A Flexible Modulated VNA-Based Channel Sounder Framework for ISAC: Architecture, Implementation, and Preliminary Validations

Integrated sensing and communication (ISAC) has emerged as a key technology for 6G wireless systems. Channel sounding plays a critical role in system design and development by providing real-world channel data required to develop and validate realistic ISAC channel models. Among various channel sounder designs, vector network analyzer (VNA)-based systems are attractive for their scalable frequency and bandwidth configurations, high dynamic range, and easy accessibility. However, conventional VNA-based sounders lack support for user-defined waveforms, and their inherent frequency-tone operations limit applicability in many ISAC scenarios. This article presents a novel and flexible modulated VNA-based channel sounder framework that extends the capabilities of conventional VNA-based sounders to support two operating modes: 1) a frequency tone sweeping mode, enabling high accuracy, flexible frequency configuration, scalable bandwidth, and high-dynamic-range measurements in the frequency domain; and 2) a modulated waveform mode, enabling high-speed, user-defined waveform measurements in the time domain. A multireceiver design further enables flexible link configurations, supporting monostatic, bistatic, and multistatic ISAC scenarios. The sounder’s performance is preliminarily validated through static field measurements at 7.2 GHz with a 160-MHz bandwidth using three types of waveforms. The measurements fall within the frequency range 3 (FR3), one of the new frequency spectra for 6G systems. The agreement between the measured multipath components and the known scenario geometries across different links and waveforms confirms the capability and reliability of the proposed sounder framework for realistic ISAC channel measurements under static scenarios, while dynamic measurement campaigns remain a subject of future validation.