Attenuation-measurement system in the frequency range of 18-40 GHz

The attenuation-measurement system of the National Metrology Institute of Japan-the dual-channel intermediate-frequency (IF)-substitution method using an inductive-voltage divider (IVD) as a reference standard-is improved to cover the frequency measurement range of 18-40 GHz. Higher accuracy is obtained by raising the IF to 10 kHz and employing two seven-decade IVDs in cascade arrangement. The use of the frequency doublers at each local port of the mixers allows the low-pass filters to be installed to satisfy the essential isolation between the channels. A 10-kHz voltage-ratio standard has been constructed and used as a reliable technique for uncertainty evaluation and long-term accuracy control of the 10-kHz null-balance receiver. The expanded uncertainties are expected to be 0.002 dB for attenuation up to 40 dB, 0.005 dB for 60 dB, and 0.03 dB for 80 dB.