| 摘要 |
A device for maintaining fine alignment between an incoming spread spectrum signal and a locally generated code in a digital communication receiver comprises: - a delay line (56) for storing a plurality of consecutive samples (E-1, E, M, L, L+1) of the incoming spread spectrum signal; - three digitally controlled interpolators (24, 26, 28) for determining by interpolation between consecutive samples an interpolated early sample (e), an interpolated middle sample (m) and an interpolated late sample (1); - two correlators (30, 32) for calculating an error signal (Sigma) as the difference between the energy of the symbols computed from the interpolated early (e) and late (1) samples; - a circuit for generating a control signal (SOUT) for controlling the interpolation phase of the digitally controlled interpolator (24) for the early sample (e), and - a digital non-linear filter (68), for smoothing the control signal (SOUT) of the interpolator (24) for the early sample (e), enabling the update operation of the control signal only when the absolute value (|Sigma(n)|) of the error signal at a time instant n is smaller than the absolute value (|Sigma(n-1)|) of the same error signal at a time instant n-1. |
