Cell-based programmable phase shifter design for pulsed radar SoC

For a pulsed Radar SoC, the programmable phase shifter is a critical timing control unit as it dictates the “time-of-arrival”, i.e., the interval between the timing a pulse signal is launched and the timing an echo pulse is sampled. A pulsed Radar SoC often sweeps this timing parameter (from a smaller value to a larger value) to set the distance of detection of an object in a scanning fashion from the center of the Radar towards the outer regions. In this paper, we demonstrate that such a programmable phase shifter can be designed with only standard cells, while being able to control the time-of-arrival in 10,000 steps with a step size of 10ps within a wide tunable range of [0ns, 10ns]. Measurements results in a 65nm process are reported.

I. Introduction

With the continued progress of CMOS process, it has been proven viable to miniaturize the short-range Radar system as a highly integrated CMOS System on Chip (SoC) [1]–[5]. This recent development has led to many new fine-resolution wireless indoor applications. Such a pulsed Radar SoC transmits a sequence of short-duration pulses periodically. Once a pulse is transmitted, it listens to any echo (or returned signal) to decide if an object is detected within a specific target range (e.g., in an indoor environment). Since the radio signal travels at the speed of light at m/s, the distance between a Radar and an object it detects is a function of a timing parameter called Time-of-Arrival (ToA), representing the elapsed time for an echo pulse to return to the Radar after hitting an object, or the timing difference between the time a pulse is launched and the time an echo pulse is sampled. Quantitatively,

$$\begin{equation*}\mathbf{Distance} = (\mathbf{speed}\ \mathbf{of}\ \mathbf{light}) \times(\mathbf{Time}-\mathbf{of}-\mathbf{Arrlval})\div 2 \end{equation*}$$