Millimeter-Wave Active Array Antennas Integrating Power Amplifier MMICs through Contactless Interconnects

Doctoral thesis, 2021

Next-generation mobile wireless technologies demand higher data capacity than the modern sub-6 GHz technologies can provide. With abundantly available bandwidth, millimeter waves (e.g., Ka/K bands) can offer data rates of around 10 Gbit/s; however, this shift to higher frequency bands also leads to at least 20 dB more free-space path loss. Active integrated antennas have drawn much attention to compensate for this increased power loss with high-power, energy- efficient, highly integrated array transmitters.
Traditionally, amplifiers and antennas are designed separately and interconnected with 50 Ohm intermediate impedance matching networks. The design process typically de-emphasizes the correlation between antenna mutual coupling effects and amplifier nonlinearity, rendering high power consumption and poor linearity. This research aims to overcome the technical challenges of millimeter-wave active integrated array antennas on delivering high power (15–25 dBm) and high energy efficiency (≥25%) with above 10% bandwidth.

A co-design methodology was proposed to maximize the output power, power efficiency, bandwidth, and linearity with defined optimal interface impedances. Contrary to conventional approaches, this methodology accounts for the correlation between mutual coupling effects and nonlinearity. A metallic cavity-backed bowtie slot antenna, with sufficient degrees of freedom in synthesizing a non 50 Ohm complex-valued optimal impedance, was adopted for high radiation efficiency and enhanced bandwidth. To overcome interconnection’s bandwidth and power loss limitations, an on-chip E-plane probe contactless transition be- tween the antenna and amplifier was proposed. An array of such antennas be- comes connected bowtie slots, allowing for wideband and wide-scan array performance. An infinite array active integrated unit cell approach was introduced for large-scale (aperture area ≈100 λ2) active array designs.

The proposed co-design flow is applied in designing a Ka-band wideband, wide scan angle (±55°/±40°) active array antenna, consisting of the connected bowtie slot radiator fed through the on-chip probe integrated onto the output of a class AB GaAs pHEMT MMIC PA. The infinite array performance of such elements is experimentally verified, presenting a 11.3% bandwidth with a peak 40% power efficiency, 28 dBm EIRP, and 22 dBm saturated power.