| 摘要 |
PURPOSE:To make forming of a built-in IC of a selected filter easy, to reduce manufacturing cost and to reduce the area of a substrate by using a local oscillator, a multiplier, a phase shifter and a matrix circuit instead of an active filter. CONSTITUTION:A local oscillator 5 generates two signals S51, S52 having a phase difference of the prescribed angle, and they are respectively multiplied by input signals in multipliers 6, 7. And phase shifters 8, 9 are constituted so that a phase shift characteristic falls approximately linearly for logarithm of a frequency at a band adjacent to a frequency of approximately one half of a difference frequency between carrier frequencies of output signals of the multipliers 6, 7, and a mutual phase difference is held. A matrix circuit 10 finds the sum and the difference of output signals of the phase shifters 8, 9, and performs signal separation. After that, sending compensation of phases is performed by phase shifters 11, 12, and demodulation is performed by demodulators 3, 4. Forming a built-in IC of a selecting filter is made easy by this constitution. |
