A Pulsed-Coherent Lidar With Sub-10 μm Precision

This article presents a pulsed-coherent lidar that uses a 19-GHz pulse-modulated optical carrier and segmented time-of-flight (ToF) detection. The receiver analog frontend (AFE) employs a down-conversion chain that consists of a phase-invariant programmable-gain low-noise amplifier (PI-PGLNA), a sub-harmonic mixer (SHM), and an inverter-based phase-invariant programmable-gain amplifier (PI-PGA). The local oscillator (LO) is generated from a phase-locked loop (PLL) with a ring-type voltage-controlled oscillator (VCO). An analog-to-digital converter (ADC) subsamples the down-converted signal, and a digital signal processor (DSP) calculates the coarse, intermediate, and fine ToF. At the receiver input, a narrowband matching is implemented between the p-i-n photodiode and the PI-PGLNA with direct wire bonding. The system achieves 6-
$\mu \text{m}$
precision with a 5-MSa/s sampling rate at a 2.5-m distance. The 2-D scanning is achieved with this lidar with the use of an MEMS mirror.