A wideband low noise amplifier （LNA） covering the whole W-band in 0.1-μm GaAs pHEMT technology is designed. To reduce the inter-stage crosstalk and obtain wideband matching， a bypass circuit composed of dual shunt capacitors is proposed to provide wideband RF grounding. The wideband input matching and optimal noise matching are implemented by a dual-resonance input matching network. The measurement results exhibit a peak gain of 20.4 dB at 108 GHz. The measured small signal gain is 16.9-20.4 dB across 66-112.5 GHz. The measured noise figure （NF） is 3.9 dB at 90 GHz. The measured input 1-dB compression point （IP_1dB） is around -12 dBm in W-band.