Method for arranging signal points in a quadrature amplitude modulation/demodulation system

A quadrature amplitude modulator device for quadrature amplitude modulating data for transmission, comprising:

• modulation data outputting means for outputting, as modulation data, one set of 2.sup.n sets of first and second coordinate values corresponding to 2.sup.n signal points on a rectangular plane, said one set of first and second coordinate values corresponding to n bits of transmission data, said 2.sup.n signal points arranged on all points of intersection of grid points and at least four concentric circles, beginning with the concentric circle smallest in diameter, before continuing sequentially with concentric circles, of increasing radius, said grid points are symmetrical with respect to rectangular axes of said rectangular plane and are arranged at intervals of unit distance, each concentric circle having a center at a coordinate origin of said rectangular plane and having a radius equal to a distance between the coordinate origin and a corresponding grid point;
• and
• amplitude modulating means for amplitude modulating two carrier components 90.degree. apart in phase with the first and second coordinate values from said modulation data outputting means and for combining modulated carrier components for transmissions.

A quadrature amplitude demodulator device for demodulating a received modulated signal resulting from quadrature amplitude modulation, comprising:

• detecting means for demodulating the modulated signal by use of two carrier components 90.degree. apart in phase to obtain a first coordinate value and a second coordinate value on two rectangular coordinate axes of a rectangular plane;
• and
• demodulating means for outputting, as received data, n-bit pattern data corresponding to a signal point near to a point on said rectangular plane defined by the first and second coordinate values from said detecting means, said n-bit pattern data being one of 2.sup.n sets of n-bit pattern data for predetermined 2.sup.n signal points on said rectangular plane, said 2.sup.n signal points arranged on all points of intersection of grid points and concentric circles, beginning with the concentric circle smallest in diameter, before continuing sequentially with concentric circles of increasing radius, said grid points are symmetrical with respect to rectangular axes of said rectangular plane and are arranged at intervals of unit distance, each concentric circle having a center at a coordinate origin of said rectangular plane and having a radius equal to a distance between the coordinate origin and a corresponding grid point.