Patent ID: 7702299

Claim:
A modulation circuit device, comprising: an angle modulator for angle-modulating an input phase signal: an amplitude shaping means for performing a non-linear filtering on an input amplitude signal; and an amplitude modulator for amplitude-modulating an output signal from said angle modulator by an output amplitude signal from said amplitude shaping means, wherein said performing the non-linear filtering of said amplitude shaping means is equivalent to at least one of (1) when said input amplitude signal becomes smaller than a first lower limit value which is a positive constant number, both of the first order differential coefficient and the second order differential coefficient of a magnitude of said output amplitude signal generated by said amplitude shaping means with respect to a magnitude of said input amplitude signal are limited to a positive value or zero in a segment in which said input amplitude signal becomes smaller than said first lower limit value, while said output amplitude signal is limited to a value not less than a second lower limit value which is a positive constant number smaller than said first lower limit value and smaller than said first lower limit, and (2) when said input amplitude signal becomes larger than a first upper limit value which is a positive constant number, (a) the first order differential coefficient of a magnitude of said output amplitude signal generated by said amplitude shaping means with respect to a magnitude of said input amplitude signal is limited to a positive value or zero in a segment in which said input amplitude signal becomes larger than said first upper limit value, and (b) the second order differential coefficient of the magnitude of said output amplitude signal generated by said amplitude shaping means with respect to the magnitude of said input amplitude signal is limited to a negative value or zero in the segment in which said input amplitude signal becomes larger than said first upper limit value, while said output amplitude signal is limited to a value not more than a second upper limit value which is a constant number larger than said first upper limit value and larger than said first upper limit value.