Ultrawideband (UWB) signal transmission in Si integrated circuits was performed by use of wireless interconnects. Linear dipole antennas fabricated on a Si substrate showed UWB characteristics in the frequency range of 5–20 GHz. The signal attenuation rates of Gaussian monocycle pulse through 10 Ωcm and 2.29 kΩcm substrates were −0.08 mV/chip and −0.03 mV/chip, respectively. Pseudo random binary signals were transmitted and received between Si chips and the lowest bit error rate of 128 bit binary signal with 13.5 Gbps was 2−6. Interference of Gaussian monocycle pulses transmitted from a dipole antenna could be suppressed by use of differential mode signals instead of common mode signals.