| Traditional systems with large numbers of solid-state devices suffer from a power-combining network loss, which grows geometrically with the number of amplifiers. A fundamental goal of spatial power combining is the use of free space as a low-loss, power-combining medium to increase the power-combining efficiency of the system.; An active-antenna array is an array of unit cells, each with an amplifying solid-state device and radiating element. Radiation from all unit cells combine coherently in free space with losses that are less than a traditional feed network for a large number of elements.; The regular array of identical unit cells of an active-antenna amplifier lends itself to traditional monolithic uniplanar fabrication. Potential applications for active-antenna arrays include analog front ends for guided munitions, collision-avoidance systems, and communication links.; This thesis presents results on two active-antenna array projects. The first project presents two low-cost Ka-band power amplifier arrays fabricated on aluminum nitride. The second presents a K-band lensing full-duplex transmit-receive array.; The two Ka-band amplifiers of identical RF design are compared. The focus of the discussion are thermal constraints on the selection of substrates and the effect on antenna design, efficiency, array layout, and bias-line configuration. Results for the Ka-band arrays are 89 W EIRP and 316 mW of output power for the first array and 145 W EIRP and 513 mW of output power at 31 GHz for the second.; The K-band array is the demonstration of a lensing active-antenna array used for full-duplex transmit-receive operation. This array employs several design enhancements over the previous array, such as increased antenna isolation, simplified fabrication requirements, and a more efficient feed. The focus of the research is on the development of full-duplex transmit-receive operation, the use of design techniques to reduce complexity, and the integration of a lens feed to reduce feed loss. The array transmits and receives at 19 and 21 GHz. Orthogonal antenna polarization and bandpass circuitry provide a simulated isolation of 50 dB at 19 GHz and 42 dB at 21 GHz between transmit and receive channels. The measured gains of the active array are 3 dB and 8.2 dB above passive for transmit and receive modes respectively. |
