How do I spec a time delay matched cable assembly set for a multi-channel coherent system?

Specifying a time delay matched cable assembly set for a multi-channel coherent system ensures all channels have the same signal propagation delay, which is critical for: coherent beamforming (phased arrays require delay matching within a fraction of the signal period), time-of-arrival direction finding (DF accuracy depends on delay matching between channels), and MIMO systems (channel estimation accuracy depends on synchronization). The specification includes: group delay tolerance (the maximum allowable variation in group delay between any two cables in the matched set; for narrowband systems: express as phase tolerance at the center frequency (equivalent to delay × frequency × 360); for wideband systems: express as absolute time delay tolerance (typically ±10 ps to ±1 ns)), frequency range (the delay must be matched across the full operating bandwidth; dispersion in the cable causes the delay to vary with frequency, and this dispersion varies between cables), operating temperature range (the cable's delay changes with temperature due to: thermal expansion of the cable length, temperature coefficient of the dielectric constant, and connector thermal expansion; specify the required delay stability over the operating temperature range or use phase-stable cables), connector type and gender (must match the system's interfaces), test data requirements (request a certificate of conformance that includes: measured delay (or phase) at specified frequency points for each cable, cable-to-cable delay variation within the set, and measurement uncertainty). Manufacturer capability: major RF cable manufacturers (Gore, Times Microwave, Huber+Suhner, Mini-Circuits) offer delay-matched cable assembly sets as a standard service.