| 摘要 |
PURPOSE: A preprocessing apparatus for a wireless transmission system using an attenuator is provided to cancel a leakage signal which flows from a transmission terminal to a receipt terminal through a circulator. CONSTITUTION: The first coupler(205) couples a power-amplified transmitting signal to output the coupled transmitting signal to a circulator(207), and changes a phase of the transmitting signal to 90 degrees to output a branch signal. An attenuator(215) receives the branch signal, attenuates a power level of the branch signal as a power level of the transmitting signal, and outputs the attenuated branch signal. The second coupler(209) receives the attenuated branch signal, changes a phase of the received branch signal to 90 degrees, couples the changed branch signal and the transmitting signal inputted through the circulator(207), and cancels the transmitting signal.
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