Phase-locked Frequency Research Articles

Analysis of ‘D type’ flip-flop frequency changers

A novel approach using Fourier analysis to model a digital system, in this case a ‘D type’ flip-flop, is presented. An analysis of the flip-flop using mathematics, with a graphical example to illustrate the logic operation of the flip flop as a frequency changer, in this case a down-convertor, is presented. This type of analysis could prove invaluable in modelling digital phase locked loops and frequency synthesisers.

Comments, with reply, on "A simple technique for analog tuning of frequency synthesizers" by J.P. Hauser

The commenter points out that an analog implementation of the fractional N phase-locked loop variable frequency synthesis technique described by J.P. Hauser (ibid., vol.38, no.6, p.1141-4, 1989) results in a novel minimization of active hardware, but that there are significant performance compromises. The original author's reply is included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Operation and theory of a driven single-mode electron cyclotron maser.

A study is made of the operation of the electron cyclotron resonance maser (ECRM), when subjected to an external rf signal. The signal is introduced both via direct injection through a coupling hole in the oscillator and by modulating the electron beam in separate cavities, upstream of the oscillator. Experiments using both one and two ``prebunching'' cavities are reported. It is experimentally found that the gyromonotron, a specific embodiment of the ECRM, can be phase locked by premodulating the electron beam at drive power levels more than two orders of magnitude below that predicted by Adler's widely applicable theory for single-cavity oscillators. A perturbation theory is used to predict the phase-locking frequency band for a gyromonotron with any number of prebunching cavities. The predictions of this theory agree with the experimental results for two- and three-cavity phase locking. An investigation is made into the general amplitude and frequency response of the ECRM to an applied external signal. Experimentally, three distinct regions of qualitatively different ECRM behavior are noted: soft excitation, which is free, self-excited oscillation; hard excitation, where the oscillation requires an external impulse for startup; and amplifier, in which the output power level and frequency are linearly related to the drive in the small-signal regime.

Interpolation techniques for time domain averaging of gear vibration

Interpolation by digital computer provides an alternative to the phase-locked frequency multiplier for the calculation of the time domain average of gear vibration signals. Higher-order interpolation techniques produce flatter passbands and lower sidelobes in the stopband but require longer calculation times. Aliasing errors are introduced into the result by replication of the sidelobes during interpolation, but in general are attenuated by time domain averaging.

Frequency of a methane-stabilized helium-neon laser

A phase-locked laser frequency chain was used to measure the absolute frequency of a HeNe/CH/sub 4/ laser relative to the primary Cs standard, with measurement uncertainty less than +or-1 part in 10/sup 12/. The frequency depends on laser parameters; a spread of 8.3*10/sup -11/ was observed. This was attributed to the variation of Lamb dip asymmetry resulting from the gas-lens effect and the accompanying diffraction loss variation near resonance. Means of improving laser frequency reproducibility by reducing cavity diffraction loss variation were studied experimentally. The frequency obtained with a cavity exhibiting the smallest Lamb dip asymmetry was found to be 88 376 181 599.07+or-0.07 kHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Improving the settling time of a digital phase-lock frequency synthesizer

The settling time of a digital phase-lock frequency synthesizer is improved by using a digital time to voltage converter (DTVC) to replace the loop filter. The synthesizer is then analysed as a sampled data control system. Analysis and experimental results show that an improvement in the settling time is obtained compared with the conventional phase-lock frequency synthesizer. However, the settling time is still a function of the frequency resolution and the frequency range required.

Exact calculation of phase-locked loop lock-in frequency

Using a novel cycle-slip criterion, two methods of computing the lock-in frequency of phase-locked loops are reported. The lock-in frequency of a second-order loop with sinusoidal phase detector is presented as a function of system parameters, and useful estimates by the pull-out and pull-in frequencies are given.

A Linear Frequency to Code Converter

Theory and operation of a novel phase-locked tracking type frequency to Code Converter (fDC) is described in this paper. Ingenious subcircuits have been developed and incorporated around the basic system to achieve speed-up, linearity and stability of conversion. Measurements on a prototype built with a few off-the-shelf TTL ICs confirmed the results of theoretical analysis. With a 10-MHz clock and a speed-up factor of 16, the conversion time is about 0.4 ms plus one period of the input Hertz for 8 bit resolution and about 100 ms plus one period of the input Hertz for 12 bit resolution. Small signal tracking time is only a fraction of the conversion time, the multiplying fraction being equal to the f-m index of the input Hertz. The system is characterized by very high resolution capability (at the cost of speed), high stability and true linearity with no offset error.

Addendum to: "Phase-Frequency Detection in Sampled Phase-Locked Frequency Multipliers"

Addendum to: "Phase-Frequency Detection in Sampled Phase-Locked Frequency Multipliers"

Ultrasonic measurement of respiratory flow.

We review ultrasonic measurement of fluid flow with emphasis on ultrasonic pneumotachometers (UPTM's). For PTM's we discuss specifications such as dynamic range, resistance, and frequency response. We review fluid flow principles and point out the problems of nonultrasonic PTM's For UPTM's we describe transducer construction, attenuation versus frequency, reflection at interfaces, and acoustic field patterns. We present four principle types: 1) time of flight, 2) sing around, 3) phase shift, and 4) phase-locked frequency shift. For each, we detail principles, advantages, disadvantages, and potential for future development.

Phase-Frequency Detection in Sampled Phase-Locked Frequency Mlultipliers

Phase-locked high-frequency multipliers which do not have powergreedy frequency dividers in the feedback loop, but which do have a sample-and-hold circuit as a phase detector are hard to design, due to conflicting requirements which determine the choice for loop gain and loop bandwidth. A circuit is described that acts as a frequency control if the loop is not locked and as a phase control once the loop can be locked. The loop filter has to be optimized for the locked condition only, and the allowable preset error is more than 80 percent of the sample frequency. The circuit also indicates whether the oscillator frequency is an odd or an even multiple of the sample frequency. Pull-in is at least an order of magnitude faster than with phase control alone.

A digital VOR converter and display unit

This paper describes a method of digital measurement and display of VOR phase signals. These are received by airborne equipment and provide navigational information to the pilot. By means of a phase-locked master frequency, the phase difference between the received signals is converted into a pulse train advancing the display counters. The phase between the two signals (indicating the position relative to the ground transmitter) La displayed as a three-digit number and by one out of 36 circular arranged LED's. Subtraction of the measured angle and a selected one is performed by EX-OR gating of two 50% duty cycle signals derived from pulses whose relative position with respect to a reference pulse represents these angles. Deviation is displayed by a linear array of LED's. By means of a phase-locked master frequency, the phase difference between the received signals is converted into a pulse train advancing the display counters. The phase between the two signals (indicating the position relative to the grou...

Phase signature radars

The identification and classification of radar targets is facilitated by a newly developed technique based on measurements of the differential phase shift of the target scattering obtained at harmonic phase-locked frequencies. These phase differences are independent of target range and relative motion. It is mathematically proved that for a smooth conducting body in the Rayleigh region the copolarized terms of the scattering matrix have zero phase shift. Based on this, the absolute target phase can be measured. The differential phase shift between two harmonic frequencies has been measured for various types of targets. The experimental results indicate that the differential phase shift is a useful parameter for classifying or identifying targets, and one that can be readily measured in practical radars.

Phase-Locked Loop Pull-In Frequency

A computerized procedure for obtaining the pull-in frequency of a phase-locked loop is described. The procedure, which consists of solving for the limit cycle of the out-of-lock loop and finding the frequency offset below which no solution exists, is quite general with respect to phase detector function and loop filter. It is applied in this study to the case of a second-order loop with a sinusoidal phase detector. The results of the study give normalized pull-in frequency X as a function of the damping factor \zeta and normalized natural frequency β of the linearized closed loop. A review of several previously published investigations of this case is given, and the limitations identified point the way to the more exact solution described here. In addition, an experimental study is described which produces excellent agreement with the new results, and a curve-fitting procedure is outlined which leads to a highly accurate functional description of X in terms of β and \zeta .

A sequence solution to the Fokker-Planck equation

In this paper a new approach to nonlinear system analysis based on the Fokker-Planck equation is developed. The development begins as a modification of the parametrix method of partial differential equation theory and provides a sequence solution to the multidimensional time-varying Fokker-Planck equation. This sequence is simplified for the case where only a steady-state solution or a solution for the variance of a particular combination of states is desired. Equations are presented in a form suitable for obtaining numerical results using a digital computer. This method is cast in a rather general mathematical framework and can provide useful results for a variety of problems. It is applied to the special case of phase-locked frequency demodulation, and curves of frequency tracking error are presented. Even though the rate of convergence of the sequence is not established in general, these numerical results prove the usefulness of the method for this special case and suggest a far greater range of usefulness.

An Automatic Control Scheme of HVDC Transmission Using Digital Techniques Part I Principles of Operation

The requirements of HVdc converter control are achieved by dicrital techniques with minimisation of circuit complexity. Feed-back control is applied to modification of the counting of clock pulses derived from the ac system by a phase-locked frequency multiplier. Symmetry of the derived firinc, oulses can be retained for all modes of operation with smooth transition from full rectification to full inversion.

Controllable phase-locked frequency splitting in two-frequency lasers

Lasers can be made to oscillate simultaneously at two frequencies by means of anisotropic or nonreciprocal resonator elements. A technique is described for stabilizing the resulting frequency separation by locking it to an external frequency source. The stabilized separation should be useful in optical heterodyne applications.

Applying the phase-locked loop in communications and instrumentation

The mode of operation of the phase-locked loop is briefly described, an analytical note being given in an Appendix. Communication applications are the tracking receiver, f.m. detection, the phase-locked homodyne and f.s.k. detection. Instrumentation applications are phase modulation, pulse-width modulation, phase-locked servo for magnetic recording and a phase-locked frequency standard. The voltage controlled oscillator, phase detector and loop filter necessary in these applications are discussed.

A Comparison of the Threshold Extension Capabilities of FMFB and Phase-Lock Loop Demodulators Employed in FDM-FM Communication Systems

A comparison of the threshold extension capabilities of the phase-lock loop and frequency modulation feedback (FMFB) demodulators is presented. The comparison, instead of being based upon the usual sinusoidal modulating signal type analysis, is based upon analyses which give consideration to the type of modulation that is of most interest to designers of frequency division multiplexfrequency modulation (FDM-FM) systems, i.e., to modulation by a band-limited noise-like signal. The basic operating parameters are defined in terms of rms values. The "clicks" analysis of Rice is utilized in the treatment for the two cases of ignoring and including the effects of modulation on the output noise clicks.

MIT vibrating string surface-ship gravimeter

The second version of the MIT VSA Surface-Ship Gravimeter is described. It consists of the military surplus (Atlas program) American Bosch Arma Lot D Vibrating String Accelerometer mounted on the Sperry Mark 19 Mod 3C Meridian Gyrocompass. Data read-out is by a uniquely simple integrated circuit phase-lock frequency filter, presenting output data in binary coded decimal and analog format directly in milligals of apparent free-air gravity. An accuracy of better than 1 mgal has been established over open-ocean gravity ranges. The system described should prove to be relatively inexpensive to produce.