The design principle of the True-Time Delay(TTD) chip is studied. Based on GaAs PHEMT technology, the ultra wideband TTD is designed and fabricated. The TTD chip is characterized with ultra wideband, large time delay and compact size and mainly applied to wideband active phased array applications. The measured results on wafer show that the 6 bit TTD provides 10 ps up to 630 ps with an interval of 10 ps in the frequency range 3 GHz to 17 GHz. The Root Mean Square(RMS) error for all 64 bit states is below 8 ps. The insertion loss is below 22 dB. And the 64-states insertion variation is reduced to ±1 dB. The input and output Voltage Standing Wave Ratio(VSWR) are better than 1.7 on the whole bandwidth. The dimension of the chip is 4.0 mm×2.6 mm×0.07 mm. The simulation results are in good agreement with the measured results.