A 35 MHz CMOS receiver for 3 ns laser pulses in pulsed TOF laser ranging

The relation between laser transmitter pulse properties and the corresponding optical receiver parameters is discussed, especially from the signal-to-noise ratio and precision points of view. It is shown that the matching of the receiver bandwidth to the laser pulse width maximizes the signal-to-noise ratio without significantly impairing the precision of the measurement. A CMOS receiver with a bandwidth of 35 MHz for the detection of 3 ns (FWHM) laser pulses is presented as a design case. This consists of fully differential pre- and post-amplifiers, biasing circuits and a Gm-RC block to control the output dc levels. The receiver achieves an equivalent total input-referred current noise of 16.5 nArms for 3 ns (FWHM) laser pulses with an 80 μm (diameter) avalanche photo detector (1550 nm). The single shot measurement precision (σ – value) is ~200 ps at an SNR of 20. The receiver is realized in 0.18 μm CMOS technology and consumes 90 mW of power.