An efficient algorithm for downconverting multiple bandpass signals using bandpass sampling

Bandpass sampling is a useful alternative for direct digital downconversion in software radio. It significantly relaxes the analog-to-digital converter (ADC) sampling rate requirement and facilitates the design goal of moving the ADC as close as possible to the antenna. This paper presents a modified interpretation to the graph of allowable sampling frequencies in uniform bandpass sampling. It is shown that the position and guard bands of a downconverted bandpass signal band are highly related to the order of the valid sampling range, called the wedge order. An efficient algorithm is then proposed, which significantly reduces the computational load in determining the valid sampling frequencies to downconvert multiple distinct bandpass signals. Conditions for the placement of bandpass signals to utilize a given sampled bandwidth are also discussed.