Digital antenna architectures using commercial off-the-shelf hardware

The use of the AD8346 and AD8347 modulator and demodulator chips as phase shifters and variable attenuators has been demonstrated. Insertion loss and phase were measured over the entire operating band of the AD8346 modulator board. Although the insertion loss was high over most of the band, it was within the manufacturer's specifications. In practice, some type of equalizing amplifier would most likely have to be used. A prototype transmit array was built, and phase scanning was verified by pattern measurements. The pattern simulations using measured modulator data showed unacceptable beam squint with frequency due to the lack of true time delay. Therefore, it appears that the AD8346EVAL modulator can only be used over a portion of the specified band. That is, the tunable bandwidth may be from 0.8 to 2.5 GHz, but the instantaneous bandwidth will be significantly less. This observation agrees with the manufacture's 60 MHz modulation bandwidth specification for the devices. Some digital time delay compensation may be possible in the receiver signal processing.