Two-tone RF signal phase drift measurement system

Modern electronic circuits designed for various applications, such as telecommunications, radar systems, and high-energy physics experiments, require increasing performance of RF signal phase (propagation delay) drift in the signal chain reaching millidegree (or femtosecond) stability levels at hundreds of MHz or GHz frequencies. Therefore, long-term phase change measurements are getting difficult and sensitive to effects rarely considered in earlier designs. Consequently, new and more precise techniques for phase drift measurements and compensation must be developed. This paper presents the concept of a novel RF signal phase drift measurement system based on a unique two-tone approach to accurately measure the phase drift, providing an improved alternative to traditional measurement methods. The idea can be used in systems with digital signal processing of measurement signals. An auxiliary (2nd tone) signal is introduced in the RF chain to allow for extracting phase changes introduced by the system components. The principles of the system are explained, including mathematical basics. Next, a detailed description of a sample system, illustrating how the concept can be practically implemented, is presented. The measured test system achieved a temperature coefficient of a signal propagation delay of just 0.67 fs/°C @ RF frequency of 162.5 MHz. The paper concludes by discussing the system’s performance and highlighting its strengths and limitations. Furthermore, the authors outlined plans for future research and potential improvements to the system. • Architecture for measuring phase drift by analyzing phase changes at two different frequencies is presented. • The effects of dispersion and impedance matching are discussed. • Proposed architecture reduces the effect of the detector’s drift. • A test system utilizing the proposed architecture archives very low self-drifts.