An efficient algorithm for downconverting multiple bandpass signals using bandpass sampling

Abstract

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 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.

Issues and New Results on Bandpass Sampling

“…There are two future research directions. First, it will be an important contribution to explicitly incorporate sampling rate uncertainties into those iterative methods in [5][6][7][8][9][10][11]. Second, it will be also important to extend the proposed method in this paper to multiple bandpass signals.…”

“…After the publication of [1], a few papers [5][6][7][8][9][10][11] have focused on bandpass sampling for multiple bandpass signals. In [5], an iterative algorithm was presented to find the sampling rate for multiple bandpass signals.…”

“…No guard bands between bandpass signals were taken into account. In [6], a graphical approach was presented for determining the sampling rate for multiple bandpass signals. Guard bands were taken into account.…”

“…However, the hardware sampler can only generate a sampling frequency that is between 1.995 and 2.005 MHz. It should be noted that, in these papers [5][6][7][8][9][10][11], the sampling tolerance was not explicitly taken into account in the design. Explicitly taking into account the sampling tolerance will be one future research direction in bandpass sampling.…”