Technical Report Number
Upsampling is required prior to the summation step in most receive digital beamforming implementations to produce an accurate summed RF line or vector. This is true in both annular and linear array systems where receive echos are digitized first and then time delayed in the digital domain to achieve proper signal alignment. The efficient, parallel, real-time upsampling circuit presented here produces M upsampled values per ADC clock, where M is the desired upsampling factor. A circuit implementation that upsamples by a factor of M=4 is presented as an example of the more general technique.
Richard, William D. Ph.D., "Efficient Parallel Real-Time Upsampling of Ultrasound Vectors" Report Number: WUCSE-2013-14 (2013). All Computer Science and Engineering Research.