A 5-bit, 0.25 dB Step Variable Attenuator at E-Band

A variable attenuator operating over 71 GHz to 76 GHz is presented. The circuit design, based on a differential Π attenuator, allows for precise control over the attenuation due to a feedback control circuit. When manufactured using the CMOS portion of a 55 nm BiCMOS technology, the attenuator demonstrated the ability to obtain approximately 0.25 dB attenuation steps with an RMS phase error of 0.9° using a 5-bit digital control signal. The total DC power consumption of the attenuator (including control circuitry) is 1 mW and the circuit occupies 410 μm×130 urn of chip area (1080 μm×600 μm in-cludina test baluns and pads).