Picosecond pulse generation with nonlinear transmission lines in 90-nm CMOS for mm-wave imaging applications

In this paper, a pulse generator circuit for mm-wave imaging systems is presented. The pulse generation system consists of a pulse generator core circuit and a nonlinear transmission line (NLTL) as pulse compressor. The width compression is the key feature of this design as a pulse narrowing in time domain corresponds to bandwidth expansion in frequency domain. A digitally generated pulse is decomposed by the NLTL into several impulse waves called solitons. Finally, the secondary solitons are degenerated by means of tapering. In this way, the compression effect is achieved. The simulation results showed that the narrowest pulse generated by the delay line-based pulse generator circuit was 37ps. Following that, the NLTL further compressed the pulse by 62% to 14 ps. Hence, an extremely wide bandwidth from 0 to a first null of 100GHz was generated. This design is implemented in 90-nm CMOS process with a supply voltage of 1.2V.