Objective   In the application of pulse laser detection, peak detection circuit is usually used to obtain target intensity information for object detection and recognition. Due to the inherent characteristics of pulse laser that the laser beam has a divergence angle, so that the light spot has a certain area. When the laser passes through some partially reflected or partially occluded multi-layered objects in space, multiple echoes will be generated and some of the echoes which are above the detection threshold will be received by the detection system. In order to avoid the echo interference generated by penetrable occluded objects and enhance capability of system recognition, the pulse laser detection system needs to be able to capture the multiple echoes, while the traditional peak detection circuit cannot accurately detect the peak values of multiple echoes. As an important functional module in the pulse laser detection system, many research institutions have carried out a lot of relevant researches. Most of them focus on improving the detection accuracy and response speed of single echo peak, while the researches on multiple echoes peak detection are relatively few.

  Methods   According to the requirements of pulse laser detection in complex scenes application, a smart pulse multi-echo peak detection circuit chip with high integration is designed based on the theory of pulse multi-echo peak detection. The chip uses a two-stage peak detector sample and hold circuit structure, which can realize the narrow pulse detection and maintain signal for a long time. Furthermore, it adopts interleaved sampling technology to reuse the first stage circuit for the rapid acquisition of narrow pulse signal, and then applies the multi-channel holding circuit of the second stage to maintain the signal for a long time, realizing the peak detection of multi-echo signal (Fig.4). The structure of the circuit module and time sequence of the logic control are described in detail (Fig.6-9). At the same time, through the error model of the peak detection circuit, the relationship between the output error of the peak detection circuit and the number of channels of the first stage circuit is simulated. The simulation result shows that the output accuracy of the peak detection circuit can be improved by simplifying and reusing the first stage circuit (Fig.5).

  Results and Discussions   The circuit was implemented and fabricated in a 0.18 μm CMOS process (Fig.10). The layout area of chip is about 2.6 mm×0.48 mm. Through actually carrying out test on the multi-echo experimental platform, the test results show that the output of each channel of the designed chip is normal (Fig.11). The proposed circuit can effectively detect pulse multi-echo signal with amplitude range of 50-500 mV and pulse width of 5 ns. The maximum error of the peak output is less than 4.8% (Fig.12), and the maximum relative error of output voltage between channels is 5.7% (Fig.13). The main parameters of the proposed peak detection circuit are compared with some similar works in the recently published papers (Tab.1). Compared with the published works, the main advantage of the designed circuit is that it can effectively detect the pulse multi-echo signal with ns-scale pulse width, and it has a low relative error. The total power consumption of the multi-echo peak detection circuit is similar to the other compared circuits.

  Conclusions  In this study, a smart pulse multi-echo peak detection circuit chip with high integration is designed. The chip uses a two-stage peak detector sample and hold circuit structure and optimizes the circuit structure by adopting interleaved sampling and multiplexing techniques to realize peak detection of multi-echo signal. Compared with the common peak detection circuit, this designed scheme has more simplified circuit structure and lower relative error between channels. The test results show that the chip circuit has good linearity in the amplitude range of 50-500 mV for multi-echo pulses with 5 ns pulse width. The designed circuit can be integrated and applied to the pulse laser detection system, which makes the multiple echoes detection capability of the system more precise.