InP-based InGaAs PIN millimeter-wave diodes were used to design and fabricate monolithic integrated transmit-receive switches for W-band automotive applications. Coplanar-waveguide InGaAs PIN diode technology with reduced parasitics was employed for fabricating MMICs and yielded switches with high isolation and low insertion loss as shown by the performance of W-band single-pole double-throw switches. 77 GHz SPDT switches demonstrated less than 1.35 dB insertion loss, more than 43 dB input-to-output isolation, and more than 30 dB output-to-output crosstalk. W-band on-wafer large-signal characterization revealed no degradation of performance when the input power was increased to the maximum available level of +11 dBm.