High dynamic range terahertz-wave transmission loss measurement at 330–500 GHz

Terahertz-wave transmission loss measurement systems at 330–500 GHz using single- and dual-channel superheterodyne receivers are described. It is shown that the phase noise effect in a single-channel system causes significant signal level fluctuation in the lock-in amplifier. The dual-channel system can eliminate the phase noise effect in synchronous detection and achieve a room-temperature noise floor of −170 dBm. The dynamic range of the dual-channel system is estimated to be 140–152 dB. The measurement uncertainty of the system is analyzed. A 0–100 dB WR-2.2 waveguide attenuator can be measured with expanded uncertainties of 0.078–0.24 dB at 480 GHz. The dual-channel system can serve as a national measurement standard for waveguide transmission measurement at 330–500 GHz and provide traceability for measurements made using commercial instruments.