23.2 A 436-to-467GHz Lens-Integrated Reconfigurable Radiating Source with Continuous 2D Steering and Multi-Beam Operations in 65nm CMOS

High-resolution and fast imaging/sensing at THz requires highly directive steerable beams for scanning the object. A coherent array of coupled sources could improve the radiated power but requires mechanical and slow scanning of the object [1]. Phased array systems could use beam steering to scan the object at a higher speed, but in both coherent-array and phased-array systems, large array sizes with high power consumption are needed to generate a highly directive and narrow beam for high image resolution [2 –4]. Although Si lens can be used to increase directivity in a phased array, the steering capability is significantly diminished [5]. Therefore, arrays of non-coherent sources are used with Si lens to illuminate different parts of the object with each source with high directivity [6]. The firing angle of each source is determined by the ratio of its displacement $(L_{dis})$ from the lens center to the lens radius $(R_{lens})$, as shown in Fig. 23.2.1 [1]. However, this type of source can only illuminate the object in discrete steps determined by beam spacing, which in turn is limited by the inevitable distance between adjacent sources on the chip. Being constrained to independent single pixels for illumination leads to loss of resolution and blind spots between the neighboring beams (Fig. 23.2.1). A larger lens can improve the resolution by reducing the beam spacing but at the cost of a smaller total scanning range.