Upconversion AM/FM Frequency Synthesizer

This paper describes a digital Phase-Locked Loop (PLL) frequency synthesizer designed for AM/FM radios. The synthesizer utilizes an upconversion technique which enables tuning of both the AM and FM bands using one Voltage Controlled Oscillator (VCO) operating between 98 and 118 MHz. The scheme reduces the cost associated with the AM front end as a result of eliminating three matched varactor diodes and the labor involved in the five to six adjustments for alignment.