Overview of Key AESA Enablers: Array Elements, Transmit/Receive Modules and Beamforming

This lecture focuses on key AESA enablers. The array elements which are the interface between the AESA and free space for transmit and receive operation. Transmit receive modules (TRMs) which provide signal conditioning (i.e., RF filtering and attenuation), amplification, phase and/or time delay steering, and receiver protection. Lastly, beamforming and how it distributes signals to the TRMs, and combines signals received from the array elements to form array beams.

For the array elements, fundamental aspects of performance such as operating in an array environment, polarization, element spacing and grating lobes relationship, antenna losses inclusive of mismatch, ohmic and active match, and scan loss are descriptively detailed analytically with illustrations. Also, A summary of key performance characteristics is provided with their relation to the components in the TRM. Various TRM topologies are described that include transmit and receive, receive only, channelization, simultaneous beams, and multi-channel TRMs. A block diagram is provided for each with accompanying detail on key features. Transmit and receive operation for the TRM are also discussed with a focus on efficiency and amplifier classes, P1dB (compression), linearity, wideband operation, and thermal design considerations due to the TRM output match. Additionally, Tile and brick AESA architectures are described and their impact on the beamformer in addition to an overview on space fed beamformers. The difference between corporate and non-corporate beamforming is discussed followed by analytical expressions for a lossless beamformer, which is the fundamental foundation for coherent beamforming and signal distribution in an AESA. Implementation of amplitude weighting for sidelobe control is explained using beamformer only weighting in addition to distributed weighting between the transmit receive modules (TRMs) and beamformer. Phase only weighting for beam spoiling is explained with a descriptive overview using quadratic phase.