| 摘要 |
PURPOSE:To remove a difference frequency component, to eliminate the need for the trap of a filter, and to improve reliability, by setting phase differences between signals 40fN and signals fSC inputted to two converters to 90 deg. and summing up two outputs. CONSTITUTION:A signal switching circuit 11 switches four signals 40fN from a 1/4 frequency dividing circuit 2 to output two 90 deg. out-of-phase signals 40fN. The output of an oscillator 6 is supplied to a converter 14 and also delayed in phase by 90 deg. through a 90 deg. phase shifting circuit 16 to be supplied to a converter 7. The two converter outputs are summed up at a part 15 to remove a difference frequency component while leaving a sum frequency component because the signal 40fN lags the input to the converter 7 by 90 deg. and the signal fSC leads it by 90 deg.. Therefore, almost no spurious component appears at the output of the adder 15 and the trap of a BPF8 is unnecessary. Therefore, the cost is reduced and the performance is improved. |
