| 摘要 |
A mixer input circuit for converting a signal from a tuning section of an unbalanced type into a balanced signal and outputting the signal. In the mixer input circuit, an RF signal from an input terminal amplified by an RF amplifier is transmitted to a tuning circuit section employing a distributed constant line. A central conductor of the distributed constant line in the tuning circuit section is electromagnetically combined with a second central conductor, thereby constituting an imbalance-balance conversion section. A middle point of the second central conductor on an output side of the imbalance-balance conversion section is grounded, and a balanced output signal from both ends is transmitted to a mixer, so as to be converted into an IF signal and then to be output from an output terminal. With the present mixer input circuit, imbalance-balance conversion can be carried out without using a transformer, and a reduction in size can be realized due to the absence of deterioration of performance.
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