| 摘要 |
PROBLEM TO BE SOLVED: To provide a transmission circuit equipped with mixers which stabilize and suppress carrier leaks. SOLUTION: The transmission circuit is equipped with two mixers for modulating a carrier wave by an input signal, outputs a signal having information about a phase and an amplitude, detects a direct-current offset for every mixer, and adds a direct-current voltage to correct the detected direct-current offset to the input signal of the mixer. A mixer 31 is a double balancing modulator provided with two load resistances 11 and 12. The transmission circuit is provided with a resistance 16 connected between connecting points of the two load resistances; a limiter amplifier 20 for amplifying a signal which appears in a connecting point, when electric potential alternately turns to first potential 28 or second potential 29 at an input terminal in a differential input signal of the double balancing modulator; and a control unit 37 for changing the first and the second potential by use of a signal outputted by the limiter amplifier. The first and the second potential converged in a return loop formed of this constitution turns into the potential of a direct current voltage which corrects the direct current offset. COPYRIGHT: (C)2006,JPO&NCIPI
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