Antenna Preprocessing and Element-Pattern Shaping for Multi-Band mmWave Arrays: Multi-Port Transmitters and Antennas

Classical MIMO arrays employ a series of identical transceiver elements with periodically spaced identical and static antenna elements at a given frequency. The fixed antenna spacing limits the frequency of operation of the array due to the appearance of severe grating lobes at frequencies where the spacing approaches one wavelength. In this article, we propose element-level programmability, where each element in an array can be independently reconfigured to synthesize a set of element patterns. Through the control of element lobe and notch, new array patterns can be synthesized with strict control of side and grating lobes over a wide spectral range for multi-band arrays. In addition, we present the co-design methodology between the unit transmitter element and the integrated electromagnetic (EM) interface that allows broadband operation and unique antenna-level processing of signals that are distinct from classical arrays. This includes signal combination through the antenna, thus creating reconfigurable element patterns, dual beams for supporting wide angles of arrival and departure, and processing of more than one independent data stream in a single radiating surface (and reciprocal properties in a receiver). As a proof of concept, we present a four-port transmitter and EM interface implemented in a 65-nm bulk CMOS process. The chip demonstrates a wide effective isotropic radiated power (EIRP) bandwidth approximately across 40-70 GHz at the broadside and a peak EIRP of 25.6 dBm at 60 GHz with the ability to create a wide array of transmitter element patterns in a single aperture. The multi-functional EM interface and the broadband transmitters can enable future efficient and compact MIMO arrays for reliable links exploiting frequency and pattern diversities.