Contents I. Introduction
Wideband beamformed yet energy-efficient solutions are highly desirable for next generation communication system to enable high speed data processing. State-of-the-art beamformed systems are, however, limited in the adoption of phase shifter [1], [2]. This is because that the frequency-dependent response sets a limit on their operational fractional bandwidth. TTD technique has been widely used to replace the phase shifter, striving to achieve beam-squint free data receiving, targeting for wide fractional bandwidth operations. On the other hand, TTD technique can also be applied for beamtraining to achieve low-latency initial access process in the same beamformed system [3]. Compared to most of the existing TTD approaches using passive elements [4], all pass filter [5], and digital approach [6], baseband (BB) TTD using sample-and-hold-circuit [3], [7], [8], [9] has attracted attention owing to its compact and digital friendly nature. Though operation mechanism and measurement results have been demonstrated to prove the efficacy of large delay range and fine resolution in TTD arrays [3], [10], [11], the circuit design considerations and trade-off analysis are insufficiently addressed. Additionally, any circuit functionalities should fit to a specific system needs and always make compromise between performance, and form-factor. However, system-level considerations has merely being quantified and discussed. This brief aims to address these gaps from circuit/component parameter selection for a scalable architecture.
