METHOD FOR QUADRATURE-QUADRATURE AMPLITUDE MODULATION WITH CONSTANT AMPLITUDE CHARACTERISTIC AND ITS APPARATUS

摘要

Currently, modulation schemes such as QPSK (Quadrature Phase Shift Keying) and MSK (Minium Shift Keying) are adopted as modulation methods in mobile communication, personal communication, satellite communication, and the like. Recently, existing Q ² PSK (Quadrature-Quadrature PSK) and QAM (Quadrature Amplitude Modulation) to improve the bandwidth efficiency of Q ² AM, that is, a pair of quadrature amplitude modulation methods.;However, the above-described quadrature amplitude modulation method has a problem in that it can not be used in the above-mentioned wireless communication system employing a nonlinear amplifier because the amplitude of its output signal varies according to transmission data.;In the present invention, for example, in a conventional bi-quadrature amplitude modulation scheme in which 8 bits are level-converted by 2-bit units and then modulated and added, a 4-bit parity bit is generated, . The redundant bit is set such that the amplitude of the output modulated signal has a constant amplitude.;In the present invention, a constant amplitude encoder for generating the redundant bits is provided. The constant amplitude coder includes a modulo-2 adder for adding data to be transmitted in a predetermined combination unit.;Therefore, the present invention provides a modulating method with excellent bandwidth efficiency that can be applied to a nonlinear system by adding a constant amplitude characteristic to a biaxial amplitude modulation system with a relatively simple structure.