| 摘要 |
A down-converter includes two low-noise amplifiers, a 90-degree hybrid coupler, and a down-converting circuit. The 90-degree hybrid coupler is coupled to the two low-noise amplifiers for transforming a first amplified signal and a second amplified signal into a first coupler output signal and a second coupler output signal. The 90-degree hybrid coupler includes a coupler main body, a first transmission line, and a second transmission line, wherein the first and the second transmission lines are coupled to the coupler main body. The coupler main body includes two input ports respectively coupled to the two low-noise amplifiers and two output ports for respectively outputting the first and the second coupler output signals. The first and the second transmission lines are each an open-circuited transmission line or a short-circuited transmission line. The down-converting circuit is coupled to the two output ports of the 90-degree hybrid coupler.
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