Patent ID: 6072374
Filing Date: 2000-06-06
Classification: H03C,H04L

Abstract:
An FM modulation system comprising:a baseband signal processing circuit for generating a baseband signal for a quadrature signal and a baseband signal for an equi-phase signal by reading out a sine wave signal of a predetermined frequency pre-stored and converting the same into an analog signal with the use of an address signal obtained by digitizing modulating signals input through a predetermined sampling process; anda quadrature modulator for generating a FM modulated high frequency signal by adding together a signal obtained through multiplication of the baseband signal for the equi-phase signal by a local signal of a cosine signal at respective predetermined frequencies, and a signal obtained through multiplication of a sine signal resulting from phase-shifting the local signal through 90 degrees by the baseband signal for the quadrature signal; andsaid baseband signal processing circuit including:(a) memory means for pre-storing the sine wave signal of the predetermined frequency,(b) a counter for generating the address signal which reads out the sine wave signal stored in the memory means by use of a clock signal,(c) a digital-to-analog converter for converting data from the memory means corresponding to the sine wave signal into an analog signal, and(d) an integrator for generating the baseband signal for the equi-phase signal and the baseband signal for the quadrature signal by integrating output signals of the digital-to-analog converter.