Boots – shoes – and leggings
Patent
1987-02-27
1989-04-04
Smith, Jerry
Boots, shoes, and leggings
331 11, 331 25, G06J 100, H03L 706
Patent
active
048191965
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a digital-based phase control system and more particularly to such a system capable of providing phase adjustment of an output signal with respect to a reference signal over a wide range of precisely controlled increments.
Phase control systems are known to provide an output signal which has a predetermined phase with respect to a reference signal. To obtain the foregoing it is generally known to utilize a phase-locked loop including a phase comparator and a voltage controlled oscillator (VCO). The output of the phase comparator is connected to the input of the VCO. The phase comparator has two inputs, one of which receives a reference signal and the other input receives an output signal from the VCO, which is generally referred to as the feedback signal. The phase comparator compares the phases of its two input signals and provides a phase error signal. In response to the phase error signal the VCO adjusts the phase of its output signal to minimize the phase error signal.
It is further known to control the phase of the output signal from the VCO to have a predetermined phase displacement with respect to the reference signal. In the known devices such phase displacement is obtained by utilizing analog or digital phase shifting or delay devices connected in the feedback signal path, or alternatively, in the reference signal path of the phase-locked loop. Known analog signal phase shifting or delay devices may include networks comprising resistors (R) and capacitors (C), or inductors (L) and capacitors (C), analog LC delay lines or analog shift registers implemented for example by charge-coupled devices. The desired phase displacement may be adjusted by varying the R, L or C parameters of the above networks or delay lines, by varying the length of the delay lines or by varying the frequency of a clock signal applied to the charge-coupled devices. However, the above-indicated analog phase shifting and delay devices are suceptible to drift due to aging and environmental changes, such as temperature and humidity. The drift must be compensated for by frequent operator adjustments and maintenance. While drift compensation circuits are known, they do not eliminate the problem entirely. In addition, most of the above-indicated devices are not suitable for remote control.
One type of known digital phase shifting or delay devices includes one or more monostable multivibrators including analog time-out circuitry comprising R and C or L elements, or a voltage-controlled constant current source replacing the R element. The time-out circuitry determines the duration of an output pulse whose trailing edge is used to determine a desired phase displacement. While it is possible to obtain phase adjustment by varying the R or C parameters of the time-out circuitry or by varying the control voltage of the current source, respectively, these devices are unstable.
Another type of digital devices includes one or more monostable multivibrators with digital time-out circuitry, for example utilizing counters. Phase adjustment of the output signal may be obtained by selecting different digital time-out values loaded into a time-out counter. However this type of digital phase shifting or delay device becomes relatively expensive when a large range of phase adjustment and fine resolution are required.
Digital shift registers are also known to be utilized to obtain output signal phase adjustment in phase-locked loops. Here phase adjustment may be obtained by varying the clock frequency of the shift register or the length of the register. However in applications requiring phase adjustment within a wide range and with fine resolution, the implementation is expensive.
The present invention eliminates the above-described disadvantages of known phase control systems by providing an adjustable digital-based phase control system in which the phase of the output signal with respect to a reference signal may be selectively changed with a high degree of resolution, precision, stability and rep
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Lilley Martin A.
Wesolowski Jan S.
Ampex Corporation
Lange Richard P.
Meyer Charles B.
Smith Jerry
Strnad Elizabeth E.
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