Digital frequency converter and method of processing in a digital frequency converter

A frequency converter adapted for receiving signal samples and comprising:

• at least one frequency transposition block adapted for transposing in frequency said received samples;
• at least one filtering block adapted for filtering said transposed samples and for delivering filtered samples y(n) verifying the formula y(n)=c(0)·x(n)+c(1)·x(n−1)+c(2)·x(n−2)+ . . . +c(p−1)·x(n−p+1)+c(p)·x(n−p)+c(p−1)·x(n−p−1)+ . . . + . . . +c(1)·x(n−2·p+1)+c(0)·x(n−2·p), wherein x( ) are transposed samples and c(0), . . . c(p) are real coefficients of the filter;
• and
• a set of memories;
• said frequency converter being adapted for, during a cycle for determining the value of the filtered sample y(n), carrying out operations for
• calculating the first terms c(0)·x(n), c(1)·x(n−1), c(2)·x(n−2), . . . , c(p)·x(n−p) by multiplying the respective coefficients and transposed samples, and storing at least certain of said first calculated terms in the set of memories;
• reading, in the set of memories, at least certain of the second terms c(p−1)·x(n−p−1), . . . , c(1)·x(n−2·p+1), c(0)·x(n−2·p), calculated and stored during the previous cycles for determining the value of filtered samples y(n−m), with m being a strictly positive integer;
• and
• determining y(n) by summation of the first and second terms;
• wherein said frequency converter is also adapted for receiving sampled real signal samples and for delivering complex signals I/Q, from the filtering by the filtering block after transposition with the transposition block of said sampled real samples,
• said converter including parallel chains for processing of the signals I and of the signals Q, at least one of said processing chains I, Q comprising N parallel routes each adapted for carrying out frequency transposition, said frequency converter being adapted for selectively distributing the real samples between said routes, each (N·n+i−1)th real sample being provided to the ith route, i=1 to N, n being a positive integer,
• at least the kth and jth parallel routes of said processing chain (VQ), k≠j and k, j integers between 1 and N, comprising a filtering sub-block adapted for determining the filtered signal y(N·n+i−1)=c(0)·x(N·n+i−1)+c(1)·x(N·n+i−1−1)+c(2)·x(N·n+i−1−2)+ . . . +c(p−1)·x(N·n+i−p)+c(p)·x(N·n+i−1−p)+c(p−1)·x(N·n+i−1−p−1) . . . +c(1)·x(N·n+i−1−2·p+1)+c(0)·x(N·n+i−1−2·p), wherein x( ) are signals from the transposition in said processing chain, with i=j on the jth route, and i=k on the kth route,
• the filtering sub-block of the kth route, respectively of the jth route, being adapted for calculating the first terms c(0)·x(N·n+i−1), . . . ,c(p)·x(N·n+i−1−p) by multiplying the respective coefficients and transposed samples, in order to store at least certain of said first terms calculated in the set of memories and for reading, in the set of memories, at least certain of the second terms c(p−1)·x(N·n+i−1−p−1), . . . , c(0)·x(N·n+i−1−2·p), calculated and stored during previous cycles for determining the value of filtered samples y(n−m), with m being a strictly positive integer, certain of said second terms having been calculated by the filtering sub-block of the jth route, respectively of the kth route.