Frequency-shifting using bandpass sampling

A frequency-shifting technique is discussed that uses a digital filter to interpolate a bandpass-sampled signal at a low-pass position. The discussion focuses on the derivation of the required digital filter. It is shown that second-order bandpass sampling offers more flexibility than first-order bandpass sampling. It is also shown how well-known quadrature-sampling methods for frequency-shifting are special cases of the general second-order sampling technique. >