Patent ID: 6768902
Filing Date: 2004-07-27
Classification: H03D

Abstract:
A double frequency converter comprising:a first mixer to frequency convert input signals with first local oscillation signals into first intermediate frequency signals; a second mixer to frequency convert the first intermediate frequency signals into output signals with second local oscillation signals; a band pass filter disposed between the first mixer and the second mixer; a first PLL circuit to control the frequency of the first local oscillation signals; a second PLL circuit to control the frequency of the second local oscillation signals; and a microcomputer to supply one of the first PLL circuit and the second PLL circuit with first frequency data to alter one at the frequency of the first local oscillation signals and the frequency of the second local oscillation signals at the prescribed intervals; and wherein a frequency of the first local oscillation signals and a frequency of the second local oscillation signals are shifted by the same frequency, the frequency of the first local oscillation signals and the frequency of the second local oscillation signals are alterable by prescribed intervals, and each frequency is shiftable by the prescribed intervals, wherein second frequency data based on the frequency of a deviation between a reference frequency of the first intermediate frequency signals and a center frequency of the band pass filter is stored in the microcomputer, and shifting is accomplished by supplying the second frequency data that has been stored to the first PLL circuit and the second PLL circuit.