IN-PHASE AND QUADRATURE SIGNAL REGENERATION

The present invention relates to the regeneration of in-phase (I) and quadrature (Q) signals in electronic devices commonly used in communication, radar and instrumentation electronics. The original signal of interest comprises two orthogonal components that are mathematically modelled using complex values, which are then decomposed into a real (I) and an imaginary (Q) component. These two components are orthogonal to each othe r and represent fully the signal of interest. The present method adaptively compensates for the gain and phase imbalances and DC offsets in I and Q signal regeneration. First, 3 phase shifted versions of the received signal, either down-converted to some intermediate frequency (IF) o r at baseband, are digitised. Although the optimum phase shift between each version is 360.degree./3, any phase shift different than 0.degree. and 180.degree. is acceptable and no a priori knowledge of the phase shifts is required. Based on these 3 digital signals representing 3 linear combinations of the I &Q signal components, the regeneration algorithm projects these signals into a 3- dimensional space composed of the I signal subspace, the Q signal subspace, and another subspace, referred to as the noise subspace. The projection is performed using an eigen-decomposition methodwhere the eigenvectors associated with the I and Q signal subspaces provide linear combination coefficients for regenerating the I&Q signals. Compensation for DC offsets is perform ed by removing an average DC offset on the phase and gain corrected I&Q signals. The regen erated digital I and Q signals are then converted back to analog signals, when required.