A General Multi-ratio Interpolation Architecture Based on Frequency Response Mask Filter in Digital Storage Oscilloscope

Multi-ratio interpolation represents a prevalent methodology within time-domain measurement devices, notably digital storage oscilloscopes (DSOs). This technique is instrumental in augmenting the sampling frequency of data acquisition (DAQ) systems, thereby facilitating a more granular observation of time-domain waveforms. As the bandwidth of the DSO increases, the oversampling rate (OSR) of the DAQ system gradually decreases. Concurrently, the interpolation ratio (IR) increases to observe more precise phase relationships. These trends reduce the transition band of the interpolated antialiasing filter, leading to a geometric increase in the order of the anti-aliasing filter, which results in a heavy consumption of hardware resources in the field-programmable gate array (FPGA). To tackle this issue, this paper presents a novel multi-ratio interpolation architecture based on the frequency response mask (FRM) filter. This architecture reduces the filter design order by interpolating filter coefficients. The architecture can adapt to multi-ratio interpolation and eliminate redundant operations using a polyphase filter. In practical testing with a 10 GSPS sampling rate and a 4 GHz bandwidth DSO, we successfully achieved multi-ratio interpolation from 2 to 100 times. Compared to the conventional anti-aliasing filter, we reduced the filter order of the polyphase interpolation architecture to 8%. Our experimental results validate that the proposed architecture can effectively implement multi-ratio interpolation in DSO with reduced hardware consumption.