Multidimensional raster-scanned LC-ladder wave-digital filter hardware for directional filtering in space-time

A raster-scanned architecture is proposed for the real-time implementation of 2D/3D wave-digital filters corresponding to doubly(resistively)-terminated LC-ladder frequency-planar networks. Such WDFs have directional filtering applications in space-time in areas such as ultra-wideband acoustical beamforming, video processing, and ultrasonic imaging. The implementation of zero initial conditions for both rectangular/linear arrays is considered. An example of 2^nd-order 2D IIR frequency-planar filter design and FPGA-implementation for space-time plane-wave filtering over uniform linear arrays is provided. The proposed FPGA circuit is simulated, using 2D impulse response tests and interference rejection models, to confirm correct operation of the WDF architecture. The FPGA implementation was targeted to a Xilinx Sx35-10ff668 device. Timing analysis shows a critical path delay of 145 ns, implying a real-time clock frequency of 6.9 MHz, and for 32 sensors, a linear-frame sampling frequency of 215 kHz.