| 摘要 |
PROBLEM TO BE SOLVED: To make a tuner for satellite broadcast reception small-sized and low-cost by solving problems in terms of characteristics of a direct conversion system. SOLUTION: The respective circuits which constitute the direct conversion type tuner for satellite broadcast reception are divided and arranged roughly in an RF block consisting of a high-pass filter(HPF) 1, an RF amplifier 2, an RF attenuator 3, an RF amplifier 4, and an automatic gain control(AGC) and a local block consisting of a mixer I/Q detector 6 having a built-in oscillator and a channel selecting circuit 7, and a shield plate F1 is provided between them. Further, the RF block is divided into two blocks of the high-pass filter 1 and RF amplifier 2, and the RF attenuator 3, RF amplifier 4, and automatic gain control and a shield plate F2 is provided between them. The shield plates F1 and F2 can improve the mutual isolation effect between the circuit blocks.
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