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This paper demonstrates the possibility of performing radio frequency (RF) measurements in the IEEE 1149.4 environment using a selected combination of mixing and sub-sampling as the method to down-convert the RF signal into a low frequency suitable for the analogue busses specified by the 1149.4 standard. Signals generated by RF signal generators (2 GHz) and a commercial VCO (3 GHz) were used to demonstrate the operation of the developed RF-to-LF circuitry in cooperation with National's SCANSTA400 IEEE 1149.4 analog test access device. The measured repeatability of RF power measurement through the whole system, i.e. from the RF input to the output of SCANSTA400, is ±0.15 dB and the measurement uncertainty of the RF frequency due to measurement instruments and signal sources is ±350 Hz. Interconnect measurements at 2.1 GHz were also demonstrated. Simple faults such as shorts, opens and missing components may readily be detected at the low-frequency output of the RF-to-LF circuitry.