Frequency (bin)

1. FLTSAT Discoverer II E-3 AWACS GMTI SAR STAP Secure Comm Tier II+ UAV RC-135V Rivet Joint Airborne Early Warning (Space-Time Adaptive Processing) SAR SIGINT E-2C Hawkeye Standard Missile h2(0,0) x2(n) Aegis Cruiser TEL X X Signal Processing Upgrade h2(0,1) x(n)x(n-1) Small Unit Operations X X x(n) Z-1 y2(n) Jammer S Dynamic Range Clutter x2(n-L+1) h2(L-1,L-1) Noise Power (dB) Target n2 n2 Z-L+1 Range X X Z-L+1 Second-order Volterra Kernel(Traditional Method for Polynomial Filtering) n1 n1 h3(n1,a2,a3) h3(n1,a2,a3) a2 a2 a3 a3 n3 n3 X Eq. Coef. H1 Partition Filter 1 Z-a1 S HN Partition Filter p-1 Z-ap-1 PHoCSArchitecture Processing Element (PE) 16 2005 2011 2017 14 80 12 After Equalization SNR 60 Before Equalization 10 Resolution (BITS) Goal Dynamic Range (dB) 8 IFDR 40 Nonlinear Distortions Target ADC performance improves on average ~1dB/year Power (dB) 6 Target Power (dB) > 20 dB Dynamic Range Improvement 106 107 108 109 1010 Effective Bandwidth Frequency (bin) Frequency (bin) Nonlinear Equalization (NLEQ) of RF ReceiversHPC-Enabled Search for a Near-Optimal NLEQ ArchitectureBenjamin Miller1, Gil Raz2, Brandon Kam1, Joel Goodman1/ 1MIT Lincoln Laboratory, 2GMR Research & Technology, Inc. Method Objective Greedy Search Algorithm: 1) Find the PE that equalizes best with the current NLEQ architecture 2) Add this PE to the architecture 3) Repeat until there are N PEs in the architecture Lowest MSE NLEQ PE1 PEi PEM n2 NLEQ NLEQ PEi n1 The Partitioned Horizontal Coordinate System (PHoCS) is a “pruned” version of the highly over-parameterized Volterra kernel. n3 Full Volterra The objective of Nonlinear Equalization (NLEQ) is to extend the dynamic range of RF receivers by reducing in-band nonlinear distortions. This enables detection of weak targets otherwise masked by distortions present after digital integration. Globally Optimal PHoCS Locally Optimal PHoCS Even with these improvements, a typical experiment requires over 5x1014 operations! LLGrid NLEQ Architecture Search Procedure Cluster Switch Compute Nodes Service Nodes Identify architecture using the greedy algorithm Network Storage Resource Manager Jobs partitioned usingMatlabMPI Construct frequency- domain database of multi-tonal signals ConfigurationServer Verify performance of identified architecture To LincolnLAN LAN Switch Results As illustrated in the chart above, the goal of NLEQ is to increase the intermod-free dynamic range of the analog-to-digital converter (ADC) decades beyond the state-the-art. NLEQ improves wideband ADC dynamic range by up to 27 dB, a 27-year improvement! With parallelization, experimentstake days rather than months MEASURED results with MAX108 ADC at 1.5 GSPS, 500MHz instantaneous bandwidth This work is sponsored by the Defense Advanced Research Projects Administration under Air Force Contract FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government