Abstract: In a frequency spectrum analyzer (2) which receives a modulation signal previously measures the frequency (F). A synchronous detection frequency (B) is determined on the basis of the frequency (F). An adder (7) obtains the difference (G) between the synchronous detection frequency (B) and the reference frequency (C). From an I signal and a Q signal which are obtained by performing synchronous detection by using the synchronous detection frequency (B), a frequency error detector (6) obtains a frequency error (E) by the phase trajectory method. An adder (8) adds the difference (G) and the frequency error (E) to obtain a frequency error.

Abstract: A high-speed FFT processing method for subjecting a plurality of FFT data sets to FFT processing, which includes step (a) for dividing the plurality of FFT data (N) into blocks suitable for accessing memory to be used in FFT processing; step (b) for sequentially transferring to the memory the data that have been divided into the blocks; step (c) for FFT processing of the FFT data that have been transferred to the memory; and step (d) for repeating processing pertaining to step (c) to thereby process all the divided blocks, thus effecting high-speed FFT processing.

Abstract: A frequency deviation measuring device is used in fields of digital mobile communication systems to measure frequency deviations with respect to .pi./4 QPSK modulation signals in accordance with the phase locus method. A center frequency is detected on the basis of a spectrum distribution measured with respect to a testing signal which corresponds to a digital modulation signal. A non-modulation signal is generated based on the center frequency detected from the testing signal. Quasi-synchronization wave detection is performed on the testing signal and non-modulation signal to produce an IQ base band signal. A first frequency deviation is detected based on the IQ base band signal in accordance with the phase locus method. A second frequency deviation is detected based on a difference between the center frequency and a testing frequency set value.

Abstract: A method of adjusting modulation accuracy corrects an I modulation signal and a Q modulation signal without using special hardware when an accurate 90.degree. phase difference between the I modulation signal and the Q modulation signal is not present. The method comprises setting I component correction .DELTA.i for a plurality of phase differences in advance to an I component corrector in accordance with an I signal, which is converted from digital modulation data in a digital data train by a modulator and an IQ converter of a phase error corrector. The method also comprises setting a Q component correction .DELTA.q for a plurality of phase differences in advance to a Q component corrector in accordance with a Q signal, controlling the I component corrector and the Q component corrector by a phase error correction controller, thereby adding the I component correction .DELTA.i and the Q component correction .DELTA.