21.7 A Fully Integrated 24GHz 8-Path Phased-Array Receiver in Silicon

Available frequency spectrum, co-channel interference, and multi-path fading determine the data-rate limits of today’s high-speed wireless communications. Higher frequencies offer more bandwidth, while enabling multiple antenna approaches by reducing the required antenna size and spacing. Versatile multiple antenna systems provide a plethora of solu-tions for communications and radar, such as multiple-input-mul-tiple-output (MIMO) diversity transceivers and synthetic aper-ture radars (SAR). Phased arrays constitute a special class of multiple antenna systems that imitate the behavior of direction-al antennas whose bearing can be adjusted via electrical means. Generally, a radiated signal arrives at spatially separated anten-na elements at different times. Phased arrays compensate the time delays between the elements and combine the signals to enhance the reception from the desired direction, while rejectin