True time-delay phased-array antenna feed system based on optical heterodyne techniques

We demonstrate a true-time delay phased-array antenna feed system based on multi-channel optical heterodyne detection techniques. The system is relatively insensitive to laser linewidth and IF frequency instabilities. We demonstrate accurate true-time delay from 0.8 to 1.5 GHz. The dynamic range for one channel is 52 dB for 1 MHz bandwidth. For a very narrow channel spacing of 13 GHz (similar to 1 Angstrom at a transmission wavelength of 1.55 mu m), the interchannel interference is negligible. Such an architecture has potential for large scale system implementations.