On-chip third-order band-pass filters for 24 and 77 GHz car radar

At microwave frequencies, the use of on-chip transmission lines as a design element becomes interesting due to the small wavelengths. At car radar frequencies, 24 and 77 GHz, the inductor can be implemented by a shorted stub, which is a transmission line, shorted at one end. This paper discusses the design, simulation and measurement results of two third-order band-pass filters with a pass-band from 22-29 GHz and 66-87 GHz, respectively. Both filters use shorted stubs as inductor. The area is small and the losses are low. We demonstrate an excellent agreement between calculated and measured filter characteristics