Multi-value modulation/demodulation method and multi-value modulation/demodulation device

1. A multi-value modulation/demodulation method, comprising the following steps:

generating N quaternary phase shift keying (QPSK) outputs having different amplitude levels r2=r1×2 −(i−1) , i=2 . . . N with respect to a maximum amplitude level r1 to form M(=2 2N )-valued/quadrature amplitude modulation (QAM);

power amplifying powers of N-1 outputs si from respective executions of quaternary phase shift keying QPSK-i (i=2 to n) except the quaternary phase shift keying QPSK- 1 having the maximum amplitude r1 at the time of the formation;

performing a combination by using a directional coupler having N-1 input terminals and one output terminal to obtain a combined signal after power amplification;

transmitting an output of the quaternary phase shift keying QPSK- 1 and the combined signal from two systems of antennas; and

vectorially superposing and combining the transmitted signals in a space.

2. The multi-level modulation/demodulation method according to claim 1 , wherein a series/parallel converter is provided before each QPSK unit to divide input data of 2N bits and input the divided data to each QPSK unit, a data converting function is used to perform gray encoding by which a code distance between codes adjacent to each other becomes 1, and a variable gain unit and a variable phase shifter adjust a gain and a phase in a signal path of each QPSK unit and a power amplifier.

3. The multi-level modulation/demodulation method according to claim 2 , wherein a signal spatial arrangement that is a non-uniform arrangement where the amplitude of the quadri-phase shift keying QPSK- 1 having the highest amplitude is increased as compared with the uniform arrangement where geometrical distances between respective signal points are equal is used as a signal spatial arrangement to perform modulation.

4. The multi-level modulation/demodulation method according to claim 3 , wherein a gain (amplitude) error and a phase error as errors at the time of vector-combining an output signal of the QPSK- 1 with a combined signal of the plurality of executions of QPSK-i (i=2 to N) are estimated from a reception signal when transmitting a known signal, these estimated values are used to consider the gain error and the phase error, and a demodulation symbol is detected from a transformed signal spatial arrangement and the reception signal.

5. A multi-level modulation/demodulation apparatus comprising:

quaternary phase shift keying units that superpose N (integer equal to or above 3) quaternary phase shift keying (QPSK) outputs having different amplitude levels, r2=r1×2 −(i−1) , i=2 . . . N with respect to a maximum amplitude level r1 after power amplification to form M(=2 2N )-valued/quadrature amplitude modulation (QAM);

a power amplifier that amplifies powers of N-1 outputs si from respective executions of quaternary phase shift keying QPSK-i (i=2 to N) except the quaternary phase shift keying QPSK- 1 at the time of formation;

means for performing combination by using a directional coupler having N-1 input terminals and one output terminal to obtain a combined signal after power amplification;

two systems of antennas that transmit an output of the quaternary phase shift keying QPSK- 1 and the combined signal; and

means for vectorially superposing and combining these transmitted signals in a space, wherein a variable gain unit and a variable phase shifter which are arranged in a signal path of each quaternary phase shift keying unit and the power amplifier to adjust a gain and a phase, a series/parallel converter which divides input data of 2N bits and inputs the divided data to each quaternary phase shift keying unit, and data converting means for performing gray encoding by which a code distance between codes adjacent to each other becomes 1 are provided before each quaternary phase shift keying unit.

6. The multi-level modulation/demodulation apparatus according to claim 5 , wherein a signal spatial arrangement that is a non-uniform arrangement in which the amplitude of the quadri-phase shift keying QPSK- 1 having the highest amplitude is increased as compared with the uniform arrangement where geometrical distances between respective signal points are equal is used as a signal spatial arrangement to perform modulation.

7. The multi-level modulation/demodulation apparatus according to claim 6 , wherein a gain (amplitude) error and a phase error as errors at the time of vector-combining an output signal of the quadri-phase shift keying QPSK- 1 with a combined signal of the plurality of executions of quadri-phase shift keying QPSK-i (i=2 to N) are estimated from a reception signal when transmitting a known signal, these estimated values are used to consider the gain error and the phase error, and a demodulation symbol is detected from a transformed signal spatial arrangement and the reception signal.

8. A multi-level modulation/demodulation method comprising the following step:

dividing an output having a highest amplitude level of outputs of a plurality of executions of quaternary phase shift keying (QPSK) by a first power division circuit, wherein, the plurality of executions are N-QPSK (quaternary phase shift keying) outputs (N is an integer equal to 3 or above) having different amplitude levels r2=r1×2 −(i−1) , i=2 . . . N with respect to a maximum amplitude level r1 to form M(=2 2N )-valued/quadrature amplitude modulation (QAM);

amplifying the power divided outputs by a power amplifier to be fed to an antenna circuit;

combining the outputs other than the highest amplitude level;

dividing the combined outputs by a second power division circuit; and

amplifying the power divided outputs, generated by the second power division circuit, by a power amplifier to be fed to an antenna element.