synthesized PLL for Low Power FM transmitter


Posted on Feb 4, 2014

This is schematic of a synthesized PLL for the Low Power FM transmitter. By the way, you also can use it with other circuits, just pay attention to recalculate the loop filter response and components, VCO tank circuit, and the correct thumbswitch programming keys, crystal value. The original project of FM transmitter was made to operate in both co


synthesized PLL for Low Power FM transmitter
Click here to download the full size of the above Circuit.

nfiguration ( synthesized or open loop free oscilattor), with synthesized version you can assure very high frequency stability, and also lock digital FM receivers ( 200KHz step in major of countries). A crystal reference of 5. 12 MHz was employed to assure 10 KHz steps ( enough sufficient to FM channeling of 200 KHz), and it also depends of R divider crystal reference, here I used R=512 to the MC145151P2 of Motorola. P - is the prescaler divider, normally P=40 to MC12016, the PLL needs downconverter the input frequency ( pin1) because the phase/frequency comparator just work at maximum of 10MHz or 15MHz input frequency.




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