Development of High Speed Modulator for W-band Millimetre-wave Imaging System

摘要

Millimetre-wave (mmW) imaging has attracted significant research interests for the promises of all-weather imaging and security scanning for military applications. Recently, we have developed a high-sensitivity mmW imaging system based on photonic devices, which relies on optical up-conversion of the received mmW signal to generate detectable sidebands. For system with lower detector reponsivity, higher resolution and wider separation between sidebands and optical carrier, a high efficiency EO modulator that works in W-band is required. Since such system does not exist commercially, we were motivated to develop our own 94GHz phase modulator. In our previous publications, we have presented design, fabrication and preliminary characterization of Lithium Niobate (LN) based devices. We continue in this paper with our post-processing techniques, updated characterization results and the packaging method between antenna and modulator. Modulation efficiency >1W~(-1) has been achieved over W-band. Using a fin-coupler for antenna integration, we have obtained insertion loss less than 3dB. The packaged modulator has been installed in our imager. Initial scanning showed high-quality images of various objects.