Digital communications using self-phased arrays

A new technique for full duplex digital communications using adaptive phase conjugation is presented in this paper. The technique is based on mixing t he RF signal to an IF where it can be easily processed, and filtering the p hase of the IF signal to separate the geometry phase and message phase, The retrodirective array automatically tracks communicating platforms and tran smits a directive return signal without the use of phase shifters. A 6-GHz microstrip retrodirective antenna array was built, together with the signal IF processing needed for full duplex operation. The measured RCS values of a linear six-element array are in good agreement with theory and results i n a 0- to -5-dB RCS for angles up to +/- 60 degrees. The measured RCS value s of a circular array are much flatter and are 0 to -5 db up to +/- 80 degr ees. Two-way digital communications at a baud rate of 78 kb/s was also demo nstrated with BER < 10(-6) for signal-to-noise ratios around 10 dB, The app lication areas are in high-performance digital mobile telecommunications fo r commercial and military applications.