An analog front-end (AFE) circuit comprising an amplifier module, a peak detector, and a timing discriminator has been designed to facilitate the target identification for direct time-of-flight (dToF) LiDAR. The amplitude saturation error (ASE) is compensated in this article for the intensity determination, which is conducted based on the combination of the pulse width and peak detector. Together with the improved walk error compensation scheme, the proposed AFE circuit can attain the distance and intensity information simultaneously with lower cost and larger dynamic range. A specific frequency compensation method is proposed with a shunt feedback TIA, which improves the stability and mitigates the impact of the package parasitics. The measured -3-dB bandwidth, transimpedance gain, and the input-referred noise current are 281 MHz, 86 dB $\Omega $ , and 4.68 pA/ $\surd $ Hz respectively. The proposed AFE circuit, which is fabricated in $0.18~\mu \text{m}$ CMOS technology, achieves the distance accuracy of ±30 ps and the intensity accuracy of ±4% in the dynamic range of 1:5000 without gain control scheme.

A Low Walk Error Analog Front-End Circuit With Intensity Compensation for Direct ToF LiDAR

This paper presents a linear and wide dynamic range (DR) receiver for pulsed time-of-flight imaging laser detection and ranging application, which can capture the pulsed echo intensity. The alternative leading edge timing discrimination scheme with two threshold voltages by differential voltage shift is utilized to compensate the walk error, and thus accurately obtain timing information. The proposed receiver was implemented and fabricated in a 0.18- $\mu \text{m}$ CMOS technology. The receiver achieves a high differential transimpedance gain of 106 dB $\Omega $ , a wide differential output swing of about 1.8 V, an input-referred noise current of 4.55 pA/Hz0.5 and a minimum detectable signal of about $0.28~\mu $ Arms at SNR = 5, leading to a linear DR of 66 dB with a 3.3-V power supply. The area of the receiver chip is equal to $0.95\times0.95$ mm2.

A Linear Dynamic Range Receiver With Timing Discrimination for Pulsed TOF Imaging LADAR Application

This paper presents a Time-of-Flight laser radar receiver based on pulse-shaping at the input to the receiver channel, in which the first zero-crossing point of the converted pulse is marked as the timing moment. In this technique, an LC resonator is combined with a nonlinear feedback TIA to achieve high accuracy and high precision within a wide dynamic range. The key advantage is that the receiver does not require any post compensation or gain control techniques so that the total complexity of the TOF radar is reduced considerably. Measurements made in a $0.35~\mu m$ standard CMOS process show a bandwidth of $230MHz$ and an input-referred noise of $70nA$ RMS. The receiver chip consumes $155mW$ power from a $3.3V$ supply. The single-shot precision and accuracy of the receiver within a dynamic range of 1:50,000 are $ \sim 15mm(SNR=12)$ and $\sim \pm 15mm$ respectively. A wider dynamic range can be achieved with a larger accuracy tolerance. The functionality of the proposed receiver channel is also verified over an input pulse variation and temperature range of $0~^{\mathrm {o}}\text{C}$ to $50~^{\mathrm {o}}\text{C}$ .

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A Wide Dynamic Range Laser Radar Receiver Based on Input Pulse-Shaping Techniques

A linear-array receiver analog front-end (AFE) circuit, which mainly consists of 16 transimpedance amplifiers (TIAs), is presented for pulsed time-of-flight (TOF) rotating scanner light detection and ranging (LiDAR) application. In particular, a single-channel TIA with a novel cascaded combination consists of a transimpedance preamplifier biased by a power supply of 1.8 V, a post amplifier (PA), and an output buffer (OB) with a 3.3-V power supply, aiming to lower the parasitic capacitance of the input stage and widen the output swing range, respectively. Meanwhile, the input-referred noise current is investigated to evaluate the detecting capability for the weak pulse current, and the crosstalk reduction schemes in circuit design and layout design are presented for the proposed AFE circuit. The proposed AFE circuit, which achieves a high gain of 100 dB ${\Omega }$ , a low gain of 60 dB ${\Omega }$ , a simulated transimpedance gain bandwidth of approximately 450 MHz, an equivalent input-referred noise current of 2.59 pA/Hz0.5, a signal-to-crosstalk ratio of 40.1 dB between adjacent channels, and a minimum detectable signal of $2.5~{\mu }\text{A}$ at SNR = 5, was fabricated in a 0.18- ${\mu }\text{m}$ standard CMOS technology. The total area of AFE circuit, which includes the circuit core, bandgap and bias circuits, and I/O PAD, is approximately equal to ${4.80}\times {0.85}$ mm2.

A Linear-Array Receiver Analog Front-End Circuit for Rotating Scanner LiDAR Application

We present a high-precision time-of-flight laser radar system based on energetic (~ 0.6 nJ) sub-ns laser pulses produced with a semiconductor laser diode. The proposed device has a single-shot precision of <5 mm at an SNR of 10 and a maximum walk error <500 ps in the dynamic range 1:250. Sub-mm precision can be achieved in ranging by means of averaging. The proposed laser radar can be used for monitoring tiny vibrations in distant targets, for example.

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Experimental Investigation Into Laser Ranging With Sub-ns Laser Pulses

This study presents a CMOS receiver chip realized in 0.18 µm High-Voltage CMOS (HV-CMOS) technology and intended for high precision pulsed time-of-flight laser range finding utilizing high-energy sub-ns laser pulses. The IC chip includes a trans-impedance preamplifier, a post-amplifier and a timing comparator. Timing discrimination is based on leading edge detection and the trailing edge is also discriminated for measuring the width of the pulse. The transimpedance of the channel is 25 kΩ, the uncompensated walk error is 470 ps in the dynamic range of 1:21,000 and the input referred equivalent noise current 450 nA (rms).

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A 700 MHz laser radar receiver realized in 0.18 μm HV-CMOS

The time domain response of high-speed avalanche photo detectors to an impulse resembling optical pulses was studied In particular, a laser diode giving an optical pulse width of about 100ps (FWHM) was used to provide excitations The results show that a commercial APD with a cut-off frequency of about 2 GHz extends the output pulse width to ∼ 270 ps and the effective responsivity is thus reduced to about half the nominal value A custom CMOS APD is capable of responding to fast laser pulses giving a ∼ 200 ps output current pulse width, but the measured effective responsivity was only ∼ 01 A/W at a wavelength of 860 nm

Time domain characterization of avalanche photo detectors for sub-ns optical pulses

Timing walk error in pulsed time-of-flight based laser range finding was studied using two different types of laser diode drivers. The study compares avalanche bipolar junction transistor (BJT) and metal-oxide-semiconductor field-effect transistor switch based laser pulse drivers, both producing 1.35 ns current pulse length (full width at half maximum), and investigates how the slowly rising part of the current pulse of the avalanche BJT based driver affects the leading edge timing walk. The walk error was measured to be very similar with both drivers within an input signal dynamic range of 1:10 000 (receiver bandwidth of 700 MHz) but increased rapidly with the avalanche BJT based driver at higher values of dynamic range. The slowly rising part does not exist in the current pulse produced by the metal-oxide-semiconductor (MOS) based laser driver, and thus the MOS based driver can be utilized in a wider dynamic range.

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Comparison of the leading-edge timing walk in pulsed TOF laser range finding with avalanche bipolar junction transistor (BJT) and metal-oxide-semiconductor (MOS) switch based laser diode drivers

A receiver channel topology for a pulsed time-of-flight (TOF) laser rangefinder is presented. The IC receiver chip realized in a 0.18 μm CMOS technology includes a transimpedance amplifier, a post amplifier and a timing comparator. Timing detection is based on leading edge detection. A multi-channel TDC is used for compensating the amplitude-dependent timing error by detecting the pulse width of the received pulse and by using this information for calibration. The receiver channel is targeted to be used with a laser diode transmitter generating sub-ns pulses. According to the simulations, the single-shot precision is < 30 ps with SNR = 10 and the total walk error 350 ps in a dynamic range of 1:100,000.

Mikko Hintikka

Papers

Experimental Investigation Into Laser Ranging With Sub-ns Laser Pulses

A 700 MHz laser radar receiver realized in 0.18 μm HV-CMOS

Time domain characterization of avalanche photo detectors for sub-ns optical pulses

Comparison of the leading-edge timing walk in pulsed TOF laser range finding with avalanche bipolar junction transistor (BJT) and metal-oxide-semiconductor (MOS) switch based laser diode drivers

A CMOS laser radar receiver for sub-ns optical pulses