How to produce this type of wave?
It looks like you are using a 1.8V amplitude pulse, why? I don't know, since your image clearly shows a peak of 60mV. Also, you are using a ns time scale, despite teh fact that I explicitly said a 1s period. Maybe you work better with visual clues (clues that are explicit in nature):



In case you're not familiar with LTspice, the source, V1, a PULSE type, from 0V to 60mV, 1Hz frequency, and 50% duty cycle. The simulation time, if it's obscured by the waveform display, is 2s.