The use of superconducting radio-frequency (SRF) cavities is a highly promising approach to search with a tabletop-sized device for gravitational waves above the LIGO/Virgo band in a largely uncharted frequency range. To fully exploit the potential sensitivity of a suitable SRF cavity, the radio-frequency (RF) control for this experiment has to ensure the highest detection performance, higher than what is currently realized in modern particle accelerators. With the help of the PIER Seed funding, such an RF control system will be adapted to the resonance frequency of the SRF cavity and will be combined with a so-called Carrier Suppression Interferometer (CSI) setup. With the CSI setup, a breakthrough in analog signal detection techniques was recently accomplished at DESY and established a 60 dB improvement of the detection noise floor at 1.3 GHz in a laboratory-controlled environment. One of the key challenges of this project consists of adapting this CSI technique to the 2.1 GHz RF control system and to demonstrate the same improvement in a proper experimental environment.