A 4-path 42.8-to-49.5GHz LO generation with automatic phase tuning for 60GHz phased-array receivers

Millimeter-Wave (MMW) phased-array receivers are used not only to overcome the large path loss and thus to relax the link budget but also to electrically steer the beam direction to suppress unwanted signals. Each element of the array requires a variable phase shift to compensate for the time difference between adjacent elements depending on the angle of the incident signals such that a maximum gain is achieved in that particular direction. Conventionally, this phase shift is controlled by the baseband with exhaustive tuning algorithms resulting in very long tuning time as the beam direction is changed, which grows exponentially with the number of elements used. This paper proposes an LO generation scheme with automatic successive phase tuning to achieve a resolution of 22.5° and an RMS error of 0.93°.