checking the FFT cores on Xilinx FPGAs

Hi, I am using a FFT core block on Xilinx Virtex-4 FPGA. On simulating a

1024 point FFT with a 64 bit 10 MHz PRBS, I seem to see the FFT data coming out as steps of zeros and FFs. My ADC samples this data at 1.5GHz, so the peak is at the very end of the spectrum as per Matlab simulations I would like to know if there are any more ways to check the FFT core in realtime by probably giving in a 10 MHz sine wave signal. Thanks in advance for all suggestions and feedback, Vivek