Boots – shoes – and leggings
Patent
1995-03-07
1997-06-03
Gordon, Paul P.
Boots, shoes, and leggings
364721, 364729, G06F 102, G06F 738
Patent
active
056361491
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of operating a direct digital synthesizer (DDS) or digital function generator having one or more channels (A, B, . . . ) each with a phase increment register and which is controllable by a computer system sending bits of information to the DDS.
DESCRIPTION OF THE RELATED ART
In function generators and synthesizers, using digital signal sources, particularly direct digital synthesizers (DDS) is known, with which signals of lower frequencies are generated from a given fixed clock frequency (see, e.g., EDN Electrical Design News, Vol 34, No. 23, Nov. 9, 1989, Newton, Mass., pp. 94-104), selected values of a stored digitized periodic function being applied to a digital-analog converter followed by a low-pass filter to generate a desired analog frequency. Selecting the values held in the storage is done by means of a so-called phase accumulator to which a phase increment is applied. This phase increment is the phase spacing of the values to be selected from the storage, applied to the phase accumulator at the clock rate. The magnitude of the phase increments is determined, on the one hand, by the clock frequency at which accumulation is done and, on the other, by the shape and frequency of the output signal to be generated. For a continuous change in frequency or phase complicated computations are necessary to continually establish the necessary phase increments which must then be continuously loaded into the registers of the phase accumulator at the speed corresponding to the change.
The application of digital signal sources thus depends on whether control is possible with small rapid changes in frequency and with quasi-continuous changes in phase. Principally the system of the direct digital synthesizer offers such possibilities, but only as long as the sequence control is possible by the controlling device to any fine degree and the interaction with this device is quickly possible.
In using the DDS system, microprocessors have been employed until recently in state of the art as the monitoring and controlling means which have been then operated either manually by a keypad or via corresponding interfaces (e.g. HPIB) by other computers.
This concept has its drawbacks for various reasons. For one thing, programming the microprocessors necessary in machine langauge or at the assembler level is tedious and thus fails to be implementable to an optimum fine degree, resulting in the advantages of the DDS system (high frequency and phase resolution) being usable only at great expense on the other hand, the microprocessors used to date are relatively slow and operating the DDS is additionally complicated by the interface between computer (e.g. for automation) and microprocessor. Apart from this, incorporating the system in computer-assisted experiments and electronic data acquisition is achievable only with difficulty. This is why those skilled in the art have recently turned to the use of a personal computer (PC) to directly control a DDS (see, e.g., Elektronik, Vol. 9/1991, J. Ewert: "Arbs": Welches Signal soll's sein?, pp. 63-70; W. Hascher: Welche "Arbs" gibt es?, pp. 72-74). However this improved control by the PC still fails to take full advantage of the DDS system.
Yet a further substantial problem is posed by the fact that to generate a quasi-continous oscillation, phase increments need to be loaded all the time in a phase increment register, the latter having only a limited storage capacity, however. To prevent an overflow, time-consuming check operations need to be executed in state of the art to establish the space still available in the register.
SUMMARY OF THE INVENTION
The present invention is accordingly based on the object of formulating a method of controlling a DDS in which the advantages of the DDS system, such as high resolution of phase and frequency, continue to be made full use of, so that with little effort both very small changes in frequency and phase as well as more particularly, major changes in frequency and phase may b
REFERENCES:
patent: 5216389 (1993-06-01), Carralero et al.
patent: 5231598 (1993-07-01), Vlahos
EDN Electrical Design News. Bd. 34, N4. 23, 9. Nov. 1989, Newton, Massachusetts US Seiten 95-104, XP000072970 Galland "Devices refine the art of frequency synthesis".
Journal of the Acoustical Society of America Bd. 79, Nr. 2, Feb. 1986, New York US Seiten 572-574 Holland et al "A high-speed digital arbitrary waveform generator".
J. Ewert, Elektronik Sep. 1991, pp. 63-70, 72-74.
M. Schanerberger, "The Implementation of a Digital Sine Wave Oscillator Using the TMS320C25: Distortion Reduction and Applications;" IEEE Transactions on Instrumentation and Measurement, vol. 39, No. 6, Dec., 1990, pp. 870-873.
Prof. E. Philippow, TB Elektrotechnik, Band 3, VEB Verlag Technik Berlin 1967, pp. 1551-1552.
Buckin Vitali
Funck Theodor
Buckin Vitaly
Gordon Paul P.
Moise Emmanuel L.
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