Multichannel signal synthesis in free space

A two antennae, software controllable phased array was designed and fabricated to study the generation and transmission of short, nanosecond, nonperiodic pulses. This system allows transmitting a train of appropriately scaled and time-shifted bipolar signals to generate received signals with major frequency components adjustable from approximately 600 MHz to 1.5 GHz. The main components in the system include two digital to analog converters (DACs), two data pattern generators (DPG), and two power amplifiers which drive two TEM Horn antennas. The horn antennas are based on a Chebyshev taper design and a Microstrip-type balun is utilized for the transition from the coaxial feed. This approach yielded a reasonably flat frequency response in a wide range from 0.2 to 3 GHz. Thus far, 100 ps synchronization between channels was achieved, and signals of varying shape and amplitude have been received via the shifting and inverting of Gaussian input pulses defined by the user generated data input vectors. This paper presents an experimental evaluation of the hardware used to generate the multichannel array, the ability to steer the signals and generate signals of varied frequency via superposition in free space.