A 25–30 GHz 6-bit digital attenuator with high accuracy and low insertion loss

A 25-30 GHz 6-bit digital attenuator with high accuracy and low insertion loss by 0.15μm GaAs PHEMT process is presented in this work. An improved structure with a parallel capacitor is applied in the attenuator architecture to enhance the attenuation accuracy. To reduce leakage of the RF signal, a cascade structure is proposed to enhance isolation and compensate the insertion loss simultaneously. The On-wafer measurement results show that the 6-bit GaAs digital attenuator has 0.5 dB resolution and 31.5 dB dynamic attenuation rage while the return loss is better than -10 dB for all states; the attenuation accuracy is better than 0.5 dB while the RMS attenuation error is less than 0.21 dB; The insertion loss is less than 5.7 dB while the insertion phase shift is less than -6.0° The total chip size is 2.0mm × 1.0mm.