| 摘要 |
PROBLEM TO BE SOLVED: To obtain a modulator of an on/off ratio of about 20 db by turning on/off a collector current so as to modulate a carrier wave, saving the occupied bandwidth of the carrier wave to be not larger than a specific value, using the modulation signal of a transmission rate in a specific range and using a frequency in a specific range as the carrier wave. SOLUTION: A collector current is turned on/off to modulate a carrier wave, a low pass filter is connected to the side of a collector to save the occupying bandwidth of the carrier wave to be not larger than 8 MHz, the modulation signal of a transmission rate ranging 500 to 2500 bit/sec is used and a frequency ranging 5 to 7 GHz is used as the carrier wave. In this modulator, a signal wave is inputted from a signal wave inputting terminal 118 at the time of switch-on, has its amplitude adjusted by an operational amplifier 115 and passes through the low pass filter consisting of capacitors 112, 113 and a coil 114. When the signal wave is on, electric charge is stored in the capacitors 112, 113, and the electric charge is discharged when the signal wave is off, thereby raising an on/off ratio to around 20 db.
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