14.6 A scalable THz 2D phased array with +17dBm of EIRP at 338GHz in 65nm bulk CMOS

In traditional phased arrays as the number of rows and columns increases, the complexity of array connections and phase shifters becomes a major obstacle. This challenge is even more detrimental at mm-Wave and THz frequencies where conductive loss, undesired couplings, phase/gain mismatch, and high power consumption are among many adverse effects of such lengthy connections. To address this issue, this work presents a novel scalable system for THz signal generation and radiation. Figure 14.6.1 shows the architecture consisting of a 2-D array of coupled oscillating elements. Each oscillator with its antenna forms a small THz radiator. While independently radiating, each element is also unidirectionally connected to its neighboring elements in both horizontal and vertical directions through variable phase shifters, ψrow and ψcol, respectively. This network is inherently scalable because it only relies on couplings with the nearest neighbors and there is no high-frequency global routing to any oscillator. The purpose of this topology is twofold: first to synchronize all the oscillators to a single frequency and next, to set a desired phase shift between the adjacent elements (Δφrow and Δφcol). We can show that by employing this particular coupling structure only a small subset of all the theoretical coupling modes are physically stable. By proper control of the couplings one can ensure the system settles into the desired coupling mode [1].