Pulse or digital communications – Spread spectrum – Direct sequence
Patent
1980-05-21
1983-04-12
Safourek, Benedict V.
Pulse or digital communications
Spread spectrum
Direct sequence
331 1A, 331 17, 328 63, 307480, H03L 706
Patent
active
043800831
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method in a system such as telecommunication system for regulating the phase position of a controlled signal in relation to a reference signal and an arrangement for carrying out the method.
BACKGROUND OF THE INVENTION
In known technique, for example when phase detecting in phase locked loops, the phase difference between two signals is usually measured by starting counting pulses of known frequency at the positive edge of the reference signal and stopping counting at the positive edge of the controlled signal, the phase difference between the signals being determined by the number of pulses.
The disadvantage of this solution is that in order to obtain sufficient measuring precision the pulses must be of a sufficiently high frequency that such an arrangement is difficult to realize in TTL-technique. Consequently this will imply a more complicated component choice resulting in higher costs.
SUMMARY OF THE INVENTION
The method and the arrangement according to the invention which is characterized according to the claims solves said problem and allows a very accurate detection of the phase difference between two signals by means of a few simple components, the measuring result being utilized for controlling the phase position of the first signal in relation to the phase position of the second signal.
An arrangement according to the invention can, for example, be utilized when controlling the different clocks included in an arrangement for majority choice of a clock signal so that the phase positions of the clocks will be as close together as possible.
BRIEF DESCRIPTION OF THE DRAWING
The invention is described more in detail by means of an embodiment with reference to the accompanying drawing, where
FIG. 1 represents a block diagram of an arrangement according to the invention; and
FIGS. 2-5 are time diagrams explaining the function of the arrangement at different phase differences between the signals.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As appears from FIG. 1 an arrangement according to the invention contains two D-flip-flops FF1, FF2 of that type which, in the dependence on the phase difference between two signals fed to two of its inputs, produces an output signal of a high or a low level respectively. The flip-flops can for example be of the type, offered by TEXAS INSTRUMENT under the designation 74S74.
To both these flip-flops are fed a reference signal C2 as well as a signal C1 to be controlled. The phase position of said signal C1 is to be regulated in relation to the phase position of the reference signal C2. The flip-flop FF1 receives on a first input a signal D1 which is the reference signal C2 delayed through a delay circuit DL1. On a second input the flip-flop FF1 receives the controlled signal C1 directly from a clock oscillator CL1.
The flip-flop FF2 receives on a first input a signal D2 which is the controlled signal C1 delayed through a delay circuit DL2 and receives on a second input the reference signal C2 directly. The delay circuits DL1 and DL2 are equal and consist of Schottky-buffers for example. In the circuits DL1 and DL2 several buffers can be connected in series and the size of the delay in the circuits is determined by the number of buffers, which number can be chosen by clamping. A delay circuit can also consist of a delay line, the size of the delay then being determined by the length of the delay line.
When the phase difference between the reference signal C2 and the controlled signal C1 according to the example exceeds .+-.5 nano seconds a correction of the phase position of the signal C1 will be carried out to bring the phase difference within these tolerance limits. The size of the tolerance limit can of course be changed by means of clamping thus connecting a different number of buffer stages in the delay circuits DL1, DL2. The output signals Q1 and Q2 from the flip-flops FF1 and FF2 respectively are set to their logical levels according to the phase differences between the signals C2 and C1 and are fed to the
REFERENCES:
patent: 3057962 (1962-10-01), Mann
patent: 3495184 (1970-02-01), Perkins, Jr.
patent: 3521172 (1970-07-01), Harmon
patent: 3614635 (1971-10-01), La Pine
patent: 3660647 (1972-05-01), Pryor
patent: 3798558 (1974-03-01), Kopperschmidt
patent: 3839599 (1974-10-01), Pitroda
Andersson Karl A. I.
Roos Sture G.
Chin Stephen
Safourek Benedict V.
Telefonaktiebolaget L M Ericsson
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