Real Time Correlator in FPGA Xu ZhiJun, Zhang XiuZhong Shanghai Astronomical Observatory China 4 th IVS General Meeting January 9, 2006

OUTLINE Main Characteristics Architecture of the Correlator FFT & MAC Board Some results Future Plan

1. 3 Stations FX Correlator ( 5 stations, 8 IFs ) 2. date rate ： M samples/s, 1 or 2 bits/sample 3. Integration Time ： millisecond – 1 hour (typical 5s) 4. Input data format: MKIV, MKV or others( VSI, VLBI) 5. data source ： Disk Array, Network 6. Output: via net and disk files ( in FITS format) 7. Fringe searcher, Phase Cal ( in Hardware) Main Characteristics

Architecture of Correlator

LTA Monitor (real time fringe display) PBD CCC LTA MOXA Card PBI (xc2v3000) FFT & MAC (xc4vsx35)

Data Output MACMAC FFT 16bits Scaled Fixed Point FRINGEFRINGE DELAYDELAY 16bits LTA 7300A PBI_1 Model Input FSTCFSTC MCC DATA CLKPBI_1 PBI_2 PBI_3 32M 160M 8M 4M DATA CLKPBI_2 DATA CLKPBI_3 FFT & MAC Board Diagram

192x3 bits 160x1024 bits （ linear model period ） CLK_4M RESET READY_PARA CLK_PARA PARASTR Model Input - Time Diagram Period of 6 coefficient polynomial = 1min

C1C1 C2C2 C3C3 CLKPBI_1 CLKPBI_2 CLKPBI_3 CLKFRINGE C 1 =6 C 2 =4 C 3 = -3 Integer Bit Delay

i= 1, 2 …, linear Model period (160x1024 bits) Sine-Cosine Look-Up Table Sine Cosine 16bits PBI-1 14bits Unsigned PBI-2 PBI-3 16bits 1 (b) 2 (b) 3 (b) 1 (a) RAM 16x2 x (a) RAM 16x2 x (a) RAM 16x2 x1024 PING-PANG RAM Xilinx IP Core 3x2x16 bits ‘1’ = x“4000” ‘0’ = x”C000” Fringe Stopping Complex Multiply

1 (b) 2 (b) 3 (b) 1 (a) RAM 16x2 x (a) RAM 16x2 x (a) RAM 16x2 x1024 PING-PANG RAM FFT 16 bits 1024 Fixed Point Xilinx IP Core DATA_R DATA_I (16 bits) Address 10 bits Index 9 bits FFT_R 16 bits Done FSTCFSTC FFT_I FFT (Fast Fourier Transform)

τ = d + e(f-1) f= 1, 2 …,FFT num per linear Model period (160) FSTC = i* τ/ N i=1, 2 …, N/2 N is FFT point Sine-Cosine Look-Up Table Sine Cosine 16bits Sign FFT_R 14bits Unsigned FFT_I 16 bits 1 (b) 2 (b) 5 (b) 1 (a) RAM 16x2x512 2 (a) RAM 16x2x512 5 (a) RAM 16x2x512 PING-PANG RAM Xilinx IP Core 1 DATA_R DATA_I (16 bits) 2 3 DATA_R = FFT_R * Cosine - FFT_ I * Sine DATA_ I = FFT_ I * Cosine + FFT_R * Sine FSTC (Fractional Sample Time Correction)

X_R 16 bits X_I Y_RY_I 16 bits Dout_R Dout_I R RAM 42x512 I RAM 42x512 R RAM 42x512 I RAM 42x512 1~1023 次 1024 次 Output RAM Acc RAM 42x2 bits DOUT_R = X_R * Y_R + X_I * Y_I DOUT_ I = X_I * Y_R - X_R * Y_I MAC (multiple and accumulate)

ML402 Evaluation Platform (V4-SX35) FFT & MAC Board

 xc2v3000 Number of MULT18X18s 37 out of 96 38% Number of RAMB16s 86 out of 96 89% Number of SLICEs 7301 out of %  xc4vsx35 Number of DSP48s 43 out of % Number of RAMB16s 76 out of % Number of Slices 6056 out of % FPGA Chip Usage

Results – Simulation data Station 1 - Station 2Station 1 - Station 3Station 2 - Station 3

Results – TC-1 Satellite The Fringe of the SH-UR Baseline TC-1 observation with Integration time of 62.5 ms

Results – TC-1 Satellite (cont.) The Fringe of the SH-UR Baseline TC-1 observation with Integration time of 4 seconds

Future Plan  5 stations, 8 IFs  Network creation  System auto-operation software development  Hardware Fringe searcher, Phase Cal

Thank you