Patent ID: 6351503
Filing Date: 2002-02-26
Classification: H04L

Abstract:
In a communication system where QPSK modulation is used to transmit data on a carrier frequency, the improvement wherein a carrier frequency phase reference is derived using a threshold extension block phase estimator (TEBPE) as described by the following equations: Î¸^=tan-1&af;[&Sum;k&it;(yk&it;D_k-xk&it;E_k)&Sum;k&it;(xk&it;D_k+yk&it;E_k)]where{overscore (D)}k=tanh(Pkcos(&phgr;kâˆ’{overscore (&thgr;)})) {overscore (E)}k=tanh(Pksin(&phgr;kâˆ’{overscore (&thgr;)})) Pk=ArkÏƒk2with and input signal given bysk=xk+jykexp(j&phgr;k) xk=A[Dkcos(&thgr;k)âˆ’Eksin(&thgr;k)]+nk yk=A[Dksin(&thgr;k)+Ekcos(&thgr;k)]+mk where A is the signal amplitude, and Dk and Ek are the in-phase and quadrature data streams with value Â±1, &thgr;k is an input signal phase, &phgr;k is a phase of a signal plus noise, rk is an amplitude of a signal plus noise, nk is an input noise, mk is a quadrature noise, and the noise variance isvar(nk)=var(mk)=&sgr;n2.