Shortwave radio -- Signal processing, Antenna arrays -- Design and construction, Phase shifters
A UHF signal processing technique is described in the Fourier Space-Angle domain that uses an array of scattering elements with reflection coefficients modulated at baseband. The illumination arrival angle distributes a UHF phase across the array, and the baseband modulator phase at each of the array elements determines the radiation angle of the desired scattered product. Undesired products are re-radiated in different directions. Example 1, 2 and 4 element arrays operate at 432 MHz array with 700 Hz modulation. 2 element arrays cancel one sideband, and the 4 element array cancels both the undesired sideband and 2nd order products. Reflection coefficient modulation uses slow electronics, and scattered signals are summed in space, so this technique is attractive at much higher frequencies.
Alkhafaji, Nasr, "Space-angle Signal Processing Using a Modulated Scatter Array" (2018). Electrical & Computer Engineering PhD Day. 5.