Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1984-04-27
1985-09-17
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455183, 455186, H04B 126
Patent
active
045425337
ABSTRACT:
A microprocessor controlled phase locked loop tuning system is disclosed which comprises a microprocessor (10) that provides frequency data to the PLL (11), this data controlling a programmable frequency divider in the PLL to determine the nominal frequency of a VCO (131) in a tuner (13). The AFC detector (141) in the intermediate frequency module (14) provides an error voltage output to the AFC comparator (15). The comparator produces a low or a high output to the microprocessor depending on whether the error voltage exceeds a second input voltage to the comparator. This second input voltage is an increasing voltage from a time constant network (16) controlled by the microprocessor. The microprocessor program includes a loop wherein the microprocessor alternately increments a register and reads the output of the comparator until the voltage from the time constant network exceeds the error voltage from the AFC detector. The value in the register is then proportional to the error voltage. This number is saved and used to alter the output to the PLL if required to correct the VCO frequency.
REFERENCES:
patent: 4280140 (1981-07-01), Skerlos
patent: 4408349 (1983-10-01), Yukawa
patent: 4451850 (1984-05-01), Kamemoto
patent: 4498191 (1985-02-01), Rogers
General Electric Company
Ng Jin F.
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