| 摘要 |
PURPOSE: An apparatus and a method for removing the DC offset of the output of a frequency conversion mixer are provided to exactly correct the DC offset of the output of the mixer of a frequency direct conversion transceiver, in frequency down direct conversion output through the mixer, and to prevent the decrease in the linearity of the output. CONSTITUTION: An apparatus for removing a DC offset consists of a mixer(610), a DC level fixing signal generation part(620), a DC offset removing signal generation part(630), and a DC level fixing and offset removing part(640). The mixer(610) executes frequency down conversion for an RF signal inputted based on an LO(Local Oscillation) signal and outputs 2 signals, an I signal(mixer_out) and an I_b signal(mixer_out_b), through 2 output terminals(out,out_b) respectively. The DC level fixing signal generation part(620) generates the first control signal(Vg) to regularly fix the DC levels of the two signals(mixer_out,mixer_out_b) outputted from the two output terminals(out,out_b) of the mixer(610). The DC offset removing signal generation part(630) generates the second control signals(Da,Db) to eliminate the relative difference between the DC levels of the two signals(mixer_out,mixer_out_b). Based on the first control signal(Vg) and the second control signals(Da,Db), the DC level fixing and offset removing part(640) regularly fixes the DC levels of the two signals(mixer_out,mixer_out_b) and eliminates the relative difference between the DC levels of the two signals(mixer_out,mixer_out_b).
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