A 60-GHz on/off-keying (OOK) modulator supporting up to 2.5-Gbps data rate is presented. The proposed OOK modulator employs the data-dependent impedance cell to improve ON/OFF isolation. Based on a single-stage cascode amplifier, the OOK modulator achieves 36.5-dB isolation and 11.5-dB forward gain, resulting in very high ON/OFF isolation of 48 dB by incorporating the data-dependent impedance cell. The OOK modulator is realized in a 0.18-μm BiCMOS process, occupies 0.95 mm × 0.95 mm with all the test pads and 0.4 mm × 0.28 mm without the pads, and only consumes 4.5 mA at 1.8-V supply voltage (PDC = 8.1 mW).