| 摘要 |
PURPOSE: A direct conversion receiver for removing a DC offset and a DC offset removing method using the same are provided to substantially remove a DC offset in order to recover an information signal from a carrier signal modulated by the information signal. CONSTITUTION: A processing unit(600a) includes mixers(602,603), low pass filters(606,607), and compensation amplifiers(610,611). The mixers(602,603) mix two I components with a signal provided from an LNA(Low Noise Amplifier)(601). The low pass filters(606,607) remove spurious signals generated from the mixers(602,603). The compensation amplifiers(610,611) compensate a DC offset signal. One compensation amplifier has a fixed gain while the other has a variable gain. A subtracting unit(614) can obtain perfect information signal by two coupled signals provided form the mixers(602,603). A feedback loop circuit(600c) includes a high gain amplifier(623), an analog-to-digital converter(621), a DSP(619) and a digital-to-analog converter(617). The high gain amplifier(623) detects a DC offset component. The analog-to-digital converter(621) converts an analog DC offset signal into a digital signal so that the DSP(Digital Signal Processor)(619) can read a signal. The DSP(619) outputs a suitable control voltage to an AGC(Automatic Gain Controller) in order to determine whether the DC offset is a zero and control the DC offset signal to be zero. The digital-to-analog converter(617) converts an output of the DSP(619) into an analog signal. Switches(624,625) are connected to a processing unit and a feedback loop unit. Amplifiers(626,627) amplify signals provided from the subtracting units(614,615).
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