Patent ID: 7224237
Filing Date: 2007-05-29
Classification: H03C,H03L

Abstract:
1. A modulator comprising: a PLL including a voltage-controlled oscillator, a frequency divider and a phase comparator, said modulator generating a modulating signal based on the modulation data having information on a wider bandwidth than the frequency bandwidth of the PLL, setting the division ratio of said frequency divider by way of this modulating signal, and outputting a modulated carrier signal from said voltage-controlled oscillator as well as performing filtering processing by way of a pre-distortion filter on said modulation data to provide a frequency characteristic inverse to the frequency characteristic of said PLL in a process of generating said modulation signal, thereby allowing wideband modulation, wherein said modulator comprises: error detection means for detecting a difference between an amplitude value in a frequency equal to or below the cutoff frequency of said PLL and an amplitude value in a frequency higher than said cutoff frequency concerning an ac component of said modulating signal appearing on a control terminal of said voltage controlled oscillator, and frequency characteristic correction means for correcting at least one of the frequency characteristic of said PLL and the frequency characteristic of said pre-distortion filter in a direction said detected difference is eliminated.