Asynchronous Dense-Frequency-Interleaved Analog-to-Digital Conversion Breaking the Trade-Off Between Bandwidth and Dynamic Range

An analog-to-digital converter (ADC) with broad bandwidth and high dynamic range is of the utmost importance for modern radio frequency (RF) applications. However, as the bandwidth increases with the sampling rate, distortions caused by manufacturing defects are deteriorated, thereby decreasing the dynamic range. To break the trade-off, a novel photonics-assisted asynchronous dense-frequency-interleaved ADC with decoupled bandwidth and dynamic range is proposed. By employing an asynchronous photonic channelizer, densely frequency-interleaving is achieved to convert a broadband RF signal into multiple spectrum segments that are then quantized independently by sub-ADCs. The dynamic range is determined only by the sub-ADCs while the bandwidth is determined by the number of segments or frequency-interleaved channels. Thanks to the asynchrony of the frequency-interleaving, frequency-shift dithering is introduced and taken advantage of to suppress the quantization spurs, further enhancing the dynamic range. The performance requirements for both photonic and electronic components are also eased. Experimentally, a dynamic range of 79.0 dB is achieved at a bandwidth of 5.5 GHz, outperforming the state-of-the-art ADCs, and the flexibility of the method in terms of operating frequency range and bandwidth is also demonstrated. The proposed method provides a unique tool for broadband digitization and paves the way toward next-generation RF applications.