| 摘要 |
PURPOSE: A frequency synthesizer circuit for radio frequency is provided to simplify a system structure, and to decrease a system noise by connecting a matching transformer and an ATT to a reference frequency generating circuit. CONSTITUTION: A frequency synthesizer circuit includes an IF LO signal generating circuit. At this time, the IF LO signal generating circuit includes a reference frequency generating circuit for PLL, a matching transformer(M.T), and an ATT. The reference frequency generating circuit for PLL receives an output signal of a PLL circuit, and generates a crystal clock OSC or a TCOX. The matching transformer(M.T) transforms an output of the reference frequency generating circuit for PLL into an 50 ohm meter. The ATT controls an output level of the 50 ohm meter. At this time, the ATT generates an IF LO signal suitable for a condition of a modulator by controlling the output level of the 50 ohm meter.
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