FIELD: radio engineering.
SUBSTANCE: first calculator calculates soft value Λ
of third demodulated symbol of 4 demodulated symbols by subtraction of distance 2a between two demodulated symbols of same axis of indication table from level 
, quadrature component Yk. Second calculator determines soft value Λ
of fourth demodulated symbol by calculating 
using first variable α. Third calculator calculates soft value Λ
of first demodulated signal by subtraction of distance 2a from level 
of common-mode component Xk. Fourth calculator determines soft value Λ
of second demodulated symbol by calculating 
using second variable β.
EFFECT: higher efficiency.
5 cl, 14 dwg, 12 tbl
