Method of processing a digital signal derived from an analog input signal of a gnss receiver, a gnss receiver base band circuit for carrying out the method and a gnss receiver

Abstract

For suppression of continuous wave interferers at, e.g., up to four interferer frequencies (f, f, f, f) in a GNSS receiver base band circuit a raw digital signal is, in a band stop unit (), shifted, by a first mixer (), by the negative of the first interferer frequency (f) in the frequency domain whereupon the continuous wave interferer is suppressed by a band stop filter (), a linear phase FIR filter with a suppression band centered at zero, e.g., a filter subtracting a mean over previous subsequent signal values from the actual signal value. After further shifting of the shifted digital signal by the negative of the difference between the second interferer frequency (f) and the first interferer frequency (f) the shifted digital signal is again filtered by an identical band stop filter () and so on. After the last filtering step the shifted digital signal is shifted back to its original position in the frequency domain to provide a filtered digital signal which corresponds to the raw digital signal with narrow interferer bands centered at the interferer frequencies (f, f, f, f) suppressed.