4 f value of 25.6/spl times/10/sup 6/, where frequency is in megahertz;, was observed for an LGT resonator; for an unplated resonator, 29.2/spl times/10/sup 6/ was measured. Still higher values are believed possible. View full abstract»

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  • Flicker noise measurement of HF quartz resonators

    Page(s): 361 - 368
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    Frequency flicker of quartz resonators can be derived from the measurement of S/sub /spl phi// (f), i.e., the power spectrum density of phase fluctuations /spl phi/. The interferometric method appears to be the best choice to measure the phase fluctuations of the quartz resonators because of its high sensitivity in the low power conditions, which is required for this type of resonator. Combining these two ideas, we built an instrument suitable to measure the frequency flicker floor of the quartz resonators, and we measured the stability of some 10-MHB high performance resonators as a function of the dissipated power. The stability limit of our instrument, described in terms of Allan deviation /spl sigma//sub y/(/spl tau/), is of some 10/sup -14/. View full abstract»

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  • Phase noise measurements of 10-MHz BVA quartz crystal resonators

    Page(s): 369 - 373
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    In this paper, we review a new piece of equipment that allows one to characterize the phase noise of crystal resonators using a phase bridge system with carrier suppression. This equipment allows one to measure the inherent phase stability of quartz crystal resonators in a passive circuit without the noise usually associated with an active oscillator. We achieved a system noise floor of approximately -150 dBc/Hz at 1 Hz and -160 dBc/Hz, at 10 Hz. A SPICE characterization of the carrier suppression system is given. An investigation of the phase modulation (PM) noise in 10 MHz BVA, SC-cut quartz crystal resonator pairs is presented. View full abstract»

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  • Phase noise measurements in dual-mode SC-cut crystal oscillators

    Page(s): 374 - 378
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    This paper describes the phase-noise characteristics and the analysis model of an SC-cut dual-mode oscillator. The C mode phase-noise sideband levels of -124 dBc at 10 Hz and -154 dBc at 10 kHz have been demonstrated using a dual-mode oscillator that simultaneously excited the C and B mode of a 10-MHz, third overtone, SC-cut crystal resonator. Based on Leeson's model, a phase-noise analysis model for dual-mode oscillators has been proposed also. Actual phase-noise levels of the C mode in dual-mode oscillation corresponded well to results calculated from the proposed model. View full abstract»

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  • Toward resonator anharmonic sensors for precision crystal oscillators: a Gaussian model

    Page(s): 379 - 389
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    This paper addresses the statistical properties of eigenfrequency modes (anharmonics, for instance) of BAW crystal resonators in oscillators excited by noise or intended modulation and considered to be sensors of environmental impact. The modulated noisy model of a closed loop oscillator is studied for its amplitude-frequency and phase-frequency modulation characteristics caused by anharmonic influence. Pursuing the aim, we consider in detail amplitude, phase, and the time derivatives of an anharmonic sensor signal and present corresponding probability distributions for the different signal-to-noise ratios (SNR). Both statistical effects caused by noise and intended modulation are considered. Experimental results are also given. View full abstract»

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  • A new type of balanced-bridge controlled oscillator

    Page(s): 390 - 403
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    A novel bridge-controlled crystal oscillator circuit with exceptional temperature stability is described. The contribution to the oscillator temperature coefficient of frequency (tempco) from the circuit components (exclusive of the crystal) is reduced to about 10/sup -11///spl deg/C, which is several orders of magnitude better than conventional oscillator circuits. This avoids a situation in which the overall tempco is limited by circuit component drift rather than crystal stability, which can easily occur with conventional circuits when the crystal is ovenized at a turnover point. Previous attempts to use a bridge in an oscillator were made by Meacham (1938), who used an imperfectly balanced bridge, and Sulzer (1955), who used a balanced pseudo-bridge. The reasons why these are unsatisfactory are discussed. Although the bridge greatly reduces reactive frequency pulling, it does not address directly the additional issue of pulling caused by variations in crystal drive current amplitude. However, it is an enabling technology for a novel ALC circuit with greatly improved stability. The new bridge-controlled oscillator is also much less sensitive to other environmental effects such as humidity (2/spl times/10/sup -11/, 5%/25% R.H. @70/spl deg/C), power supply voltage, load impedance, and stray capacitance. View full abstract»

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  • An improved method of MCXO

    Page(s): 404 - 406
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    To improve the MCXO performance and simplify its structure, a new MCXO design method has been developed. Through deleting pulses of clock signal of a microcomputer and shifting its phase, the frequency-temperature stability of MCXO can be made satisfactory, and the DDS chip, which is often used in high performance MCXO, can be eliminated. Several different MCXOs have been made with this method and different performance specifications can be obtained. According to the simplicity, in a wide temperature range from -40 to +80/spl deg/C, the frequency-temperature stability of the MCXOs can be from /spl plusmn/3/spl times/10/sup -8/ to /spl plusmn/2/spl times/10/sup -7/. View full abstract»

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  • Correlation between upper and lower sidebands

    Page(s): 407 - 410
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    Experimental measurements supported by a simple model show that the upper and lower phase modulation (PM) noise sidebands are always equal and 100% correlated, independent of the noise power originating from multiplicative or additive processes. Similarly, we show that the upper and lower amplitude modulation (AM) noise sidebands are also equal and 100% correlated, independent of the noise power originating from multiplicative or additive processes, Moreover, the single sideband (SSB) PM noise is always equal to one-half the total PM noise. The same is true for the AM noise. Although the upper and lower PM or AM noise sidebands are equal and correlated for broadband additive noise, the phase between the AM and the PM sidebands varies randomly with time. These conclusions still hold even when the RF noise sidebands are not symmetric about the carrier. View full abstract»

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  • Low phase noise operation of microwave oscillator circuits

    Page(s): 411 - 420
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    In this paper, we describe a theoretical basis, leading to new results, on the general conditions to be fulfilled by oscillator circuits to achieve a very low phase noise. Three main conditions must be fulfilled by a transistor oscillator circuit to reach the minimum phase noise. The energy stored in the resonator must be maximum. Its transfer to the controlling voltage port of the transistor current source must be first maximized. A possible conversion noise at the transistor output port will be also minimized by maximizing the energy transferred to that port. The proposed method has been applied to an experimental oscillator set up with a PHEMT transistor. A state-of-the-art phase noise of -80 dBc/Hz at 100 Hz offset from carrier with a 1/f/sup 3/ slope has been measured at room temperature with a 9.2 GHz, oscillator. The application of these new results to free-running oscillator circuits with one-stage then multistage transistor amplifiers demonstrate clearly the validity of the design method. The efficiency of this design method and its ease of use represent a real breakthrough in the field of low noise transistor oscillator circuit design. View full abstract»

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  • High-Q whispering gallery traveling wave resonators for oscillator frequency stabilization

    Page(s): 421 - 426
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    Usually a frequency-stabilized standing wave resonator-oscillator incorporating a resonator as a frequency discriminator requires a circulator to separate the injected and reflected wave, A ferrite circulator is a noisy device and can limit the phase noise or frequency stability. Moreover, we show that the noise in a circulator varies, and detailed low noise measurements are necessary to choose an appropriate quiet circulator. Thus, by realizing a configuration that does not require a circulator, an improvement in performance and reliability can be obtained. A solution to this problem is to design a high-Q whispering gallery traveling wave (WGTW) resonator. This device naturally separates the injected and reflected wave in the same way as a ring cavity at optical frequencies, without degrading the frequency discrimination. Q-factor measurements of a WGTW sapphire resonator are presented, along with a derivation of critical parameters to maximize the frequency discrimination. New measurements of noise in ferrite circulators and isolators have also been made, which is followed with a discussion on oscillator design. View full abstract»

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  • The use of thermosensitive quartz sensor for thermal regulation at cryogenic temperatures: application to microwave sapphire resonator references

    Page(s): 427 - 431
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    We demonstrated the use of thermosensitive quartz resonator oscillator as a thermal sensor for temperature control at the liquid nitrogen temperature. The high sensitivity of the quartz enables an efficient thermal regulation at ambient temperature as well as liquid nitrogen temperature. LC-cut quartz oscillator phase noise measurements show that the temperature measurement resolution is not limited by the intrinsic noise of the sensor and that a resolution of 10 /spl mu/K can be achieved. This thermal regulation is applied to control a microwave temperature-compensated sapphire resonator oscillator at a temperature above 77 K, enabling the achievement of a flicker floor of 9.10/sup -13/ at 9 GHz. View full abstract»

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  • First performance results of PTB's atomic caesium fountain and a study of contributions to its frequency instability

    Page(s): 432 - 437
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    At the Physikalisch-Technische Bundesanstalt (PTB), an atomic caesium fountain was constructed. Ramsey fringes with a full width at half maximum (FWHM) of 0.86 Hz were obtained by launching the atoms to a height of 83 cm above the cooling region (40 cm above the microwave cavity center). A first measurement of the homogeneity of the magnetic flux density yields 0.33 nT (rms), only 0.16% of the mean value of 0.205 /spl mu/T used in normal operation. The inherent elementary noise contributions of the fountain and of a thermal beam atomic clock are compared in some detail. View full abstract»

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  • An alternative cold cesium frequency standard: the continuous fountain

    Page(s): 438 - 442
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    We report on the primary frequency standard now under construction at the Observatoire de Neuchatel (ON). The design is based on a continuous fountain of laser-cooled cesium atoms, which combines two advantages: the negligible contribution of collisions to the inaccuracy and the absence of stability degradation caused by aliasing effects encountered in pulsed operation. The design is reviewed with special emphasis on the specific features of a continuous fountain, namely the source, the microwave cavity (TE/sub 021/ mode), and the microwave modulation scheme. The possible sources of frequency biases and their expected contributions to the error budget are discussed. Based on present data, an accuracy in the low 10/sup -15/ range and a short-term stability of 7/spl middot/10/sup -14/ are attainable simultaneously under the same operating conditions. View full abstract»

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  • Recent results of Physikalisch-Technische Bundesanstalt's primary clock CS1

    Page(s): 443 - 448
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    This paper describes the current performance of the Physikalisch-Technische Bundesanstalt's (PTB) primary clock CS1. After major reconstruction during 1995 and 1996, routine clock operation was started in May 1997. An evaluation of the CS1 Type B uncertainty yielded 7/spl middot/10/sup -15/ (1/spl sigma/). The performance of the CS1 is illustrated by results of a comparison lasting 2 yr with other clocks at PTB and with the international Atomic Time (TAI) and free atomic time scales. With reference to TAI, e.g., a frequency instability of 3.9/spl middot/10/sup -15/ at an averaging time of 30 d was observed. View full abstract»

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  • Analysis tools for the accurate evaluation of a small frequency standard

    Page(s): 449 - 456
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    The short, optically pumped cesium beam tube developed at Laboratoire de l'Horloge Atomique has been carefully evaluated. For that purpose, we have developed a digital servo system that controls three parameters: the frequency of the ultra stable oscillator (USO), the microwave power of the signal experienced by the cesium atoms, and the static magnetic field applied to the atoms. The frequency standard shows a very satisfactory level of short- and medium-term frequency stabilities. A relative frequency offset, measured to be 4.10/sup -12/, results mainly from the residual phase difference between the oscillatory fields in the two interaction regions, which is due to imperfection in cavity symmetry. We present two different means of analyzing the causes of this spurious frequency offset using theoretical and experimental considerations. First, a numerical simulation of the beam tube response is performed as a function of the microwave field amplitude for different values of the residual phase difference /spl Delta//spl Phi/. Results include the cavity-pulling effect. Compared with the measured frequency offset, the numerical simulation leads to a second-order Doppler shift of -3.3 mHz and a residual phase difference, /spl Delta//spl Phi/, between the fields interacting with the atoms in the second and first regions of the Ramsey cavity, amounting to +150 /spl mu/rad. Second, an experimental method of measurement of /spl Delta//spl Phi/ without beam reversal is implemented. The latter yields /spl Delta//spl Phi/=155/spl plusmn/17 /spl mu/rad. Finally, the clock accuracy is determined. It is equal to /spl plusmn/14.10/sup -13/. View full abstract»

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  • A new design of a diffused laser light optically pumped small cesium beam frequency standard

    Page(s): 457 - 460
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    A new set-up of a small Cs clock has been successfully experimentally tested. The short-term stability (2/spl times/10/sup -12/) and the long-term stability (3.5/spl times/10/sup -13/ for a day sample time) have been measured. Only one laser is needed without any frequency shift device. The light frequency shift caused by diffuse light was calculated and measured. View full abstract»

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  • Phase and light shift determination in an optically pumped cesium beam frequency standard

    Page(s): 461 - 465
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    The determination of the phase shift and the light shift in our optically pumped Cs beam is reported here. We show that an error on the phase difference value determined by our fit method, without beam reversal, can be induced if the light shift is not taken into account. If the experimental data are corrected for the light shift, the results of the fit method are in very good agreement with the beam reversal results. This allows us to reduce the related uncertainty in the accuracy budget of our standard. The resulting overall accuracy of the standard is now estimated to be 6.3/spl times/10(-15). View full abstract»

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  • The light shift effect in the coherent population trapping cesium maser

    Page(s): 466 - 470
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    The light shift, as observed in the coherent population trapping (CPT) maser, was investigated theoretically and experimentally. It was found that the light shift originates from the various sidebands that are present in the spectrum of the frequency-modulated laser used to observe the CPT phenomenon. View full abstract»

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  • A dynamic analysis of the LO noise transfer mechanism in a Rb-cell frequency standard

    Page(s): 471 - 474
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    Frequency noise of the local oscillator at even harmonics of the modulation frequency is known to contribute to the short-term instability of passive frequency standards. The mechanism by which this noise transfer takes place in Rb-cell standards is described here in a comprehensive approach that includes both signal theory methods and a time-dependent quantum mechanical analysis. The resulting calculated transfer coefficients for the various even harmonics are discussed in relationship with measured coefficients in an actual experiment. View full abstract»

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  • Cs frequency synthesis: a new approach

    Page(s): 475 - 479
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    The paper describes a new approach to synthesizing the Cs hyperfine frequency of 9.192 GHz that is designed to be sufficiently rugged for use in space, specifically for the Primary Atomic Reference Clock in Space (PARCS) planned for the International Space Station, as well as ground applications. This new approach requires no narrow band filters or frequency multiplication, and the primary source of cooling is conduction. Instead of frequency multiplication, it uses a custom regenerative divider stage followed by two commercial binary dividers and several mixing stages. A fractional frequency step of 2/spl times/10/sup -17/ is achieved by mixing the output of a 48-bit numerically controlled oscillator with the microwave signal. Preliminary tests on the new synthesizer design indicate an internal fractional frequency stability of 1/spl times/10/sup -15/ at 10 s and 1/spl times/10/sup -18/ at 1 d, dominated by the daily room temperature variations. The phase and amplitude noise are similar to our previous designs that used frequency multiplication and narrow band filters. The temperature coefficient is less than 0.2 ps/K. View full abstract»

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  • A practical method to process time and frequency signal

    Page(s): 480 - 483
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    A new practical time and frequency signal processing method can be used to generate an accurate time signal, for stable phase step, for frequency change and synthesis, and for other related uses. The method accomplishes the time and frequency signal processing by changing the period and phase of the machine cycle of a microcomputer. It is based on pulse deletion of a high frequency clock signal, quantified phase delay, and other intentional variations in a microcomputer clock signal circuit. The pulse deletion and phase delay can be implemented periodically or individually for different purposes, and a frequency change and synthesis or phase shift of the microcomputer output signal can be obtained. With this method, the time signal processing precision can be from several tens of nanoseconds to less than 1 ns. View full abstract»

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Aims & Scope

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control focuses on the theory, design, and application on generation, transmission, and detection of bulk and surface mechanical waves.

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Editor-in-Chief
Steven Freear
s.freear@leeds.ac.uk