Multiband Quadrature Bandpass Sampling

Global navigation systems (GNSS) receivers are designed to be highly accurate. Next generation receivers may also need to provide high flexibility to exploit the probabilities of new specifications and algorithms. Quadrature bandpass sampling (QBPS) RF front-ends offer a possible architecture to meet this requirement. For QBPS, delay offset errors between analog-to-digital converters will introduce phase distortions. Quantification of the effects of these distortions on signal reconstruction was performed and characterized using image rejection ratio (IRR). This article investigates the best delay offset when using QBPS in multiband systems. It first analyzes the combined effect of delay offset error and in-band frequency offset for a single frequency component, then a combined IRR is defined for multiband receivers. Also, a delay offset setting scheme is proposed to maximize the combined IRR. The results show that, for a specific GNSS all-system receiver, the optimal delay offset is 158.7ps in noise-free conditions. Further, the optimal delay offset can be shifted in the presence of sampling jitter.