the BB TTD SSP as well as the digital back-end. The wide modulated bandwidths and the large number of downconverted channels from mmW to baseband due to both differential and quadrature configurations challenges the signal generation and post-processing. In addition, all the channels should be sychronized in time with picosecond accuracies to enable efficient data communications. Fig. 18 shows a sample closedloop testbed for 800MHz TTD SSP recently demonstrated in [26]. High speed DACs and ADCs in ZCU RFSoC family make it possible to generate wideband signals from DACs and perform data capture from the high speed ADC through the same graphic user interface control which serves both as an arbitrary waveform generator and spectrum analyzer in [22]. In [26], 800MHz modulated bandwidth with 16 synchronized channels was generated and the outputs post-processed after digitization in MATLAB offline. Besides synchronization and large number of channels, repeated parameterized sweeps across frequencies and angles to characterize a multi-antenna transceiver undertakes significant efforts without closed-loop automation in place. In [23], the TTD SSP (in particular, TDC and the time amplifiers) were optimized using particle swarm optimization techniques from [88]. While the optimization was limited to TDC only and not the entire SSP, this method shows the potential opportunities to further extend the test bench automation for closed-loop signal path optimization. In their recent work, the authors have used computer Figure 18. recent discrete-time ttd ssPs supporting 800mhz BW. [26] vision techniques for testbed automation in [89]. These techniques reduces the strenuous manual calibration and test process significantly and enables generation of data-intensive 3D plots (Fig. 19(a)) and frequencyangular maps (Fig. 19(b)) that can be used to create accurate dictionaries for calibration in data communications mode. The shown plots represent 72 individual configurations when the 4-element array is configured to −45° with 500MHz modulated bandwidth at the input. The measured half-power beamwidth is close to the theoretical estimated 35°. Similar map can be generated Figure 19. measured 3d plots of 4-element 500mhz BW array for (a) data communications, and (b) rainbow beam-training. Fourth quartEr 2022 IEEE cIrcuIts and systEms magazInE 19