2 results about "Digital down conversion" patented technology

The invention particularly relates to an inter-channel phase difference and amplitude difference high-precision measurement method comprising the following steps that (A) supposing that multichannel input signals are r(k); (B) digital down-conversion processing is performed on each channel and the IQ data r<ddc>(k) after down-conversion are obtained by the decimation filter; (C) any one channel r(m) is selected to act as the reference channel and conjugating of r<ddc>(m) is performed so as to obtain r<*><ddc>(m); (D) the down-conversion data of other channels and the down-conversion conjugatedata of the reference channel are multiplied so as to obtain the processed complex signal r<mul>(k)=r<ddc>(k).r<*><ddc>(m); and (F) the phase difference phi<delta>(k) and the amplitude difference A<deltah>(k) between the kth channel and the mth channel are calculated according to the obtained complex signal: mean filtering is performed on the DC component after conjugate multiplying and there is no spectrum leakage so that the calculation precision is higher than that of conventional FFT; and mean filtering is realized by using the first-order CIC filter so that the calculation amount is muchlower in comparison with that of the conventional FFT method and the advantage is more obvious especially in case of high number of channels.