초록 ▼

A universal demodulator programmable for any digitally modulated carrier signal having a known constellation format which can be characterized by a unique constellation pattern of phase-amplitude states. The demodulator also generates phase and gain-error signals for locking onto the phase and ampli

A universal demodulator programmable for any digitally modulated carrier signal having a known constellation format which can be characterized by a unique constellation pattern of phase-amplitude states. The demodulator also generates phase and gain-error signals for locking onto the phase and amplitude of the digitally modulated carrier. The demodulator splits the received digitally modulated carrier signal into an inphase component, Dx, and a quadrature-phase component, Dy. Using a preprogrammed memory device keyed to the identified modulation format, each Dx signal is mapped into one of a plurality of one-dimensional zones each having Rx center values. Using a second preprogrammed memory device also keyed to the identified modulation format, each Dy signal is similarly mapped into a plurality of orthogonal one-dimensional zones having Ry centers. Each pair of Rx and Ry values represents a point in a two-dimensional signal space corresponding to one of the transmitted phase amplitude states. The data assignment signals, Ax and Ay, are generated and outputted by selecting a predetermined portion of the Rx and Ry center values. Using the digital signals Rx, Ry, Dx and Dy and signal vector relationships, a logic circuit generates for each periodic signal pair a phase-error signal Fe corresponding to the phase difference between the phase angle associated with (Dx and Dy) and the phase angle associated with (Rx and Ry). Also generated is a gain-error signal Ge corresponding to the amplitude differential between the amplitude associated with (Dx and Dy) and the amplitude associated with the signal pair (Rx and Ry). The phase and amplitude of the modulated carrier signal is adjusted in accordance with the phase-error signal Fe and the gain-error signal Ge respectively.

대표청구항 ▼

In a digital communication system including a transmitter for generating a digitally modulated carrier signal having any one of a known plurality of phase-amplitude modulation formats, each format characterized by a unique constellation pattern of transmitted phase-amplitude states, and a receiver f

In a digital communication system including a transmitter for generating a digitally modulated carrier signal having any one of a known plurality of phase-amplitude modulation formats, each format characterized by a unique constellation pattern of transmitted phase-amplitude states, and a receiver for demodulating the digitally modulated carrier signal, apparatus for demodulating the digitally modulated carrier signal and for locking onto to the phase and amplitude of the digitally modulated carrier, said apparatus comprising: receiving means for receiving the digitally modulated carrier signal; splitting means for splitting the received digitally modulated carrier signal into in-phase and quadrature-phase signal components; A/D converter means for periodically digitizing said in-phase and quadrature-phase signal components to form the signal pair (Dx,Dy), Dx being the periodic digital representation of the in-phase signal component and Dy being the periodic digital representation of the quadrature-phase component; identifying means for identifing the particular modulation format of said received digitally modulated carrier signal; first memory means for periodically receiving said Dx in-phase signal component as a memory address, said first memory means containing for each modulation format first and second tables, each of said first tables for converting values of Dx into corresponding Rx reference values, and each of said second tables for converting values of Dx into corresponding Ax data assignment values; second memory means for periodically receiving said Dy quadrature-phase signal component as a memory address, said second memory means containing for each modulation format third and fourth tables, each of said third tables for converting values of Dy into corresponding Ry reference values, and each of said fourth tables for converting values of Dy into corresponding Ay data assignment values, where (a) a corresponding reference pair (Rx,Ry) and a corresponding assignment pair (Ax,Ay) exist for each (Dx,Dy) signal pair, (b) a one-to-one correspondence exists between each (Rx,Ry) reference pair and one of the transmitted phase-amplitude states mapped onto a two-dimensional x,y signal space and, (c) a one-to-one correspondence exists between each (Ax,Ay) assignment pair and one of the transmitted phase-amplitude states mapped onto a two-dimensional x,y signal space; selection means coupled to said first and second memory means for selecting each of said tables for said identified modulation format; first logic means coupled to said first memory means for generating the digital signal Ex by subtracting Rx from Dx; second logic means coupled to said second memory means for generating the digital signal Ey by subtracting Ry from Dy; third logic means for generating a phase-error signal Fe, where Fe=(RyEx-RxEy) and a gain-error signal Ge, where Ge=(RxEx+RyEy); first feedback means coupled to said receiving means for correcting the amplitude of said digitally modulated carrier signal in accordance with said gain-error signal Ge; and, second feedback means coupled to said splitting means for correcting the phase of said in-phase and quadrature-phase signal components in accordance with said phase-error signal Fe.