A 700 MHz laser radar receiver realized in 0.18 μm HV-CMOS
Summary (1 min read)
1 INTRODUCTION
- The pulsed time-of-flight laser range finding principle is based on the measurement of a transit time of a short laser pulse travelling from the laser transmitter to the target and back to the pulse detector electronics.
- A particularly interesting semiconductor laser approach is based on the “enhanced gain switching” principle, which is capable of producing laser pulses with an energy level and pulse width of ~ 1 nJ and ~ 100 ps, respectively [7, 9].
- The input referred noise current is one of the most critical parameters in a trans-impedance amplifier (TIA), which is normally used as the preamplifier in a pulsed mode laser radar receiver.
- If the laser pulse energy can be kept constant, that will improve the signal-to-noise ratio and also the timing walk error.
- The jitter in the pulse detection is proportional to the ratio of the receiver noise and the slew rate of the timing signal.
3 RECEIVER CHANNEL
- Typically the receiver channel electronics used in a TOF based laser range finder consists of a trans-impedance pre-amplifier, a voltage type-post amplifier and a timing discrimination generating the timing mark from the received echo pulse.
- The bandwidth requirement for the receiver arises from the characteristics of the laser pulse used in the ranging.
- The inner feedback loop makes a voltage amplifier compose of two transconductance gain stages (gm2) and the active feedback (gmf).
- As already mentioned, the noise of the TIA is an important parameter which determines the sensitivity of the receiver and thus needs to be optimized.
- As discussed in [28], there is an optimum value for input capacitance which should be matched with the external capacitance.
4 MEASUREMENT RESULTS
- The receiver channel together with the timing discrimination was designed with 1.8 V supply voltage devices, and the CMOS level shifter together with the output pads for the STOP signals was using 5V transistors.
- The minimum signal was chosen to be ten times higher than the input referred noise current (SNR 10) to avoid unwanted stops from the noise spikes.
- Low jitter enables to achieve a very accurate single-shot precision when leading edge detection is used.
- High speed of the laser pulse also improves the single-shot precision (discriminated from the leading edge of the pulse) with a factor of ~ 3 at SNR = 10.
LIST OF REFERENCES
- Asymmetric-Waveguide Laser Diode for High-Power Optical Pulse Generation by Gain Switching.
- Area-efficient CMOS transimpedance amplifier for optical receivers.
- Integrated receiver including both receiver channel and TDC for a pulsed-time-of-flight laser range finder with cm-level accuracy.
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Citations
30 citations
Cites methods from "A 700 MHz laser radar receiver real..."
...A wide bandwidth TIA has been proposed in [8], and the high-energy sub-ns laser pulse is utilized for promoting the precision....
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29 citations
16 citations
Cites background from "A 700 MHz laser radar receiver real..."
...edge of the pulse and Stop 2 for the trailing edge) [28]....
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...The input referred noise current is approximately 450 nA with a discrete APD at the input [28]....
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7 citations
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References
53 citations
52 citations
"A 700 MHz laser radar receiver real..." refers background in this paper
...Even though the usage of a shorter pulse width would be beneficial from the accuracy point of view, the problem is that the peak power level available from commercial laser diode sources giving a single sub-ns pulse is limited to sub-W range [10, 11]....
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33 citations
33 citations
"A 700 MHz laser radar receiver real..." refers background in this paper
...Typical TOF based laser radars are using laser pulses with a pulse width of 3 – 5 ns limited by the limitations of high-speed laser diode drivers [5]....
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28 citations
"A 700 MHz laser radar receiver real..." refers background in this paper
...However, recently, a number of special gain-switched laser constructions have been suggested to increase the available energy level [6, 9, 12, 13]....
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