Precision measurement of attenuation and phase-shift at microwave and millimeter-wave frequencies.
Date of Issue2012
School of Electrical and Electronic Engineering
We have developed novel microwave attenuation measurement systems using heterodyne receivers at 0.05−26.5 GHz. The leakage, noise floor and DR of the system have been analysed. The receiver noise floor is around −172 dBm, with a record high DR of ~186.7 dB at 26 GHz. A microwave phase-shift measurement system at 0.05−18 GHz has been developed using dual-channel heterodyne receivers. The phase-shift measurement uncertainty is 0.09−0.32 degrees for a 0−140 dB coaxial step attenuator at 18 GHz. The phase-shift measurement uncertainty of our system for a 100 dB attenuator at 18 GHz is ~106 times smaller than that of a vector network analyser (VNA). A coaxial beadless air line has been used as a phase-shift standard to verify the phase-shift measurement system. Millimeter-wave attenuation measurement systems in 75−110 GHz, 140−220 GHz and 330−500 GHz have been developed. The DR of the measurement system is around 163 dB at 220 GHz and 152 dB at 480 GHz, respectively, which are much higher than that of a VNA. The proposed system has achieved a room-temperature noise floor at around −170 dBm at 480 GHz. The measurement systems have been verified using several precision rotary vane attenuators (RVA). We have also developed a novel millimeter-wave phase-shift measurement system at 220−325 GHz. The differential phase-shift measurement uncertainty is estimated to be 0.58−1.32 degrees for a 0−60 dB RVA at 325 GHz. The phase-shift measurement uncertainty of the proposed system for a 50 dB attenuator at 325 GHz is ~44 times smaller than that of a VNA. A waveguide line standard has been measured as a phase-shift standard to verify the phase-shift measurement system. This thesis has shown that dual-channel heterodyne receiver design is very effective to reduce the measurement errors due to phase noise at microwave and millimeter-wave frequencies. Such a design can significantly improve the sensitivity in measurement using a lock-in amplifier. These systems have been used as the Singapore national standards for attenuation and phase-shift measurement at the National Metrology Center. Variable attenuators, air lines and waveguide shims calibrated by these systems can provide traceability and serve as reference standards for calibration of VNA, power meters, radiometers, spectrum analyzers, etc. The proposed measurement techniques can also be used to achieve high DR in instrumentation, communications, radar, imaging, spectroscopy, material measurement, etc.
DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio