Substrate-Guided-Wave Hologram Based Continuously Variable True-Time-Delay Module for Microwave Phased-Array Antennas

摘要

A continuously variable optical true time delay module, based on substrate-guided-wave and holographic optical elements, is designed and fabricated. The dispersion effect of volume holographic gratings is combined with a novel structure to obtain continuously variable time delay intervals from tens of picosecond down to sub-picosecond, which can be employed for K-band (18 GHz ― 26.5 GHz) and Ka band (26.5 GHz ― 40 GHz) phased-array antennas. The insertion loss of the packaged module is 10 dB, including fan-out loss and propagation loss, while the non-uniformity of insertion loss is within 0.6 dB among all channels. The crosstalk among channels is less than ―40 dB. An optical true time delay module is designed to provide delay signals for ―60 degrees to +60 degrees continuously steering of an eight-element K-band phased-array antenna system. Antenna field patterns are simulated with the change of optical wavelengths. The demonstrated architecture can be used in both the transmitting and the receiving modes and can be easily scaled up for large arrays.