| 摘要 |
PROBLEM TO BE SOLVED: To provide a micromini radio transmitter having resistance to fluctuation in a supply voltage, consuming low amounts of power and being suited to a capsule type endoscope. SOLUTION: This radio transmitter includes: a comparator 4 operating within a prescribed supply voltage range, shaping input signals 41 into rectangular wave-like balance signals and outputting them; a low pass filter 5 for attenuating components more than third and higher harmonics contained in the output signals 43 from the comparator and outputting sinusoidal balance signals; a mixer circuit 7 consisting of a circuit using a CMOS switch mechanism non-passing a direct current, mixing the sinusoidal balance signals with oscillating frequency signals and outputting the balance signals of radio frequency; a power amplifier 8 for converting the balance signals of radio frequency from the mixer circuit 7 into unbalance signals and amplifying them; and a band pass filter 9 for removing signals in unnecessary frequency band from the output signals of the power amplifier 8. The respective sections are formed in a CMOS process containing no organic substance. COPYRIGHT: (C)2008,JPO&INPIT
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