A Lower Power Up-conversion Frequency Synthesizer for AM/FM/WB/SW Applications

The conventional superhetrodyne AM receiver utilizing a 260 to 450 KHz Intermediate Frequency has been with us since its invention in the 1920's. The block diagram shown in fig. 1 has typified automobile radio design: an RF amplifier drives two tuned circuits which are necessary to protect the mixer from cross-modulation from nearby strong signals, and a local oscillator to produce the desired IF. Although widely implemented, this approach is expensive because of the severe requirements placed on the varactor tuning diodes, and the excessive number of adjustments.