Waveform Coding for Passive Multiplexing: Application to Microwave Imaging

This paper proposes a novel passive technique for the collection of microwave images. A compact component is developed that passively codes and sums the waves received by an antenna array to which it is connected, and produces a unique signal that contains all of the scene information. This technique of passive multiplexing simplifies the microwave reception chains for radar and beamforming systems (whose complexity and cost highly increase with the number of antennas) and does not require any active elements to achieve beamsteering. The preservation of the waveforms is ensured using orthogonal codes supplied by the propagation through the component's uncorrelated channels. Here we show a multiplexing technique in the physical layer that, besides being compact and passive, is compatible with all ultrawideband antennas, enabling its implementation in various fields.