| 摘要 |
PROBLEM TO BE SOLVED: To provide a small radio transmitting device in which a defect that band width is not widened due to the restriction in an IF (intermediate frequency) frequency and the attenuation characteristics of a filter, is removed in a transmitter changing frequencies by replacing a channel cassette. SOLUTION: A microwave transmitting circuit comprises: a local oscillator oscillating at a frequency lower by an IF frequency portion than a specified microwave frequency; a frequency mixer mixing an IF signal with output from the local oscillator; a bandpass filter for taking out only an RF (radio frequency) frequency portion formed by adding the IF signal to a local oscillator frequency from the mixer output; and a power amplifier amplifying the output from the filter up to the specified level. Where, the transmission device conducts the reception and delivery of the microwave signal of the channel cassette through a push-on connector by forming the local oscillator and the filter to one replaceable cassette in order to switch the specified microwave frequencies (channels). COPYRIGHT: (C)2004,JPO
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