Free-standing TiO2 nanotube array membranes are mounted in the active coupling gap of a planar ring-type microwave resonator with f0 of 5.5 GHz and Q of 220. When illuminated by ultraviolet radiation, the S-parameters of the resonator vary as a function of time due to changes in the dielectric constant and electrical conductivity of the membranes, which in turn occur due to the Alling of trap states and photoexcitation of charge carriers respectively. Monitoring the amplitude and frequency response of the resonator enables photodetection and carrier lifetime measurements in a simple, compact and low-cost configuration. TiO2 nanotube membranes decorated with gold nanoparticles are found to have a much faster temporal microwave response upon illumination compared to bare, undecorated membranes, which we attribute to fast and enduring charge separation at the Au-TiO2 heterojunction.