MODULATION METHOD DETECTION APPARATUS, MEASUREMENT APPARATUS INCLUDING THE SAME, MODULATION METHOD DETECTION METHOD, AND MEASUREMENT METHOD

To provide a modulation method detecting apparatus capable of accurately detecting a modulation method in a short period of time even for a signal modulated by a multilevel quadrature amplitude modulation method.SOLUTION: A modulation method detection apparatus 30 includes: a variance value calculation unit 33 that calculates variance values of amplitudes of a real axis component and an imaginary axis component; a multilevel determination unit 34a for determining whether a modulation system of an input signal is a multilevel quadrature amplitude modulation system having a value larger than four values; a signal point arrangement conversion unit 50 for converting a signal point arrangement of an input signal on the basis of data of the real axis component and the imaginary axis component into a signal point arrangement in which a modulation rank is lowered when it is determined that the system is the multilevel quadrature amplitude modulation system; and a modulation method detection apparatus 34 that detects a modulation method by a first threshold value predetermined on the basis of a variance value of an amplitude of the signal modulated by the quaternary quadrature amplitude modulation method and a signal-to-noise ratio and a second threshold value predetermined on the basis of a variance value of an amplitude of the signal and the signal-to-noise ratio when it is converted to a quaternary signal point arrangement.SELECTED DRAWING: Figure 1 【課題】多値の直交振幅変調方式で変調された信号であっても、その変調方式を短時間かつ正確に検出することができる変調方式検出装置を提供する。【解決手段】変調方式検出装置３０は、実軸成分及び虚軸成分の振幅の分散値を算出する分散値算出部３３と、入力信号の変調方式が４値よりも大きい多値の直交振幅変調方式であるか否かを判断する多値判断部３４ａと、多値の直交振幅変調方式であると判断された場合に、実軸成分及び虚軸成分のデータに基づく入力信号の信号点配置を変調ランクを下げた信号点配置に変換する信号点配置変換部５０と、４値の直交振幅変調方式により変調された信号の振幅の分散値及び信号対雑音比に基づいて予め定められた第１の閾値と、４値の信号点配置に変換された場合の信号の振幅の分散値及び信号対雑音比に基づいて予め定められた第２の閾値とによって変調方式を検出する変調方式検出部３４と、を備える。【選択図】図１