Excavating
Patent
1983-02-07
1985-11-19
Fleming, Michael R.
Excavating
375 81, 375 90, 375102, G06F 1110
Patent
active
045546657
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a data processing system of the kind (hereinafter referred to as the kind set forth) in which there is a transmission of a code format having a pattern that provides a plurality of reversals 10101100 etc. from which it is desirable to be able to differentiate between valid data and invalid data. Invalid data means the absence of data, data corrupted by noise or data alien to the system.
SUMMARY OF THE INVENTION
According to the present invention there is provided a data processing system of the kind set forth wherein means are arranged to provide the times between n zero crossings as herein defined to measure said times to establish the number (R) between said zero crossings as given by the expression: ##EQU2## where I is the integer part of x, n is an integer representing the number of zero crossings and t.sub.i is the duration of the ith interval between zero crossings measured on a bit base of unity thereby to permit the use of said number (R) when compared with a predetermined tolerance range to provide an indication of the quality of said transmission.
In one construction n is between 8 and 100 and in a convenient construction n is 32 or 64.
By the term zero crossing is to be understood the time at which zero volts is crossed when going from a positive voltage to a negative voltage or vice versa.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood from the following description given by way of example only with reference to the figures of the accompanying drawings and the following Example in which
FIG. 1 is a circuit block diagram of a pager incorporating data operated squelch of the invention and
FIG. 2 is a flow diagram of the operations performed by the present invention.
FIG. 3 is a graphical presentation of the transfer function of the expression used in the invention to illustrate a refinement of the circuitry.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Consider as one Example a transmission in which the code format has sixty four zero crossings as shown in the table below and the values for z=t.sub.i -I(t.sub.i -0.5) are:
TABLE ______________________________________
Z Z Z Z
______________________________________
3.2 1.2 9.1 1.1 1.7 0.7 2.8 0.8
1.6 0.6 9.2 1.2 1.7 0.7 2.7 0.7
1.2 1.2 5.8 0.8 1.8 0.8 2.7 0.7
1.3 1.3 6.3 1.3 1.9 0.9 2.7 0.7
2.4 1.4 4.7 0.7 1.8 0.8 2.7 0.7
6.1 1.1 4.3 1.3 1.8 0.8 6.8 0.8
7.8 0.8 4.2 1.2 1.6 0.6 6.8 0.8
6.2 1.2 4.2 1.2 1.6 0.6 3.1 1.1
5.3 1.3 4.2 1.2 1.5 0.5 2.1 1.1
1.7 0.7 7.1 1.1 2.3 1.3 1.7 0.7
1.6 0.6 7.6 0.6 2.7 0.7 1.6 0.6
1.5 0.5 7.6 0.6 6.4 1.4 1.5 0.5
1.2 1.2 7.1 1.1 5.8 0.8 1.4 1.4
1.2 1.2 7.1 1.1 3.7 0.7 7.3 1.3
1.2 1.2 6.2 1.2 3.6 0.6 6.2 1.2
1.4 1.4 3.1 1.2 3.7 0.7 2.3 1.3
______________________________________
Then taking the first three examples in the table (1) is: ##EQU3## and (2) is: ##EQU4## and (3) is: ##EQU5##
Clearly the sixty four values in the table for Z summated is 60.9 thus: ##EQU6##
The value R with a tolerance can, therefore, be used to make a decision for a satisfactory squelch that is to say a system which switches at least a part of a receiver between a quiescent and an active state depending upon the quality of the signal received.
The tolerance having been chosen to be for example 0.8 to 1.1 then R at 0.9515 is seen to fall within that tolerance and thereby indicate a signal of a predetermined quality.
The squelch may be used to obtain good sensitivity in a radio pager for example without wasting battery life.
Referring now to FIG. 1 the circuitry operates in such a way as to produce a specific transfer function of the form shown graphically in FIG. 3. The input is the time interval (t.sub.i) between adjacent transitions of the input signal. The output is numerical and is averaged over the required number (n) of transition interval samples to form the resultant (R). The decision of the squelch circuit is made by comparing this resultant (R) against some preset limits so that within this
REFERENCES:
patent: 3671935 (1972-06-01), Lipp et al.
patent: 3995264 (1976-11-01), Ouchi
patent: 4223326 (1980-09-01), D'Amato et al.
patent: 4229822 (1980-10-01), Bench
patent: 4264972 (1981-04-01), Drullmann et al.
patent: 4276649 (1981-06-01), Groenendeal et al.
Fleming Michael R.
Jones, Jr. Maurice J.
Motorola Inc.
Paniaguas John S.
Southard Donald B.
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