A UWB Impulse-Radio Timed-Array Radar With Time-Shifted Direct-Sampling Architecture in 0.18- CMOS

This paper presents a ultra-wideband (UWB) impulse radio timed-array radar utilizing time-shifted direct-sampling architecture. Time shift between the sampling time of the transmitter and the receiver determines the time of arrival (TOA), and a four-element timed antenna array enables beamforming. The different time shifts among the channels at the receiver determine the object's direction of arrival (DOA). Transmitter channels have different shifts, as well, to enhance spatial selectivity. The direct-sampling receiver reconstructs the scattered waveform in the digital domain, which provides full freedom to the backend digital signal processing. The on-chip digital-to-time converter (DTC) provides all the necessary timing with a fine resolution and wide range. The proposed architecture has a range and azimuth resolution of 0.75 cm and 3 degrees, respectively. The transmitter is capable of synthesizing a variety of pulses within 800 ps at a sampling rate of 10 GS/s. The receiver has an equivalent sampling frequency of 20 GS/s while supporting the RF bandwidth from 2 to 4 GHz. The proposed designs were fabricated in a 0.18- $\mu{\rm m}$ standard CMOS technology with a die size of $5.4\times 3.3\ {\rm mm}^{2}$ and $5.4\times 5.8\ {\rm mm}^{2}$ for the transmitter and the receiver, respectively.