An experimental digital beamforming array

A digital beamforming (DBF) array was fabricated and tested using commercially available parts to demonstrate beam agility and reconfigurability. The antenna portion of the DBF system consists of a 2*4 array of microstrip patch elements. The patch radiators are corner-fed square elements with a diagonal slot for circular polarization designed at 2.95 GHz in Duroid. The signal is split into I (inphase) and Q (quadrature phase) channels, and each channel is converted into a digital signal by an 8-b A/D (analog-to-digital) converter at a 5 MHz rate. The I and Q channels of each element are multiplied by an 8-b weight vector. The results of the I multiplications and Q multiplications are separately summed and then detected and converted to a DC voltage output proportional to the input received signal level. Numerous different patterns were obtained by varying the I and Q weight vectors appropriately. The experimental and theoretical patterns of a flat-top-beam and a difference pattern obtained by inverting the phase of half of the array are shown. >