公开(公告)号：US3854102A

公开(公告)日：1974-12-10

申请号：US38707973

申请日：1973-08-09

Applicant: ITT

Inventor： SEIPEL A ,  DEUTSCH J ,  THOMPSON B ,  HAUSSMANN R

IPC: H03L7/185 ,  H03B3/04 ,  H03B19/00

CPC classification number: H03L7/185

Abstract: There is disclosed herein a dual frequency band frequency synthesizer employing a single phase locked loop to control the frequency of the output signal of a voltage controlled oscillator so as to provide signals having a selected frequency in a selected one of the two frequency bands with the frequency of the signals in each of the two frequency bands having different incremental frequency steps. The phase locked loop includes therein a programmable binary divider having a different range of division factors for each of the two frequency bands with the output of the programmable divider being coupled directly to the phase detector of the phase locked loop when the lower frequency band is selected and through a modulo-6 binary counter when the higher frequency bands is selected. The programmable binary divider is programmed by frequency setting switches which produces 9''s complement binary coded output for each of the selected decimal values. The coded decimal values of each of the frequency selecting switches are employed directly or through a decoding circuit to select the appropriate one of the two frequency bands, to program the programmable binary diver to the proper division factor for the frequency selected by the frequency setting switches and to bypass or incorporate the modulo-6 counter. The decoding circuit includes binary adders coupled to each of the switches intermediate the most significant switch and the least significant switch so as to add in digital form a first given constant value to the digital output of the switches when operating in the lower of the frequency bands and a second constant value in digital form when operating in the higher of the frequency bands so as to provide the proper division factor for the programmable binary divider for the frequency selected by the frequency setting switches. An automatic level control arrangement is also incorporated in the phase locked loop responding to the output signal in each frequency band to maintain a constant amplitude of output signal in each of the frequency bands.