A x18 frequency multiplier chain has been designed in this work based on a 250-nm InP HBT technology. Three frequency multipliers are cascaded to form the integrated frequency multiplier chain: a 38-GHz frequency tripler, a 115-GHz frequency tripler, and a 230-GHz frequency doubler. The performances of the circuits are characterized based on simulation and presented in this paper, which will be verified with measurement when chip fabrication is completed. The 38-GHz cascode frequency tripler shows a saturated output power of 2.6 dBm at 38.3 GHz, while the 115-GHz single-balanced differential tripler exhibits an output power of 2.3 dBm at 115 GHz. With the 230-GHz frequency doubler, saturated output power of 3.2 dBm was obtained. The fully integrated multiplier chain shows a saturation output power of -3.4 dBm at 230 GHz, with a peak conversion gain obtained as -2.9 dB at an input power of -1.0 dBm. The 3-dB bandwidth is 27 GHz, covering a frequency range of 223 - 250 GHz.