section - Bitsavers
section - Bitsavers
section - Bitsavers
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PHASE LOCKED LOOP APPLICATIONSPROGRAMMED PHASE OR FREQUENCY SHIFTHoward E. Clupper of Chadds Ford, Pennsylvania, submittedthe following circuit in which Ita digital phaseshifter is inserted in the loop between the VCO and thephase comparator. The phase shift is programmed bysequentially selecting the ring counter outputs by means ofthe multiplexer and up-down counter."As shown in Figure 8-74, the eight ring counter outputsare separated by 45 0 , which is within the lock-in range ofthe loop. Output 1 is constrained to follow the phaseshift introduced and may be used, for example, to drive asynchronous motor above or below its normal speed, whilestill maintaining reference with the input. This is accomplishedby monitoring the contents of the up-downcounter (which may be any length). As long as the counterdoes not overflow, the motor may be advanced or retardedin any manner and then returned to the original relationshipwith respect to the 60Hz reference input by runningthe UfO counter to the initial value.For higher frequency outputs, a divide-by-N counter maybe added in the normal manner and the output takendirectly from the VCO at output 2. Operation in thismode would provide means to generate a preciselycontrolled FM signal of any arbitrary center frequencydepending upon the frequency of the reference input andthe value of N."The 565 may be used in this circuit in place of the 562 forlower frequency applications (less than 500kHz).PROGRAMMED PHASE OR FREQUENCY SHIFTER60HZ'~'" ON,"' ~r------------------- -- -----------I12 13 14",COMP.L.P. FILTERVCO- - --,IIOUTPUT-2I 1115I1.. ___ _r8-STATE TWISTED RING COUNTERI II +N I, ,~- -..L __J-,~--------.---------~----------~~--~ II OUTPUT-l1---+---1._--0 60 ± ~ HZSINGLE -.Jb45° STEP IIPHASESYNCH,.......t-.......... ....Io...y-L l_L,ADD'LCAPACITY ,...... --.;;.---,r--- - - ___ J8-INPUT MULTIPLEXERIN8230RING COUNTER WAVEFORMSA~B~C~D~A~- IB~c~ID~IFigure 8-7470