Electrical transmission or interconnection systems – Nonlinear reactor systems – Parametrons
Patent
1987-04-10
1988-10-25
LaRoche, Eugene R.
Electrical transmission or interconnection systems
Nonlinear reactor systems
Parametrons
307262, H03K 5159
Patent
active
047806818
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a phase changer for, upon generating an output signal with a frequency which is adjustable in relation to a basic frequency assigned an oscillator signal sent from an oscillator, coming into phase with a nominal frequency signal, said phase changer including a calculating unit for comparing the nominal frequency signal with the output signal and for calculating control signals in time stages, the output signal frequency being adjusted with the aid of such control signals. The output signal has come into phase with the nominal frequency signal if the frequency of the one signal is a whole number multiple of the frequency of the other. Timing pulse signals have come into phase if the calculating unit in combination with required whole number frequency conversions adjust the output signal frequency so that the phase difference between the signals is constant. However, the phase equalization does not need to go as far as exact phase equality, i.e. zero phase difference.
BACKGROUND ART
In the article "Phase-locked loop design fundamentals" with the Application Note AN-535 issued by Motorola Semiconductor Product Inc, voltage controlled VCXO crystal oscillators included in phase changing arrangements are described. These generate an output signal for synchronising different digital units. The known calculating unit includes an analog regulating filter and a charge pump controlled by a phase detector, and has its control signal output connected to the regulating voltage input on the oscillator. An analog controlled VCXO oscillator is about five times more expensive than an XO standard oscillator, which generates a signal of fixed frequency without any regulating capacity. The use of commercially available VCXO oscillators also brings with it as technical disadvantages that the generation of the analog regulating voltage obstructs digitalisation of the phase changing arrangement, and that the frequency adjustment range is limited.
DISCLOSURE OF INVENTION
A phase changer in accordance with the invention serves its purpose with the aid of a simple, non-regulatable XO crystal oscillator, the basic frequency signal of which is fed to a digital delay circuit generating an output signal of adjustable frequency. The delay circuit achieves delays which time is changing linear on the average. Positive or negative degrees of delay change result in frequency reductions or frequency increases. THe greater the change degree variation, the greater the frequency adjustment range. The proposed phase changer includes a digital calculating unit which compares the nominal frequency signal with the output signal of the delay circuit. When the comparison relates that there is a frequency difference, the calculating unit regulates the degree of change in the delay circuit so that the output signal comes into phase with the nominal frequency signal.
According to a first embodiment of the phase changer, the degree of change in the delay circuit is varied stepwise between two change degree boundaries associated with two output signal boundary frequencies. The task of the calculating unit is to calculate digitally in time stages and to order the relevant degree of change for adjusting the output signal to the nominal frequency signal. According to a second embodiment, the delay circuit operates either with a positive change degree boundary or an equal negative change degree boundary or with a change degree equal to zero, so that the circuit generates an output signal either with a lower boundary frequency or with an upper boundary frequency or with the oscillator basic frequency intermediate between the boundary frequencies. The calculating unit in accordance with the second embodiment determines which os said three degrees of change shall be used, and for what length of time, to obtain an output signal having a mean frequency resulting in an acceptable phase adjustment to the nominal frequency signal. Both embodiments enable, in a digital way, phase equalization of the output signal in relation to a
REFERENCES:
patent: 4119796 (1978-10-01), Jones
patent: 4677648 (1987-06-01), Zurfluh
LaRoche Eugene R.
Mottola Steven J.
Telefonaktiebolaget L M Ericsson
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