  The variances of matched and sidelobe free mismatched filter estimators are
given for arbitrary coherent targets in the case of aperiodic transmission. It
is shown that mismatched filtering is often better than matched filtering in
terms of estimation accuracy. A search strategy for finding general
transmission codes that minimize estimation error and satisfy constraints on
code power and amplitude range is then introduced. Results show that nearly
perfect codes, with performance close to a single pulse with the same total
power can be found. Also, finding these codes is not computationally expensive
and such codes can be found for all practical code lengths. The estimation
accuracy of the newly found codes are compared to binary phase codes of similar
length and found to be better in terms of estimator variance. Similar
transmission codes might be worth investigating also for sonar and
telecommunications applications.
