| 摘要 |
PROBLEM TO BE SOLVED: To provide an arc tangent type FM demodulator that it is unnecessary to provide any AGC circuit, and the simplification of the constitution and the reduction of costs can be attained. SOLUTION: In this FM demodulator, a reference signal R being a sine wage with fixed frequencies is outputted from a reference signal generator 1, and inputted to an A/D converter 2, and an FM signal is inputted to a limiter amplifier 3, and converted into a rectangular wave, and turned into a sampling pulse 3 to the A/D converter 2. An A/D converted digital signal A is turned into two orthogonally crossing signals B and C by an orthogonalizer 4, and an angular signal D corresponding to an arc tangent value is calculated by an arc tangent arithmetic unit 5 based on the rate, and the difference is calculated by a difference calculator 6, and finally outputted as a digital FM modulation signal. Thus, it is not necessary to provide any AGC circuit in an input stage for an FM signal, and it is possible to simplify the constitution of an arc tangent type FM demodulator, and to reduce costs.
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