FREQUENCY CONVERTER

PROBLEM TO BE SOLVED: To perform frequency conversion high in stability with a simple configuration by using a high-resolution local oscillator which can tune within the tuning step range of a local oscillator on the prestage for a local oscillator of a frequency converting part on the poststage thereby performing fine tuning. SOLUTION: This converter is composed of two stages of frequency converting parts, a PLL synthesizer that is stable and can tune within a wide band frequency range is used for the local oscillator in a frequency converting part on the prestage, and a PLL synthesizer which is stable and has a short tuning interval (tunable within the tuning step of the prestage synthesizer) is used for the local oscillator on the poststage to constitute the frequency converting parts to convert a receiving signal into a frequency at a certain point. Thus, coarse and fine tuning roles are allocated by such a manner that the stable and wide band PLL synthesizer 6 on the prestage performs coarse tuning and that the narrow band and high resolution PLL synthesizer 6 on the second stage performs fine tuning between the tuning intervals on the poststage.