JAJSTV7 March 2024 DAC39RF10-SEP , DAC39RF10-SP , DAC39RFS10-SEP , DAC39RFS10-SP
PRODMIX
The radar chip waveform used for testing is a non-linear frequency modulated (NLFM) pulse, lasting 4096 samples at the 250MSPS complex input rate. At baseband, the frequency ramps from -100MHz to + 100MHz, following a frequency ramp curve developed by Price and shown in Equation 6 [Price R. Chebyshev Low Pulse Compression Sidelobes via a Nonlinear FM. National Radio Science Meeting of URSI; PortSaid, Egypt: 1979.] with T = 4096 samples, B = 0.8, Bl = 0.5611 and Bc = 0.238.
The NLFM Chirp frequency ramp is shown in Figure 8-13, complex time domain baseband waveform inFigure 8-14, baseband frequency spectrum in Figure 8-15 and auto-correlation in Figure 8-16.
The output spectra for the NLFM Chirp at 3.2GHz is shown in Figure 8-17. The largest spur is the duty-cycle image at 4.8GHz, which is suppressed 50dB. Figure 8-18 shows a 1 GHz span centered at 3.2GHz. the interpolation filters confine the output spectrum to a 250MHz wide band at 3.2GHz. The spectra purity of the 200MHz is shown with a fullscale tone in Figure 8-19. The largest spurs are ~ 80dBc at 3.16GHz, which is the 4th harmonic (aliased back into 1st Nyquist zone), and the 6th harmonic at ~ 86dBc.
The output phase noise for a tone at 3.2GHz using the recommended clocking circuit is shown in Figure 8-20. The additive phase noise for the DAC by itself is shown in Figure 8-21.