Directional Modulation using independent waveforms at each element of a phased array radar

This work demonstrates the utilization of digital at every element signal generation to show the effect of directional modulation for radar. For example, where the code modulation used for pulse compression can be changed as a function of angle, such that the code of interest is only generated at the direction of the beam with different codes appearing just off the beam axis, allowing for angular discrimination based on the transmit signal. Target returns from within the main lobe or a side-lobe can be discriminated by intelligently transmitting different waveforms on different antenna elements, where the desired waveform is only formed external to the antennas in the air through wave combination. Therefore the angular pattern of the coherent return of the pulse will be different than the power pattern typically associated with the transmission from the array. In this paper, methods for constructing the waveform for relatively small, simple four-element arrays as a demonstration of how the concept could scale to larger systems. The directional modulation capability is shown by looking at the correlation of the code at various locations from the antenna array. The capabilities of the directional modulation effect were demonstrated by measuring the incident signal at various target locations, which was passed through matched filter bank to make angular determinations based on the relative peak magnitudes of each matched filter.