| 摘要 |
<P>PROBLEM TO BE SOLVED: To measure the error of local frequency that is a differential between the actual value of a local frequency of a quadrature demodulator and a desired setting value. <P>SOLUTION: The quadrature demodulator 10 includes an in-phase multiplier 16I for multiplying RF input (frequency:fc+Δf) by a local signal; a quadrature multiplier 16Q for multiplying the RF input by a quadrature local signal; and a local signal output unit 12, and the frequency of the local signal is set to a predetermined value fc. A local frequency error measuring apparatus 20 measures the frequency error ferr, with respect to the predetermined value fc for the frequency of the local signal in the quadrature demodulator 10. The local frequency error measuring apparatus 20 includes an in-phase side A/D converter 24I, a quadrature side A/D converter 24Q, a phase characteristic deriving section 26 for deriving the phase of output from the quadrature demodulator 10, in association with a time, and a frequency error derivation section 28 for deriving the frequency error ferr. Moreover, the sampling frequency fs of the in-phase side A/D converter 24I and the quadrature side A/D converter 24Q is set to Δf or to Δf/(2<SP>n</SP>) (where, (n) is a positive integer). <P>COPYRIGHT: (C)2011,JPO&INPIT |
