Higher than Nyquist test waveform synthesis and digital phase noise injection using time-interleaved mixed-mode data converters

In this paper, a higher than Nyquist RF test waveform synthesizer with digital phase noise injection is proposed. The proposed system uses time-interleaved digital-to-analog converters (DACs) and associated digital signal processing algorithms to enhance the spectral image of the synthesized waveform in the high-order Nyquist zones by increasing the effective sampling rate and eliminating unwanted signals inside the bandwidth of interest. The generated spectral images are used as the primary output of the proposed system. The waveform synthesizer is capable of digitally controlling the phase noise characteristics of the output signal in the high-order Nyquist zones. In addition, it utilizes relatively low-cost off-the-shelf integrated circuits (ICs) for multi-GHz signal generation. In hardware validation, dual DACs operating at 2.5Gb/s (effective Nyquist rate of 5 Gb/s) are used to generate a signal centered at 3.2GHz (corresponding to a Nyquist rate of 6.4 GHz). In addition, controlled phase noise generation is demonstrated.