Fig. 3: Digital representation of a broadband electronic signal.
From: 320 GHz photonic-electronic analogue-to-digital converter (ADC) exploiting Kerr soliton microcombs
The analogue signal covers the spectral ranges 0 GHz…80 GHz, 160 GHz…240 GHz, and 240 GHz…320 GHz. The spectral region 80 GHz…160 GHz is empty. The electronic signal comprises three QAM data signals, centred at carrier frequencies 24.4 GHz (30 GBd 32QAM), 233.4 GHz (40 GBd QPSK), and 264.4 GHz (10 GBd 16QAM). From the digital representation indicated by horizontal braces, three constellation diagrams can be extracted. In the “empty” region, clock tones from the real-time sampling oscilloscope are to be seen. In the middle of the empty overlap regions, stitching tones (orange) help to adjust the phases of neighbouring slices
